Engine runs extreemly rough, Need help

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countrymudboy

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So been going rounds with my project for about a yr minus winter. It starts up but runs rough really rough. It has no low end power and pops and back fires upon acceleration. Also and here is the key i believe the intake (to air filter) sounds like a jet airplain. Way to strong of a vacumm i believe.

Truck is 1989 Ford Bronco Eddie B edition. 5.0 engine.

Here is what's been done....

when I first got it I replaced all plugs wires distribtor cap rotor.

truck had been sittiling for supposably a year inow believe it was longer... so next I drained the tank

replaced fuel filter and then fuel pressure regulator.

that got it to the point of running but about like it is now verry rough surging idle when first started and some back firing.

Constantly recheck for vacumm leaks..

checked timing and ran even worse at 8BTD Where the haynes says to put it. (I know may guys on here set to 10 I have been playing with that)

Next I replaced the MAP sensor. didnt' do much

next couldn't find a leak at hoses but with carb cleaner discovered upper intake leak

replaced upper intake gasket and cleaned that and throttle body.

helped but didnt' cure

since i have replaced IAC EGR EGR possition sensor.  and just yesterday replaced distibtor thinking it was the guts of that causing misfire/ timing issues. still to no avail.

Bronco still has same symptoms and runs worse than it was before winter. I can't seem to find any more vacumm leaks so running out of ideas.

when i tried to pull codes again all i got was 33 that's why i replaced the possition sensor day before distributor. that was the koeo test can't seem to find the right link for the koer test and can't remember the pedal steering combo to get it started right so only did enginge off test.

Have not check codes yet since doing distributor and egr possition sensor but wasn't any change running wise

Lost on direction now sooo ANY ideas PLEASE share.

 

miesk5

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WELCOME!

for the koer test see it by my pal, BroncoJoe19

http://broncozone.com/topic/14269-code-reader/?pid=74587&mode=threaded

Can you obtain or use a local parts store loan a tool proggie for a vacuum gauge?

The vacuum gauge should read between -51 and -74 kPa (15 and 22 in-Hg) depending upon the engine condition and the altitude at which the test is performed. SUBTRACT 5.5 kPa FOR EVERY 500 METERS ABOVE SEA LEVEL. SUBTRACT ONE INCH FROM THE SPECIFIED READING FOR EVERY 1,000 FEET OF ELEVATION ABOVE SEA LEVEL.

The reading should be quite steady.

careful study of the vacuum gauge reading while the engine is idling will help pinpoint trouble areas.

Most vacuum gauges have a "normal" band indicated on the gauge face.

When vacuum leaks are indicated, search out and correct the condition. Excess air leaking into the system will upset the fuel mixture and cause conditions such as rough idle, missing on acceleration, or burned valves. If the leak exists in an accessory unit, such as the power brake, the unit will not function correctly

see the potential gauge readings @ http://www.diesel-dave.com/vehic/manual/stj/stj30013.htm

See my vac. test @ http://broncozone.com/topic/23994-90-58l-getting-continuous-code-33-and-running-code-44/

post #14

CM KOER

- 33 EGR valve not opening

DTC 33 is triggered when the EVP sensor is not closing;

Testing & Operation; "...The EGR Valve Position (EVP) sensor monitors the position of the EGR valve pintle. The EVP sensor converts the mechanical movement of the pintle into an electrical voltage signal which is relayed to the PCM. The EVP sensor is a linear potentiometer in which resistance varies with the EGR valve pintle movement.

Voltage is fed to the EVP by the signal return circuit. As the EGR is opened the EVP directs more voltage to the EEC and less down the voltage reference circuit. The EVP sensor provides the PCM with information on EGR flow and EGR system failures. The EVP should read between 0.24 and 0.67 volts at idle with a closed EGR valve..." read more

Source: by Ryan M (Fireguy50) at http://web.archive.org/web/20130912124008/http://www.oldfuelinjection.com/?p=35

excerpts;

Damaged EVP sensor

•Corroded or dirty connector

•Damaged EGR valve

•Faulty Vacuum system

•Broken wire in harness

•Grounded harness

•Damaged Computer

 
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countrymudboy

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UPDATE

Ok so set timing with the light and pip disconected since i hadn't done so since replaced distributor yesterday. it is now back at 8 degrees BTDC.

then i pulled codes again

koeo

code 33 EGR opening not detected

KOER

code 33

code 77 operator errer

I think i got the operator error because i do not have an overdrive button. every set of instructions i found say to push it before hitting gas

in the end it is much better in fact after i pulled codes it was almost mint only slight rough idle then i put in gear and back to crap for low end and a little backfire.

I shut engine off unplugged jumper and plugged pip back in. started again and wanted to do if i didn't hit gas as idle droped. eventually leveled out but idles rough and ocasional backfire.

Should i recheck timing since i reved enginge before plugging pip back in. Forgot to do that before I pulled codes not sure the effect?

 
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countrymudboy

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UPDATE

Ok so set timing with the light and pip disconected since i hadn't done so since replaced distributor yesterday. it is now back at 8 degrees BTDC.

then i pulled codes again

koeo

code 33 EGR opening not detected

KOER

code 33

code 77 operator errer

I think i got the operator error because i do not have an overdrive button. every set of instructions i found say to push it before hitting gas

in the end it is much better in fact after i pulled codes it was almost mint only slight rough idle then i put in gear and back to crap for low end and a little backfire.

I shut engine off unplugged jumper and plugged pip back in. started again and wanted to do if i didn't hit gas as idle droped. eventually leveled out but idles rough and ocasional backfire.

Should i recheck timing since i reved enginge before plugging pip back in. Forgot to do that before I pulled codes not sure the effect?
By the way both the EGR and EGR position sensor is NEW as in sensor yesterday and EGR about a week ago

 
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countrymudboy

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rechecked timing i guesse i ended up setting at 10 btdc last time at 8btdc it wont stay running.

this time i set it closer to 12 BTDC and remember to plug the spout back in before playing with things. Seems to make a decent difference. Still a little week on low end power but overall it's semi driveable now at least. Going to run it up the street and top off the tires see how that goes. I Think it's down to the vavumm connections from the pump to can to rail thing. I can hear that leaking a fair amount like a flutter sound

 

miesk5

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Backfire;

by Ford for EFI engines;

http://www.thedieselstop.com/faq/9497faq/maint/vra/vra02016.htm#vra02chart12

Some checks for now;

Spark Plug Wire Routing & Firing Order TSB 94-04-10 for 87-93 5.0

The firing order for 1987-1993 5.0L is 1-5-4-2-6-3-7-8. If #7 and #8, or #2 and #4 spark plug wires are routed next to each other at the separation bracket, an induction crossfire condition can occur.

Diagrams

1.gif

2.gif

3.gif

4.gif

Source: by Tank92 (Tank) at SuperMotors.net

The air supply from the SMOG pump is controlled by the air by-pass valve, sometimes called a dump valve. During engine deceleration, the air by-pass valve opens, momentarily diverting the air supply through a silencer and into the atmosphere, thus preventing backfires within the exhaust system when deceleration supplies larger-than-normal amounts of unburned fuel to the exhaust ports. check valve is incorporated in the air inlet side of the air manifolds. Its purpose is to prevent exhaust gases from backing up into the Thermactor system. This valve is especially important in the event of drive belt failure and also during deceleration, when the air by-pass valve is dumping the air supply. The air manifolds and air supply tubes channel the air from the Thermactor air pump into the exhaust ports of each cylinder, thus completing the cycle of the Thermactor system.

The air supply from the SMOG pump is controlled by the air by-pass valve, sometimes called a dump valve. During engine deceleration, the air by-pass valve opens, momentarily diverting the air supply through a silencer and into the atmosphere, thus preventing backfires within the exhaust system when deceleration supplies larger-than-normal amounts of unburned fuel to the exhaust ports. check valve is incorporated in the air inlet side of the air manifolds. Its purpose is to prevent exhaust gases from backing up into the Thermactor system. This valve is especially important in the event of drive belt failure and also during deceleration, when the air by-pass valve is dumping the air supply. The air manifolds and air supply tubes channel the air from the Thermactor air pump into the exhaust ports of each cylinder, thus completing the cycle of the Thermactor system.

Air Bypass (AIR BPV) Location pic in a 90 5.8 (should be same for your 5.0); "...Be advised that the ACV (Air Control Valve) is the TAD (Thermactor Air Diverter) Valve and the AIR BPV is the TAB (Thermactor Air Bypass) Valve. The VRESER is the Vacuum Reservoir Can where the red & black vacuum lines plug into; On my 1990 ex-5.8L, the Yellow Vacuum Line goes from the TAD Solenoid (driver's side forward solenoid) to the TAD (Diverter) Valve located at the rear of the Intake Manifold. You have to climb up onto the engine to feel the Diverter Valve or remove the Intake Manifold. I'd rather climb up using plans, ala a scaffolding type set-up; maybe remove hood depending on circumstances such as me now, w/ backache..."

thermactor-tab-air-bypass-valve.jpg

Source: by SeattleFSB (Seattle FSB)

 
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countrymudboy

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a little bit more playing around with it replaced clamps on all the hose to and from bypass valve. can't hear any more leaking or flutter. didn't change run quality much so tweaked timin a bit more may to 13 btdc or so. if i went any more i start to get spark knock so stayed there. Still have verry minimal ocassional backfire but at least now i can get up to speed and up hills. as long as it sat for I'll try taking it to work for a day or so and see what prevails.

any way to test that air dump? that's the next culprate i think already considered it but looks like a b**h to change so been avoiding it lol.

 
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countrymudboy

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sorry wasn't clear in last pose the hose and clamps i did was the hoses coming from the pump to can and to air rail area

 

miesk5

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The mechanical AIR system uses a belt-driven pump as well as a check valve to deliver air into the exhaust system where required. The belt-driven air pump runs continuously so a bypass valve and/or diverter valve is used to direct airflow to the exhaust manifold (upstream air), the COC catalyst (downstream air), or directly to atmosphere (bypass/dump).

by Ford motorcraftservice.com

secondaryair.jpg

See the Muffler out to atmosphere at Air Pump, from B (Air bypass valve, aka Air Control Valve)?

Air By-Pass Valve; "...By-pass valves are part of the thermactor system and act to vent air from the air pump into the atmosphere or exhaust system. Valves may be remote (in-line) or ^^^mounted on the air pump^^^..." - 80.6 MB pdf

Source: by Ford fordinstallersupport.com

ACV (Air Control Valve) is the TAD (Thermactor Air Diverter) Valve (AIR Bypass (AIRB) and AIR Diverter (AIRD) valve combinations

Filter, Silencer, Waste & Intake Hose Location pic in a 93 5.8

http://web.archive.org/web/20110704090403/http://www.supermotors.net/getfile/148977/fullsize/5.8l-right.jpg

Source: by Steve

The air supply pump does not have a pressure relief valve, a function performed by the bypass valve. There are two general groups of air bypass valves, normally closed and normally open. Each group is available in remote (inline) versions or pump mounted versions. The bypass valves are part of the thermactor system.

Normally closed valves supply air to the exhaust system with medium and high applied vacuum signals during normal operating modes, short idles and some accelerations. With low or no vacuum applied, the pump air is dumped through the silencer ports of the valve. Normally open air bypass valves are available with or without vacuum vents and testing procedures are different for each type. Normally open valve with a vacuum vent provide a timed air dump during decelerations and also dump when a vacuum pressure difference is maintained between the signal port and the vent port. The signal port must have 3 in. Hg more vacuum than the vent port to hold the dump. This mode is used to protect the catalyst from overheating. Normally open valves without a vacuum vent provide a timed dump of air for 1-3 seconds when a sudden high vacuum of about 20 in. Hg is applied to the signal port to prevent backfire during deceleration

Air Control Valve Functional Test' "...1.Run the engine to normal operating temperature, then increase the speed to 1500 rpm. 2.Disconnect the air supply hose at the valve inlet and verify that there is airflow present. 3.Reconnect the air supply hose. 4.Disconnect both air supply hoses. 5.Disconnect the vacuum hose from the valve. 6.With the engine running at 1,500 rpm, airflow should be felt and heard at the outlet on the side of the valve, with no airflow heard or felt at the outlet opposite the vacuum ******. 7.Shut off the engine. 8.Using a spare piece of vacuum hose, connect direct manifold vacuum to the valve's vacuum fitting. Airflow should be heard and felt at the outlet opposite the vacuum ******, and no airflow should be present at the other outlet. 9.If the valve is not functioning properly, replace it..."

Source: by Chilton

Normally Closed Air Bypass Valve Functional Test; "...1.Disconnect the air supply hose at the valve. 2.Run the engine to normal operating temperature. 3.Disconnect the vacuum line and make sure vacuum is present. If no vacuum is present, remove or bypass any restrictors or delay valves in the vacuum line. 4.Run the engine at 1500 rpm with the vacuum line connected. Air pump supply air should be heard and felt at the valve outlet. 5.With the engine still at 1500 rpm, disconnect the vacuum line. Air at the outlet should shut off or dramatically decrease. Air pump supply air should now be felt or heard at the silencer ports. 6.If the valve doesn't pass each of these tests, replace it..."

Source: by Chilton

Normally Open Air Bypass Valve Functional Test; "...1.Disconnect the air supply hose at the valve. 2.Run the engine to normal operating temperature. 3.Disconnect the vacuum lines from the valve. 4.Run the engine at 1500 rpm with the vacuum lines disconnected. Air pump supply air should be heard and felt at the valve outlet. 5.Shut off the engine. Using a spare length of vacuum hose, connect the vacuum ****** of the valve to direct manifold vacuum. 6.Run the engine at 1500 rpm. Air at the outlet should shut off or dramatically decrease. Air pump supply air should now be felt or heard at the silencer ports. 7.With the engine still in this mode, cap the vacuum vent. Accelerate the engine to 2,000 rpm and suddenly release the throttle. A momentary interruption of air pump supply air should be felt at the valve outlet. 8.If the valve doesn't pass each of these tests, replace it. Reconnect all lines..."

Source: by Chilton

Operational Description & pic; This pumps fresh air into the exhaust system, to burn left over hydrocarbons, lowering emissions. The computer uses 2 air valves (TAB & TAD) to control where the air flows depending on engine operation. Thermactor Air Bypass (TAB) shunts air to the atmosphere, when no air is needed. When air is needed it sends air to the second valve TAD. Thermactor Air Diverter (TAD) diverts air either to the exhaust manifold, or directly to catalytic converter. MIESK5 NOTE; If da Engine Coolant Temperature Sensor (ECT) is Below 50 degrees F, then TAB is grounded & sends air to atmosphere; If Between 50 and 190 Degrees F, Bypass Valve sends air to Diverter and to Manifold; If Over 190 Degrees F, it is in closed loop & Air goes to Catalytic Converter; Bypass when at idle/Wide Open Throttle (WOT), and with failing Oxygen Sensor. The fastest way to see if vehicle is in open loop is to see where the air is going; to Catalytic Converter, it is in Closed Loop; to Atmosphere or Manifold it is in Closed Loop, provided the thermactor system is working.

Source: by Ryan M (Fireguy50)

 
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Rons beast

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Hey countrymud,

I have been reading through all the posts and while all the info from M5 is of absolute value to get your AIR system performing correctly, it doesn't make any sense that it would so adversely effect the running of your engine. 

A change of 2 or 4 deg. of timing should not be the difference between running poor and even acceptable.  There is some other variable in action here. Especially if you are describing pops and backfires. Those are the products of vacuum leak/s and/ or ignition malfunctions.

If the truck is running as bad as you say there are chances that internal mechanical problems are to blame...I.E. a loose or slipped timing chain.

Another thought is to check the balancer. It is not unheard of that the outer ring slips because the rubber deteriorated. Then you are lining timing marks but the ignition timing is not correct.

Finally if you believe the timing is set correctly, yet a bit more gives detonation and still you lack power there is something wrong with the fuel mixture.

This problem has me intrigued.

Could you please post your fuel pressure, base timing, engine temp. and tire size and gear ratio if you know it.

I would like to find a correlation between all .

Thanks

Good Luck   

 
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countrymudboy

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Hey countrymud,

I have been reading through all the posts and while all the info from M5 is of absolute value to get your AIR system performing correctly, it doesn't make any sense that it would so adversely effect the running of your engine. 

A change of 2 or 4 deg. of timing should not be the difference between running poor and even acceptable.  There is some other variable in action here. Especially if you are describing pops and backfires. Those are the products of vacuum leak/s and/ or ignition malfunctions.

If the truck is running as bad as you say there are chances that internal mechanical problems are to blame...I.E. a loose or slipped timing chain.

Another thought is to check the balancer. It is not unheard of that the outer ring slips because the rubber deteriorated. Then you are lining timing marks but the ignition timing is not correct.

Finally if you believe the timing is set correctly, yet a bit more gives detonation and still you lack power there is something wrong with the fuel mixture.

This problem has me intrigued.

Could you please post your fuel pressure, base timing, engine temp. and tire size and gear ratio if you know it.

I would like to find a correlation between all .

Thanks

Good Luck   
Not sure the gear ratio's it's all stock eddie baurer edition though.

since last post I replaced the egr vacuum solenoid and one of the ruber conectors for the hose from it. That gained me a lil more power. now the only poping i get is ussually between 1400rpm and 2100 rpm mostly on inclines only. I am going to recheck timing today and see if adjusting helps since getting egr system fully functioning. When not on road revs up fine slow or fast. I am gonna recheck brake system this weekend also. It almost feels one them may be dragging a bit.

The only thing steering me away from saying a sticky valve or cat, is the fact the I only get the popping on acceleration when on inclines or trying to gun it. None when in park.

Also threw some mid grade gas in it and a can of B12 fuel system cleaner in it yesterday. 

 
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countrymudboy

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yo,

The mechanical AIR system uses a belt-driven pump as well as a check valve to deliver air into the exhaust system where required. The belt-driven air pump runs continuously so a bypass valve and/or diverter valve is used to direct airflow to the exhaust manifold (upstream air), the COC catalyst (downstream air), or directly to atmosphere (bypass/dump).

by Ford motorcraftservice.com

secondaryair.jpg

See the Muffler out to atmosphere at Air Pump, from B (Air bypass valve, aka Air Control Valve)?

Air By-Pass Valve; "...By-pass valves are part of the thermactor system and act to vent air from the air pump into the atmosphere or exhaust system. Valves may be remote (in-line) or ^^^mounted on the air pump^^^..." - 80.6 MB pdf

Source: by Ford fordinstallersupport.com

ACV (Air Control Valve) is the TAD (Thermactor Air Diverter) Valve (AIR Bypass (AIRB) and AIR Diverter (AIRD) valve combinations

Filter, Silencer, Waste & Intake Hose Location pic in a 93 5.8

http://web.archive.org/web/20110704090403/http://www.supermotors.net/getfile/148977/fullsize/5.8l-right.jpg

Source: by Steve

The air supply pump does not have a pressure relief valve, a function performed by the bypass valve. There are two general groups of air bypass valves, normally closed and normally open. Each group is available in remote (inline) versions or pump mounted versions. The bypass valves are part of the thermactor system.

Normally closed valves supply air to the exhaust system with medium and high applied vacuum signals during normal operating modes, short idles and some accelerations. With low or no vacuum applied, the pump air is dumped through the silencer ports of the valve. Normally open air bypass valves are available with or without vacuum vents and testing procedures are different for each type. Normally open valve with a vacuum vent provide a timed air dump during decelerations and also dump when a vacuum pressure difference is maintained between the signal port and the vent port. The signal port must have 3 in. Hg more vacuum than the vent port to hold the dump. This mode is used to protect the catalyst from overheating. Normally open valves without a vacuum vent provide a timed dump of air for 1-3 seconds when a sudden high vacuum of about 20 in. Hg is applied to the signal port to prevent backfire during deceleration

Air Control Valve Functional Test' "...1.Run the engine to normal operating temperature, then increase the speed to 1500 rpm. 2.Disconnect the air supply hose at the valve inlet and verify that there is airflow present. 3.Reconnect the air supply hose. 4.Disconnect both air supply hoses. 5.Disconnect the vacuum hose from the valve. 6.With the engine running at 1,500 rpm, airflow should be felt and heard at the outlet on the side of the valve, with no airflow heard or felt at the outlet opposite the vacuum ******. 7.Shut off the engine. 8.Using a spare piece of vacuum hose, connect direct manifold vacuum to the valve's vacuum fitting. Airflow should be heard and felt at the outlet opposite the vacuum ******, and no airflow should be present at the other outlet. 9.If the valve is not functioning properly, replace it..."

Source: by Chilton

Normally Closed Air Bypass Valve Functional Test; "...1.Disconnect the air supply hose at the valve. 2.Run the engine to normal operating temperature. 3.Disconnect the vacuum line and make sure vacuum is present. If no vacuum is present, remove or bypass any restrictors or delay valves in the vacuum line. 4.Run the engine at 1500 rpm with the vacuum line connected. Air pump supply air should be heard and felt at the valve outlet. 5.With the engine still at 1500 rpm, disconnect the vacuum line. Air at the outlet should shut off or dramatically decrease. Air pump supply air should now be felt or heard at the silencer ports. 6.If the valve doesn't pass each of these tests, replace it..."

Source: by Chilton

Normally Open Air Bypass Valve Functional Test; "...1.Disconnect the air supply hose at the valve. 2.Run the engine to normal operating temperature. 3.Disconnect the vacuum lines from the valve. 4.Run the engine at 1500 rpm with the vacuum lines disconnected. Air pump supply air should be heard and felt at the valve outlet. 5.Shut off the engine. Using a spare length of vacuum hose, connect the vacuum ****** of the valve to direct manifold vacuum. 6.Run the engine at 1500 rpm. Air at the outlet should shut off or dramatically decrease. Air pump supply air should now be felt or heard at the silencer ports. 7.With the engine still in this mode, cap the vacuum vent. Accelerate the engine to 2,000 rpm and suddenly release the throttle. A momentary interruption of air pump supply air should be felt at the valve outlet. 8.If the valve doesn't pass each of these tests, replace it. Reconnect all lines..."

Source: by Chilton

Operational Description & pic; This pumps fresh air into the exhaust system, to burn left over hydrocarbons, lowering emissions. The computer uses 2 air valves (TAB & TAD) to control where the air flows depending on engine operation. Thermactor Air Bypass (TAB) shunts air to the atmosphere, when no air is needed. When air is needed it sends air to the second valve TAD. Thermactor Air Diverter (TAD) diverts air either to the exhaust manifold, or directly to catalytic converter. MIESK5 NOTE; If da Engine Coolant Temperature Sensor (ECT) is Below 50 degrees F, then TAB is grounded & sends air to atmosphere; If Between 50 and 190 Degrees F, Bypass Valve sends air to Diverter and to Manifold; If Over 190 Degrees F, it is in closed loop & Air goes to Catalytic Converter; Bypass when at idle/Wide Open Throttle (WOT), and with failing Oxygen Sensor. The fastest way to see if vehicle is in open loop is to see where the air is going; to Catalytic Converter, it is in Closed Loop; to Atmosphere or Manifold it is in Closed Loop, provided the thermactor system is working.

Source: by Ryan M (Fireguy50)
Thanks for these test I will do these hopefully this weekend if enough free time opens up

 

Rons beast

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Hey Country, Missing, or popping when the engine is under load, ( like trying to accelerate up-hill.) is a sign of a breakdown in the secondary ignition system.

You could have a bad wire, scar on the dist. cap, or the plug gap could be wrong. That is more likely than a vacuum leak.

Good Luck 

 

miesk5

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RUNS ROUGH - MISSES - BUCK/**** - HESITATION/STUMBLE - SURGE - BACKFIRES While Acceleration

by Ford http://www.thedieselstop.com/faq/9497faq/maint/vra/leftside=vras7al.htm&rightside=vras7ar.htm

This supplements the info in my Post # 8

System

Possible Causes

Visual/Mechanical

EEC

Air/Vacuum •Check vacuum lines for leaks or wear.

•Check air intake system.

•IAC solenoid

•MAP/BARO sensor

•MAF sensor

•TP sensor

•IAT sensor

•IMRC solenoid

Fuel •Check for correct fuel pressure.

•Check for fuel contamination/quality.

•Check fuel filter.

•HO2S(s)

•Fuel Pump System:

FP circuit

FPM circuit

FP relay

•FPRC solenoid

•Fuel Injection:

INJ 1, 2 (MFI)

INJ 1, 2 .. (SFI)

Ignition

•Check for correct base timing.

•Check distributor cap, adapter, and rotor.

•Inspect spark plugs and plug wires.

•Inspect ICM for damage.

•Ignition System:

PIP circuit

SPOUT circuit

Power and Grounds

•Check for generator/regulator noise interference.

•Inspect electrical connections, wires, and harnesses.

•EEC Power:

VREF

•EEC Grounds:

SIG RTN

Other

•Check engine coolant level.

•Check thermostat for proper operation.

•Check EGR valve sticking.

•Check PCV valve for correct operation.

•Check for restricted exhaust.

•Check camshaft timing and cylinder compression.

•Check for broken or weak valve springs.

•ECT sensor

•EGR Systems:

EVPsensor

EGR solenoid(s)

•EPC solenoid

 

jnorwooddds

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Yeah, I used to have a bronco that did the same thing. How did I finally fix it? Sold it. I just purchased an 82 bronco with 79k miles. Excited to be a bronco owner again, but with an older engine that's easier to interpret when it misbehaves!!!'

 

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