Surging idle? 1 code..

[92Beast]

I just did a gasket(oil pan up, minus timing chain) overhaul on my 351 but now it ''surges'' at idle and or in gear. By surging I mean. goes from 8-1000rpm to 4-500rmp,up and down numerous times.

No CEL but I pulled codes and got a 334,(but by searching I don't see how there related. Where do I start testing???

Doing the overhaul I installed a new fuel pressure reg,freshen up the injectors, new plugs and wires,new vac reservoir(coffee can),thermostat,water pump,and did the 3g swap. If any of this matters.

 

[miesk5]

yo!

I'd do da 334 clean-up, check the TPS and also ck for vac leaks;

Vacuum Leak Test; "...On idling engine...Check for vacuum leaks using a mechanic's stethoscope with the probe removed, or a ~3' garden hose. Don't spray flammables on a running engine. Also check the brake booster, the 2ndry air (coffee can) & HVAC vacuum reservoirs..." around intake manifold; and maybe under dash behind control panel vac line area

Source: by miesk5 & Steve83 at Ford Bronco Zone Forums Vacuum Leak Test; "...On idling engine...Check for vacuum leaks using a mechanic's stethoscope with the probe removed, or a ~3' garden hose. Don't spray flammables on a running engine. Also check the brake booster, the 2ndry air (coffee can) & HVAC vacuum reservoirs..." (copied Steve83's info, thnx) around intake manifold; and maybe under dash behind control panel vac line area

Source: by miesk5 & Steve83 at Ford Bronco Zone Forums

Vacuum Gauge Diagnosis - BEST!

Source: by Craig U at classictruckshop.com http://www.classictruckshop.com/clubs/earlyburbs/projects/vac/uum.htm

&

"...The vacuum gauge should show 18-22 in-Hg @ idle, and maintain a steady needle. Rev it up to ~2500 rpm, hold it steady, and you should see the needle drop, then slowly increase to a level close to the idle reading (though slightly lower is normal)..."

Source: by SigEpBlue

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DTC 334

Failed sensor, & as rla2005 wrote; carbon between EGR pintle valve and seat holding the valve off its seat. Remove the EGR valve and clean it with carbon remover. Prior to re-installing see if you can blow air through the ****** side of the EGR by mouth. the egr is not closing properly which can cause detonation. remove the egr and clean off any carbon built up on it with carb cleaner and a brush if necessary.

Source: by miesk5

The EGR Valve Position (EVP) Sensor used exclusively by Ford, can be the cause of driveability problems without ever setting any trouble codes. The relationship between the EVP sensor and the EGR valve is important to understand. Either one being out of spec can cause similar symptoms. Understanding this relationship will help you to diagnose uncoded driveability problems like stumbles, hesitations, rough idles and stalling.

Failed sensor, carbon between EGR pintle valve and seat holding the valve off its seat. Remove the EGR valve and clean it with carbon remover. Prior to re-installing see if you can blow air through the ****** side of the EGR by mouth. If it leaks, there is carbon stuck on the pintle valve seat, replace the EGR valve ($85-$95).

Read through this for now by TOMCO; it is for 34 but is sim. to 334... you'll need a hand op. vac. pump and DVOM; also some long thin straight pins to backprobe harness connectors.

Ck for Vacuum Leaks "....The PFE hose should be examined carefully. We have seen them with pinhole leaks. This causes the exhaust pressure to bleed off giving an inaccurate reading to the PFE sensor. They can also deteriorate because of the corrosive exhaust gases they carry. This weakens the rubber and may cause porosity or cracks. A quick check is to hook a vacuum pump to one side and plug the other side to see if it can hold vacuum..." http://www.tomco-inc.com/Tech_Tips/ttt34.pdf

More EVP testing by Fireguy50) at fordfuelinjection.com http://fordfuelinjection.com/index.php?p=35

My ISP stinks today; Comcast is really messing up here again so I can't open some of these Links now; some may be repetitive

EVR Overview & Test

Source: by Ryan M (Fireguy50) at fordfuelinjection.com

EVP Operation & Testing, Ford

Source: by Ryan M (Fireguy50) at fordfuelinjection.com He used Voltage measurements in da test;

TOMCO uses R in test; such as "...While watching the ohmmeter, gradually and steadily apply vacuum to the EGR valve (not exceeding 10 PSI). The ohmmeter should show a steady decrease in the OHM reading. If the ohmmeter needle has any sharp movements or shows a slight increase while applying the vacuum, the sensor is bad. There is also a range that the OHM readings should fall between. In some cases this ranges from no higher than 5,500 OHMs, to no less than 100 OHMs. Check with your service manual for the exact specifications for your vehicle..."

http://www.tomco-inc.com/Tech_Tips/ttt19.pdf

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TPS Overview, Ford part numbers & pics; "...Monitors the throttle opening for the computer to adjust fuel flow. FAILURE SYMPTOMS, Hesitation, tip in surge, engine pinging, no torque converter lock-up. "Check Engine" light on. Inspect for proper operation and adjust voltages when necessary. Check for corrosion on connectors..."

Source: by tomco-inc Overview, Ford part numbers & pics; "...Monitors the throttle opening for the computer to adjust fuel flow. FAILURE SYMPTOMS, Hesitation, tip in surge, engine pinging,no torque converter lockup. "Check Engine" light on. Inspect for proper operation and adjust voltages when necessary. Check for corrosion on connectors..."

Source: by tomco-inc

Test in a 92 (loosen the 2 Phillips screws until voltage is less than 1.0 volts @ idle (.97 volts)

Source: by Richard C (Bigric, Money Pit) at SuperMotors.net http://www.supermotors.net/clubs/superford/vehicles/registry/media/118940

Test Video; "...This is a short clip compressed video clip that shows how to test the throttle position sensor on a 5.0L Ford engine with EEC 4 electronics. Test include the TPS signal, reference voltage, signal return and explains how the sensor operates. This is just a scene from a much longer chapter on EEC 4troubleshooting..."

Source: by Kenneth C at Bad Shoe Productions via youtube.com http://www.youtube.com/badshoeproductions#p/u/0/lJEGigONelc

Test & Operational Description & Parameters

Source: by Ryan M (Fireguy50) at fordfuelinjection.com http://fordfuelinjection.com/index.php?p=30

Sometimes, a TPS failure or connector, etc. won't pop a DTC

 

[92Beast]

Ok after some driving today the CEL came on,pulled codes and the only new one is 173 along with the 334.

Bad o2 sensor?

Vacuum and tps tests good.

 

[92Beast]

bump

 

[miesk5]

yo 92

173

(R,M)

Oxygen sensor not switching - system is or was rich - Single, Right or Rear HO2S - Fuel control

DTC 173 Oxygen sensor not switching - system is or was rich - Single, Right or Rear HO2S; "...I'd guess there's either an obstruction in the exhaust pipe directing the exhaust away from it, preventing it from detecting & operating normally (not likely), OR there may be a fault in the heating element circuit (more likely). It comes off the purple/yellow circuit (can't remember which fuse) which also feed A LOT of other things and runs around the front of the radiator to the R side near the battery where it drops down by the engine mount & goes to the sensor. Make sure you have good power & ground to the appropriate terminals in the connector, and test for a signal voltage. Then, using the old & the new sensors, trace the fault..." by Steve83 (Steve, That dirty old truck)

miesk5 Note check Purple/orange for 12v in this Wiring Diagram in 92-95 Bronco & F Series Source: by Steve83 (Steve, That dirty old truck) at SuperMotors.net

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DTC 172, 173 or 41 for HO2S Failure Or Fuse "E" Inoperative, ABS Light On, Back-Up Lamps Inoperative, DRLs Inoperative, MIL On, Inadvertent Self-Test, Speedometer Inoperative & Trailer Battery Charge Relay Inoperative in TSB 95-5-21 for 92-95 Bronco & F Series; "...the HO2S wires in the 12A690 (subassembly of the 14B060 battery cable) harness may become chafed and the vehicle could exhibit any one of the following conditions....Lack of proper HEGO operation may cause, or be the result of a rich or lean fuel condition, which could cause additional heat in the catalyst. Perform self test KOEO and KOER, service any codes. CHECK FOR PROPER HEGO GROUND. If the HEGO ground is good, the following areas may be at fault: ..." READ MORE by Ford via Chilton

Fue E may be labelled Fuse 5 in some years in Power Distr Box next to air filter box

334

(O,R,M)

EVP sensor is/was high - EVR

DTC 334 EGR (EVP) closed valve voltage higher than expected; "...Failed sensor, & as by rla2005 (Randy) wrote; carbon between EGR pintle valve and seat holding the valve off its seat. Remove the EGR valve and clean it with carbon remover. Prior to re-installing see if you can blow air through the ****** side of the EGR by mouth. the egr is not closing properly which can cause detonation. remove the egr and clean off any carbon built up on it with carb cleaner and a brush if necessary..."

Read through this for now by TOMCO; it is for 34 but is sim. to 334... you'll need a hand op. vac. pump and DVOM; also some long thin straight pins to backprobe harness connectors. Ignore the PFE; dwell on EVP stuff

More EVP testing by Fireguy50) at fordfuelinjection.com http://fordfuelinjection.com/index.php?p=35

The EGR may not be sticking, but it can be unseated enough that the measured value is too high. I had a piece of aluminum casting get stuck in a EGR valve once. It threw the same code, same can happen if there is carbon build up. The closed position EVP signal should be below .67 volts. The EVP sensor itself could also be bad. Checking and cleaning the EGR valve is cheaper than replacing parts, I would start there

Ck for Vacuum Leaks

Source: by rla2005 (Randy) & miesk5