stutter when highway cruising above 90 km.. please help.

[gunr]

in town my bronco seems to drive fine, however, when i am cursing between 90km and 110km the bronco stutters intermittently.

(a little history)trying to fix this i have changed: spark plug wires, spark plugs,TPS and cleaned the IAC. the fuel pump and fuel filter were change less than 6 months ago, the alternator and battery were replaced about 3 months ago. the transmission fluid has been changed several times because the radiator was leaking into the transmission cooler. to solve this i have just by passed the oe trans cooler and added and external trans cooler.

last night i did the KOEO test and got these codes:

11

11

13 ISC did not respond properly (extends to touch throttle then retracts for KOEO) I have no idea what the part in "( )" < those means

actully this looks to have been a Continuous Memory Code

so might meen this? "ISC sticking, open ITS circuit or TP sticking:

34

(KOEO, KOER, MEM)

PFE, PFE sensor is/was out of range.

16 Electronic ignition. IDM circuit fault. Ignition Systems

26Mass Air Flow (MAF) or Vane Air Flow (VAF) out of range.

[return]

26

Transmission Oil Temperature (TOT) sensor out of range.

76 Vane Air Flow (VAF) did not respond to "goose" test. 4comp2.htm. VAF

41 (Mem) System was lean for 15 seconds or more (no HO2S switching).

62AXOD (KOEO only) 3/2 circuit short to ground.

OR THIS E4OD excessive converter clutch slippage.

67

Data Output Link Fault

[return]

67

Park/Neutral circuit fault.

[return]

67

Transmission Manual Lever Position (MLP) sensor circuit.

[return]

67

(Mem)

Intermittent Park Neutral Position (PNP) sensor fault.

BTW, bronco is 1990 EB 5.8L.

 

[Rons beast]

WOW! First let us know what your working on...year, engine size, etc.

That's alot of codes. Erase them with a scanner tool or by disconnecting the battery. Then drive the truck for at least 15 miles and see what codes if any have returned.

 

[gunr]

sorry just updated post with info about bronco year and engine.

any other useful info i should have added?

 

[gunr]

cleared codes, drove, then did KOEO test, got these codes:

11

11

13(KOEO)ISC did not respond properly (extends to touch throttle then retracts for KOEO)

33 (KOEO, MEM) ALL. EGR did not open/ respond during test or if memory code, did not open intermittently.

3

 

[miesk5]

yo,

for now

DTC 67 Neutral Drive Switch (NDS) Circuit Open; "...In some cases all of us at one time or another have had to "jiggle' the column shifter to get the vehicle to start because over time things losen up from DD useage.....in the Haynes Manual transmission section and www.broncolinks.com there's a diagram referring to "Point A" which is the column shift linkage and the transmission tab. A sure way to correct the "jiggling" is to go underneath the BKO on the drivers side and LOSEN the "nut" on column shift linkage and tranny tab JUST ENOUGH to click the tranny tab all the way back until it stops then 2 clicks forward and tighten the "nut".....now the column shift linkage and transmission are in sync when you go thru the grears, assuming the steering column is in resonable condition this should help correct that problem.......TOO MANY TIMES THE NSS IS DEEMED THE CULPRIT for none start when it isn't so this is a simple check to make sure. There is also another PRNDDL adjustment, but you need to remove the black plastic collar on the steering wheel, this is usually done when an actuator breaks and using pliers drive the rod downward with key on to start.....there is usually a white cable that wraps around and attached to a small mm ***** IIRC that when lossened a bit it allows you to adjust the "needle" that registers on each letter of the PRNDDL..be careful because it's attached with a very fine wire loop and easily broken. The "upper ignition actuator" is another culprit because they're made of cheap *** metal.....and a PITA job to do..."

Source: by JKossarides ("The Bronco", Jean)

DTC 67; "..One poss is that the NSS (or also called the MLPS) was ok...or connector was/is bad/corroded; or AC was left on, or transmission was in gear during the Self Test..." read more

Source: by miesk5 at http://fordfzone.com/topic/5375-1990-code-help/

Water Intrusion of Manual Lever Position (MLPS) also called Transmission Range (TR) Sensor TSB 95-2-12 for 89-94; Some vehicles may exhibit a shift concern and/or a harsh engagement concern due to water intrusion into the MLP/TR sensor and vehicle harness. There may also be a number of different DTC's along with those concerns Source: by Ford via miesk5 (Al M) at http://home.comcast.net/~miesk5/technical_service_bulletins.htm#Water%20Intrusion%20of%20MLP/TR%20Sensor%20TSB%2095-2-12%20by%20Ford%20for%2089-94

note depending on year the tranny uses a MLPS or the Neutral Safety Switch (also referred to as Park/Neutral Position (PNP) & Back-Up Switch)

As of 1994, the Neutral Safety Switch is referred to as a Manual Lever Position Sensor (MLPS) or Transmission Range (TR) Sensor

DTC 67 & 634 indicate the MLP sensor is out of Self-Test range when the gear selector is in PARK; "...Possible causes: Misadjusted linkage. Open or short in harness circuits. Damaged MLP sensor. Damaged PCM. miesk5 NOTE;... for ******/Tracer tranny MLPS etc.; but the Bronco troubleshooting process will be similar exc for connector pins, etc. Source: by Ford

DTC 67 & DTC 634; Nagging Neutral Nonsense & Pinpoint Test, Manual Lever Position (MLPS) also called Transmission Range (TR) Sensor. "...One of the most-difficult problems to diagnose on a Ford car or truck is a sudden neutral condition while the vehicle is cruising in 4th gear.

Now this can have a number of causes, depending on which transmission is in the car or truck, but the cause we are going to discuss here is that #(~! *&A% Manual Lever Position Sensor – that’s right, the old MLPS. This sensor is responsible for more malfunctions than any other sensor in the system, and the kicker is that it seldom stores a code 67 or 634. Actually there is a standing joke in our industry that says, “You got a problem with a Ford, change the MLPS; it fixes everything,” which ain’t that funny because it’s not that far from the truth. Some of the problems the MLPS can cause are wrong gear starts, TCC hunting, no 4th gear, engine stalling, high or erratic line pressure and the problem that this article is about – a sudden neutral condition. Whether the MLPS is attached to an E4OD, AXODE, AODE or CD4E, the operating characteristics are the same. What that means is the MLPS is classified as a step-down resistor. The MLPS is supplied 5 volts from the computer as a reference voltage, and as the shift lever is moved from park toward manual low, the voltage in each gear-shift position will decrease as shown in Figure 1. The MLPS also can be checked for correct resistance, also shown in Figure 1. This way, if the resistance checked good on the bench but the voltage does not check good in the vehicle, you know there must be a wiring or ground problem. I know what you are thinking: You replace the MLPS on every job you do, so why should you check the resistance on a new part? Well, that’s fine, but one thing has become very clear lately: NEW DOES NOT MEAN GOOD! Now, let’s get to the meat of the problem. As you can see in Figure 1, the voltage in the drive/overdrive position can be 1.88 to 2.30 volts. The O.D. Cancel button, on those vehicles equipped with one, has no effect on the voltage seen in the drive position, nor does it matter whether the vehicle has a gas or diesel engine. This would be the voltage seen in the D or D position if it were available on the scan-tool screen in the data mode. Unfortunately, this information is not always available, and this “glitch” may occur faster than the scan-tool’s update capability so the voltage jump would be missed. Therefore, a digital multimeter must be used to monitor this voltage. This is of the utmost importance in diagnosing the sudden-neutral condition. This voltage should be monitored when the neutral condition occurs by placing the multimeter’s positive lead to computer terminal 30 if it is an EEC-IV system, as illustrated in Figure 2, or to terminal 64 if it is an EEC-V system. This wire is light blue/yellow on all applications except vehicles with the CD4E. On these the signal wire is red/black. Now, here is where this gets a little involved. The negative lead of the multimeter should be placed at the MLPS signal-return ground terminal at the MLPS. The reason is that the ground circuit for the MLPS can be shared by as many as FIVE other sensors, as seen in the wiring diagram in Figure 2. This means that there are factory splices in this ground circuit. If you check this ground at computer terminal 46 for the EEC- IV or computer terminal 91 for the EEC-V, the ground may check good but could be bad at the MLPS if there is a problem on the MLPS side of the splice, as also can be seen in the wiring diagram in Figure 2. The ground-circuit wire for 1989-90 F- and E-series trucks is black/white; all other vehicles use a gray/red ground wire except for CD4E applications, on which the ground wire is black/blue. Once the multimeter is connected to these circuits, as seen in Figure 3, place the meter where it can be seen while driving. When the transmission suddenly neutrals, be sure to have someone observe the multimeter, or use the meter’s MIN/MAX feature to record the highest and lowest voltage readings that occurred in the circuit. If the voltage jumps toward 3 volts as shown in Figure 3, and at that very moment the transmission neutrals, either the MLPS is faulty or the MLPS ground circuit is poor. Under normal conditions, this voltage reading SHOULD NOT CHANGE! When the voltage jumps toward 3 volts, this indicates a neutral-shift- lever position to the processor. This confuses the computer’s logic system, and therefore the computer is unable to fire the shift solenoids correctly (I think), and – BAM – you have a sudden-neutral condition. Why does the voltage jump because of a poor ground? The poorer the ground, the higher the resistance will be in that ground circuit. The higher resistance will cause the voltage in the overdrive or drive position to rise toward the 5-volt reference voltage, much like putting a bend in a garden hose would raise the pressure in the hose behind the bend. Ground- circuit integrity can be verified by placing the positive multimeter lead to the MLPS ground terminal at the MLPS and the negative multimeter lead to the negative battery post, as seen in Figure 4. With the multimeter set to DC volts and the engine running, the maximum voltage should be 0.1 volt. If more than 0.1 volt is seen on this ground circuit, it is NOT a good ground. In order to correct this condition, cut the ground wire close to the MLPS, attach it to a known good ground and recheck as previously described. Two things must be remembered here. One is that the return electricity will seek the path of least resistance. This path MUST be the ground circuit, NOT your multimeter. That’s why you should see a maximum of 0.1 volt on any 5-volt-reference ground circuit; 0.3 is acceptable on a 12-volt-reference voltage supply. The second thing to remember is that most electrical- fault phone calls I receive on the ATSG helpline are ground-related problems, so be sure to use the voltage-drop method of checking grounds as described. It may help to prevent you from falling into this trap..." See Diagrams & instructions

Source: by Pete L at http://www.transonline.com/transdigest/magazines/1998-10/Shift%20Pointers/index.html

===========

O = KOEO test key on engine off

R = KOER test key on engine

running

M = in memory - after separator

(10) in KOEO test

-------------------

16 ® bad idle air valve, dirty throttle body

Erratic idle during test or throttle was touched (try tests again)

The RPM is low causing the HEGO (heated oxygen sensor) sensor to sense rich. It can also be caused by an adjustable fuel pressure regulator set too high. If this is the case, reduce fuel pressure.

-------------

34 (O) Low exh.press., blocked sensor tube or bad EGR Valve Position (EVP)

® EVR: EVP signal too high - rerun test

------------------

13 (O) ISC did not respond properly

vacuum leak, base idle off, idle air valve dirty or bad, EGR stuck open®, RPM’s out of specs (usually too high)

(M) Idle Speed Control ISC (motor) sticking, open Idle

Tracking Switch ITS circuit or Throttle Pos. Sensor (TPS) sticking

----------------

34 EGR sticking open, bad EVP sensor, clogged exhaust or cat. convertor

-----------

 

[miesk5]

yo,

WOW! I never saw you re-test when I began my reply; maybe I passed out?

13

KOER

DTC 13:

vacuum leak, use garden hose section to listen for leak noise;

TB base idle off- Idle Air Control (IAC) Sludge; Poor Idle TSB 91-25-07 for 85-92 Bronco & F Series & many others; "...Hard cold starts, hesitation and stalls on initial start-up or during idle or decel may be caused by sludge in the throttle body and/or idle by-pass valve. Sludge deposits or oil film on the throttle body bore and plate or the idle air by-pass valve may cause one or more of the following conditions. Hard Cold Start, Stall On Initial Start-Up, Stall During Idle, Stall During Decel, Rough Idle, Rolling Idle, Hesitation During Acceleration. A new idle air by-pass service kit (F2PZ-9F939-A) is now available for service use to correct sludge contamination concerns of the throttle bore and plate only. It eliminates the need to clean the majority of past model throttle body applications. Cleaning is not required on sludge tolerant throttle body designs released for 1991 and newer model years..."

Source: by Ford via Steve83 (Steve, That dirty old truck) at http://www.supermotors.net/registry/media/724437

idle air bypass valve dirty or bad -

Overview & Testing; "First let me say this little thing has many names. But they all talk about the same item under the hood. Here all the names I’ve had the torture of learning throughout the years: Idle Air Bypass •Idle Air Control •Idle Speed Control •Throttle Bypass Air •Idle Bypass •Inlet Air Controller •Inlet Air Bypass •Intake Air Bypass •Intake Air Control..."

Source: by Ryan M (Fireguy50) at http://fordfuelinjection.com/index.php?p=39EGR stuck open

Vacuum Leak Test; On an idling engine check for vacuum leaks using a mechanic's stethoscope with the probe removed, or a ~3' garden hose section. Don't spray flammables on a running engine. MIESK5 NOTE; Also check: vacuum hoses; intake manifold gasket & throttle body; PCV line; vacuum reservoirs: EGR Sys Vacuum Tank & 2ndry air (coffee can); AC, heater, defroster, vent control ckt & vacuum tank (plastic ball type), under dash & lines to heat/blend/etc. doors; power brake booster; cruise control ckt, etc.... where applicable; (combined w/ Steve83's info, thnx) BEWARE OF BELTS/PULLEYS, FAN AND HOT ENGINE

Source: by miesk5 & Steve83

=============

33

KOER

EVP sensor indicates EGR is not opening properly

EGR is bad, EVP is bad, and/or there is a vacuum leak

DTC 33 is triggered when the EVP sensor is not closing; so EZiest & cheapest checks are to inspect & repair/replace repair any bad vac lines. for a <$ vac line test; I pull em off and use the straw sucking test; one finger over one end; includes EVP testing & Links

or get a hand operated Vacuum Pump from Auto Zone;

Gauge reads 0 to 30 inches of mercury. All aluminum construction with reverse pistol grip for easy one-handed operation. One 24 inch piece of clear plastic tubing included with pump. OEM27010; see, http://www.autozone.com/autozone/inourstores/lat/latLanding.jsp?bodyContent=valvetrainRepair

AutoZone's Loan-A-Tool® service. It's the most complete selection of seldom-used, expensive-to-own specialty tools that will help you do the job right. We offer more than 60 different tools for all sorts of jobs - steering and suspension work, air conditioning jobs, engine repair, and more.

Using our Loan-A-Tool® service is easy. Just leave a deposit at the store when you pick up the tool. When you're through, just bring it back, and we'll refund the deposit.

A complete listing of the available tools is listed by category in the column on the right. Or stop by your local store and ask an AutoZoner for assistance.

EGR Valve Position (EVP) - MIESK5 NOTE: EVP is used on all years except for 95 5.8L California models & all 96, they use the DPFE Sensor instead of EGR Valve Position Sensor (EVP)

EVP is light gray & attached to the top of the EGR Valve

DTC 34- EGR voltage above closed limit - 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. 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 at Ford Bronco Zone Forums

DTC 33 & 34 "...DTC 33 is triggered when the EVP sensor is not closing... To prevent the EGR valve from opening when the engine is cold, the vacuum line to the EGR valve may be connected to a parted vacuum switch or a computer-controlled solenoid. Vacuum is not allowed to pass to the valve until the engine is warm. EGR isn't needed when the engine is cold, only when it is warm and under load. Any of these codes could indicate a faulty EGR valve as well. as well as a problem in the ...vacuum solenoids. code 33 is triggered when the EVP sensor is not closing, and a code 34 indicates no EGR flow. Any of these codes could indicate a faulty EGR valve as well as a problem in the EGRC or EGRV vacuum solenoids. Other codes include a code 83 (EGRC circuit fault) and code 84 (EGRV circuit fault). Both indicate an electrical problem in one of the solenoid circuits. The solenoids should have between 30 and 70 ohms resistance..." Miesk5 note; da TAB & TAD again; so repair those vac lines 1st

Source: by Larry C at aa1car

EVP 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 0.67volts at idle with a closed EGR valve..." read more

Source: by Ryan M (Fireguy50) at http://fordfuelinjection.com/index.php?p=35

Testing; "...Using the Haynes manual's procedures, you should be able to back-probe the EVP line and ascertain whether the EVP voltage is correct. It should be below 0.67V @ zero vacuum on the EGR, slowly increasing with applied vacuum from a hand pump. DO NOT apply more than 10 in-Hg to the valve..."

Source: by SigEpBlue (Steve)

 

[gunr]

thanks i really appreciate your thorough response. Any idea what specifically would be causing the stuttering on the highway? i ask because it looks like i have a lot to do and i don't know where to start.

thanks again for your help.

 

[miesk5]

yo!

YW

Because at one time, I was on a ship and we didn't have much (mostly none) $ to spare, so I tend to suggest the most likely, cheapest checks first

Vacuum Leak Test; On an idling engine check for vacuum leaks using a mechanic's stethoscope with the probe removed, or a ~3' garden hose section.

Don't spray flammables on a running engine.

MIESK5 NOTE; Also check: vacuum hoses; intake manifold gasket & throttle body;

PCV line;

vacuum reservoirs: Emission Sys Vacuum Tank (coffee can);

AC, heater, defroster, vent control ckt & vacuum tank (plastic ball type),

under dash & lines to heat/blend/etc. doors;

power brake booster;

cruise control ckt, etc.... where applicable; (combined w/ Steve83's info, thnx) BEWARE OF BELTS/PULLEYS, FAN AND HOT ENGINE

==

next

for a lot of EGR sys tests, you'll need a hand operated vacuum pump; it is avail at Auto Zone LOAN-A-TOOL® PROGRAM

AutoZone's Loan-A-Tool® service. It's the most complete selection of seldom-used, expensive-to-own specialty tools that will help you do the job right. We offer more than 60 different tools for all sorts of jobs - steering and suspension work, air conditioning jobs, engine repair, and more.

Using our Loan-A-Tool® service is easy. Just leave a deposit at the store when you pick up the tool. When you're through, just bring it back, and we'll refund the deposit.

A complete listing of the available tools is listed by category in the column on the right. Or stop by your local store and ask an AutoZoner for assistance

Vacuum Pump - Gauge reads 0 to 30 inches of mercury. All aluminum construction with reverse pistol grip for easy one-handed operation. One 24 inch piece of clear plastic tubing included with pump.OEM27010

==========

DTC 13: by Ryan M (Fireguy50)

Idle Air Control (IAC); also called, Idle Air Bypass (IAB), Idle Speed Control (ISC), Throttle Bypass Air, Idle Bypass, Inlet Air Controller, Inlet Air Bypass, Intake Air Bypass, Intake Air Control This is really easy to test. First as with all problems you should gather the trouble-codes from the computer. Follow the codes for testing and repair. If you get a code that points to a problem with the IAB start the vehicle and bring the engine up to operating temperature. Allow the engine to idle without any driver input to the throttle or pedal. Go under the hood, and disconnect the electrical connector to the IAB. If the engine begins to stubble or stalls the IAB is functional and does not need to be repaired. If the engine idle does not change you should remove the IAB for inspection.

The IAB can pass and still need repair, or it can fail and not need replacing. The plunger and internal spring can get clogged with dirt and oil. This will slow down the air flow and not allow the IAB to function properly. Remove the IAB and clean it. There are 2 halves to the IAB, and you can not buy just one half, but you can take it apart to clean it. But if the internal solenoid is faulty the IAB needs to be replaced.

..................

Location pic in a 90 by SeattleFSB



MORE IAC LINKs in my site @ http://www.broncolinks.com/index.php?index=397

==========

For the EGR SYSTEM - EVP... you'll need a digital meter

Wal Mart has some good low-cost meters or find a relative or pal with one.

..

Exhaust Gas Re-circulation (EGR) System LINKs in my site @ http://www.broncolinks.com/index.php?index=146

including;

Vacuum Reservoir Can (Tank) (VRESER)

Location in Engine Bay pic in a 89 F 150

Source: by Booba5185

http://i14.photobucket.com/albums/a304/booba5/overhead-2.jpg

markes as "cannister on pass. side of engine bay

& check all vacuum lines from "vacuum tree" on top of intake manifold; as I mentioned above..to HVAC and EGR & brake booster, etc.

he shows the EGR Valve and the EVP (light gray on top of the EGR Valve) in this pic

http://i14.photobucket.com/albums/a304/booba5/EGRcolor.jpg

and by SeattleFSB inj his 90 5.8

egr-evp

on pass side, front of engine

other vac lines to TAD & TAB, EVR, FPR

http://i14.photobucket.com/albums/a304/booba5/overall2.jpg

check vacuum reservoir for the A C

either a plastic ball, or an irregular box glued to the evaporator cover

check line to Vacuum Control Valve; located near left hand (passenger side) hood hinge as shown in this pic by Dan,

http://img12.imageshack.us/img12/9306/actuatorclose.jpg

and more by KEN @ http://www.supermotors.net/registry/17787/68977

A/C Switches to Defrost in MAX Mode; "...If MAX A/C only blows out the defrost registers, or if it switches to defrost during hard acceleration, this vacuum line (to the recirculate motor) is the reason. The white plastic is far more susceptible to UV light than any other color, and the gap along the edge of the hood allows it to degrade..."

"...The vacuum hoses used in the passenger compartment control circuit are constructed from PVC plastic material. The vacuum hoses used in the engine compartment are constructed of Hytrel. Because of the materials used, the vacuum hoses should never be pinched off during diagnosis to locate a leak. Use Rotunda Vacuum Tester 014-R1054 or equivalent to locate vacuum leaks. A wood golf tee can be used as a plug when it is necessary to plug one end of a vacuum hose for leak test purposes..." from F-150, F-250, F-350, F-Super Duty and Bronco, F-Super Duty Motorhome Chassis Workshop Manual

Source: by Ford

"...Use "Hard (Heavy Duty)" vacuum line for booster. Regular rubber hose such as used for WS washer fluid line will likely collapse after about say, 20 years. Inspect for any sign of kinking or collapse. Check vacuum draw available with a gauge connected between engine and booster. At idle, healthy engines draw somewhere between 17 and 22 in Hg. Check vacuum by depressing brake pedal firmly until it stops. The gauge should read a drop to approximately 10 in. Hg and then quickly recover to a normal reading. If vacuum takes too long to recover, there is a restriction in the volume, i.e.: fitting clogged or vacuum hose collapsed. Repair as necessary. While a defective booster will cause a hard pedal, a spongy or low pedal requires a hydraulic system check..."

Source: by miesk5 at Ford Bronco Zone Forums

Air Injection (AIR), Secondary Air Injection; Pump (Smog Pump), Thermactor Air Bypass (TAB) & Thermactor Air Diverter (TAD) Solenoids; Diverter, Check & Bypass Valves, Cross-Over Tube, etc. LINKs in my site @ http://www.broncolinks.com/index.php?index=416

 

[gunr]

i have been searching for a vac leak with no success /emoticons/[email protected] 2x" width="20" height="20" />

something odd i noticed, the small vac hose on the top of the egr dose not **** at all. will there only be suction from this hose when the egr is supposed to open? not being able to find a vac leak im thinking about replacing the egr and sensor on the top but i am worried that the problem is the lack of vacuum.

are those pics from your bronco?

 

[gunr]

so apparently there is not supposed to be vacuum going to the egr at idle.

however i connected a constant vacuum line and the egr valve open.

there appears to be no vacuum leak to the egr valve so what would cause it not to open? could a bad evp sensor cause the misfire?

 

[miesk5]

yo,

Vacuum is not allowed to pass to the valve until the engine is warm. EGR isn't needed when the engine is cold, only when it is warm and under load.

If you can borrow or buy a relatively inexpensive Vacuum Gauge, it helps a lot and is one of best DIY repair tools and alos a helpful way to improve MPG while driving if you get the so-called MPG type that has colored bands on the gauge that show by accelerating in a way that keeps the gauge pressure as high & as steady as possible.

Diagnosis - BEST!; Normal engine; Steady gauge 18"-20" at all speeds..." READ MUCH MORE

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

gas master vacuum gauge test run Video @

No that isn't my Bronco. The new engine is by SeattleFSB in his 90 5.8