More Problems! Stumbling and Hesitation

[MarkV]

Well I had some stumble the other day and lack of power and hesitation. Code 42 popped up. Now, I unplugged the battery replaced the o2 sensor, air filter, checked everything for tightness and checked the spark plugs. I also ran 91 octane and fuel system cleaner along with seafoam. I drove about 70 miles then the code popped up again. Now, I know we have been through the 42 thing before but, I am thinking there is another issue causing 42 to be clicked on. Could it be a faulty TPS? or a Coolant Temperature Sensor? Giving off faulty readings? I looked at the CRT diagnostic and the Coolant Temperature Sensor is giving off about 86 degrees (this is not confused with the dash sensor which says anywhere between 180-210). Is this temperature normal? Would this cause stumbling/hesitation? Could the TPS cause this and set off a chain of events ending with 42? There are no other codes popping up. This issue is intermittent and when I restart the car the light disappears and it is fine for a while. I am at a complete loss!

Items replaced:

plugs

wires

02 sensor

IAC

MAF

Battery

Radiator

Thermostat

Cat Converter

Fuel pump

fuel relay

cam sensor and magnet

cleaned throttle body

Coil

Ignition Module

Computer

Transmission rebuilt

Edited September 30, 2013 by 1948Lincoln (see edit history)

[Guest Mc_Reatta]

The short answer is no. The code indicates that the ECM is not seeing the signal from the ICM. Also diagnostics reports the coolant temp in deg C while the gauge readout shows deg F. 86 C = 187 F so it is fine.

Assuming that the replacement ECM and ICMs were good, and the intermittent nature of the problem really points to bad wiring somewhere between the ICM and ECM.

You need to wiggle wires while the engine is running and listen for any stumbling. I would start at the ICM connector and then move to the ECM. Also rap on the ECM to see if an internal connection might be causing this. Hopefully at some point you can duplicate the problem and zero in on the location of your problem. Obviously you need to exercise caution when sticking your hands near a running engine.

[MarkV]

I wiggled all of the wires and there was no change this problem persisted when I had the old ecm as well so, I know it is not ecm based.

[Guest Mc_Reatta]

Only thing I can suggest is to start over by reading the FSM section covering the 42 code starting on page 8D1-54 and repeat all the checks. Since your problem is intermittent, and not bad enough to completely stall the engine, it may be a bear to find. But it comes down to a faulity ECM, ICM, or connection in between them.

[MarkV]

Well and code 44 pops up after about 15 min of idle both of these are strange. Then on the next drive 42 will pop up. It seems that both are related in some way

[Guest Mc_Reatta]

Code 44 is the O2 sensor running lean.

Only common hardware with 42 is the ECM. But if ECM / ICM are having problems with spark control circuit, it could possibly have the engine running poorly allowing the other code to set. However my gut would expect a rich condition rather than a lean condition, but I guess either might occur.

I'm still thinking a bad connection somewhere between the ECM and ICM.

[MarkV]

Would a failing fuel regulator be the cause of a lean condition?

[D-a-n-i-e-l]

Well and code 44 pops up after about 15 min of idle both of these are strange. Then on the next drive 42 will pop up. It seems that both are related in some way

Replace your o2. You ran seafoam in the car everytime I use it my o2 goes bad. That is the two times I have used it. Also there is no reason to use high octane fuel in these cars. It drops fuel milage and really has no benifit unless you are running around at 5k rpm all day.

[MarkV]

I just replaced the 02 3 different times and am now running a delco o2. This situation happened previous to the seafoam being run through the system. And no dirt or particles or smoke came out of the tailpipe. I drove the car home today and the problem is getting worse. Which leads me to believe that it is a failing part. I am wondering if it is a failing regulator, TPS or a failing injector. The car does this when you get up to about 30 then it starts hesitating and goes into the default mode with the SES light popping on. In the default mode the car got me home, but, I want it to run good again!

[2seater]

I think McReatta hit on the common item which is the ECM. Possible a bad harness across the front of the engine which connects to the ICM and a couple of sensors, as well as the ECM. Possible to have a wire rubbed through or otherwise damaged. If it is a heat issue after a somewhat consistant amount of time, you might consider pulling the ECM and letting it hang by the harness on the floor. Remove and check the three plugs on the ECM for obvious things like a bent pin or backed out female in the plugs. Reseat the plugs. Remove the EEPROM cover, reseat the chip, and operate the car with the ECM on the floor and the small cover removed to see if it changes the character of the failure mode. It should stay cooler if it is a heat issue and change the time to failure.

[padgett]

Failing/leaking fuel regulator will show up as low rail pressure (should be close to 40 psi running).

[MarkV]

The problem only occurs under load not in idle (under idle it is fine) all the ecm stuff has been replaced (no solution to the problem) and now it is much worse and happening every time I drive, it was intermittent before.

[2seater]

Sorry, I missed computer, aka ECM? A fuel pressure gauge on the rail that can be watched under load would answer most fuel delivery issues. Ignition breakdown, or loss of timing signal would certainly result in loss of performance, but I guess we already know that

[2seater]

The harness across the front of the engine would be a prime suspect, since it connects the sensors, ICM and ECM together. Pretty certain that harness on an '89 is a seperate piece that can be replaced. An extended fuel pressure gauge can be be made using a female #4 JIC hydraulic fitting, a piece of fuel injection hose and a 60-100 psi pressure gauge. The one downside is the little tire valve inside the fuel rail fitting must be removed.