Stumbling Problem--Need Help (posted for new member) - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 09-22-2003, 04:41 PM   #1
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Default Stumbling Problem--Need Help (posted for new member)

I received this as a PM. Please help this gentleman out:

________________________________________________

From: vincea51
To: 95BonnevilleSESC
Posted: Sun Sep 21, 2003 7:42 pm
Subject: 95 Bonneville 3.8 v6 K check engine light and purformance
Hi I am new to the club.
I purchased a 1995 bonneville with 83k in 2001. since I owned the car I had the check engine light on. Now I am a mechanic and own a scanner. So I checked the fault code, which was code 341. (intermitting cam sensor signal). I was able to reset the fault with the scanner and sprayed the cam sensor with go old wd40. the fault stayed out for about two weeks. the car ran great otherwise so I did not pay too much mind to it. I did purchase and carried a spare cam position sensor in my trunk. I also purchased a spare crank sensor and ignition module just in case. Being a mechanic I like to have parts on hand since I could change most sensors myself.
Well, now the plot thickens. this past week the car started to break up pulling away from a stop light. At times it has so little power that I could just make it to the side of the road.
So far the engine stayed running during this problem. once I get past the initial stumbling and backfiring, it gets full power and I can pull onto the main hiway again.
Using the scanner while driving, I can check all the sensors out puts.
I noticed during the backfiring problem, the timing, which normally is say, 18 deg before TDC, will go to a -4 or -5 deg retard setting. Also during the some period the RPM drops off, say from 1500 rpm to about 400 rpm concurring with the drop in timing.
Not both these setting, the timing and the rpm come from the crank sensor.
this week I replace both the cam and the crank sensor, but still have the same problem.
Now there are two other sensors that retard the timing on the K engine. They are the foward and rear knock sensor. I purchased a spare and checked it against the specs in the Pontiac trouble shoooting manual. The new know sensor should read about 2.890K ohms and when placing an AC volt meter between the sensor terminal and the case ground or the engine ground if it is installed you should read about .018-.030 VAC and when you tap on the case of the sensor, or tap on the engine block near the sensor you should get a slight raise in Voltage readiing. Normal taping should make a good sensor go from about .030 VAC to about .150 VAC. You should not get any raise with an idling engine that is not knocking. Both my knock sensors on the bonneville today checked out fine. so I returned the spare knock sensor.
I am now wonder about the Idle Air Control. I have heard that this could cause this problem.
I noticed today that if I apply full throttle from a light the car will just stumble abit then take off with full power..Purhapes this could be cause by the IAC sensor?

Do you have any experience with this type of problem. You can post this letter for all to see. It might be helpfull

Signed Vincea51
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Old 09-22-2003, 05:26 PM   #2
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I seem to remember the ignition module having something to do with this below a certain RPM. I'll check later.
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Old 09-22-2003, 09:17 PM   #3
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This is a complicated code.

You get this code when the ratio of fuel control pulses to cam pulses does not equal 6:1.

I would look for poor connections at the crankshaft or camshaft position sensors.

Connect a voltmeter to the black wire at position "F" on the ignition control module. Ground the other terminal of the voltmeter. Turn ignition to run, but not on. If you don't get 5 volts, bump the engine with the starter.

Now move the following harnesses around, looking for a loose connection (Watch the voltmeter, should be constant 5V):

1. Ignition jumper harness
2. Engine harness to PCM connector
3. Dash harness to PCM connector

Then connect a voltmeter to the purple/white wire at position "D" on the ignition control module. Turn ignition to run, but not on. Move the same harnesses around and watch the voltage for a loose connection.

Let us know if you find anything.
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Old 09-23-2003, 11:18 AM   #4
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I just had another PM form Vince:

_____________________________________________

From: vincea51
To: 95BonnevilleSESC
Posted: Mon Sep 22, 2003 5:37 pm
Subject: Re: 95 Bonneville 3.8 v6 K , Problem solved
Hi Tim
Today I have some good news. I have been looking over my computer problems and came to a conclusion. Because I first loat my traction control and the next week I started getting the cam sensor message. these two problems has circuites that go through the ECM computer. this month I started have low charging voltage at times, then it climbs back up to normal voltage. Finally this week I started have driving problems, very bad.
I purchased a remanufactured ECM from 1a Cardone rebuilding co. It cost me $140.00
Tim all 4 problems went away, great.

Thanks again for you return email.
P.*. You can post this if you like.
Vince
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Old 09-23-2003, 06:18 PM   #5
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May have been a bad/oxidized connection at the PCM wiring harness.

Congratulations!
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