Thank You for sharing your findings as well. 
No codes, intermittent rough running
Thread Starter
Melting Slicks
Joined: Mar 1999
Posts: 3,326
Likes: 0
From: Taylor TX
NCM Sinkhole Donor
No codes, intermittent rough running
I hate intermittent stuff - especially when there's no codes to give me a clue.
My '98 with 34k miles started to run real rough intermittently. Kinda felt real low on power, and would hesitate/stumble at idle when it occurred. It seems like it was starved of fuel, but it would only do this under about 2000 rpm/25mph. If I stabbed the pedal or downshifted to increase rev's it would run fine.
The only codes I have are history ones for the LDCM and RDCM losing communication. So not much to go on there. Never have seen a Check Engine light or Reduced Power message.
In my search, I have put together this list of things it could be:
Fuel Pump/Fuel Filter
Throttle Actuation Control module
Mass Air Flow sensor
Throttle Position Sensor
MAF harness being shorted on fuel rail bracket
My thoughts/observations:
- A fuel related problem should not make the symptoms better with acceleration, such as I have seen. So this isn't it.
- MAF looks clean because I pulled induction system apart to inspect
I'll look at the harness tonight. Can I check the other 3 things somehow? (MAF, TPS, TAC)
My '98 with 34k miles started to run real rough intermittently. Kinda felt real low on power, and would hesitate/stumble at idle when it occurred. It seems like it was starved of fuel, but it would only do this under about 2000 rpm/25mph. If I stabbed the pedal or downshifted to increase rev's it would run fine.
The only codes I have are history ones for the LDCM and RDCM losing communication. So not much to go on there. Never have seen a Check Engine light or Reduced Power message.
In my search, I have put together this list of things it could be:
Fuel Pump/Fuel Filter
Throttle Actuation Control module
Mass Air Flow sensor
Throttle Position Sensor
MAF harness being shorted on fuel rail bracket
My thoughts/observations:
- A fuel related problem should not make the symptoms better with acceleration, such as I have seen. So this isn't it.
- MAF looks clean because I pulled induction system apart to inspect
I'll look at the harness tonight. Can I check the other 3 things somehow? (MAF, TPS, TAC)
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bad plug wire?? plug....also check to see if one of your plugs may have backed out a bit...sounds stupid but..BTDT...
Thread Starter
Melting Slicks
Joined: Mar 1999
Posts: 3,326
Likes: 0
From: Taylor TX
NCM Sinkhole Donor
Here's an update to my persistent problem.
The hesitation progressed into what seems like half the cylinders running, or a lot of misfire. It smokes like crazy after just a few minutes of run time. It is running very rich (heavy fuel smell).
I unplugged the MAF and ran without it. I also replaced all plugs & wires with new. Same symptoms.
After it got this bad, I finally got a new code: P0134 O2 Sensor B1 S1 Insufficient Activity.
So I replaced that O2 sensor with a new one. SAME PROBLEM!
Any other ideas?
The hesitation progressed into what seems like half the cylinders running, or a lot of misfire. It smokes like crazy after just a few minutes of run time. It is running very rich (heavy fuel smell).
I unplugged the MAF and ran without it. I also replaced all plugs & wires with new. Same symptoms.
After it got this bad, I finally got a new code: P0134 O2 Sensor B1 S1 Insufficient Activity.
So I replaced that O2 sensor with a new one. SAME PROBLEM!
Any other ideas?
Last edited by lotzahp; May 30, 2005 at 11:39 AM.
Thread Starter
Melting Slicks
Joined: Mar 1999
Posts: 3,326
Likes: 0
From: Taylor TX
NCM Sinkhole Donor
And one final update: problem fixed!
The engine coolant temp sensor connection was either loose or dirty. I pulled it, cleaned, reseated, and everything is perfect again.
I don't know why a code for that wasn't set. And I guess the rich condition tricked the 02 sensor code.
The engine coolant temp sensor connection was either loose or dirty. I pulled it, cleaned, reseated, and everything is perfect again.
I don't know why a code for that wasn't set. And I guess the rich condition tricked the 02 sensor code.
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