Long and Short Term Fuel Trim Question - Page 2 - 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 10-16-2006, 05:16 PM   #11
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Quote:
Originally Posted by mnuttall
Well, I have some more information now.

First, I checked the fuel pressure. It stays about 142 whether it is at idle or revved up. When the car dies, there is no dip in fuel pressure. It appears that other than a noisey fuel pump, it is working fine.

...It still died.

...I have noticed a couple of changes today. First, the LT Fuel Trim is at 148 and doesn't change now. The ST Fuel Trim is at 128 and has quit changing. The O2 sensor seems lower now with the readings staying below 200 mv.

There are also two other things that bother me. First. When I try to run it at WOT, it will surge and not seem to get to full throttle. I don't see any fluctuation in the TPS voltage. Also tonight it started surging while at idle. This seemed to start happening about the time the LT and ST Fuel Trim went high.
I assume you have a mistype there. Here are the fuel pressure specs for '95 (from TECHINFO):
Quote:
1995 L-1: 41-47
1995 K: 48-55
So, is it fair to assume you are reporting 42 psi?

If so, it'* important for us to know what your trim level is. Is your car supercharged or NA? There is a difference in the expected correct fuel pressure.

You say your fuel pump is noisy. That is usually a warning sign.
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Old 10-16-2006, 06:09 PM   #12
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Agreed Lash..that fuel pressure number looks off..unless it was reading 142 KPA which would be around 20 lbs and I doubt the car would even run off that.

Can you describe what happens around the time it stalls. Anything else acting wierd. I'm going to hop out on the tree branch here and say it might..might be a pcm. But I'd want the pcm master to hear more info as to what it'* doing and how it'* running before we condem the pcm.
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Old 10-18-2006, 12:45 AM   #13
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That was some interesting information. My Bonnrville is a K and is not supercharged. I had found the fuel spec in a Haynes manual, but I must have read it wrong. It sounds like the fuel pressure is low at 42 psi. It is also quite loud when it is running.

There are a couple of things that are different also. When I try to go to WOT, it surges. The last time I ran it at idle, it started surging there also. I didn't get a fuel pressure reading while that was happening though.

Before the surging started at idle, the LT Fuel Trim was pretty close to 128. It would change up to the 130'* and then back. The ST Fuel Trim would oscillate above and below 128 a few points.

After the surging started, the LT Fuel Trim was at 148 and not changing. The ST Fuel Trim was setting at 128. The O2 voltage was also low.It seemed to be staying between 100and 200mv.

Hopefully that will give you a little more to help me track this down. I am going to be out of town until Saturday, so I will have to wait until then to do any more testing.

I appreciate your help with this.
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Old 10-18-2006, 09:28 AM   #14
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That LT trim number means you are running way too lean.

First, check and clean if necessary, you MAF and IAT sensors.

Second, you need to do more readings from the pump.
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Old 11-17-2006, 02:56 PM   #15
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Default Problem Solved

I was finally able to get this problem solved. My reader quit connecting to the computer so I got a used computer and replaced it and all the problems went away.

Thanks for all the feedback and help on this. This is a great forum on Bonnevilles!
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Old 11-17-2006, 03:08 PM   #16
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Default Re: Problem Solved

Quote:
Originally Posted by mnuttall
I was finally able to get this problem solved. My reader quit connecting to the computer so I got a used computer and replaced it and all the problems went away.

Thanks for all the feedback and help on this. This is a great forum on Bonnevilles!

Keep in mind this is a common problem for the 95'*.... I wish i would have caught this thread earlier... I myself am on PCM #3

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