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Old 01-27-2015, 05:30 AM   #1
gtrman79
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97 Lumina, 3.1, 128k miles, weird response from accelerator

OK. I have owned a 97 lumina, 3.1, for a couple years. I traded my Corsica with a 2.2 to my grandma, who didn't drive much. Her Lumina was a much better drive for my 35 mile on way trek to work. And it was mint, like any 82 year old's car that is parked in the garage, for 8 days at a time.


Anyways, it has had almost zero issues, and I put mostly highway miles on it. I have changed the problematic intake gaskets, I have replaced the CAM sensor, and plugs & wires.

Well I started having MAF sensor codes coming up. So i got some cleaner and cleaned the sensor. The code went away for a couple months, then came back. I cleaned it again. After about 2 weeks after cleaning it, I started having hesitation issues. The big issue was after taking off from a stop light on a light acceleration, i would start to lose power after the pedal was depressed a couple inches. As i pressed the pedal more, it would not make a change until I had it almost floored. Then the gear would kick down and i would race ahead like normal.

As a test, only because i had issue before, i got a remanuf MAF sensor. This did not change it. And it had been 35k miles since the plugs and wires. Not too long for my tastes, but I changed them anyways. I used AC Delco plugs. None of these things helped. So I took it in to the local GM dealer, told them what I did, and that they should probably just hook it up to their machine.

I was suspecting TP sensor. So I got a call yesterday (they had about 4 hours in it). They could not figure it out. They checked ALL sensor readings and ranges. Nothing was out of the ordinary. They had 2 tech's drive it and monitored with the scan-tool as the issue happened. They also tapped in a fuel pressure gauge while they drove. It was also normal. They did a back pressure test, thinking it was catalytic converter. That also passed.

So they took it for another drive and this time they disconnected the EGR valve connector. Then it drive with out the hesitation. I came and picked up the vehicle, they want me to drive it with the EGR disconnected and see how it drives. The tech said "if this works, just leave it. It won't hurt anything other than an engine light." They charged me only 1.5 hours of labor. I didn't think that was bad at all.

So, I drove home from there. The hesitation is not as severe. But it's not totally fixed. I will try this to work and back for a week and see how it goes.

What are you opinions? Are they guys a bunch of idiots? Are they missing something? The next thing they were going to do was to drop the exhaust from the manifold and inspect the converter. But then they tried this EGR thing. So if it runs like shit this week, I will probably call them to take it back and try other things. Or does anyone think I should't take it back there?

ALSO, all the issues happen after the car is warmed up.

Damn this was a long post, I have to leave for work now...

Last edited by gtrman79; 01-27-2015 at 09:59 AM.
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Old 02-07-2015, 02:21 PM   #2
jeffcoslacker
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Re: 97 Lumina, 3.1, 128k miles, weird response fro accelerator

Well...only after warm-up points to closed loop operation...where it is actively responding to sensor inputs, not just using a "known good" air/fuel map strategy.

If it were mine, I'd throw a TPS on it anyway, they are under $30 and easy to replace. 2 screws. They seem to go bad around the mileage you have as well. That would at least rule that out. They rarely seem to code for any kind of failure. Any issues with upshift point when accelerating from a stop? That's common with TPS failure too. The tranny takes it's upshift point cue in part from the throttle opening. If it's sensing it wrong, the upshift gets a little weird. Hangs too long, etc.

I'd look at the intake hose between the MAF and the intake. Any air getting in between those points will render the MAF useless, as unmetered air is bypassing it. This would also include a bad PCV valve, or broken/cracked PVC tube, as well as a missing grommet where the breather side connects to the rear valve cover. ALSO, while I'm thinking about that, part of that line goes to the top of the throttle body, there's a little "tab" on the throttle cable bracket that helps keep it in place. It can suck air there too, if deteriorated. In short, just make sure there's no unmetered air getting in. Once that's ruled out, you can move on.

I'd be interested to know what your fuel trim readings looked like. Did they give you a report with a snapshot or anything?

I have this feeling (could be wrong) that you are dealing with unmetered air...that's why disabling the EGR made it better...the EGR is essentially just a big vacuum leak, far as the engine is concerned. Although the dynamic is a little different. So if it was already at the fringes of how much lean it can compensate for, the EGR opening under load (like it should) might put it over the top and affect engine. But that should show in fuel trim under acceleration.

Never heard of a dealer recommending leaving an EGR disconnected. That's unusual.

Anyway...start with what you know...you had a MAF code...what exactly was the code saying? Make sure everything going to the intake pipe is secure, look at the pipe carefully for damage (sometimes they crack when you bend/twist to remove a MAF)...rule out that area between there and the motor before making any more assumptions.
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Old 03-02-2015, 05:18 PM   #3
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Re: 97 Lumina, 3.1, 128k miles, weird response fro accelerator

I just came back to check this post after a month. Im still driving with it disconnected. I did removed the EGR and cleaned it. Did not help.

I will check the intake areas for leaks. Now that you mention the lean compensation, the tech did ask if I had changed the O2 sensor because of how clean it was when they checked it. He said it looked like it's been running lean for a while.
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