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Old 12-06-2008, 02:34 AM   #1
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1997 Buick Lesabre Limited 3800 SeriesII

Hi all... I tried searching for my answer a few different ways but came up with similar but not same results so here is the problem I am having with my Buick.

It all started just out of the blue by the engine loping a bit when I would slow down or come to a stop sign and sit in gear at idle. Just a slight lope, roughly 500 rpms or so.

The next week it got worse. Engine light came on. 1000-1500 rmp lope and the voltage would drop and then increase as the rpms climbed back up. Back and forth it would lope somtimes constantly, sometimes constantly and then the engine would die, sometimes it would lope and then level out.... but always it was loping either in gear at idle or in park or neutral.

Went to O'Reilley's auto and told them what was going on and the guy put a tester on my battery. The battery was fine but he said my alternator was shot. The alternator was drawing 30 amps when it should have been drawing 140. Said thats the problem, replace that and you will be good to go. So I spent $120 on a new alternator. Woah! Everything was a lot stronger now... Popped right off when I turned the key now, the fan had a bit more uhhh.. blow? to it... and even the lights seemed a bit brighter (probably my imagination) but... it didn't fix the problem. Engine still loped, but now.. only when I put it in park or neutral. grrr.. ok. Did some research on the net and saw a lot of different problems that it could be.

So far I have done these things:

-- Alternator - replaced
-- Battery terminals - wires cleaned and posts replaced
-- Ran my gas down to empty and filled with premium and poured some injector cleaner in there
-- Checked vaccuum hoses for leaks
-- PVC valve - replaced
-- Mass flow air sensor was gummed up - cleaned it
-- Idle Air Control Motor - replaced

Other things that I looked at as far as possibilities:

No fluid leaks or low fluids, I mean as far as coolant or oil or tran fluid.

Not sure what is next. ??? It is starting to get cold out here and I'm almost at the point where I am going to have to take it in if i don't figure this out soon. I did have it tested on a machine for the codes.. First one was oxygen sensor but I was told that it was a false reading due to the alternator failing. Next one was was mass flow air sensor but I cleaned that and that code went away.

Right now it is idling / loping erratically again, off and on, at stops in gear, in park, neutral. Even a drop in accelration will drop my rpms and my voltage drops. Wants to die but catches itself and then lopes again.... argh... help!

This is a picture of my engine for a sort of visual

Last edited by midwestman : 12-06-2008 at 02:39 AM.
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Old 12-07-2008, 09:12 AM   #2
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Are you sure the O2 sensor is a false reading? Clear the codes with the new alternator, drive it around and check again. Not positive, but that may be the issue. Check to see if it's a faulty sensor or possibly a clogged cat.
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Old 12-09-2008, 02:36 AM   #3
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No. I'm not I once again ran a diagnostic on my car. Had the codes cleared.

The only code left is P0107 - Manifold Absolute Pressure / Barometric pressure Circuit low input.

MAP Sensor. Attempting to find it and clean it if possible. Did some research but lack the tools to do what is recommended.
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Old 12-11-2008, 03:34 AM   #4
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Silly MAP sensor is right over the pcv valve on next to the manifold. When I pulled it off to check it It had actually broken in half.
Replaced it at O'Reilleys for 60 bucks and installed it right there at the parts store. Got in, check engine light was still on. Had to stop a number of places.... by the third place the engine light had gone off after starting. The rpm's would still go up and down when coming to a stop in gear at idle. But not as bad. If I gave it some gas the rpms would level out and stay put. So I am now thinking is this the computer adjusting itself little by little? Are things going to be good now? I hope so.
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Old 12-11-2008, 08:39 PM   #5
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Sorry for three posts in a row but I like to keep it separated.

Well well well. its back to revving rpms........ Check engine lights are off and it has gotten worse. Lopes in idle at park or neutral 1 to 3 k rpms. And engine is running a bit rough too.

Now what?

Going to do some more reasearch on this and keep you all informed if I find anything and of course the end result I will post here.
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Old 12-15-2008, 02:09 AM   #6
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What a nightmare!

Found a vaccuum hose that had broken off and was spewing gas vapor into the engine compartment. Dont know the name of it but it was a Tee style hose fitting. One went to the fuel pressure regulator on the fuel rail, the other went down along the front drivers side to the evap tank, and the other went right into the throttle body.

Went to O'reilleys again, and they could not find the part to replace that. Thinking its one of those genuine GM parts . Will be stopping at the GM dealer with broken Tee in hand and see if they have one there or order it quick.

Removing it from the vehicle resulted in me breaking the fitting, (insert expletive here) I was planning to just wrap some tape around the cracked part until I could a replacement.
Soooooooo, I bought a Plastic Tee, three different sizes of hose and fit it on so I could drive it as I need my car. It actually started fine and idled great! Seemed a bit hesitant but I thought again that it was probably trying to adjust to the new - rigged - part. I thought my problems were over - - but then I went to the store for supper. Again at stop lights at idle the rpm's started loping up and down. This is driving me batty now.. Tomorrow I am planning to take it out on the highway for 40 miles and see if that helps clear up the problem.
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Old 12-18-2008, 12:43 AM   #7
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Well, figured it out. It was the fuel pressure regulator.

Sometimes my stupidity even amazes myself as I had read a certain thread 4 times looking for the answer to this problem. (btw please don't validate my last sentence as I will very much agree with you and validate your response...)

The certain thread stated:
Testing for a Blown Fuel Pressure Regulator Diaphragm. A fuel pressure regulator is used in the fuel injection system. This component regulates fuel system pressure by using a diaphragm and spring combination. When the fuel pressure regulator diaphragm ruptures it allows raw fuel into the vacuum feed line and then into the intake system of the engine. This condition creates a rich black smoke from the tail pipe on start up and while running. (in my case there was no black smoke present)
To check for this condition remove the vacuum line from the regulator, if fuel is present in the line the regulator has failed.

Well there was fuel in the line most definately but I had so many people telling me that it was electrical or a vaccuum... wait a minute a line going to the FPR is a vaccuum line durrrr.. Anyways it is running all better now except that right after installing the FPR I started it and after the third start there was a loud hissing or what I thought sounded like purging. Took it for a spin and when I got back It made that sound again. Also, When I replaced the FPR I didn't bleed the line and gas spurted out a bit. No big deal I guess but after putting the new one in am I supposed to bleed the fuel line at the regulator? There is a tire tube style port there which I believe is for using a pressure tester. It has a plunger that I can depress but haven't yet and haven't come across anything online and local shops will not tell me anything except bring it in and we'll look at it. Guess they need the business which I don't blame them for.
So two questions... After losing all that gas in the fuel rail from replacing the regulaotor Is It going to take awhile for everything to get back to normal? aaAAaand .. Do I bleed the fuel line?
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