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Trevorusn
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Trevorusn

Name : Trevor
Joined : 2016-02-22
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PostSubject: Not sure where to keep looking...   Not sure where to keep looking... EmptyThu Jul 23, 2020 5:59 pm

Ok, interesting thing going on.  So replaced the MAF and upstream O2 sensors in my 96 supercharged Riv, yet my car is still stalling after a bit and sputtering, eventually not going past 3k RPM then gradually hitting lower RPMs before total loss of acceleration.  No SES light, but my traction control light and, admittedly once, the security light came on.  However, when I turn the car off then on again, all the issues go away for a bit before returning.  At first I thought it was a fuel issue, but could it now be electrical?  Not sure where to begin looking for the cause now.

Some added info.  When I turn it off then on to make the issues stop temporarily, if I mash the gas right after starting it seems to get held up in first and sputter, until I release the gas and hit it again, which then clears up for a few minutes.  All this seems to happen after the car has been at operating temp for a while, doesn't seem to happen when the engine is cold or warming up.  And, when sputtering during acceleration, the exhaust seems to, well, increase in sound where my cat is.  Not sure if it is clogged cats, bad fuel pump, crank sensor, etc.
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Jack the R
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Jack the R

Joined : 2007-01-16
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PostSubject: Re: Not sure where to keep looking...   Not sure where to keep looking... EmptyFri Jul 24, 2020 1:59 am

I'll offer what little help I can.  I would rule out the fuel pump.  Usually they work or they don't work, there is no halfway.  The crank sensor also seems unlikely, unless you've ignored the early signs of failure.  Mine needs to be replaced, and so far it has only stalled out a few times.  The car does seem to run unevenly after being driven for a while and I believe it's getting progressively worse, so perhaps this is your problem.  If you know the crank sensor hasn't been changed already, you can't go wrong by getting it done.  The AC Delco part is $50, not too bad, but you have to pull the front passenger side wheel, fender well liner, and harmonic balancer to get to it.  It's also possible your harmonic balancer has separated (it's two metal pieces connected by a rubber piece that eventually fails).  

After replacing the crank sensor you have to do a "case learn" procedure on the computer.  We've had some debate over whether this can be done without a Tech II scanner or not.  

Eventually you'll have to change the camshaft position sensor as well.  It's easiest to replace it while getting everything else on the front of the motor - tensioners, belts, idler pulleys, water pump, camshaft position sensor, and coolant hoses.  Expensive and time consuming but better than going in there again and again as individual parts fail.

The camshaft position sensor picks up the movement of a magnetic part inside the motor, and this sometimes falls apart.  I'm not sure how to fix that - I'm hoping I can upgrade my cam before it happens.

Clogged cats is unlikely unless you've got an enormous amount of miles, or you've been using an octane booster with a chemical that can clog the cats.
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Trevorusn
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Trevorusn

Name : Trevor
Joined : 2016-02-22
Post Count : 57
Merit : 0

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PostSubject: Re: Not sure where to keep looking...   Not sure where to keep looking... EmptyFri Jul 24, 2020 5:36 am

[quote="Jack the R"]I'll offer what little help I can.  I would rule out the fuel pump.  Usually they work or they don't work, there is no halfway.  The crank sensor also seems unlikely, unless you've ignored the early signs of failure.  Mine needs to be replaced, and so far it has only stalled out a few times.  The car does seem to run unevenly after being driven for a while and I believe it's getting progressively worse, so perhaps this is your problem.  If you know the crank sensor hasn't been changed already, you can't go wrong by getting it done.  The AC Delco part is $50, not too bad, but you have to pull the front passenger side wheel, fender well liner, and harmonic balancer to get to it.  It's also possible your harmonic balancer has separated (it's two metal pieces connected by a rubber piece that eventually fails).  

After replacing the crank sensor you have to do a "case learn" procedure on the computer.  We've had some debate over whether this can be done without a Tech II scanner or not.  

Eventually you'll have to change the camshaft position sensor as well.  It's easiest to replace it while getting everything else on the front of the motor - tensioners, belts, idler pulleys, water pump, camshaft position sensor, and coolant hoses.  Expensive and time consuming but better than going in there again and again as individual parts fail.

The camshaft position sensor picks up the movement of a magnetic part inside the motor, and this sometimes falls apart.  I'm not sure how to fix that - I'm hoping I can upgrade my cam before it happens.

Clogged cats is unlikely unless you've got an enormous amount of miles, or you've been using an octane booster with a chemical that can clog the cats.[/quote

Thanks. The car has almost 171k miles, thoigh I have only put about 1500 of those on. It was running great initially, then one day the SES light popped on and it has been an investigation ever since.]
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LARRY70GS
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LARRY70GS

Name : Larry
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Location : Oakland Gardens, NY
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PostSubject: Re: Not sure where to keep looking...   Not sure where to keep looking... EmptyFri Jul 24, 2020 9:34 am

You need to monitor fuel pressure while driving the car.  Attach a gauge to the fuel rail and tape the gauge to the windshield.

To test for an exhaust restriction, attach a vacuum gauge to the engine.  Our engines will easily make 20" of vacuum fully warm, in Park.  Open the throttle and run the engine, in Park, at 1500-2000 RPM steady.  Watch the gauge.  The vacuum should remain high and steady.  If you see it drop off, you have an exhaust restriction.

_________________
98 Riviera SC3800  All stock except gutted air box.
1970 Buick GS455 Stage1, TSP built 470BBB, 602HP/589TQ
Best MPH, 116.06 MPH, Best ET, 11.54
https://www.youtube.com/watch?v=UHCda-t_Jls
https://www.youtube.com/watch?v=sfT2tEO4XcU
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Trevorusn
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Trevorusn

Name : Trevor
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PostSubject: Re: Not sure where to keep looking...   Not sure where to keep looking... EmptyFri Jul 24, 2020 9:51 am

LARRY70GS wrote:
You need to monitor fuel pressure while driving the car.  Attach a gauge to the fuel rail and tape the gauge to the windshield.

To test for an exhaust restriction, attach a vacuum gauge to the engine.  Our engines will easily make 20" of vacuum fully warm, in Park.  Open the throttle and run the engine, in Park, at 1500-2000 RPM steady.  Watch the gauge.  The vacuum should remain high and steady.  If you see it drop off, you have an exhaust restriction.


Thanks, I'm gonna see about doing this next week, good info to know.
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Trevorusn
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Trevorusn

Name : Trevor
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PostSubject: Re: Not sure where to keep looking...   Not sure where to keep looking... EmptyFri Sep 25, 2020 5:06 pm

Ok, so seem to so far have fixed the sputtering and non driving issue. New plastic fuel tank lock ring, new fuel pump as well as the new plugs. However, after about 200 miles of driving now I have p0171 code back again. Not sure where else to poke around to fix lean burning, any ideas?
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LARRY70GS
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LARRY70GS

Name : Larry
Age : 64
Location : Oakland Gardens, NY
Joined : 2007-01-23
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Merit : 124

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PostSubject: Re: Not sure where to keep looking...   Not sure where to keep looking... EmptyFri Sep 25, 2020 10:00 pm

Trevorusn wrote:
Ok, so seem to so far have fixed the sputtering and non driving issue.  New plastic fuel tank lock ring, new fuel pump as well as the new plugs.  However, after about 200 miles of driving now I have p0171 code back again.  Not sure where else to poke around to fix lean burning, any ideas?

Vacuum leak.  Look at the fuel trims.  If they are positive, and large, the PCM is adding fuel.

_________________
98 Riviera SC3800  All stock except gutted air box.
1970 Buick GS455 Stage1, TSP built 470BBB, 602HP/589TQ
Best MPH, 116.06 MPH, Best ET, 11.54
https://www.youtube.com/watch?v=UHCda-t_Jls
https://www.youtube.com/watch?v=sfT2tEO4XcU
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albertj
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albertj

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Location : Finger Lakes of New York State
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PostSubject: Re: Not sure where to keep looking...   Not sure where to keep looking... EmptySat Sep 26, 2020 1:42 am

Trevorusn wrote:
Ok, so seem to so far have fixed the sputtering and non driving issue.  New plastic fuel tank lock ring, new fuel pump as well as the new plugs.  However, after about 200 miles of driving now I have p0171 code back again.  Not sure where else to poke around to fix lean burning, any ideas?

Your P0171 *might* be unrelated. I chased a P0171 code for several months. Ended up calling it the Hide And Seek Code. To fix a P0171 I ended up replacing the supercharger plenum and intake manifold gaskets (the hint - faint whistling upon acceleration. Others have reported oil on the lower intake manifold as "the hint"), the exhaust manifold (it had a crack) and the MAF sensor (with a junkyard unit out of a Camaro - mine was original, it was working but the *range* of the output was wrong. Obvious with a scanner, not obvious otherwise. The one I pulled from that Camaro was a genuine Hitachi rebuilt by somebody and epoxied back together, and works **great**.) While I was at it, I also cleaned the TB and replaced the IAC.

P0171 can come from lean burning (caused by leaking intake manifold gaskets, remember the intake has a vacuum) but can also come from air intrusion into the exhaust (cracked exhaust manifold).

This might help you avoid frustration: Do you think that in order to reach 150,000 miles trouble-free some things have to be engineered to run a certain number of MILES, others a certain number of HOURS, and others just for serviceability? The rotating drive train stuff like wheel bearings, would be miles. The electronics, hours. The engine, serviceability (as defined by engineers who don't necessarily have to buy the tools their designs require to be used and don't necessarily have empathy for those who do). What I think I learned chasing the P0171 this time was that content of a cluster of failures are unpredictable without knowing what standards the components are engineered to, and some failures are inevitable. After reaching the engineered life of the vehicle (I was told once it was 150,000 miles/ten years but I don't really *know*) stuff will fail that isn't on any of the maintenance schedules and the OBD software isn't designed to pinpoint (lacks precision in some areas) although it is designed to 'flag' it (reasonable accuracy overall). The point is that for something like this it might take a while to fix if only because there could be a number of causes all setting the same code so to speak. Quiet as it's kept, the nice thing is that a code is set at all, because a number of these failures that set Hide And Seek codes are not "sudden death" but are in fact the things that lead to unrecoverable failures if not fixed.
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Trevorusn
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Trevorusn

Name : Trevor
Joined : 2016-02-22
Post Count : 57
Merit : 0

Not sure where to keep looking... Empty
PostSubject: Re: Not sure where to keep looking...   Not sure where to keep looking... EmptySat Sep 26, 2020 10:50 am

albertj wrote:
Trevorusn wrote:
Ok, so seem to so far have fixed the sputtering and non driving issue.  New plastic fuel tank lock ring, new fuel pump as well as the new plugs.  However, after about 200 miles of driving now I have p0171 code back again.  Not sure where else to poke around to fix lean burning, any ideas?

Your P0171 *might* be unrelated. I chased a P0171 code for several months. Ended up calling it the Hide And Seek Code. To fix a P0171 I ended up replacing the supercharger plenum and intake manifold gaskets (the hint - faint whistling upon acceleration. Others have reported oil on the lower intake manifold as "the hint"), the exhaust manifold (it had a crack) and the MAF sensor (with a junkyard unit out of a Camaro - mine was original, it was working but the *range* of the output was wrong. Obvious with a scanner, not obvious otherwise. The one I pulled from that Camaro was a genuine Hitachi rebuilt by somebody and epoxied back together, and works **great**.) While I was at it, I also cleaned the TB and replaced the IAC.

P0171 can come from lean burning (caused by leaking intake manifold gaskets, remember the intake has a vacuum) but can also come from air intrusion into the exhaust (cracked exhaust manifold).

This might help you avoid frustration: Do you think that in order to reach 150,000 miles trouble-free some things have to be engineered to run a certain number of MILES, others a certain number of HOURS, and others just for serviceability? The rotating drive train stuff like wheel bearings, would be miles. The electronics, hours. The engine, serviceability (as defined by engineers who don't necessarily have to buy the tools their designs require to be used and don't necessarily have empathy for those who do). What I think I learned chasing the P0171 this time was that content of a cluster of failures are unpredictable without knowing what standards the components are engineered to, and some failures are inevitable. After reaching the engineered life of the vehicle (I was told once it was 150,000 miles/ten years but I don't really *know*) stuff will fail that isn't on any of the maintenance schedules and the OBD software isn't designed to pinpoint (lacks precision in some areas) although it is designed to 'flag' it (reasonable accuracy overall). The point is that for something like this it might take a while to fix if only because there could be a number of causes all setting the same code so to speak. Quiet as it's kept, the nice thing is that a code is set at all, because a number of these failures that set Hide And Seek codes are not "sudden death" but are in fact the things that lead to unrecoverable failures if not fixed.
This is what I'm starting to think. My MAF and O2 sensors are brand new, and when I accelerate near a barrier I hear a somewhat gargly sound, definately not the supercharger bearing either, but I don't hear a whistle. I'll look over the manifold and upper exhaust, hopefully it's not the s/c plenum. Just a bit crazy how this one code has led to a plethora of repairs and investigation this year.
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