My first post here at new forum.
Car chocked and has bad detonation/knocking under boost.
When adding gas gently no detonation but when it start reaching area after 4 in boost gauge,it starts detonating.
And sometime it's like you have to play back and forth with gas pedal to find area when it starts accelerating and not hesitating under boost.
It has #5 cylinder misfire but it was there since I bought this car two years ago and there was no hesitation/detonatio/chocking.

Any idea where to look,what to clean etc? I was researching back on old forum some time ago but didn't find much in relation to my particular symptoms.

New spark plugs.
New wires.

I don't know why signature isn'r here. I did add it in my profile.

It's 1995 Bonneville SSEi

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1995 SSEi
%$#@&ing thing keeps me busy

if you have missfire on cyl 5, have you checked cyl 2? How about checking the resistance on the coils?

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92 Olds 98. L67, Gen 3 M62, 2.55 pulley, FWI, PLIM, 1.8 YTs.

[quote="Wes"]if you have missfire on cyl 5, have you checked cyl 2? How about checking the resistance on the coils?[/quote

That would be too easy

Scanner shows misfire on #5 only.
Coils,ICM, PCM, fuel injectors - everything was swapped and rechecked.
It's something else with that misfire.
Right now I'm more concern about detonation/chocking .

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1995 SSEi
%$#@&ing thing keeps me busy

Inspect carefully for vacuum leaks. Start the car and let it idle. Spray carb cleaner carefully around all the vacuum connections, the base of the supercharger, and where the LIM meets the heads. Also around the EGR (each end of the pipe from the valve to the LIM). When you find a leak, the carb cleaner will be sucked in and will combust, slightly changing the idle.

If you run lean under boost, it will cause your symptoms. In addition, it would be good to check your fuel pressure:

1. Key on (no start), wait two seconds for prime, key off, repeat 3 times. What's the pressure?
2. What's the pressure at idle?
3. What's the pressure with the vacuum line pulled off the FPR at idle?

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Click here for mod list for both cars
93 SSEi, 95 SLE (supercharged) 97 Buick LeSabre Limited
PontiacDad at WCBF '04: Cruise control? That's like surrendering!
Comprehensive guide to troubleshooting, rebuilding, and modifying Eaton Superchargers

Fuel pressure was checked. Everything is as per FSM specification. I didn't check it while driving though,only at idle.
Maybe when pressing gas pedal sharply caused weak fuel pump not to deliver enough fuel?
I will recheck pressure and post it here.

LIM and supercharger gaskets where changed recently (a month ago or so). There is no leak there and this condition was present before changing gaskets and still present now, so I think that can be excluded.
I will re-check vacuum lines again more carefully. Maybe I missed something.
I don't know if it helps but will clean that ground bus under a carpet on driver's side. I think there is another on passenger's side. I'll be doing it tomorrow. Today I'm taking rest after night shift. Will post update after finishing .

Thanks for replying.

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1995 SSEi
%$#@&ing thing keeps me busy

recently going through the ordeal of a weak pump, I can say from experiance, that just idle pressure is not sufficient. You must drive it to get an accurate reading.

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92 Olds 98. L67, Gen 3 M62, 2.55 pulley, FWI, PLIM, 1.8 YTs.

I will try to get reading while driving.
Dunno if that hose is long enough to be able to close a hood and find a place to check it without interruption of other cars.
It's a *dang* big city with a lot of cars. LOL

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1995 SSEi
%$#@&ing thing keeps me busy

Ok. Kind of late response.
I couldn't do it sooner,was very busy.
Here is the pressure reading.

Pressure after three ignition On 39 PSI (allmost 40)
Pressure at idle 36 PSI
At idle, vacuum tube off FPR 41 PSI

When rev engine to 3000 RPM pressure rise to 39 - 40 PSI a moment ,then drop to 35- 36 .
Doesn't drop lower. I guess FPR does it's job.

Another scanner data,maybe usefull :

Fuel trim at idle 143

When rev engine fuel trim reading drop to 125.

One more question.
Is 13.3 volts a little too low at running engine ? When I turn lights on it even drop to 12.9 sometimes and isn't going higher than 13.1.
But isn't going lower either.

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1995 SSEi
%$#@&ing thing keeps me busy

Your fuel pump is shot. You should be reading 41 psi MINIMUM with no load.

Anything in the mid-30's or lower is just spooky. Stay out of the boost until you get it fixed, and if you're running a smaller than stock pulley, go back to stock now.

_________________

Click here for mod list for both cars
93 SSEi, 95 SLE (supercharged) 97 Buick LeSabre Limited
PontiacDad at WCBF '04: Cruise control? That's like surrendering!
Comprehensive guide to troubleshooting, rebuilding, and modifying Eaton Superchargers

I had the same symptoms on my 96 and it ended up being the fuel pump internally eating itself away

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1991 SSE+I ( supercharged)
1994 ssei




WCBF '08

Thanks for quick reply.
I guess you are right.
Next thing is to fix it.
How much is a reasonable $$ for pump and replacement job?
This one I won't be able to do by myself on the street like I did with LIM gasket,supercharger etc.

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1995 SSEi
%$#@&ing thing keeps me busy