misfire under load - 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 05-07-2003, 04:36 PM   #11
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My car HAS been stuttering sometimes lately. It feels like the engine is shaking (just a little) and can feel it through the pedals, if that makes sense. Most of the time it was at idle when this would happen. I was worried as hell! I stopped the car, then started it again and it was fine. But it has happened a couple times. Every time I turned the car off and started it again it would not stutter or shake. Does this sound like a misfire? Thanks for the help.
Sometimes it starts up slow, or barely seems to start.
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Old 05-07-2003, 06:41 PM   #12
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Could be, but it'* really hard to tell without actually hearing it. Change your plugs and wires and see what happens.
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Old 05-07-2003, 10:24 PM   #13
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ok
try this. under higher rpms, our valve springs are sorta weak to begin with, only like 75-90 lbs. maybe you have a weak spring and the valve isnt closing fast enough. also the 3800 injector connectors are prone to go bad. they sell replacement connectors for them too.
the best way to check fuel delivery is not to just use a gauge and check pressure.... you need to install the gauge, start the car, and then hit the gas 3 times really quick and see if your fuel pressure drops at all. if it does, your pump may have good pressure at idle but cant keep up with the needs of the motor.
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Old 05-08-2003, 03:31 PM   #14
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Those are some good ideas. How do you check the connector to see if it is bad?

I have driven the car with the fuel gauge attached and the pressure does increase like it'* supposed to.
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Old 05-08-2003, 07:03 PM   #15
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Default My Non Supercharged 92 SSE misses at low RPM too

I have a NON supercharged SSE that does this. It usually only happens at low RPM in overdrive.

Maintaining speed is usually ok, but going up a hill or under acceleration, the car stutters or lurches every half second or so, the harder I put my foot on the gas, the more it does it.

It doesnt matter if the AC is on or off.

My mechanic has replaced the fuel filters, fuel pump, plugs, plug wires, swapped out the ignition "computer" thats controls the plugs firing.

My mechanic seems to be out of ideas. He says there are no codes, no check engine light or anything else showing up.

It runs normally and has OK power still under hard acceleration or in low gear at high RPM
.
It does idle a bit rougher than it used to.

Oh one more thing, my gas mileage used to be 30Mpg on the highway, now I get about 22Mpg.

Any ideas ?

Thanks,

Andrew
92 SSE
97 SSEi
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Old 05-08-2003, 08:30 PM   #16
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Iím still trying to figure mine out still.
Same Problem as you.
I am going to bypass the SC and still see if I have the same problem. I bet I do.
Still waiting on the O2 sensor.

Looked for hours(and hours) through old posts,
I have come across this problem mention before.
This seems to be a fairly common problem. (So whatí* up?)
But so far I have not seen a good answer. (Bad for us)
Tried smaller gap. No good.
Anyone know a good mechanic in the Seattle area?
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Old 05-08-2003, 08:47 PM   #17
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Default Maybe a clue ?

After reading tons more messages, maybe I can answer my own questions....

I saw some posts about the TCC solenoid in the Transmission. Its supposed to lock the trans in OD to give better economy and reduce friction. I guess if it slips, it can decrease performance and economy.

I just had a trans service and new filter recently and nothing changed.

I saw a post with someone mentioning a broken Diff Pin- - whats that ?

I get a high pitched chirping noise for a few seconds when the trans slips into overdrive, and then when I accelerate in OD ? The 'chirping' noise only happens in OD and seems to be when the trans is under load. I can reproduce the sound at will.

I'll keep reading and searching. Maybe i'll answer my own questions eventually, hopefully some things I am finding will help others ? I hope so.

BTW, you guys rock !!! You all know so much about these cars I am really impressed

Cheers,

Andrew
92 SSE
97 SSEi
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Old 05-08-2003, 09:38 PM   #18
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If the same problem seems to happen at the same throttle angle every time, it'* possible you may have a dead spot in the throttle position sensor, and it may need to be checked. The easiest way to do it is with a Tech 1. Move the throttle sensor slowly from idle to wide open and see if there are any jumps, or if the resistance increases in a uniform fashion. You can also do it with a multimeter too.

Is it also possible you could have a bad fuel injector?

Just an idea if you've tried everything else.
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Old 05-08-2003, 11:21 PM   #19
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Quote:
Originally Posted by fuddyduddy121
If the same problem seems to happen at the same throttle angle every time, it'* possible you may have a dead spot in the throttle position sensor, and it may need to be checked. The easiest way to do it is with a Tech 1. Move the throttle sensor slowly from idle to wide open and see if there are any jumps, or if the resistance increases in a uniform fashion. You can also do it with a multimeter too.

Is it also possible you could have a bad fuel injector?

Just an idea if you've tried everything else.

Quote:
Originally Posted by UserBrett
Car starts fine, Idle is fine,Runs good until load and boost and low rpms
but can get the problem in 3 going up a hill but a lot harder to do.
Injectors rebuilt and tested,
new coils,icm(used),maf,map,fuel filter,nose cone,sparks plugs(2 sets),wires,
orderedO2(comming soon, Delco. I dont think this will help).
No back pressure problem.
?
The Funny thing is I unplugged the MAP sensor with no difference in the problem,
so I got a new one. No change.
The throttle is fine. Smooth change in voltage Wide open reads 4.08 v
Should this be closer to 5v?

Could be the injector but had them tested.
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Old 05-08-2003, 11:33 PM   #20
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After pulling the injectors to see if they were fouled, I put it all back and started it up. Now the freakin' thing is way worse The miss happens all the time now. And there is a strong sulfur smell from the exhaust. I had to walk away from it for tonight. Tomorrow I'll go back and check my work, but does this give anyone any ideas?
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