Just not making enough power - 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 11-24-2006, 04:01 PM   #1
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Default Just not making enough power

Howdy. Pretend I'm dealing with a '95 SSEi, but it'* actually the supercharged LN3.

The past couple days, it seems its just not making the power it should. It'* like the Reatta'* being pulled by a Tech 4 or something :( . I can step it to the floor and its just not pulling like it should. It'* not like a low boost issue, but like a smaller motor'* been put in, or I'm towing A TON, as in 2k pounds. It'* much slower than stock. I'm having to give it a lot more gas for just a little acceleration. The transmission seems to be shifting fine. I'll try to point out what I've tried.

-I had a power steering leak which was getting on the belt at the same time. I fixed it, replaced the belt (the longer one that runs the water pump, */C, A/C) and cleaned the pulleys. I thought maybe the */C belt was slipping. No change.

My AC Delco plugs have about 20k miles on them, maybe a little less. I pulled them all out and they all appear to be the same and look normal. No evidence of an injector stuck open, misfire, etc.

Plug wires are about the same age. I removed all of them and checked them out. All are within like 4k-6k ohms.

I spun all the serpentine acessories by hand, and all spin freely and without noise.

I swapped in a known good ECM while transfering my memcal. No change.

I'm running an Accel coil pack. Swapped in with a known good Magnavox. No change.

Oil pressure is high/good, no abornmal noises or knocks.

No CEL or hidden codes. TPS operation is good and not very old. Crankshaft PS was replaced not too long ago, though I will be visually inspecting it.

Put it in neutral while on the freeway and the car coasts freely/normally.

Checked the fuel pressure, 38 psi key on, 32 psi or so idle. Which seems to be good as far as I know. Spikes up and settles as it normally does when revved. No gas in the regulator vacuum line. Fuel pump, screen, and filter were replaced about 12k miles ago.

Have bought smaller amounts of gas while this has been happening, so I doubt its a bad batch of gas.

Starts and idles fine. No backfires, no missing.

Seems to rev fine in park, but this may info might not help any.

Air intake/filter is reasonably clean. Made a quick run with it off, infact. No change.

MAF wires appear to be clean.

TPS is fairly new and checks out good in Diagnostic Mode (slowly depressing the gas with the engine off and voltage increases like it should. You know what I mean. No dead spots)

Catalytic converter was replaced about 25 miles ago.

Seems to lack power everywhere in its RPM range.

What do you guys suppose is wrong? Thank you.
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Old 11-24-2006, 04:03 PM   #2
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What'* your boost pressure, and does the BCA work properly?
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Old 11-24-2006, 04:06 PM   #3
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Did the problem happen before the new cat?
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Old 11-24-2006, 04:07 PM   #4
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Will: I still wish I had a boost gauge. The BCA is freely when revved in park, though. I can hear the boost when accelerating and it seems a little more pronounced than before. Thanks for the help in advance. If you think it'* worth trying, I have a spare, brand new BCA I can try, but I don't think its the issue cuz its moving like it always does.

Also wanted to add that my oxygen sensor was also replaced around 20k miles ago, but my issue is present both in open loop and closed loop mode anyway.
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Old 11-24-2006, 04:10 PM   #5
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dillcc: The issue was not happening before the cat was replaced. That was like 2 years ago when I knew a lot less about engines than I do now. A shop went ahead and replaced it to fix a drivability issue (misfire), but it didn't help anyway. Turned out to be just a bad ECM, but I figure that it had 140k or so miles and replacing it wasn't going to hurt anything.

Anyway, I wanted to add that my issue is present whether the motor'* warm or cold, restarted while warm, etc...nothing seems to change it.
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Old 11-24-2006, 04:26 PM   #6
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Shouldn't the fuel pressure be higher?
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Old 11-24-2006, 04:38 PM   #7
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Hmmm...with my work with Ryan of GMtuners/Sinister Performance that did my ECM tuning, he suggested using a fuel pump prescribed for an '89 Turbo Trans Am (Grand National). My pressure is within the specs he provided and its worked out ever since then.
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Old 11-24-2006, 04:40 PM   #8
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I was under the impression pressure should be around 40-42 at idle, 48 at WOT/key on/pulled vac line off FPR.
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Old 11-24-2006, 04:46 PM   #9
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Perhaps so. I'm not discounting that or anything, so don't get me wrong, but it'* ran fine when I had a bad pump and like 20 psi idle and wasn't holding perssure for more than a few seconds.

I read an old post about EGR-less 3800s burning valves. I don't use EGR. Coiuld this be the issue? I have a compression gauge but don't know yet how to use it...please fill me in

Could I possibly have a bad plug wire that'* causing a slight misfire? or plugs?
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Old 11-24-2006, 05:41 PM   #10
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These are all the symptoms of a clogged up catalytic converter, but you said is was replaced. I'm at a loss on this one.
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