No power, LOUD CAI until 3/4 throttle - 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 12-12-2005, 04:56 PM   #1
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Default No power, LOUD CAI until 3/4 throttle

This is kinda a strange one...it just started happening a couple of days ago. There isn't a single thing I've changed before this happened, I've been running with a K&N filter for 2 months, CAI and Magnaflow exhaust for a year, and no MAF screen for longer than that. No other mods.

Whenever I'm below 3/4 throttle, I have VERY little power. Even if it downshifts, I'm still stuck with a serious power loss. At this time, my CAI is VERY loud. Once I get above 3/4 throttle, the power gets much closer to normal, but it'* still lacking a little bit. At this point, the CAI is normal sounding. There'* a definite point in throttle travel where it changes -- i.e. it'* not a gradual quieting of the CAI while the power comes back. At a certain point, the 'whoosh' from the CAI disappears very bluntly and my power gets back close to normal.

I've checked for vacuum leaks as a first step (just on a quick hunch) but didn't find any. I'm still running with a completly original block/head/upper intake (as far as I know, Marty needs to chime in if this is different), including original lower intake gaskets and such. Any suggestions on where to start would be great, as I'm in St Paul and all my tools and diag equipment are in St Cloud.

I was thinking about cleaning the MAF sensor wires, since that'* never been done, but I doubt that will have any large effect on this problem.

Any thoughts would be appreciated.
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Old 12-12-2005, 05:02 PM   #2
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I'd think fuel but it'* good higher in RPM. So that falls through.

Look for the obvous like plug wires arching etc. Maybe a bad tank of fuel?
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Old 12-12-2005, 05:04 PM   #3
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How old is your cat?
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Old 12-12-2005, 05:10 PM   #4
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My first guess was a failing fuel pump, but the symptoms are backwards from a failing pump -- too much power in the high end for it to be a pump. The wires should be good, it'* possible the plugs are in need of replacement, but I'm not sure when they were changed last. Marty needs to chime in on this one. I doubt it'* a bad tank of gas, since this has occured over the course of a tank and a half of gas. I suppose it'* possible, I just believe it'* unlikely at this point to blame bad gas.

My first thought was a failing cat, as it'* original (and actually, now that I think about it, it'* from a 92 SSEi [i believe, i know it'* not original and 92 seems to stick in my mind] because of the larger diameter -- unsure of the mileage or age from that car). But wouldn't that lead to a loss of power in the upper end as it'* trying to force more exhaust through a clogged cat?

Thanks for all the quick replies, after helping other people for so long, it'* great to see the response in 10x when I have an issue. #1 reason I like BC so much more than DSMtalk.com (horray for my 95 Eagle Talon TSi AWD! 1 month and a blown motor!)
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Old 12-12-2005, 05:47 PM   #5
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Get a scantool on it and check to see what the MAF is reading... Even without the MAF these motors will rev... They usually set of the SES if there is a problem...

And just for giggles, check the fuel pressure anyhow and see what you have...

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Old 12-12-2005, 08:02 PM   #6
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What are some normal readings for the MAF? I don't remember off the top of my head, and I don't have my 'normal readings' document around...

I seriously doubt it'* a fuel pump, as it'* only under a certain amount of load that it'll "break free" of it'* hesitation. Doesn't matter where in the RPMs that it is, it'* all relative to where in the throttle I am. I'm curious if the TPS has a smooth wave to it...lots of variables that need to be checked.

I'm surprised the question hasn't come up yet -- the check engine light is NOT on. I wish it were, at least I'd have someplace to start diagnosing!

Thanks for all the help!
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Old 12-13-2005, 11:01 AM   #7
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Quote:
Originally Posted by CSFiend
What are some normal readings for the MAF? I don't remember off the top of my head, and I don't have my 'normal readings' document around...

I seriously doubt it'* a fuel pump, as it'* only under a certain amount of load that it'll "break free" of it'* hesitation. Doesn't matter where in the RPMs that it is, it'* all relative to where in the throttle I am. I'm curious if the TPS has a smooth wave to it...lots of variables that need to be checked.

I'm surprised the question hasn't come up yet -- the check engine light is NOT on. I wish it were, at least I'd have someplace to start diagnosing!

Thanks for all the help!
The TPS is another possibility... You may want to check that and see if its smooth with relation to the Throttle position and voltage.... Making sure there are no dead spots..

And what speeds does your trans shift at when under load... Shifting way early can be another dead giveaway for a bad TPS...


For the MAF you may want another with a 94 to give you some general numbers as a reference point..

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Old 12-13-2005, 11:11 AM   #8
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My shift points haven't changed, the only thing that has changed is how hard my trans shifts. My vacuum modulator isn't leaking, but when the vacuum line going to it is unplugged, there is a bit of a racket coming from the port on the modulator...this really is a strange problem...

I'll keep this updated as I figure out more, but I defiently appreciate any suggestions anybody might have.
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Old 12-13-2005, 04:08 PM   #9
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All I know is I changed the plugs just before you bought the car from me. Can't remember exactly what plugs, but IIRC they're NGK TR-55'*.

Good luck.
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Old 12-13-2005, 04:15 PM   #10
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Let'* step back and take another look at this.

You haven't done anything to the engine right?
Has odd sound and no power in the low end
Good power and feels normal higher rpm.

This rules out fuel, plugged cat, and many other things.

Check your coil packs, look at your wires and maybe pull the plugs to see if one or two are fouled. If you have an ignition problem, it may seem like it goes away at higher rpm.
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