Heat related lean condition... UPDATE - 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 04-17-2004, 05:49 AM   #1
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Default Heat related lean condition... UPDATE

When my car has been running for a while and it'* warm outside (as in the problem doesn't show up in the winter) my car will lose all power at WOT. After everything under the hood is "heatsoaked". At that time, my A/F gauge drops off the lean end and stays there until I let off. Power is pretty normal until 3/4 throttle. The engine will miss very bad if I stay on the gas. This problem has been around a long time. A hi-flow cat made it a little better last fall. No codes.

Injector or fuel pressure regulator, maybe?

Either way, the injectors and FPR are getting replaced tomorrow (Saturday).
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Old 04-17-2004, 11:42 AM   #2
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Be sure to let us know on this. I have pretty much thew same issue in Ol Blue. I know if my fuel pump hadn't died at the track last year I'd have been deep into the 15'* (had a 2.2 60'). I changed the fuel pump, but still had these lean at WOT issues where she'd just bog and the more I let off the more I could feel the power coming back.
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Old 04-17-2004, 01:36 PM   #3
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Maybe you need to look at your MAF, and then adjust the AFC? I bet you're getting slight detonation. Maybe colder plugs too....
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Old 04-17-2004, 03:23 PM   #4
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This has happened before and after AFC and with several different settings. Other situations seem to run how they should with respect to A/F. I think the lean condition is causing some knocking when I keep on it. My plugs are 2 ranges colder. I've tried 3 range colder plugs before, same result then they fouled. I don't thik it would be the pump, as it wouldn't get really hot. I'm going out to swap the other components I mentioned now.

I used to think it was a coil, but that wouldn't kill the fuel flow, would it? Unless the PCM had something to do with it.
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Old 04-17-2004, 03:48 PM   #5
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Maybe the Injector O rings aren't liking the heat.

Do you have a heat sheild on your intake? That'll cause heat soak much quicker if you don't.
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Old 04-17-2004, 06:43 PM   #6
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New injectors now (my original injector tips were awful, not just carbon buildup, but a few tips were slightly melted), with good o-rings. Intake is shielded.
Mostly same problem, but have not had an extended drive yet.
After discussion with dad, it could be my fuel pump.

Don't know about the fuel pressure regulator yet. I ordered a series II NA regulator, as per someone'* suggestion, and it does not look like it will fit. The tip seems too short and narrow. The o-ring probably wouldn't seal.

EDIT: BTW, the coils ohm out fine when they are cool. Haven't had a chance to test them hot yet.
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Old 04-17-2004, 09:50 PM   #7
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I am having the exact same problem right now and earlier I had pics on the club showing my injector tips being melted as well . I put them back in and it runs fine except for the hot problem. My next step when I get to it is the ignition coils. They are still original on mine and so they are 12 years, 250 000kms old. As the coils heat up the coils may be becoming weaker and when WOT is put on it requires a very good spark under those conditions to jump that gap. I know when the car is cold it has oodles of power and it is only when it gets hot. I have yet to check any of the resistances, although maybe this week or so. I will keep an eye on this thread
Bonne chance
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Old 04-18-2004, 01:15 AM   #8
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Coils aren't always very heat tempermental. How old are your wires?
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Old 04-18-2004, 04:01 AM   #9
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Wires are a year old, MSD 8.5mm.
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Old 04-18-2004, 11:37 PM   #10
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After a ten minutes into a two hour drive, it goes real lean at any throttle that gets boost. At a certain point, it starts slowing down, so that the cruise keeps trying to give more, but only slowing the car down. At this point, I think it has to be the pump or regualtor.
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