I have had a problem with my throttle response. I was pretty sure it's a vacume prob, (read on please but I wasn't sure. Today, sicne it was a cloudy rainy texas day and it was only 73º outside, I decidd to fix my ciggerette lighter, so I could plug in my radar detector again (not that I speed, no not me!, not that red trans am! hehe) Well I figured since I was out there I might as well check the vacume. Normal idle it is around -18" of vac, which I am pretty sure is normal. If you hit the throttle hard, I would get 2" of pressure, not vacume. You could also hear an audiable vacume/pressure noise (not sure anymore). But after the motor would choke and nearly die, it would rev up and hit around 20". I know the standard tests for vacume leaks, but they seem realitivily difficult to do since the leak is only happening on hard throttle. Where should I be looking? Also, can anyone tell me where the O2 sensor is? I believe the wire to the sensor is loose, but I don't think the problems are related.
Thanks
Corry

edit: I just realized, I hit an extra letter in the word spike I

[This message has been edited by Corry (edited August 26, 2001).]

 

Sounds like a restriction in the exhaust like a plugged catalyst or something. It is normal to see like 2psi when taken from a point in the exhaust itself (like O2 sensor hole, called backpressure) but never from the intake. It should drop to near 0"HG, when "goosed" and return, it should not read pressure.

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Well, it would jump up to 2" and back to 0, then back up to around 18-20". With this though the car would stumble, and sometimes detonate! This accompanied by a fairly loud hiss, but only when you get on it hard. You can slowly rev the thing up w/ no probs. Also later in driving I get an o2 lean condition, maybe my O2 sensor doesn't have a problem? I really don't mind the noise, but I do mind the stumbling, and I really can't stand the detonation! Any suggestions?

[This message has been edited by Corry (edited August 26, 2001).]

 

The lean condition and the stumbling on rapid throttle opening could all be symptoms of a vacuum leak. Check the vacuum hoses around the motor for cracks or splits, or just plain looseness at the fittings. Are you familiar with using something like WD40 to check the gaskets for leaks? Spray this around the engine intake gaskets while watching a vacuum gage very carefully.

If you had access to an Auto X-ray or similar scantool I would say that overly high BLM values would also be a strong indication of a lean condition, but from the tone of your post I don't expect that you have one available.

Do you ever get error codes for your TPS sensor? A malfunctioning TPS sensor can also cause stumbling upon rapid acceleration as the computer can't tell when you are cranking on the gas pedal and you immediately go lean as a result.

 

Yes, I know about the tests for vac leaks as mentioned. I have tried them and turned up diddly. It seems more like it is several pinhole leaks in gaskets somewhere, but I really don't want to be spraying carb cleaner around hot parts of the motor. I di have a scan tool, but I really don't trust it, BLMS are aften very low at idle, not really sure at higher speeds...since I just fixed my cig lighter, I'll plug it in on the way to work tomorrow. The TPS is fine, it was bad recently, but I replaced it about 2 months ago, and set it. No tps codes since, and I actually have some throttle response as opposed to when it was broke, and was reading a big fat which really threw the ECM off. I thought the lean condition was because of that, since it also caused MAF and MAP errors like crazy. I knew the TPS was off though so I ignored the others, replace the TPS, clear codes, and no more MAF and MAP, but the lean stays, and I guess because of the lean condition I get nasty detonation. Usualy when I hit it hard, it may audiably detonate once, but sometimes, it will go 3-4 times. note, I only did that fior testing purposes, normally I just ease onto it now...but it gets annoying when some ***** that has half a clude of how to build his car comes up, and if I give it even 1/2 throttle off the bat, the thing stumbles for almost a full second, maybe detonates, then starts to go, only to have the EST retard timing to some insane amount that leaves my car practially in a limp home mode ~50 hp! I know the dangers of detonation, so I don't gas it too hard, but accelleration is why I got this car. I could care less about the car being able to go 200+ MPH or whatever people consider fast, I like 0-60 in say 4.0 secs WHy, you do not feel speed, maybe you feel yourself get tunnel vision, but accelleration is a force, and you can feel that! (probably why I like turning at high speed too ) So if anyone has any more suggestions fire them out. I know I get a` bit wordy, but please, try and read the entire posts!
Corry