2000GT4.6

Just for ****s and grins pull the negitive battery terminal for a few minutes. It really almost seems like the ECU is just ****ting itself. I would really look into that headlight short etc.

rw98

hey, that a good idea!!!!!!!!

jersey98gt

i had this problem before actually very very similar, my headlights would dim and my instrament cluster would also dim, and the car ran like absolute ****, howevee i dont have ABS so that light didnt come on, long story short it was my idling pump which cost about 150 bucks.

eternal981

the headlight problem is only with the passenger headlight. and i can grab the individual wire, push it in, and it works fine. pull it out, and it quits.

i really don't think it's related.

i've reset the computer a million times in the last few months, it's probably getting ticked off at me. thats a good idea though. i'm going to pull codes first. does anyone know how to do the test through the odometer?

eternal981

just an update real quick...

went out and started it up. starts great. idles great. until its warm. as soon as it was warm, there was about a 30 second period where you could hear it getting worse. after that 30 seconds, it just idled like crap. although i couldn't get it to stall on me today. i played around with all the small vacuum lines. i didn't notice any big change with any of them. when i pulled the vac line off the TB, it died. fast.

can anyone explain to me why a vacuum leak makes an engine run so bad? what does it change?

could a vacuum leak allow the engine to run fine when cold, and bad when warm? or should i start looking elsewhere?

i've also heard that if an engine is missing, the oil will smell like gas. is that true?

eternal981

reset the computer, ran fine until warm, started missing and stalled. again. i'm going to have a hard time even getting this car to the nearest mechanic.

but i think i've figured out the solution.

broomstick for the clutch, heavy brick for the gas pedal, large body of water....

01yellowgt

all the hoses and stuff for the intake on good? pull the iac off and clean it with carb cleaner let it dry, then spray a little wd40 in it and let it dry before putting it back on.

the mas sees how much are is going into it, any air that doesnt go through that throws all that off.
I had something simular and the cai came loose after the mas, made for some interesting idles and driving.

for as the abs light. Hows the brake fluid, full?

GodAmGT00

First off, to answer your question about vacuum leaks:

ALL of the air that goes into your engine (in an IDEAL environment) is Metered. This means that every particle is counted, and then the ECU uses that number, to apply a certain amount of Fuel (through injectors) into your engine for the efficient combustion (I think it's called Stoic). IF there is any type of Leak, or gap, extra air is added to your engine, that isn't metered. That causes the engine to run like crap, in short....


I haven't thoroughly read through this post, however, I thought of 1 thing..


Have you bothered to pull the ABS fuse to see if that solves the issue??


Part of me thinks the vacuum signal going to your Brake Booster is kinked, split, or otherwise damaged. That alone would cause a Vac. leak like you describe. The headlight thing almost seems inconsequential..

Have you put a Vacuum tester on any of your open-looped vac. lines??



JT

eternal981

brake fluid is perfect.

i thought these brake systems had a hydraulic boost using the power steering, not vacuum. i can tell you this much....there definitely is not the "same old" brake booster sitting behind my master cylinder. the ~0.5" lines running out of it go straight to my power steering pump.

that DEFINITELY explains why vacuum leaks hurt idle, since it doesnt take a big leak to equal a big percentage. unless the vac leak is HUGE though, it should go away at higher RPMs, right?

this doesn't. [sm=smiley5.gif]

unfortunately, this problem isn't just at idle. when it gets REAL bad, it wont even stay at 2000+ rpms. i thought i was going to have to push my car home on my own last night. that wouldnt have looked very impressive. i dont think the sound of me grunting is NEARLY as tough sounding as my exhaust.. haha.

the ratio is called stoichiometric ratio. i understand that part pretty good. i guess my question about vacuum issues was more driven by my misunderstanding about what symptoms they can cause. i'm pretty sure i get it now though. sometimes it just needs to be spelled out in front of me. thanks!

i haven't pulled the ABS fuse yet. thats worth a shot. i haven't heard of ABS causing idle problems, but if there's a faulty wire somewhere, who knows WHAT it could be doing.

(a little side note for you guys: a year ago, in one of my work vans, the ABS system was doing more bad than good, so i pulled the ABS fuse. apparently GM has the ECU set so that if you pull the fuse, it wont allow the transmission to shift beyond either 1st or 2nd..dont remember. it didnt take long to force us to put the fuse back in. just one more little bit of information that might help you out someday)

what do you mean a vacuum tester? do you mean a gauge, or a vacuum pump? if you mean a gauge, i have a vac/boost gauge in the car, that seems to be right on the money.

i've had my IAC off about 20 times in the last couple months, trying to fix a hanging idle problem. its been cleaned a million times. somewhere, there's still a seperate problem with my idle also. i'm hoping they're all related, so i can fix everything all at once. but i HIGHLY doubt i'll be that lucky.

i hate to keep adding to this, BUT...i just pulled 4 of my spark plugs to see how they looked, and they really didnt look bad. is there any way you can check the coils? bad coils should throw a code though, shouldnt they?

GodAmGT00

Well, since you have forced induction, any type of Vac. Leak becomes a Boost leak after you build any boost... Vacuum leaks don't usually heal over any RPMs though, since you're still leaking, and in some instances, they get worse w/ RPM..


Funny you mention the Coils.. On an old car I had, it had similar symptoms when the Plug wires went out. That car TOO was Forced Induction. Car sputtered, and stumbled, and I couldn't build boost.. Changed the wires and plugs, all was cured.


This is slightly different now though, since it's COP. Bad Coils SHOULD throw a code, but you may be able to individually test them. I, unfortunately don't have the Impedence #'s, or the Voltage cycle for the Coils, so I am of no help there. The FSM should have it though, if you can get your hands on one...



JT