Ideas?

[WhiteMonteZZZ]

Have had my 95 Monte Z34 for a lil over 2 yrs now and still haven't figured out my problem yet. I have a small throttle tip-in hesitation. To start, i'll post what i've changed/done to "combat" the problem:
New tps, iac, rapidfire plugs, accel wires, fuel filter isn't too old, new upper and lower intake gaskets, new egr gaskets (done w/intake gasket change), new o2 sensor (obd1.5 only has one), no codes present. I've probably changed other things that i can't think of right now. Batt/alt are both new, just to throw that out there. I've also replaced some of the more accessible vacuum lines on the vehicle. What do you guys think could be causing this? In the 2+ yrs i've had my car, the stumble has stalled the car only twice, but when launching, it seriously kills my times. Are there any "hidden" vacuum lines that might be culprit to this? Also, would an egr valve w/a sticking solenoid do this? I checked the "plungers" on the bottom of the valve and they move freely, tho a bit carboned up. No codes are present nor are any stored. Thanks in advance for reading my long post. I've learned to live w/the hesitation long enough

[timg]

RE: Ideas?

if the intake is not shielded from engine air, it can cause the hesitation and stalling.

Tim

[WhiteMonteZZZ]

Tim,
I have the stock box in right now. No change.

-WMZZZ

[dohcfiend]

only other things i can think of is intermitent tps or coilpack fault.

[WhiteMonteZZZ]

Got some MSD Coil packs cheap that i'm gonna throw in in a few weeks, whenever it warms up some. In the meantime i'm going to try to find a cheap EGR valve and plug it in to see if that helps any, and again when it warms up i'm going to try to find and replace the vacuum lines on the car. I'm just stumped as to what it could be.

[dohcfiend]

oh and also it could be an injector fault try any cleaner? i also just got in a set of 97 injectors

[Doubt_Incarnate]

my car had a real bad hesitation problem at low speed, it was the icm. mayebe your is on the edge of bad.or if you dont the the tps adjusted right, if it is the kind you need to adjust.maybe the evaporative purge solinoid, if it is opening you motor will get more air than its expecting without the feul to compensate, my dads 3100 did that, but it threw codes. another thing you wouldnt think of is a rupter is a vacuum diaphram. moms bravada ran grewat until you depressed the brake pedal, then it would die. turns out the diaphram in the power booster was bad.

[WhiteMonteZZZ]

What's the ICM? Also, the brake booster and booster hoses are all good (in fact I just checked those prior to reading the post mentioning them).
AFAIK, tps isn't adjustable (I replaced it last summer, but it didn't have slotted holes so I don't see how it's "adjustable"). Where's the evap canister/solenoid and all that stuff at? I was thinking maybe checking the vacuum ball vac lines as well. I plan to re-do all the vacuum hoses I can get to with silicone vacuum hose (my dad has it on his 77 trans am, not only is it practically lifetime hose but looks nice as well). Also, would the EGR valve not throw a code and produce these symptoms? Say, if a solenoid is sticking open and giving it too much air?
This morning on overnight cold startup, the car surged ~200 rpms for about 10 secs. I KNOW the intake gaskets are done right. Leads me to think of vacuum leak. Only reason I question other factors is the fact that I feathered it at 1200 to keep it warming up/steady and it was rough. I dunno who can relate, but if you ever start a cold carbed car and feather it to warm up, you know that rough-but-smooth idle you get? Thats what I got this morning. So hence me asking about the EGR valve. My dad's 77 T/A is slightly over-carbureted and at cold startup will idle like my car (minus the computer-controlled surging). Makes me think of too much air. I dunno. Sorry for the long post, again.

WMZZZ

[Doubt_Incarnate]

im not sure on your car, but if you can find the charcaol canister, it usually has the solinoid in it. my cavalier had it mounted low in the inner fender on the pssenger side, but moms bravada had in back, by the tank. the purpose of it is to nullify the fumes vented from the fuel tank, during normal operation the pcm tell the solinoid to open so it can use the fumes, if its stuck open it just like a vacuum leak. dads car threw a code for it but then his pcm needed reflashed. im not sure about the egr, i think they have a sensor to tell the pcm its position, if it was sticking, the pcm would know whats going on and throw a code.

the icm is the ignition control module. its located directly beneath the coils. all 3 coils bolt onto it. its sort of like a stand alone igniton system, it just gives reference signlas to the pcm for injection timing, and the pcm tells it when to retard due to knoxk or what not. i think.

as for the tps being adjustable. i just threw that in because mine was, i wasnt sure if yours was or not. in the instruction it tells you to adjust it for a specifc voltage reading at closed throttle. more like calibrating.

if yours is a 95, i think its obd1.5 or something. maybe it just needs reflashed, or a new chip. i dunno what the 1.5's take.

[WhiteMonteZZZ]

Thanks again for the quick response. I dont think the icm is at fault. Only reasoning for that is that at WOT, the car pulls like a bat out of hell. That, and the light surging at overnight startup. I never thought of the charcoal evap canistor deal though. Gotta find out over at MyMonte.com where that is on our cars. Yeah 95 is obd 1.5. I was thinking computer also, but thats a lil pricey to just say "let's try it" Do you or does anyone know if the charcoal canister can be bypassed? MI doesn't have emmissions testing, and I was going to replace the cat with a glasspack then my exhaust piping is redone. I was gonna get rid of a few of the emmissions things on the car as well to free up that last neuonce of power. Would the stumble (vacuum leak or otherwise) cause my mileage to be down to 13 mpg in all stop and go short-trip city driving? Or is that about on par for the DOHC in those conditions?

[Doubt_Incarnate]

that does seem like crappy milage. my v8 car does 20 in the city. i dont think you will benifit any power from dropping the canister. but if it bothers you , put a plug in its place on the vacuum port. having such bad milage makes it seem like you have too much fuel getting in, that will make it hesitate. if you dads ta is over carbed, that might be why you say they idle similarly. if such is the case, i think the pcm is at fault. you could maybe get one at a junk yard for 50$. it doesnt smoke does it? smell strange? the cat isnt glowing after its run is it?

[WhiteMonteZZZ]

Cat doesn't glow, doesn't smoke. At cold startup, car smells a little funny, but doesn't smell "familiar." Can't say it smells rich, maybe though. I have an autometer a/f gauge, but that won't really tell a whole lot as the mixture constantly varies.

WMZZZ

[Doubt_Incarnate]

there is always the plugs, they can tell you how things are in the chamber.

[WhiteMonteZZZ]

I had Bosch plats in originally until I found they were shitty plugs. When I pulled them (probably had 8000-10000 miles on them) and they were burning perfect. That's the odd thing. But the car does smell, odd at startup some. Hmm....so many choices. I'm going to see about getting a cheap replacement computer from someone and try that. If for nothing else, having the spare comp isn't that bad an idea. I'm gettin confused as to what it could be tho. Any number of things

[bud36light]

the cannister purge solenoid is located on the rear left corner of the intake manifold(standing in front of the car). Id look this area over really close.