Ok, just to give you a little background it’s a 94 Z with 83,000 babied miles, I am the second owner and the first was a grandmother school teacher. I have had the car since last year and only put about 500 miles on it or so. The car is in storage right now for the winter and we plan on taking it to Florida this year. It has a SLP loudmouth 1, Hypertech chip (not the programmer) and I just put on a K&N FIP kit and did the TB bypass. After I did that I started it up (like a do every week) let the car run for awhile and snapped the throttle sounded great. Once the car got warm I did the same thing and it fell on its face, shook bad and back fired. I even held it at about 2 grand snapped it and it fell on its face?? But when I bring the revs up slowly it does fine?? Any ideas??? I kept the opti covered up, no antifreeze got on it. Also last year I replaced the thermostat (180) because it was sticking. My car gets all the way up by the orange hot line before the fans kick on?? Is that normal?? When the car fell it was right in the middle on the temp gauge. Is in the fuel pump, opti??
Cody

 

bump........

 

Your temp shouldn't go that high. Is the stat back to stock, or is it the 180*? Even with the stock stat, it should go no higher than about 225* (which looks like this: http://i67.photobucket.com/albums/h2...Untitled-2.gif)

Are your fans tuned for the thermostat? Bleed the lines

 

thats about right it might get alittle higher. Yeah its a stock 180degrees thermostate. But what could cause the falling, and the backfiring?? Also does anybody know the proper amount of fuel pressure so i can test it??? Thanks
again

Cody

 

No the fans are not tuned, do you think i need one for the exhaust and intake difference??

 

ses light? o2 sensor bad?

 

No SES light on, thats whats got my thinking

Cody

 

bump......

 

bleed the line.

 

Ok, i will bleed the line, but as far as the car backfiring and falling on its face? What could that be??

Cody

 

check the IAC valve.

 

ok, so it is safe to say that the opti, and fuel pump are ok??

Cody

 

i have that problem also with it heating up that hot at idle or town driving, mines a 96. i havn'ted figured it out ethier, but when i get mine out im going to put in a 160 thermostat and a manuel fan switch. ive heard that help that problem.

 

Any other ideas besides the IAC??? Are these the same type of symptoms of an opti or fuel pump going out, or do the act up at different rpms, times etc???

Cody

 

Ok, i went back down today started it up, ran fine, drove the car around. First time i tried to get on it, it back fired and spark knocked bad?? The only thing i did was put a Cold air intake and the TB bypass for crying out loud. I did not take the neg battery cable off when i did that?? could that be it, does the mass air flow need to be re-adjusted??

Cody

 

Is the car backfiring or stumbling? Do you notice black smoke dumping out of the exhaust when you try to rev it?

You can do some quick and easy trouble shooting to see if it is a certain sensor, or if it is in fact ignition related.

I'm not sure why the MAF would be bad -- but go ahead and un plug it and see how the car runs. The car will put up a Service Engine Soon light, but if it runs and revs fine, then that is your culprit.

If the car still runs like crap -- then you'll have to dig a little deeper. Pull all of your spark plugs and check them to make sure they're not fouled or just plain old. Also double check all of your spark plug wires to make sure none of them are cut, burnt, or otherwise not in good working order. I'm going to guess it is one of those two.

If you pull all the plugs and they look fine, and all of the plug wires look fine (no cuts, burns, etc. along the ENTIRE length of the wire) then I'd take a look at the ignition coil and ICM. You can do a little bit of reading here:
http://shbox.com/1/4th_gen_tech2.html#opti_test

If all else fails, then come back and we'll try to help you diagnose it further. From this point its kind of taking a random guess as to what it is. There are a million things that can be causing it to stumble while under load and when just revving it. With all of these tests, you don't have to spend a dime either. The worst thing to do to figure a problem out is to just start randomly throwing parts at it and hope it fixes it. Do it once, do it right.

And finally -- do yourself a favor and ditch the hypertech. It probably isn't doing much for you, and you'll get a lot better gains from getting the car tuned (either mailorder or on the dyno). Plus, the driveability of the car in general will be better as well. However, don't look into that until you get this issue figured out.

 

thanks
Cody

 

Fuel filter?

 

its got a new fuel filter

 

get rid of the hypertech, it will run fine after that. it is running bad because its so hot. you have to have a 160 t-stat for it to run ok. but i would remove it for good. the same thing happened to me a long time ago and i traded the chip in for the programer and installed a 160 t-stat. it ran great after that. hypertechs tuning is pretty good for a stock car but once you start adding big horse power bolt ons it hurts you.