96camaroz281988

Ok my car is a 96 camaro z28. So at first the car got a small little stumble almost unnoticeable but it is getting worse everyday and now it is so bad the car almost cant get moving or when going up a hill it stumbles really bad. The check engine light is on and when it really starts to stumble really bad the ses light blinks. I went to auto zone to have them scan it for me but the scanner could not connect to the computer at all and I couldn't get any information from it. And now the throttle it start to stick and doesn't want to idle down. Does any body have any ideas what it could be. This car is my daily drive and is my only transpertaion to get me to work.

Injuneer

Check the cig lighter fuse. The ALDL port for the scanner needs power, and that's where it gets the power. If the fuse if blown, scanner won't connect.

In addition to checking the codes, check the fuel pressure.

96camaroz281988

Ok I will check that out. And also I guess I should have let u guys know that from 0-3000 rpms is when the car stumbles and anything after 3000 the car sreams and runs real good and also when I unpluge the battery to reset the computer the car runs super smooth and runs perfect and also when the car is cold and not at running temperature it runs good but once it reaches temperature it starts acting up.

96camaroz281988

Ok so I checked the fuse and it was good and I even tried the lighter and it got hot. So does any body know why the scanner would not be able to link to the computer

*UPDATE*: went to oreillys and tried using there scanner and it worked and it threw code p0300 and p0507

Injuneer

P0300 = random misfire

That's why the SES light "blinks" - to indicate that you have a misfire severe enough to damage the catalytic converters.

If you find a shop with a scanner that has "GM enhanced parameters" they can pull up the misfire count by individual cylinder. That may point you to the cause.

How old are the plugs and plug wires? Have you checked the plugs and wires?

P0507 = idle control system high idle speed

Possibly a problem with the idle air control valve, or possibly a vacuum leak or a sticking throttle blade.

The fact that it runs better when you clear the PCM, and when its cold may be indicating a problem with the O2 sensors.

96camaroz281988

I replaced the spark plugs about 5-6 years ago maybe a let less. Im guessing the wires are factory and I have not checked them yet. I decided to get a tps just for the hell of it and it help just a little but not a lot but I cleared the coeds again And drove the car around again and both codes came up again. The throttle body is good I just took it off the car to fully clean it and check it and everything is good on it and for the o2 sensors I replaced the one before the catalytic converter but i would guess the one after is factory.

96camaroz281988

I kinda feel I might be kinda explaining this wrong. The car doesn't stumble thats the wrong word to use it more bogs down and lags and the only time it does it is when the car has a load so like when u are going up a hill or ur at a red light then go that's when the car takes off then u can here the rpm dance just a little and then takes off again then it does it again and u can hear the rpms dance again then once when u clear 2000 rpms it doesn't do it anymore. Is there a way to test the O2 sensors do any scanners have the ability to see how there working.

moparman

When it gets good and dark tonight, start it up, raise the hood and see if there is any arcing along the plug wires.

96camaroz281988

I'm pretty sure it's not plugs or wires. Because everytime I clear the computer it runs fine. I'm pretty sure ur right injuneer about the o2 sensor because I have noticed I have been getting bad gas mileage lately and smelling really strong gas fumes from the exhaust pipes.

Injuneer

You are aware there are two catalytic converters on a 96, with a pre-cat sensor before each cat and an after-cat sensor downstream of each cat.

The after-cat sensors do not control the way the engine runs. They are just there to monitor the cats.

Many scanners (other than pure "code" scanners) can monitor O2 sensor activity. What you want to look at is the long term fuel corrections for each bank of the engine, in the various "cells". Best thing to accomplish that with is scanning/data logging software like AutoTap.

sweetsoul

i had a similar problem with my corvette once. it was the fuel pressure regulator.it had a pinhole in it.took me 6 months and a few thousand dollars to find it was a $60 part.that experience is the one that makes me steer away from the technology on my hot rods.

L.dookie

have you checked for any intake/vacuum leaks. My throttle body gasket blew out and i had similar symptoms. it was running very rich and would stumble/lug under heavy loads.

4montecarlo

sweetsoul - how did you diagnosis the pin size hole?
thanks
matt

Injuneer

If the fuel pressure regulator diaphragm gets a hole in it, you will have wet fuel or a very strong fuel smell in the vacuum compensation line.

sweetsoul

i didn't.i gave up , and took it to a corvette specialist.he chased problems like i did , i paid him $1100 total before he found it.