Whenever my amazing 91 Z-28 TPI engine is cold it runs and starts so incredibily smooth and I'm just like ahhh...I love my baby. BUT when it warms up after like 10-20min or so it'll start to surge when it's idling. Then another 10min later the surging will start even when driving like anywhere between 50-70mph. AND then another 10min later it'll start to surge at any speed and the ride is just nothing but shocks and close encounters with engine stalls. Sometimes when I brake it seems like I hear clunk noises coming from the engine. Another 10min later and the car has become pretty much undrivable and even the breaks go out. The weird part is that whenever I turn on my blinkers it'll surge like CRAZY so I'm thinking this is some kind of electrical problem related to temperature. Engine light comes on and off but it never stays on long enough for me to run a OBD scan on it.

Car is undrivable....let it cool.....Runs like NEW

I mean seriously...what in the freak is this????

 

hook it up to a scanner (not for codes, but while it is running) and report what the values are.

Seems like a problem when it switches into closed loop mode. Could be an O2 sensor or something stuipid, could also be something else, but its hard to just guess based on what you have. Could also be expensive and stupid just to throw parts at it when you don't know what is causing the problem

 

The codes stay stored in the computer, you can check them even when the light is not on.

 

i just got taught the way to check for codes... (in my '84 LG4 anyway) you take a paperclip or wire (whichever you prefer/have) and bend it properly to fit in the TOP RIGHT and TOP LEFT ports on the ALDL connector on the dash (should be above your right leg) put the key in the ignition but only turn it far enough to let the radio come on... there will be a 'hello' code (meaning, the check engine light will flash then pause, flash then pause... i forget the correct number) each code will flash 3 times w/ a 6-8 second delay after each code... I ran mine and got 13, 24, 42...

to give you a better understanding of what a code 42 would look like, the check engine light would flash 4 times, then slight pause, then 2 times, then puase, 4 times, slight pause, 2 times, pause, 4 times, slight pause, 2 times. MAJOR PAUSE... next code would begin flashing...

get your 'thrown codes' and post them here and someone can de-code them for you to let you know what codes have been stored in the computer

-Skeet

 

I believe that for a '91, that the two holes on the ALDL port to probe for checking error codes are the top row, two most right side holes. I have an '87 TPI, I'm pretty sure this is correct.

 

i would get a bunch of opinions on which are the proper holes... u dont wanna stick something in the wrong place and fry your electrical even worse....

 

Go to autozone tell them you need one of the key pins to pull codes they gave me some for mine 85 TA. Just a thought. Now i keep it in the map pocket and just slide this key in and pull the codes its pretty slick or jsut use the cheap paper clip it works too. And its the top row last 2 holes on i think all pre 94 GM cars.

 

It's the top right and the one just to it's left. Like this:

|OOOOOOXX|
_|OOOOOOOO|_

Just jump the holes that are marked X and then turn the key to "RUN." It'll flash the codes at you.

 

yep, Top rite 2 holes.

 

When you have no codes in the computer, and everything is dandy the computer will flash code 12 if you try to check them.

It will flash code 12 3 times before moving onto any stored codes. If no codes were set, then it will continue flashing code 12 until you shut the ignition off and pull the paper clip out.