I have a 91' Z28 with 5.7 TPI. One day it runs great, the next it won't want to start without some throttle. Sometimes while driving the serviceengine light willturn on and off numerous times.When theservice engine light turns onthree problems occur. The car runs poorly(hesitates), thespeedometerstops working, andthe enginestalls when the car comes to a stop. There are no codes being thrown. Any and all advise will help.

 

Maybe your computer is crapping out.

 

Sounds like a squirell problem. Also, the computer is probably taking a **** on you. Now... By coming on and off numerous times, do you mean intermitantly, in an excessive amount, or do you mean that it's a constant, steady blinking when it's on?

 

Do you know how to check for codes with a paper clip? Did you at least get code 12?

 

if the ses light comes on, then there is a code somewhere. If you don't have access to a tech 1 or tech 2, then go to autozone and use their scanner and find out what code it is. You can also use the paper clip as madmike refers to in the lower left hand two terminals with the ignition on but engine off and you should see code 12 flash 3 times and then any codes that are left will flash after (3 times each).
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I have the same problem with my check engine light but not the other problems like stallin. How exactly do i check with a paperclip...im not following.

 

You know where the OBD 1 port is in the car, under the steering collumn cover? Use a paperclip or jumper wire to jump the two leftmost terminals on the port, and then watch the SES light.I can't remember if GM used the single or double digit method for flash codes, but it's easy to tell the difference. The SES light will either flash 12 times, or once then twice, long pause, repeat, pause, repeat, and then flash any other codes on the PCM in the same fashion. Beats the hell out of buying an OBD 1 compliant tool if you're not gonna use it that often. You should be able to find a list of codes on the internet somewhere, or I'm sure someone on here could probably tell you what any code is off the top of their head.

 

The ALDL (pre obdII) will be on the right side of the column. Jumper the a and b terminals (there should be small letters on the connector) and turn the key on but engine off. Watch the "check engine" light and count the flashes. It should flash a code 12. One flash, pause, two flashes. It will repeat this 3 times then flash any codes stored three times each. Then when it returns to flashing code 12 that is the end of the code(s) stored and is strating over again.
OBDII has the connectors on the left side and use the "service engine soon" light. Your 91 is pre OBDII.

 

yes it throws code 12 when i use my GMcode reader but no others. The SES light flickers on and off with no pattern, one day it will act up then it will run great for a few days.

 

Im getting a remanufactured ECM this week from the dealer hopefully it will fix the problem