[kwik73]

When I drive my automatic 89 z24, I get on the interstate for 20 min and car is usually fine. When I slow down to take the ramp (or for any other reason) my check engine soon light comes on. Light remains on until I shut the car off. When I restart the car, the light is off and all seems normal. I get up to speed and decellerate and my light comes on again. This has been happening for about 6 months.
I recently replaced the alternator, and while it was out, I changed the oxygen senson (with a used one from my parts car) thinking that was it... but much to my disapointment, the problem still exists.
Can anyone offer any assistance?
When I attach my little GM code reader under the dash, it doesn't pick up any errors (code 12). You plug it in and turn the key forward while engine is OFF. Of course... the Check Engine light doesn't come on until later when you slow down from a higher speed.. :roll:

FYI: I've recently noticed some sporatic variation in my throttle at idle. SOmetimes it will rev up and almost die and rev again. What's up with that?

 

[npwinder]

for starters i dont know a lot about cars this is just what i heard.

There are 2 types of codes soft codes and hard codes. Soft codes go away when the car is shut off so the reader wont read it until it comes on again. The hard codes stay on til the negative battery cable is taken off.

As for the Reving up. When my car did that the fuel pump went out.

 

[was_that_a_minivan]

Don't take this as a definate answer, but I know GM sensors and guages lick nuts. Almost everyone I know who owns a GM has had sensors or guages malfunction, especially the CHECK ENGINE sensors. If nothing else seems to be wrong with the car (particularly after 6 months) then I'd say it's likely nothing to worry about, but maybe worth fixing eventually since then if something does go wrong you'll know, plus it's kinda annoying..

 

[seanski]

get one of those snap on scan tools and drive with it hooked up and let the engine light turn on and see if the computer shows it throwing a code

 

[soup]

ok you will not get any codes from this!!!! I have the same problem!!! wemet aslo had the same. Your gonna need to check your vaccuum lines. ONe may be broken or disconnected somewhere, wemet fixed his (disconnected vaccuum line) I havent had the chance to look at mine yet. I would put money on this being your problem, let me know what you find

 

[kwik73]

get one of those snap on scan tools...

Where can I pick one of these up at? Are they expensive to buy or is it something that is more commonly rented?

 

[kwik73]

...Your gonna need to check your vaccuum lines...

Thanks Soup... I'll check the vaccum lines first.

 

[upy]

Thats what mine was doing but my 5 speed would always die whenever I would press in on the clutch and it was the vaccum lines.