Few Problem's With '89 GT

[TwoToneHatch]

Hey All,

I am having some problems with my '89 GT and hope I can get some help.

When I first fire it up the idle drops real low where it almost shuts off and then shoots up to over 1000rpm and then either surges a little or goes back to normal.

Secondly My Check Engine Light turns on sometimes after the car warms up but then goes away only to come back on again.

My gas mileage has also dropped significantly It just drinks gas now.

I gave the car a tune-up last summer and have since cleaned the throttle body and IAC . I am about to order new o2 sensors(the car still has original ones) and EGR valve (because mine is buzzing). Will the new EGR and o2 solve my problems or is there something else wrong I should address.

 

[Foxfan88]

if this is happening on a cold start it wouldnt be the o2s causing the problems.

the o2s only function and give the EEC feedback during closed loop mode (up to temp and no hard faults within the EEC)

is your CEL a solid contant light, or does it go on and off.
go to the parts store and use their code scanner, it will scan and tell you what the code is.

sounds like it could be the IAC giving you fits, check the codes and if it is, pull it off and clean it out with carb cleaner and blow it out and try.

before doing anything i would unhook the battery for a while to clean the codes and run it and let only current problems register before scanning codes. you may have saved codes from before or something i am not sure if you have.

also before you try and make the repair, like cleaning the IAC or something, be sure to unhook the battery again to clear codes so you will be know if it fixed it or not.

 

[TwoToneHatch]

So the O2's and EGR are not at fault? I'm guessing that any major parts store will have a scanner (like autozone) ? What about my poor gas mileage? I haven't changed my driving habits or anything yet now it just drinks gas like hell.

 

[90blacknight]

So the O2's and EGR are not at fault? I'm guessing that any major parts store will have a scanner (like autozone) ? What about my poor gas mileage? I haven't changed my driving habits or anything yet now it just drinks gas like hell.

Most autoparts stores should carry a scanner. Pull the codes!

 

[TwoToneHatch]

Ok guys thanks alot for the help ! :SNSign:

I'll go get the codes pulled as soon as I can this week.

 

[corvetteguy]

A clean MAF will help the idle.

Summer gas will help the mileage.
The best I ever got on my 89 GT was 20.
In winter I ran less than 15.

 

[svtpower]

tune up

What exactly did you do for the tune up?

Did you do air filter, plugs, wires, cap and rotor?

What are you running for exhaust?

 

[NIKwoaC]

Make sure your vacuum lines are all in place and undamaged. Vacuum leaks could cause a rich condition and therefore, poor gas mileage.

 

[mustangfan1990]

he said that the CEL came on when the car warmed up I would say the gas issue is the o2s

 

[Foxfan88]

So the O2's and EGR are not at fault? I'm guessing that any major parts store will have a scanner (like autozone) ? What about my poor gas mileage? I haven't changed my driving habits or anything yet now it just drinks gas like hell.

not sure if its the EGR or not, but the o2s wont cause problems during a cold start and warm up in open loop.

if your CEL is on when the car is warmed up then the o2s may be a fault. causing poor milege. without the feedback from the o2s the EEC is guessing in the dark

your local oreilys or autozone should let you borrow the scanner to take out side and scan the codes. just plug it into the diagnostic plugs under the hood and if its the good scanner it will tell you what to do.

 

[HISSIN50]

Stop guessing and pull the codes. It takes 5 mins and requires but a piece of wire.


Good luck.