Hey guys:

Don't you all HATE it when that damn little light comes on? I know I get red as a hell everytime I see it pop on....

Recently, I had my car tuned up and it turned out that my ERG switch wasn't functioning properly (apparently someone messed with it before I bought the car), causing the car to stall at low RPMs, so we unhooked it, and the car runs great now... however...

When the car gets up to 45mph-50mph or higher, and I hold that speed for more than a minute or two, the "Service Engine Soon" light comes on. Now, the car still runs perfect, (as far as I can tell), but that god damn light stays on and bothers the hell out of me...

Only when I turn off the car, and restart, will it disappear... and again, if I bring the car back up to highway / freeway speed, it will always come back on.

I can drive around the city fine, like I said, as long as I stay under 40mph, the light won't come on, even if I floor it around a turn or accelerate fast, so I am not sure what is going on. For some reason, the computer is getting some error when I get up to and hold 50mph+...

I am about to buy a GM Code Reader (don't have one yet), so that I can find out what code the engine is telling me... but I wanted to ask you guys first.

Any ideas on what could be causing this?

Worn out Air flow sensor?

Could it be the faulty ERG switch that is sending an error to the computer?

Thanks guys

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Year: 1990
Make: Chevorlet
Model: Z-28 / IROC-Z
Engine: 5.0L V8 TPI
Trans: 700R4 Auto
Additional:'92 Z-28 Rims, T-Tops, Tinted Windows, Edelbrock Suspension Kit, Edelbrock Catback Exhaust (Chrome tips), K&N Air Filter

 

With the EGR diagnostic switch disconnected, and driving at highway speeds, the computer expects the switch to change state (off to on) when it commands EGR solenoid to open the valve. If it does not detect the switch changing state, it will set a code. (hence, the lite comes on.....)

The switch runs about 35 bux at your local auto parts store, but is a real drag to get at. Gotta remove the plenum (TPI).

HTH

 

Thanks for the fast response-

I had a feeling it had something to do with the EGR, now I need to get that taken care of...hope it's not too expensive to get done...I don't like the sound of having to get past the TPI system...

For my own peace of mind....Having the EGR not function properly only makes it so my car doesn't pass smog, correct?

Are there any other negative effects I should watch for? (other than that damn light)

The mechanic made it so we can simply plug the EGR back in to pass smog, but I need to know if this causes anymore problems that I am not seeing?

Thanks again

 

IROC,

Read the Tech Articles about the importance of the EGR system in allowing you to gain performance and power.

If you want your car to run right, you'll get the system repaired (or better yet, do it yourself). In order to access the EGR diagnostic temperature sensor (it's an analog sensor, not a switch) you'll need to remove the plenum:



To get to that point, you'll get in about this far:



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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

Excellent, thanks again guys, I'll get that EGR fixed ASAP

 

Incidentally,

Welcome to ThirdGen.org!