will the "Service Engine Soon" light always be on if you have a bad EGR?

It sure can. It happened to me.

- Mike Harvey -

is this a trick question? i'd guess that under some conditions you'd have a bad egr and no check engine lite, but normally i'd say a bad egr would set a code. on the other hand a code set for the egr doesn't mean 100% for sure you have a bad egr. there are other parts in the system. you need to look at a flow down trouble shooting guide for a bad egr and follow it out to find your problem.



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-=ICON MOTORSPORTS=-
1st & 3rd

i was asking because my light never comes on yet i think i have an EGR problem...at low speeds i get some detenation and slight pinging...and i put premium fuel in and it helped a little bit so could this actually be the timing?

Here is the best way to tell if your EGR valve is leaking and bad. Spray WD-40 at the base of the EGR valve. Don't worry nothing will catch on fire and make sure the engine is running. If the EGR is bad then the WD-40 would be sucked in by the EGR. It's a simple easy way to find out w/ out being a mechanic

- Mike Harvey -

BB,

The EGR system is not normally operational until you are at a part-throttle cruise under moderate loads, like highway operation at 50-60 MPH. The EGR should be fully closed when accellerating or on a cold engine.

The detonation you are experiencing is more likely a function of lean mixture, advanced timing, poor fuel, of heavily carboned chambers/valves.

Does the SES lamp illuminate when you first turn on the ignition?

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Later,
Vader
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"No matter how hard you try you can't stop us now"
Adobe Acrobat Reader 4.0

Vader the SES light does turn on when i start the car...is this somehow imperative to my problem?...thanks

No, Vader was just making sure that your "no SES light" wasn't because some knucklehead yanked the bulb out.

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'87 Trans Am
S/D TPI retrofit including functional PassKey,
22# injectors,
JET AFPR,
Ported Plenum,
TB Coolant Bypass,
SSM SFC,
Boxed LCAs,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
KYB Shocks
-->14.97 @ 94.9 MPH<--

'97 Bonneville SSE

i had some crazy detonation problems with my 85 tpi. i changed the timing chain and now it runs excellent. if it has the chain from the factory and has a lot of miles the chain may be streched and could also be skipping a tooth. just my experience. i still have the check engine light coming on only on the highway that i still cant get rid of though. i may have an egr problem, but the detonation is gone now!


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beau-t-ful yellow 85 iroc