Driving on Highway = Service Light.. ???? argh
Thread Starter
Junior Member
Joined: Aug 1999
Posts: 31
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From: Columbus, OHIO
Driving on Highway = Service Light.. ???? argh
Okay,
Whats up everyone.. lately (last 3 months) I've noticed more and more often that when I'm driving on the highway (60-80mph) I get a Service light within 20 minutes of getting on the highway. Car seems to run fine when the light comes on.. I'm baffeled. I get off the highway goto a store for about 20 mins come out start up the car and the light is gone. Also.. I have noticed when letting the car sit for awhile after being run I will sometimes stall when i first start it. Argh.. i want a new car...
Thanks As Always,
Joe
305 88 Red Trans Am
Whats up everyone.. lately (last 3 months) I've noticed more and more often that when I'm driving on the highway (60-80mph) I get a Service light within 20 minutes of getting on the highway. Car seems to run fine when the light comes on.. I'm baffeled. I get off the highway goto a store for about 20 mins come out start up the car and the light is gone. Also.. I have noticed when letting the car sit for awhile after being run I will sometimes stall when i first start it. Argh.. i want a new car...
Thanks As Always,
Joe
305 88 Red Trans Am
Moderator
Joined: Jan 2000
Posts: 19,651
Likes: 309
JC,
Scan the ECM for error codes. I'm guessing you'll find a code '32' lurking in the recesses of your ECM's memory. This means your EGR is not functioning correctly. The problem is minor, but should be repaired.
The stalling problem is not likely related to the DTC at highway cruise, but it could be if the EGR is inadvertently getting a vacuum signal at cold start/idle.
The EGR will operate when the engine is at relatively light load cruise (low TPS input, higher RPM). The ECM will signal the EGR solenoid to open, allowing vacuum to the EGR valve operator. The EGR valve will open if there is a slight backpressure in the exhaust holding the pilot valve closed, and if the diaphragm in the EGR is not damaged. Presuming that the EGR passages in the intake manifold are clean and not plugged, hot exhaust gas will begin to flow into the intake charge. This hot gas will increase the temperature of the EGR diagnostic temperature sensor, signalling back to the ECM that the system is functioning.
If one of these steps is not occurring, you'll get the MIL lamp as you are reporting.
If the code is something different, I'll swallow my words and try to help with whatever error codes you report.
------------------
Later,
Vader
------------------
"Make Me Bad"
Adobe Acrobat Reader 4.0
Scan the ECM for error codes. I'm guessing you'll find a code '32' lurking in the recesses of your ECM's memory. This means your EGR is not functioning correctly. The problem is minor, but should be repaired.
The stalling problem is not likely related to the DTC at highway cruise, but it could be if the EGR is inadvertently getting a vacuum signal at cold start/idle.
The EGR will operate when the engine is at relatively light load cruise (low TPS input, higher RPM). The ECM will signal the EGR solenoid to open, allowing vacuum to the EGR valve operator. The EGR valve will open if there is a slight backpressure in the exhaust holding the pilot valve closed, and if the diaphragm in the EGR is not damaged. Presuming that the EGR passages in the intake manifold are clean and not plugged, hot exhaust gas will begin to flow into the intake charge. This hot gas will increase the temperature of the EGR diagnostic temperature sensor, signalling back to the ECM that the system is functioning.
If one of these steps is not occurring, you'll get the MIL lamp as you are reporting.
If the code is something different, I'll swallow my words and try to help with whatever error codes you report.
------------------
Later,
Vader
------------------
"Make Me Bad"
Adobe Acrobat Reader 4.0
Last edited by Vader; Mar 31, 2018 at 09:31 PM. Reason: Updated links
Thread Starter
Junior Member
Joined: Aug 1999
Posts: 31
Likes: 0
From: Columbus, OHIO
Wow, thanks Vader... I'm almost cetian this could be my problem.. Would a bad EGR effect gas mileage at all? My tank mileage seems to be getting less and less. Also how much does one of these EGR things cost?
Thanks for all your help!
I really appreciate it!
Joe
Red 88 305 TBI Trans Am
Thanks for all your help!
I really appreciate it!
Joe
Red 88 305 TBI Trans Am
Member
iTrader: (2)
Joined: Feb 2000
Posts: 466
Likes: 0
From: Robbinsville NJ
Car: 88 IROC
Engine: 350
Transmission: auto
My light does the same thing, but mine is a TBI. Do i also have an EGR? My gas milage is real bad too (14mpg all around).
------------------
Mods:Hooker Aerochamber 3" exhaust, gutted kitty,
March 2 piece underdrive pullies, smog pump gone,;these two made a very noticable difference.
14x4 K&N open air element filter-the best mod so far
Eibach springs with KYB's all around.
Appearance: Harwood cowl hood, Z-28 wing, painted black(7/20/00)-original color was light blue
*All these mods were made this year
Stock Options:117,000 miles on motor, 5spd, TBI, 305, T-tops
Run a best of 16.7 @85mph with traction problem. Have to try again sometime.
------------------
Mods:Hooker Aerochamber 3" exhaust, gutted kitty,
March 2 piece underdrive pullies, smog pump gone,;these two made a very noticable difference.
14x4 K&N open air element filter-the best mod so far
Eibach springs with KYB's all around.
Appearance: Harwood cowl hood, Z-28 wing, painted black(7/20/00)-original color was light blue
*All these mods were made this year
Stock Options:117,000 miles on motor, 5spd, TBI, 305, T-tops
Run a best of 16.7 @85mph with traction problem. Have to try again sometime.
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