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93 & 96 Fleetwood
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Discussion Starter #1
My check engine light has been on for a while in my 93 Fleetwood and I've been trying to determine why. The smog pump was bad so I replaced it, along with the TPS, EGR valve and O2 sensor. Any ideas on why a check engine light would only turn off at high speeds (possibly only at WOT)?
 

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94 Fleetwood Brougham
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The car is in somewhat of a open loop mode at WOT, where not much is working, just goes to data tables to determine fuel and timing.

I would be leaning towards EGR to look at, next TPS. smog pump won't set a code on OBDI cars, OBDII it will. So don't look that way.

When the TPS was installed, was it set to the right voltage as per the FSM?

"I'm sorry officer, the only way I can comply with emissions laws is to keep my car at WOT, I am really trying to save the environment so I HAVE to do it...."
 

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Discussion Starter #3
N0DIH said:
The car is in somewhat of a open loop mode at WOT, where not much is working, just goes to data tables to determine fuel and timing.

I would be leaning towards EGR to look at, next TPS. smog pump won't set a code on OBDI cars, OBDII it will. So don't look that way.

When the TPS was installed, was it set to the right voltage as per the FSM?

"I'm sorry officer, the only way I can comply with emissions laws is to keep my car at WOT, I am really trying to save the environment so I HAVE to do it...."
How's that done? I just slapped on the new TPS.
 

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94 Fleetwood Brougham
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I don't know the TBI injection that well, but the 2 screws that hold the TPS in place are often the adjustment screws. Loosen them and turn the TPS one direction or the other. You need a digital voltmeter and the book or someone who can post instructions how and it is quite easy. Sounds like that is the issue.

(meaningless rambling to follow....)
Most are set to 0.45v +/-.05. Some higher, some less, but I don't think I have seen any farther out than 0.5v or lower than 0.4v. Most set faults at 0.8v or higher at idle. Later systems were more dynamic and less sensitive to absolute TPS voltage and made assumptions that if the car started with a TPS voltage of say 0.6v, it made the assumption that was idle, and that became the reference. So WOT was x volts higher than idle volts basically.

GM started it in the late 80's early 90's on the 3800's ("C" and higher at least), but I don't know if Chevy got it yet.

But still on those TPS, they did have a min ballpark setting.
 

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93 & 96 Fleetwood
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Discussion Starter #5 (Edited)
Last night I was able to get rid of 2 out of 3 trouble codes. The one that I haven't been able to take care of is 26. I think it is the purge canister solenoid valve. If replacing that doesn't help I look into the TPS.
 

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Discussion Starter #6
Scratch that. I found a website that had the trouble codes specific to my car only and it states that code 26 is Shorted Throttle Signal Switch.
 

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Discussion Starter #7
Alright, this is gonna make me look bad.

I figured out why my check engine light was on. When I was putting in my chrome wheel wells I somehow got the harness for the vapor cannister caught underneith. When I was puting everything back together I plugged the harness for the windshield fluid motor into the vapor can, and since the harnesses are identical and since I deleted the wiper fluid resevoir from the car, I never noticed it. When I was messin' around with the car tonight I noticed the harness under the wheel well and switched out..........no more engine light.
 
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