1994 Cadillac Seville P085 code

LEITTHOUSE

MEMBER
1994 CADILLAC SEVILLE
V8
FWD
AUTOMATIC
180,000 MILES

For a long time the car intermittently backfired through the intake when starting. I've passed smog twice here in California with flying colors. Finally I stumbled on a websight that clued me into a fuel pressure regulator located in the intake. I've been procrastinating doing it until the check engine light came on. I don't like driving with any check engine lights on, so I finally repaired it. It was a leaking FPR. The car starts and runs great, but the P085 code still plagues me. I've cleaned the throttle body valve and ID, cleaned the air filter (K&N), checked the TPS voltage, and reset the PCM code repeatedly, but it keeps coming on. Today I reset the PCM while driving (safely) and even though I did not let the enigne idle, doing about 45mph, the service engine soon light went out, then came right back on. The code was p085. How can it know the throttle valve angle is high at idle when the hasn't idled? I'm also inclined to take the beauty cover back off of the intake and reseal it, dumb idea?

Sorry to be so lengthy, A confused mantainer.

3 Replies

BUZZSAW

MECHANIC
1,198 POSTS

Explain to me how you set up the TPS? And does it have an ISC motor?

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Monday, February 4th, 2008 AT 6:40 PM

LEITTHOUSE

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Explain to me how you set up the TPS? And does it have an ISC motor?[/Quote:e3d2564f5b]

I didn't set up the TPS, I hooked up a voltmeter and watched the voltage as instructed in Chiltons. It did as Chiltons said and regulated up to close to 5 volts. I also checked the resistence and it was not erratic, and increased nice and smooth from idle to WOT. I believe it does have an ISC motor. Chiltons said to override it, I did, and it retracted as it was supposed to. If the ISC motor was bad, wouldn't I have an erratic idle? Something I noticed tonight driving home, I put the PMC on data monitor, 01 (TPS), and the degree at idle was -2.9, I think the lowest it should've gone would be 0.0 degrees, right?

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Monday, February 4th, 2008 AT 8:32 PM

BUZZSAW

MECHANIC
1,198 POSTS

Explain to me how you set up the TPS? And does it have an ISC motor?[/Quote:2ba50f7f9e]

I didn't set up the TPS, I hooked up a voltmeter and watched the voltage as instructed in Chiltons. It did as Chiltons said and regulated up to close to 5 volts. I also checked the resistence and it was not erratic, and increased nice and smooth from idle to WOT. I believe it does have an ISC motor. Chiltons said to override it, I did, and it retracted as it was supposed to. If the ISC motor was bad, wouldn't I have an erratic idle? Something I noticed tonight driving home, I put the PMC on data monitor, 01 (TPS), and the degree at idle was -2.9, I think the lowest it should've gone would be 0.0 degrees, right?[/Quote:2ba50f7f9e]

well with the ISC motor with full extension it would show it like that, if you set it at.5 volts not 5, with ISC motor fully retracted it should be.5 volts and then adjust idle with set screw, should idle 550 or 600 I think. Do you unplud the ISC motor, plug it back in and do an idle relearn, it sounds dumb, but has to be done. Warm up engine, shut it down, cycle key 3 times( off and on, counts as 1 ) start car and let it run for 3 min with out no heat or ac, next turn on ac, let idle 3 min like that, then put foot on the brake and put into gear for 5 min AC still on

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Tuesday, February 5th, 2008 AT 1:34 PM