Mechanics

HIGH IDLE ISSUE AND INTERMITTANT SHIFTING CAUSE IAC, TPS?

1999 Buick Century • 170,000 miles

Hello, I have a 99 Buick Century and recently I have experienced very high idle speeds and erratic shifting issues. I have cleaned the IAC valve, and did notice my throttle body was rather dirty on the inside. I had cleaned the throttle body with a cleaner, cleaned the IAC, and started the car. The idle was still high. I disconnected the IAC, the TPS, the air box sensor, the sensor on the air intake tube and the EGR sensor, I thought the car should have shuddered or something, so it ran high still. I connected all the sensors back, started the car and still high. My next thought is to disconnect the IAC alone, then the TPS alone. Is there anything I am missing? I have seen others with the same problem, but have not seen any sort of resolution. I thank you for your assistance.
Dennis
Avatar
Dlvaughn1963
September 24, 2012.



Ok.I'm like running low on funds. LOL and I have been reading about the BG44K that is supposed to be at professional repair centers. Anything on the market that seems to work really well? Something I can get at an automotive store or maybe at walmart?

Tiny
Dlvaughn1963
Oct 16, 2012.
You can buy the 44k on ebay an it works well I used it for many years at the saturn dealerships I worked at.

Saturntech9
Oct 16, 2012.
Will try a cleaner

Tiny
Dlvaughn1963
Oct 16, 2012.
Here's the latest.
After all the replacing of components, I believe I told you the high idle issue is gone, and the next troubling issue was random misfire. To get you up to speed I had done the following: 1. Replaced the plugs, coils, wires
2. Checked for power to the ICM, and it was good.
3. Cleaned the EGR passages and replaced the gasket.
4. Checked the Fuel Injectors for power and operation.
5. Checked the positive terminals on the ICM for power with coils removed all good.
6. Put Seafoam cleaner in fuel tank for first tank after all the maintenance, improved performance, but still had initial ramdom misfire but not as severe as before, and only lasted till the car was warmed up.
7. Replaced the fuel filter ( it was a mess plenty of trashy fluid came out). Replacing the fuel filter has also improved engine performance, although still slight misfire, but even less than before.
8. One more Seafoam application this morning after I filled tank with misfire, and now (fingers crossed) I do not seem to have the misfire. After the Seafoam application in the vac system, and fuel, whatever was there, seems to be gone.
I will update you later for progress.I can say that I have, for the first time, accelerated the car above 90 MPH! I've never been this fast in my car LOL. So acceleration is very peppy, and the car sips fuel. Again a final update later.
Dennis

Tiny
Dlvaughn1963
Oct 26, 2012.
Alright sounds good keep me posted.

Saturntech9
Oct 27, 2012.
Update: Still have random misfire. I'm not sure at this point if the issue is the CAT, or a bad ICM. The car initlally surges when cold, but after about 5 min of running, it still is a little sluggish, but not as bad as before. Anytime the car has sat for more than 20 min, and restarted, the initial engine performance is bad but soon gets better. If the Cat is bad, would it cause these issues?

Tiny
Dlvaughn1963
Dec 4, 2012.
I don't suspect the cat, because I have no Cat codes.

Tiny
Dlvaughn1963
Dec 4, 2012.
Oh and the ONLY things I have not replaced would be the EGR valve Map sensor and the ICM.I really think it has to be vacuum, cause it shudders and misfires as if the Vac hose is removed from the egr.I'm just at a loss.

Tiny
Dlvaughn1963
Dec 4, 2012.
Its not a cat have you replaced the coolant temp sensor yet?It could explain the symptoms.

Saturntech9
Dec 4, 2012.
Ok finally got to changing the cts. How long will it take for the ECM to learn this part, or is there no learning? It still idles erratic at start, but settles quickly. I'm thinking the hose I ordered is not good.

Tiny
Dennislvaughn
Dec 11, 2012.
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