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
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Dlvaughn1963
September 24, 2012.



I'll keep u posted but looks like bad wires.#5 wire when I pull it off the coil does not surge. So will know in a bit.

Tiny
Dlvaughn1963
Oct 13, 2012.
When you did the heads you never changed the spark plugs shame on you especially when you described what they look like. Also keep me posted on ho it works out with the plug wires.I would remove the egr valve clean it and with the egr valve off start the engine for a few seconds. The engine should race and you should hear a loud exhaust leak?That helps blow the loose carbon out that can can make the new egr valve stick.

Saturntech9
Oct 13, 2012.
You must be talking about the the guy doing the engine overhaul. I never did such a thing. : ). I got the wires hope to give you an update tomorrow.
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Tiny
Dlvaughn1963
Oct 13, 2012.
This is exactly why I usually make people start there own questions it just gets way to confusing who did what who iam actually talking to etc. So greghoward please start a question for your car. Start it off by saying this one is for saturntech9 and they will leave the question for. That way I can continue helping you nothing personal its just hard enough helping someone over the internet fix there car but then two different people on the same question that's too much.

Saturntech9
Oct 13, 2012.
Replaced wires seems to be working. Have only had two hiccups in 50 miles of driving, and 8 starts and stops. Looks as if the reset of the wiring of the ignition control module has this possibly (the second problem) for the moment fixed. There's great acceleration and the car sips fuel instead of gulping. I've not seen an issue with the O2 sensor. All is good for now.

Tiny
Dlvaughn1963
Oct 14, 2012.
Thats what we like to hear keep me posted on how it works out.

Saturntech9
Oct 15, 2012.
Ok now I'm stumped.
Ignition system everything has been changed but the ICM. Plugs, wires, coils. Still misfires but is intermittently. Guess on my next few days I will check to make sure it pulses.I did check the contacts on the pink wire.I get 12 volts, and each coil when I pulled them off, I checked for voltage on the contact pins, and they do get 12 volts. The only thing I did not check is the pulse. With a led light. Three fuel injectors I checked on the forward side is pumping fuel. The misfire is very random any clues?

Tiny
Dlvaughn1963
Oct 16, 2012.
Possibly a dirty injector I have seen them cause very random missfires.

Saturntech9
Oct 16, 2012.
So what I need to put some fuel cleaner in the tank?

Tiny
Dlvaughn1963
Oct 16, 2012.
You can try that I would use a product called bg 44k you can get it on ebay. The best way to clean them is have it cleaned by running it off a pressure canister with some cleaner. Plus putting cleaner in the tank.

Saturntech9
Oct 16, 2012.
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