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TPS Sensor cause rough idle?


bikemikey

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In some of my previous posts I talked about a rough idle and the things I've done. One of the few things I have not done is consider the TPS. I went into the diagnostics mode and checked the TPS for smoothness, it seemed to be okay. I also checked the ED01 for voltage and it showed .42, the manual shows it is suppose to from 0-5.100, is this .42 okay, the engine was not running for these tests. Thanks

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I didn't think it was the TPS, just thought I'd check. I hope it's not that little magnet , the camshaft interrupter, I just changed out the water pump, I was right there, could of fixed it then but I did not realize it was there until later. Once the car is warmed up, it runs pretty good down the road. I think this car sat for a long time, maybe the valve guides are gummed up. could be internal, hope not. Anyway, I'll let you if I find out anything. Thanks

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John, This has nothing to do with the TPS, but I read where if you accelerate the engine and all is well until it gets back to idle, it could be the IAC valve. My problem starts when the engine goes into closed loop mode, the loop light will light up as well as the 02 light, I've cleaned the IAC valve twice. I don't understand how this valve works, is it normally closed or open on a cold engine, does it retract or extend to close or open. I'm thinking maybe I can take the valve off on a cold engine , leave wires connected, have someone turn on the key to see if valve will function, that is if it works that way, or does the engine have to be hot? Mike

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I think I found the problem , a dirty TB , it wasn't the IAC. After cleaning the TB , the engine ran a lot better. This TB had been cleaned, sprayed, about three months ago, I guess we didn't do a good enough job. I thinking now to pull the TB and give it a thorough cleaning with a tooth brush and also to get to the backside of the plate. Does anyone know if this TB has a protective coating inside like a ford. Thanks

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Just for reference, the IAC extends to slow the idle and retracts to speed it up. The tapered end extends into a hole in the casting where the air flows around the throttle blade to allow computer idle control. It works like a giant needle jet. I "think" it is a stepper motor and the counts are related to the pulses required to open the valve.

If you decide to remove the throttle body, be prepared to deal with the two steel coolant tubes that connect to the bottom of the T/B. Generally not fun.

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Thanks for telling me about those water lines, I did not realize they were there. After watching a forum on how to clean the throttle plate, I went ahead and cleaned it again, this time I got behind the plate with a tooth brush, it was still dirty. I might be wrong, but I think you can take off the Maf sensor casing which would put me closer to the throttle plate for a better inspection. I might do that instead of taking the whole TB off the engine. Mike

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Yes, it will be vastly easier with the MAF housing removed. The four mounting screws are non-magnetic stainless steel so be prepared with something underneath to catch them if dropped. Hard to retrieve. If they have never been off before, they may be a little stubborn so be sure to use a good fitting screwdiver and it sometimes helps to work them back and forth if very stiff. I use one of those hand impact drivers when at the junkyard.

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I think I found the problem , a dirty TB , it wasn't the IAC. After cleaning the TB , the engine ran a lot better. This TB had been cleaned, sprayed, about three months ago, I guess we didn't do a good enough job. I thinking now to pull the TB and give it a thorough cleaning with a tooth brush and also to get to the backside of the plate. Does anyone know if this TB has a protective coating inside like a ford. Thanks
I hate to be negative but I can't see how cleaning the throttle body and plate are going to make much of a difference in improving a poor performing engine. Certainly not enough difference to go to the trouble of pulling it off and scrubbing it with a toothbrush. On the other hand it won't hurt to have a really clean throttle body.
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I know about those little screws getting lost, I've already had to go to the bolt store to buy more. I'll probably just pull the Maf housing and clean the TB the best I can and leave it at that, the engine seems to idle a little better with the cleaning I've already done. I also decided to buy some GB remanufactured fuel injectors, I could have an imbalance problem that's small enough not to show up under diagnostics. I should have them installed in a couple of days. I'll let you know what I find out. Mike

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Have not yet checked the compression, but I think I will after I install the injectors if that does not fix the problem. I had thought about a burnt valve, but the idle is fine when cold, and okay at operating temperature, it's just when the temperature starts to get warm right at closed loop, in between, but it still could be a burnt valve.

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