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89 supreme wierd idle then dies


dru_666

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hello. just got this car. seems pretty good. i got new plugs, wires and o2 sensor. cleaned out the Tb and iac sensor. but AFTER it warms up when i stop, the idle drops then goes up then drops then goes back up, goes down to around 400rpm and up to about 900rpm. then when i take my foot off the brake and give it gas, it dies. starts up pretty good though. i have a code 34; knock sensor thing, anyone have any clues with this could be? thanx

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Do you mean code 34 or 43? 43 is the knock sensor and you typed 34. 34 is the MAP sensor. What you are descibing sounds like that MAP sensor which is the code 34. Lemme know if you meant 34 or 43.

 

Robby

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okay, here ya go. Based on the code 43, your problem is either the Electronic Spark Control (ESC) knock sensor or you ECM. Im guessin the ESC knock sensor. Okay, spark knock is when the mixture in the combustion chamber detonates before the spark plug creates the spark. So, the knock sensor will recognize this and send a singal to your ECM to tell it to retard the timing up to 15 degrees, to elimate the knock. When the knock sensor goes bad, it will tell the ECM to always retard the timing. Thus, giving you sluggish performance. So, all you have to do is replace teh knock sensor. Its located on the engine block, probably on the rear or crank pulley side of the motor. The sensor is a black round thing that screws into the block. The entire sensor has a circular shape, but on top, there a hex shape, so it can be detached using a wrech. On the outside of edge of the sensor where it screws in, will have many little marks in it, like teeth, but they are more like little identions. Anyway, disconnect the battery if you want, I wouldnt. There will be a wire running into the top of the sensor, disconnect that, then simply unscrew the sensor. But the new one in the opposite of how you took the old one off. Hope this helps, if you have any other questions, let me know.

 

Robby

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well it could be an coil or ignition module but to check the knock sensor cause at autozone it costs 39.99 so i would at least chekc to see if it is bad

 

 

here is what ya do.....

 

1. take it off the motor

2.drain coolant

3. get a voltmeter

4.switch the vlotmeter to the lowest voltage scale and connect the negative probe to the ground and postive to positive

5.with voltmeter connected to the sensor gently tap the end of the sensor with a hammer or similar device and if the volts fluctuasts then the sensor is good if it doesn't get a new one

 

 

a tip get a 1/4 inch pipe plug so you don't have to drain all the coolant

 

 

hope this helps

 

-jeremy-

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to be honest in stead of just shelling out 40 bucks i would go and take your map sensor to like an autozone and have that looked at first cause it seems like it could be your map sensor i mean autozone does it for free so i would check it just my 2 cents

 

jeremy

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Well.. I would hold on there before shelling out $$ for a new sensor.. There are a number of things that could set off that code which doesn't mean automatically that the sensor is bad.. In fact I've had codes go off on me (like knock sensor) because of simple things related to Emission control problems. Additional steps I would take is to make sure all the things you replaced or cleaned (O2 Sensor, TB, IAC valve) were put back into place properly and are functioning.. IAC valve is a tricky little, flimsy bitch. If you handeled it a bit rough you can easily damage, which would set off the yo-yoing of your idle.

 

If on cold start your idle is yo-yoing or shooting up high (and then slowly falling back down) then take a close look at IAC valve, Throttle Position Sensor and Vacuum lines.

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hey robby...dont make me smack you..(smack smack)..you just decribed the crank position sensor to him.......the knock sensor is near the crank sensor on the 3.1..(backside of motor against the fire wall). it's a silver metal can type sensor with 1 wire running to it...it threads into the block similar to a oil pressure sensor. and as far as the advice for testing at auto zone..go for it...in fact they can test the knock sensor, the crank sensor, and the map sensor

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hey robby...dont make me smack you..(smack smack)..you just decribed the crank position sensor to him.......the knock sensor is near the crank sensor on the 3.1..(backside of motor against the fire wall). it's a silver metal can type sensor with 1 wire running to it...it threads into the block similar to a oil pressure sensor. and as far as the advice for testing at auto zone..go for it...in fact they can test the knock sensor, the crank sensor, and the map sensor

 

I was going by the pic in my Haynes manual. I know Haynes is not the best, but its all I got a college. And the crank sensor is very different, from the pics, than what I desribed. Well on a second look, I didnt do a good job desribing it. Well, I meant to descibe the knock sensor. Sorry for the confusion. And, yes Drache Rott, you can smack me for that.

 

Robby

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heh..I gave up on that haynes manuel a while back....the fireing orders are wrong and all kinds of specs are wrong.....they are good for other cars but thry dropped the ball with the 2.8/3.1 motors...and the discription you gave was actuly fairly accurate for the crank sensor.... small and black slides into the block and is held in with 1 bolt....

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