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Discussion Starter · #1 ·
My car just had the HG work done on it, and my mechanic said that he keeps getting an idle surge. He says after it warms up, the idle will hunt up and down, and sometimes it will be ok. He says it seems like it has do do with the AC compressor kicking in... He has bled it, and gotten the air out, and still no luck. I really need your help on this one becasue I am selling the car, and I cannot sell it with this problem. He aslo cannot pull any codes from the computer.

Please help....:)
 

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The two problems I can think of would be clogged PCV valve, though unlikely because your mechanic should have cought that or the idle adjustment screw on the throttle body. Next time it starts hunting around pop the hood and make the adjustment. The screw is located at the top of the throtte body and it is ressesed in. If you wanna try the PCV valve remove it it from the valve cover, just pull it out and slide back the clamp. Shake the valve, if you hear something rattling inside freely then it's ok. Clean the end and blow through it just to make sure :) Hope this helps.
 

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Discussion Starter · #3 ·
I just got off the phone with him....

Checked PCV valve, idle adjustment screw, etc,....He said that he has ran it quite a bit, and that there would be no air in it. He was getting a code 43 and code 44 from his scanner, and that it comes up fuel left bank and fuel right bank.... He said it could be O2 sensors. I am going to pick it up this afternoon and drive it around and see how it is....
 

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hmmmm i'm wondering do we have an idle sensor on our cars????
 

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The idle air control valve controls the amount of air that is bypassed into the intake manifold as controlled by the signals from the PCM in the auto or ECM in the manual. Electrical signals from things like the A/C, gear selector position switch, idle thermosensor, etc go the the PCM and then the PCM tells the idle air control valve how to position itself....so if there are some faulty or missing signals from one of the many sensors you can get an unusual or failed response from the idle air control valve. For example, the idle thermosensor depends or coolant temp to send the proper signal, with air in the system it doesn't get a constant or correct sense of coolant temp (sometimes in air, sometimes immersed in coolant) so surging idle is possibility. However, the IAC valve can also be failed or leaking. I would first check all connectors and hoses, since someone has just pulled your heads and disconnected everything. Surging is not a symptom of misadjusted idle adjusting screw....it means air is being varied into intake manifold by some fairly large amount. The IAC is either moving in response or failure to respond to an electrical signal or it is leaking. Most common failure is thermosensor (or air in system). If this is in the IAC system you should pull a code 14 from the malfunction indicator light
 

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Hey bigdad, u mentioned that a sensor going off may offset the IAC i believe thats what u said, in short do u think if something like the speed sensor going off,(u know when your speedo starts acting up and your D4 light blink) could that in some way affect anything else regarding the idling problem, cuz mines does it from time to time.
 

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The vss doesn't affect the idle control system...the examples I gave were those specific to the idle control system. For example, when the AC kicks in the engine is under greater load so the PCM senses the AC activation and increases idle speed to maintain engine speed. Same thing when you put it in Drive from Park, or when Power Steering pressure goes up in parking (otherwise the car would possibly stall). Most of these signals increase the idle speed as necessary for compensation of an engine load. When the starter is activated there is even bypass to allow easier starting. Surging is most likely to be failures in the IAC valve itself or in the hoses/connections or the fast idle thermovalve (by a faulty coolant sensor or air). There can also be other circuits that could affect idle quality, but most would be fairly constant, like rough stumbling idle from faulty EGR, or PCV valves. The throttle position sensor could possibly be faulty and intermittent, but the problem seems to be related to the AC activation in this guys case, so that is where he should look first....is compressor activation setting off the poor idle? Does the idle drop significantly when AC compressor starts?
 

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Discussion Starter · #8 ·
Well I got my car back and I have not noticed the idle fluctuating yet. However my next problem is the check engine light. My mechanic diagnosed it as a code 43 and 44.... something to do with the fuel delivery system... It is up for sale tomorrow and I cannot sell it with the check engine light on...What a piss off...:(

Bigdad, thanx for your info... I am going to take it to my mechanic tomorrow and see what he makes of it..
 

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if the code is 43 and 44, it is likely the O2 sensor misreading. It may even be ok now (driving and running the engine at 3000 rpm for a while can clear them) and the PCM or ECU just needs to be cleared and reset. Remove the jumpers to diagnose and pull the no. 15 fuse (7.5a) for at least 10 seconds from the under dash box to reset. Then restart engine and run until radiator fan comes on. After hot rev engine to 3000 rpm for 2 minutes in Park. If the check engine light is out you are ok...may still be intermittent due to loose wires though. If still on, further electrical testing of the system is necessary...could be open in wire somewhere, O2 sensor, ECU or PCM, etc ...
 

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Discussion Starter · #10 ·
WEll BIgdad, I tried what you said to do, and the second it hit 3000 rpm, the sensor went off, this was consistenet throughout the evening. It would also go off consitently at about 82km/h (~2200 RPM). What do you make of that? Thanx for your help.. I am getting somewhere I think:rolleyes:
 

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when you say the sensor "went off" do you mean the check engine light went out or on? If the MIL (malfunction indicator light) went out, I would bet your problem is just O2 sensors getting heated up and clearing...Just drive the car for awhile and see if this rectifies itself...this sort of thing sometimes does. You might do some tracing of connectors and try disconnecting and reconnecting them using a bit of conductive grease. I doubt you have a serious problem, but just an annoyance that needs to be found...and I am sure you will with some patience. My son had a similar problem after replacing tranny...kept getting the flashing D4 light, EXCEPT when I cleaned the engine and got the tranny shift solenoid connector wet...went out....when it dried, it came back on...just a poor contact when reconnected by the shop.....
 

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Discussion Starter · #12 ·
Sorry for the poor communication there... I was tired:)

What I meant was the check engine light came on.... The little yellow one on the right side there. So I guess the circumstances were right at that speed or RPM for it to come on. It has never turned off while I have been driving. Only after I have turned the car off and back on agian. And it is like I said, the light is on, I will stop, turn the car off, turn it on again immediately, drive until I hit 80 km/h or 3000 rpm and it will come back every time..... If that sounds like the O2 sensor to you, then I might just replace them and see. Thanx.:)
 

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Just finished writing a big reply and got kicked off the net and lost it all...so here goes again! The codes 43 and 44 are also used for fuel delivery/supply problems...since you don't get the light until the engine is going fast under load, you may have a fuel supply problem...especially if any driveability problems become evident, like stalling, stumbling, rough engine....O2 sensor failures don't affect driveability. Here's what you need to consider on the fuel supply side: fuel pump (probably ok or car wouldn't run), main PGM-FI relay (same), fuel pressure regulator and the fuel filter. The fuel pressure regulator feeds back fuel to the tank when pressure exceeds 43 PSI.........fuel pressure should be between 36-43 psi at the fuel filter service port taken on top of the banjo bolt (with regulator vacuum line disconnected). If lower than 36 psi you may have a clogged filter (easy to replace and pretty cheap $20 or so at non-dealer parts house) or leaking fuel hose or pipe somewhere, or faulty fuel regulator. Occam's razor theory dictates the simpliest things usually are the cause of the problem...You can check fuel pressure regulator by putting on the fuel pressure gauge and read pressure...should be between 44-51 psi, then disconnect the vaccuum line to the fuel pressure regulator and pinch it...pressure should drop to the 36-43 psi range. Reconnect the vaccuum line....pressure should go back up. if not replace fuel pressure regulator. I think you will find your problem in the fuel system delivery noted above.....rots o ruk
 

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Discussion Starter · #14 ·
Well it does not suffer from poor drive ability... no rough idle or stalling or anything...... I was going to go and check the voltage on the o2 sensor this afternoon, and maybe replace the fuel filter as well. Thanx for your help..:)
 

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I kind of doubt that both O2 sensors would go bad at once, but who knows if they somehow became poisoned....more likely some kind of connection fault or the fuel delivery problem I mentioned. One thing for sure, you will figure it out!
 
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