Engine cuts off while driving. Service engine light on.

Tiny
GACHAGO
  • MEMBER
  • 2001 INFINITI QX
  • 6 CYL
  • 4WD
  • AUTOMATIC
I have an infiniti QX4 2001 thats regularly serviced. For some reason its been cutting cutting off almost like the fuel is not getting where its not getting to. But shortly after it will start up again and drive like it's 100% fine. Pep boys diagnosed it and an erros code came up with the IAC but thats new and so is the computer. They also suggested it could be a probelm with the vaccum in teh air hose but they couldnt quite get to it to make sure. I took it to the infiniti dealer and they said the codes for teh IAC had o be relearned. It thne drove fine on a 2hr trip back to my area and then as I slowed down to it cut off again and this morning cut off thrice. But before the tow truck could get there it started up and drove smoothly back to my house where Im trying to figure out this problem.
Thursday, March 17th, 2011 AT 2:47 PM

11 Replies

Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
It sounds like maybe carbon in the airway leading to the iac. Or a large vacuum leak that's. Intermittent check pcv and egr for normal operations.
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Thursday, March 17th, 2011 AT 2:54 PM
Tiny
MERLIN2021
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Other item is a failing fuel pump, test pressure
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Thursday, March 17th, 2011 AT 2:56 PM
Tiny
GACHAGO
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Thank you kiind sir. The fuel pressure was recently checked when the computer and IAC were replaced and it was 100% fine. I seem to thik it may be more of a vacuum leak as the Pep Boys guys said. They had it for 2 days. Whats is PCV and EGR? How would the vacuum leak be repaired?
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Thursday, March 17th, 2011 AT 3:02 PM
Tiny
MERLIN2021
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Pcv =positive crankcase ventilation, a small vacuum operated valve, egr= exhaust gas recirculation. Another vacuum operated valve at least on most cars I would need to look yours up to make sure. I will recheck after 2:00pm when I get to my main compuer.
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Thursday, March 17th, 2011 AT 3:33 PM
Tiny
GACHAGO
  • MEMBER
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I look forward to hearing your thoughts on how to repair this problem. I'd prefer to do it myself.
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Thursday, March 17th, 2011 AT 3:43 PM
Tiny
MERLIN2021
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Can you post all codes found, I can look these up and see if Pep boys may have overlooked something, Autozone will read codes for free, maybe pepboys too, write them down and post here. It really does sound like an IAC problem more than anything else.
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Thursday, March 17th, 2011 AT 7:08 PM
Tiny
GACHAGO
  • MEMBER
  • 7 POSTS
Pep Boys: P0505 and they said they beleive there's an air vaccum leak but they couldn't get to it hence they suggested the dealer.
Infiniti - diagnosed it as the IAC needing to relearn the codes so they apparently reprogrammed the codes.(But acknowledged the IAC and ECM were new)
2.5hrs later @ Advance Auto Parts showd the following codes:
P0505 -idle air control system
P0732 - Gear 2 incorrect ratio
P0733 - Gear 3 incorrect ratio
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Thursday, March 17th, 2011 AT 7:33 PM
Tiny
GACHAGO
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The receipt from Infiniti reads as follows:
Customer states sees light is on and car cuts off at random crusing and at stop (actually that happened when I left it idling for a while not at stop).
Inspect and found IAC valve out of calibration /proceed to calibrate IAC, reset ECM, perform road test /B1/B2 catlsistic.
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Thursday, March 17th, 2011 AT 7:37 PM
Tiny
MERLIN2021
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On your throttle body there is a vacuum operated idle control check to see if a hose or the control diaphram hold vacuum. A hand operated pump is needed autozone will loan it to you
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Friday, March 18th, 2011 AT 8:39 AM
Tiny
GACHAGO
  • MEMBER
  • 7 POSTS
I just got your reply this morning after enduring the car cutting out on me 4-5 times yesterday? If there is a vacuum what then ie how do you fix it and if there is no vacuum what else would I need to check? Is it possible that a fuel filter replacement could be the fix?
PS I forgot to mention that when it first cut out on me (Friday) I had just driven about 2hrs and was basically at empty for gas. As I came off the exit the first thing I did was fill up on gas and then drove for about 1.5 - 2 miles and as I was turning ino my destination it stalled out on me and thats when my problems began. In addition I've been having this problem for a couple of weeks where every now and again when I turn the ignition nothing happens except the lights on the dash come on (no crank) and then after turning the key in the ignition about twice or thrice it cranks up perfectly like there was never a problem cranking in the first place.
So Im wondering now whether this is all related !Thanks for you advice. Last thing I need to do is spend money I dont have.
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Friday, March 18th, 2011 AT 12:25 PM
Tiny
MERLIN2021
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With a car like yours investing in a hand held scan tool would be wise. It seems your problem could be ignition related if it wouldn't crank. Have the igntion switch and anti theft modules checked. A vacuum leak or bad fuel pump will not cause a no crank.
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Friday, March 18th, 2011 AT 4:03 PM

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