04 Infiniti Qx4 Surging Idle

[alexk243]

So I have spent a lot of time reading all the posts on this, but I am stuck...

Repair: Idle Air Control Valve replaced due to failure to idle (then car sat for 6-8 months on a maintainer.... which may have failed, jumped and ran)

Currently: runs and drive, power level seems low, engine idles at 1600-2000rpm and surges from 1500-2200rpm, when in gear the RPMs go down but if you let off the brake the car wants to go quickly.

What I've done:
-Found large vacuum leak, fixed
-Tested TPS - checked out (.55v at idle, <4v at WOT engine off)
-Tested MAF - checked out (1-2v at idle, 3-4v at 1/4 throttle engine on)
-Inspected for additional vacuum leak - none
-Clean airbox, air lines and anything prior to Throttle body
-Wiped clean throttle body
-Unhooked battery for 12+ hours
-"Attempted" to complete the relearn process (how-to-ecu-relearning-procedures-t445702.html) but cannot get the "service engine soon" (CEL) to flash, I suspected that maybe the battery voltage was too low so I attached a charger during the process. Went through the process and this time it did start flashing... but didn't stop, just alternated between a slow flash for approx 10 seconds then a quick flash for approx 10 seconds. I turned the car on and the CEL appeared to echo the surging on the engine in no real pattern (sounds weird I know...). Re-stared and the CEL is off... no codes stored with OBDII scanner.

I am lost and not sure what else to check... I am going to try another 12+ hours unhooked battery then try the relearn again. I found it odd that fixing the vacuum leak did not correct the surging issue.

Would appreciate any help. Been researching on here and trying my hand at it for two days now.

[mdmellott]

'04 Infinity QX4 ? I have an '02 Pathfinder. Mine does not have a drive-by-wire TPS like the '03 and later models but I have recently read through the procedures for testing the TPS components and the relearning procedures for the IAC valve on those later Pathfinder models and thought they might be the same or similar to the QX4. However, before I go any further, I am stumped on one basic issue. I can find no information on Infinity dealership websites, Infinity OEM parts websites, or a service manual on this NICOclub website that would indicate Infinity ever made a 2004 QX4. 2003 was the last year I can find indicated that Infinity made the QX4.

[alexk243]

I'm sorry... It's a 2002 Infiniti Qx4 and it has a mechanical throttle body

[mdmellott]

That makes a big difference and the relearning procedure you followed does not apply. The process is similar in some ways but differs in others. For one, the TPS assembly on your '02 QX4 is the only adjustable component in the engine control system. To check it and if necessary adjust it, you will need a multi-meter to check for continuity and a couple of feeler gauges (.05mm and .15mm) The IAC valve relearn procedure follows a similar pattern of process steps as the drive-by-wire system process you were trying to perform but there won't be any pumping the accelerator 5 times within 5 seconds. Instead you will be disconnecting the throttle position sensor connector and then reconnecting it within 5 seconds. The TPS check, adjustment, and memory reset procedure can be found on the '02 QX4 factory service manual, Engine Control System, page EC-121. Do that procedure step first. Next, you can perform the IAC valve relearn procedure found on page EC-70 of the manual. Click on the following link to bring up the Engine Control System section of the manual. https://www.nicoclub.com/service-manual ... 002/EC.pdf These procedures are exactly like those for my '02 Pathfinder which I just performed last week. These are fairly straight forward procedures. Good luck and welcome to NICOclub.

One more note regarding the TPS: In the procedure for checking continuity between pins 5 and 6 on the throttle position switch; That's the lower grey connector you have to remove. For the relearn procedure, you will be disconnecting and reconnecting the upper brown connector of the throttle position sensor on the TPS assembly. There are two (I think) 7mm screws (maybe 8mm) on the body of the TPS assembly you will have to loosen if adjustment is needed to rotate the TPS assembly in order to dial in the continuity checks you will make with the feeler gauges pinched between the throttle stopper screw and throttle drum contact point.

[alexk243]

Ok, Tried the new procedure... twice and no difference in the idle. Still 1600+ at idle with surging.

Was able to get the throttle body set using the multi-meter and continuity test, but didn't seem to make a difference after both of the learning procedures.

[mdmellott]

The Basic Service Procedure steps, after the relearn procedure has failed, indicates replacing the IACV. It may be bad and with your a multi-meter you can test it. Unplug the connector from the IACV. Measure the resistance across terminals 1 and 2, 2 and 3, 4 and 5, 5 and 6. The resistance of a good valve motor should be approximately 20 to 24 ohms across each pair. I have read other's posts that state even if the resistance values measure good at the time you measure them, the IACV may be intermittently operating bad. One thing that can kill the IACV is a leaking gasket between the valve body and the throttle body. This gasket separates air flow and coolant flow through the valve body. I found that testing the resistance measurements of the IACV stepper motor was a bit of a pain because you can't see the terminal pins given the angle of the installed motor. It may be easier just to remove the two screws mounting the motor to the valve body so that you can pull the motor out and easily check the resistance across the terminal pins and at the same time you will be able to see if there are any indications that the pintle at the end of the motor or the air flow cavity within the valve body is wet with coolant. I replaced the gasket in mine two weeks ago because it was showing signs of failure. Fortunately, I got it in time before it did damage to the IACV motor.

[alexk243]

Ok, Ill give that a shot. Thank you so much for the info!

The IACV was replaced within a year to fix a no-idle issue though (I did not do this repair so not sure the details).

[rgk]

If what mdmellot says is true, and the idle relearn procedure is the same as for the 02 Pathfinder, then you have to follow the instructions to the letter. That means if the instructions say to drive the car for ten minutes, you better get your stopwatch out and drive it for at least ten minutes. Otherwise the procedure won't work. Been there, done that.

Don't skip the pre-conditioning steps on EC-69:

PRE-CONDITIONING
Before performing “Idle Air Volume Learning”, make sure that all of the following conditions are satisfied.

Learning will be cancelled if any of the following conditions are missed for even a moment.

I Battery voltage: More than 12.9V (At idle)
I Engine coolant temperature: 70 - 99°C (158 - 210°F)
I PNP switch: ON
I Electric load switch: OFF
(Air conditioner, headlamp, rear window defogger)
On vehicles equipped with daytime light systems, if the parking brake is applied before the engine is started the headlamp will not illuminate.
I Cooling fan motor: Not operating
I Steering wheel: Neutral (Straight-ahead position)
I Vehicle speed: Stopped
I Transmission: Warmed-up
For A/T models with CONSULT-II, drive vehicle until “FLUID TEMP SE” in “DATA MONITOR” mode of “A/T” system indicates less than 0.9V.
For A/T models without CONSULT-II and M/T models, drive vehicle for 10 minutes.