Hello all!
Here are the details on my car:2001 QX4 4 wheel drive version49,xxx miles Kansas City, MO
Here is my issue...Around a month ago I started having an idle problem with my qx4. Normal idle is around 700 to 800 rpms. I noticed once around a month ago my car was idling pretty high... around 2000 rpms... maybe even a little higher. So, when I let off the brake, it was like I was pressing the gas a little bit. When I put the car into park, the idle would go up even a little bit more... getting close to 3,000 rpm's. I would rev the engine a little bit while in park hoping it would drop back down to a normal range.... it did not. I was in a hurry, so I just turned the car off and went on with my business for the day. When I turned the car back on later in the day, the idle was normal (700-800), but the check engine soon light was on. I took it to the Infiniti Dealer and the first time they did not find anything... they just reset the check engine light. Less than a week later, same thing happened. It started to idle really high again. While it was doing this, no lights came on, but after I turned the car off and then back on, the check engine soon light came on, but the idle was fine again. So, I took back to the dealership again and this time they found some valve that caused the light to come on. They replaced this timing valve for about 50 bucks and I was on my happy way thinking this was fixed. Well, it has been about 3 weeks and the past 2 days I have had the exact same idle issue. The only difference now is that the check engine light does not come on when I restart the car.
Here are the details in the past couple of days:I will leave work around 5pm and return home to my place about 5:15 or 5:20pm. I live in a condo so I would leave my car running in park while I went in to get my mail (2minutes max). I would return to my car, put in reverse to back up some, then put into drive. While driving I would notice I would not be stepping on the gas at all yet the car would take off as if I were stepping on it a little bit and the rpms were around 2,000. I would get it into my garage, put into park and the rpm's would shoop up a little bit more. I reved the engine some, but it would always return to the high idle. I then put it into reverse like an idiot and because of the high idle, it shifted into gear really hard... probably not so good on the ole transmission. I put it back into park, turned off, turned back on and everything was fine. This has happened the past 2 days.
Any help would be greatly appreciated. I'm afraid the dealer won't be able to find what the issue is unless they can duplicate it and we all know when you take the car to the dealer it never acts up.
Thanks all!Doug
2001 QX4 Electrical Idle Issue... Please Help!
-
driverdriver
- Posts: 3397
- Joined: Fri Aug 01, 2003 10:36 am
- Car: NICO's longtime resident Canuck!!!
- Contact:
-
SpecDRacing
- Posts: 351
- Joined: Mon Apr 25, 2005 3:36 pm
Re: 2001 QX4 Electrical Idle Issue... Please Help! (dougdude)
That "valve thingy" that they replaced.....could you get a copy of the Consult II printout next time. If it said "shift solenoid" (I doubt for $50 bucks) or IAC then maybe the problem lies elsewhere.
2001 QX4's dont have the same problems as the older models. I cant remember if that was the year that you could get either the VG33 and VQ35 or not...its been a little while since I've worked on these. If you have the VG33 (3.3L)engine, then I'd check the Throttle Positioning Sensor. If you have the VQ35 (3.5L) then I'd have them check for wiring issues. The hard thing about an odd occuring instance is that it not always happens when we need it to (speaking from a dealer standpoint). The best would be to take it to them as its idling high and not shut the engine off.
The reason for the MIL to come on after you cut the car off and back on is because the system that is malfunctioning works under, whats known as, two trip logic. Some malfunctions will cause the light to come on immediately, while others need to happen several times consecutively for a code to set. I must also ask had any recent service work been performed, durring your ownership or just prior too. THere are so many variables that could cause this. If we could see the codes that were given as they are stated ont he printout and maybe the freeze frame data, we may be able to help. This one unfortunately may need to be left up to the dealer, as without the vehicle in our hands, we would have no way of testing this for different scenarios.
Engine hot? Cold? Early in the drive or after hours of running? Thanks!
2001 QX4's dont have the same problems as the older models. I cant remember if that was the year that you could get either the VG33 and VQ35 or not...its been a little while since I've worked on these. If you have the VG33 (3.3L)engine, then I'd check the Throttle Positioning Sensor. If you have the VQ35 (3.5L) then I'd have them check for wiring issues. The hard thing about an odd occuring instance is that it not always happens when we need it to (speaking from a dealer standpoint). The best would be to take it to them as its idling high and not shut the engine off.
The reason for the MIL to come on after you cut the car off and back on is because the system that is malfunctioning works under, whats known as, two trip logic. Some malfunctions will cause the light to come on immediately, while others need to happen several times consecutively for a code to set. I must also ask had any recent service work been performed, durring your ownership or just prior too. THere are so many variables that could cause this. If we could see the codes that were given as they are stated ont he printout and maybe the freeze frame data, we may be able to help. This one unfortunately may need to be left up to the dealer, as without the vehicle in our hands, we would have no way of testing this for different scenarios.
Engine hot? Cold? Early in the drive or after hours of running? Thanks!
-
SpecDRacing
- Posts: 351
- Joined: Mon Apr 25, 2005 3:36 pm
Re: 2001 QX4 Electrical Idle Issue... Please Help! (dougdude)
Oh, and by the way....that "timming valve" is a common component to fail on the newer QX4's and some G35's. This valve means you have the VQ35 engine.
Quick explanation of that valve.....
Your engine has variable cam timing on both banks. There is one of these valves and one sensor per bank. The sensors appear as INT TIM SENSOR/CIR (actual printout) on the Consult if they malfunction. Those sensors tell the computer where the cam is at so it can figure its relative position to the crank. Under heavy throttle, the ECM sees the need for a more advanced intake cam timing, and operates an INTAKE TIMING VALVE using oil preasure to adjust the opening time of the engine valves earlier or later.
EXAMPLE: At idle, your cams are in near perfect alignment with your crank, so if you were to watch the intake timing at idle, it would bounce around 0-1 degrees of advance...0 because there is no advance at idle. If you were to raise the RPMS to 2500, the cam timing would change to 20 degrees or more. That meaning that the valve is opening sooner than it would at idle because the engine demands more air. The higher the RPM, the faster intake charge (speed of air into the cylander) and this type of system tries to take full advantage of the everchanging velocities of airflow through a manifold.
PHEW! So now that you've gotten a little crash course on Intake Valve Timing, and how it works on the new Nissans. Here's a possibility (not an answer) as to what might be happening. Infrequent oil changes leave deposits in the system. On this engine, even 3500 mile intervals have shown to accumulate deposits. These deposits (also refered to as buildup or crud) can clog passageways. The intake timing valves on the front of your engine have pencil lead sized passage ways for oil to travel through. This oil is under preasure, but if a deposit becomes large enough, even the high preasure cant force the oil past those deposits. If the ECM commands "x" amount of oil preasure through the intake timing valve and it doesnt actually happen, the intake timing sensor sees no change in the operation of valve timing and inturn that little light on the dash comes on (MIL).
What can happen if something isnt working right:
-If the sensor is malfunctioning, it will give a WAY wrong reading. At idle it may read something like 97 degrees of intake valve timing when its actualy 0 degrees.-If the Solenoid goes bad, improper oil preasure can be sent to the intake timing valve which wont allow the computer to perate the cam timing as it should. The ECM may command 60% duty cycle to the solenoid, but no change in valve timing occurs. (This solenoid adjusts the oil preasure to the intake timing valve to get the desired cam position)-If the Intake Timing Valve goes bad, then the oil preasure is getting there, but the valve isnt functioning right. This valve is the actual unit that does the work to allow the cam timing to change.
I hope this helps everyone out on how the Intake Valve Timing System works on the VQ35DE and similar engines. This is a bit indepth for this topic, but the relation is...if one or more of those three components are malfunctioning, an improper cam shift will occur, which can cause high/low idle. Most cases, no change occurs as the computer does not allow cam timing operation to change if it sees a malfunction, but if the valve is sticking, then the engine will idle high and the computer wont be able to correct it. You may need the other valve replaced as well.
Sorry for the long post, and I hope this help!
Quick explanation of that valve.....
Your engine has variable cam timing on both banks. There is one of these valves and one sensor per bank. The sensors appear as INT TIM SENSOR/CIR (actual printout) on the Consult if they malfunction. Those sensors tell the computer where the cam is at so it can figure its relative position to the crank. Under heavy throttle, the ECM sees the need for a more advanced intake cam timing, and operates an INTAKE TIMING VALVE using oil preasure to adjust the opening time of the engine valves earlier or later.
EXAMPLE: At idle, your cams are in near perfect alignment with your crank, so if you were to watch the intake timing at idle, it would bounce around 0-1 degrees of advance...0 because there is no advance at idle. If you were to raise the RPMS to 2500, the cam timing would change to 20 degrees or more. That meaning that the valve is opening sooner than it would at idle because the engine demands more air. The higher the RPM, the faster intake charge (speed of air into the cylander) and this type of system tries to take full advantage of the everchanging velocities of airflow through a manifold.
PHEW! So now that you've gotten a little crash course on Intake Valve Timing, and how it works on the new Nissans. Here's a possibility (not an answer) as to what might be happening. Infrequent oil changes leave deposits in the system. On this engine, even 3500 mile intervals have shown to accumulate deposits. These deposits (also refered to as buildup or crud) can clog passageways. The intake timing valves on the front of your engine have pencil lead sized passage ways for oil to travel through. This oil is under preasure, but if a deposit becomes large enough, even the high preasure cant force the oil past those deposits. If the ECM commands "x" amount of oil preasure through the intake timing valve and it doesnt actually happen, the intake timing sensor sees no change in the operation of valve timing and inturn that little light on the dash comes on (MIL).
What can happen if something isnt working right:
-If the sensor is malfunctioning, it will give a WAY wrong reading. At idle it may read something like 97 degrees of intake valve timing when its actualy 0 degrees.-If the Solenoid goes bad, improper oil preasure can be sent to the intake timing valve which wont allow the computer to perate the cam timing as it should. The ECM may command 60% duty cycle to the solenoid, but no change in valve timing occurs. (This solenoid adjusts the oil preasure to the intake timing valve to get the desired cam position)-If the Intake Timing Valve goes bad, then the oil preasure is getting there, but the valve isnt functioning right. This valve is the actual unit that does the work to allow the cam timing to change.
I hope this helps everyone out on how the Intake Valve Timing System works on the VQ35DE and similar engines. This is a bit indepth for this topic, but the relation is...if one or more of those three components are malfunctioning, an improper cam shift will occur, which can cause high/low idle. Most cases, no change occurs as the computer does not allow cam timing operation to change if it sees a malfunction, but if the valve is sticking, then the engine will idle high and the computer wont be able to correct it. You may need the other valve replaced as well.
Sorry for the long post, and I hope this help!