So for the past few weeks my 1998 Infiniti QX4 (125000 miles) has been stalling at lights and when idling. It only happens after warming up, but then happens at most stops. When stopped at lights, RPM is at about 7-800, but then it will stagger and drop to 0. Sometimes I have time to tap the gas and bring it back up, but it usually just stalls. I first figured it to be the MAF because of all of the similar problems on forums like this so I bought some cleaner and tried that..nothing. Took it to a repair shop, they diagnosed it and test drove it, nothing. I told them it happens after warming up and wanted the MAF checked. They said that it was normal and they also checked and replaced an old fuel filter and added some conditioner in the fuel. Drove it today thinking it would be fine, but after 10 minutes of driving, it was back at it.
No codes come up and we have checked multiple times.
What else could it be? I am really just lost.
98 QX4 stalls at idle, staggers
Re: 98 QX4 stalls at idle, staggers
check your vacuum lines?
Re: 98 QX4 stalls at idle, staggers
As said check for vacuum leaks with a propane bottle. Propane not lit, move propane nozzle around vacuum lines with a rise in engine RPM a leak is found.
Check for a stuck EGR, at idle bang the EGR with a hammer slightly to see if carbon removes.
Check IAC, Idle air. The valve bypasses the throttle at idle.
Verify idle RPM at 650-750 RPM
Fuel delivery, and fuel filter are clean and the lines are pressurized, a quick check is to squeeze the lines feeling for resistance that is a pressure build up. Best to use a gauge.
Often over looked is the interior of the distributor. When dusty the LED components cannot read the light because of dirt and the main transistor lose the ability of amplifying and/or switching.
Pull the cap and at the very least blow low pressure compressed air. If you get a reddish dusting effect, pull the components and clean them, then blow it out at least yearly..
Check the static and dynamic timing using a timing light and verify that the timing is correct at idle and verify the timing advances when you open the throttle.
You may have to chalk the marks to see them, light on #1 at idle should be at the mark that indicates your timing in the book and when you rev it up that mark will move
Verify all aspects if idle does not improve check your transmission torque converter for nor releasing lock up, but only after the rest has been verified.
Check for a stuck EGR, at idle bang the EGR with a hammer slightly to see if carbon removes.
Check IAC, Idle air. The valve bypasses the throttle at idle.
Verify idle RPM at 650-750 RPM
Fuel delivery, and fuel filter are clean and the lines are pressurized, a quick check is to squeeze the lines feeling for resistance that is a pressure build up. Best to use a gauge.
Often over looked is the interior of the distributor. When dusty the LED components cannot read the light because of dirt and the main transistor lose the ability of amplifying and/or switching.
Pull the cap and at the very least blow low pressure compressed air. If you get a reddish dusting effect, pull the components and clean them, then blow it out at least yearly..
Check the static and dynamic timing using a timing light and verify that the timing is correct at idle and verify the timing advances when you open the throttle.
You may have to chalk the marks to see them, light on #1 at idle should be at the mark that indicates your timing in the book and when you rev it up that mark will move
Verify all aspects if idle does not improve check your transmission torque converter for nor releasing lock up, but only after the rest has been verified.
Re: 98 QX4 stalls at idle, staggers
I am not the most knowledgeable when it comes to cars. The EGR valve. When you say bang on it and see if carbon removes, what should I be looking for? A rise or drop in RPMs?
How do I check the IAC valve?
This video shows almost exactly what my car's RPMs is doing. I watched it without sound so I dont know what the person is saying, but after warming up (10 minutes or so of driving) it will do this at stop lights unless I hit the gas. If i dont catch it fast enough when it drops, it will tall.
Video:
http://www.youtube.com/watch?v=FUWHMO0qGb0
Also, I do not have access to a lot of tools and such. I have a hammer, wrenches, screwdriver, etc, but not too much more than that. I will probably pick up some more things today including some carb cleaner for the iac valve.
How do I check the IAC valve?
This video shows almost exactly what my car's RPMs is doing. I watched it without sound so I dont know what the person is saying, but after warming up (10 minutes or so of driving) it will do this at stop lights unless I hit the gas. If i dont catch it fast enough when it drops, it will tall.
Video:
http://www.youtube.com/watch?v=FUWHMO0qGb0
Also, I do not have access to a lot of tools and such. I have a hammer, wrenches, screwdriver, etc, but not too much more than that. I will probably pick up some more things today including some carb cleaner for the iac valve.
Last edited by ewall88 on Thu Aug 25, 2011 6:52 pm, edited 1 time in total.
Re: 98 QX4 stalls at idle, staggers
Okay, I was able to drive it a bit more today. In park and neutral RPM was at around 700, when in drive and idling, the RPMs drop to 500-600. Sometimes it will just sit there, but after a while it will slightly bounce up and down and then give out and fight me to die. I realized that the problem is more intermittent than I previously may have implied. I can sit through some lights hovering at 550 RPM, but every so often it will just drop and lose power. The longer I drive the vehicle the more often it seems to do it, but it is still intermittent and only after sitting at a light for a while. I have to constantly give it gas. When I started it up today and accelerated, the car "bucked" a little and did not accelerate smoothly. It did this again a little later when accelerating from a stop. I stalled at one point and really struggled to get it started again. I had to keep pumping gas into it and switch to drive to get it going again otherwise it stalled. I bought some carb cleaner and I am hoping to take a look at the IAC valve and clean it out. I've never done it before but I am sure I can find some sort of walkthrough. I'll also take a look at the EGR.
Any other suggestions?
Any other suggestions?
Re: 98 QX4 stalls at idle, staggers
Sure sounds like the idle air control valve that comes into play when the throttle plate is closed, when you are off the gas. Look in your manual for this valve, problem takes place when it is carboned up, a cleaning or replacement may fix the problem.
Idle and just off idle are affected by carbon, even your inlet housing where the throttle is the TPS and its affliate switches. Pull the air filter off, the hose to the intake and have a peak. If it is black carburettor cleaner is needed, if the intake is dirty chances are the the idle control valve is blackeded too.
Idle and just off idle are affected by carbon, even your inlet housing where the throttle is the TPS and its affliate switches. Pull the air filter off, the hose to the intake and have a peak. If it is black carburettor cleaner is needed, if the intake is dirty chances are the the idle control valve is blackeded too.
Re: 98 QX4 stalls at idle, staggers
Does anyone know a good walkthrough or guide for the best/easiest way to clean/replace the idle control valve?
Re: 98 QX4 stalls at idle, staggers
ewall can you identify the idle air on your vehicle? The manual has a layout sketch identifying things, compare that to your car and see if you can actually touch the valve. Likely it is plugged and stuck, check out the holes for carbon black, if there it is dirty and need a cleaning or to be tossed. While your at it go through the other things mentioned with you book at your side to identify things.
With gasoline these days it is easy to foul little bitty holes up. When you get then clean operating your car with a little MMO or Seafoam or 2 stroke oil can help but the operative word is little.
Marine grade 2 stoke oil about 5 oz to a full tank does wonder to the upper cylinder are and don't use high test if your engine dos not require it. This will cause more carbon fouling to the engine.
No manual, download one from here
With gasoline these days it is easy to foul little bitty holes up. When you get then clean operating your car with a little MMO or Seafoam or 2 stroke oil can help but the operative word is little.
Marine grade 2 stoke oil about 5 oz to a full tank does wonder to the upper cylinder are and don't use high test if your engine dos not require it. This will cause more carbon fouling to the engine.
No manual, download one from here
Re: 98 QX4 stalls at idle, staggers
Okay, I think I know where the IAC valve is. Unfortunately, it seems like it is in an inconvenient location... From what I understand, i need to disconnect all of the tubes connected to it, remove it from the engine and spray it clean with carburetor or throttle cleaner (or what you recommended), but not too much. Just enough to get it clean.
Anything else? As you can see, I am very new to cars, but I am trying to do more and more to learn for myself.
Should I do this as well?
how-to-clean-3-3l-throttle-body-t428817.html
Anything else? As you can see, I am very new to cars, but I am trying to do more and more to learn for myself.
Should I do this as well?
how-to-clean-3-3l-throttle-body-t428817.html
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Re: 98 QX4 stalls at idle, staggers
Certainly try cleaning your throttle body, it's a 5-10 minute thing to do. It can't hurt, just make sure the intake tube makes a proper seal when you put it back on. I'm not at all familiar with the VG33 engine so can't offer much more advise, sorry. What type of "fuel conditioner" did you add?
Re: 98 QX4 stalls at idle, staggers
If you clean the throttle body with carb cleaner, remove the conduit up to the metal throttle body, pick a rag under the threshold of the throttle body, use an old long handle tooth brush that is clean.
Engine off. Spray inside, open throttle to full and hold open, spray, then brush every surface including the throttle plate both sides. Spray agin, close throttle plate let sit for 5 minutes, come back re spray and look for more carbon especially where the throttle plates rests around the circumference.
Try opening and closing the throttle plate, do you feel sticking? You should not, but if you do re clean. When done the inside bore of the tunnel and the plate will be shiny and clean. The further down your intake throttle you can not brush clean but you can spray with cleaner let sit examine then put everything back and try to start the engine.
It will take a couple times to have enough fuel over power that chemical soup and carbon crap that would run down into the fire chambers. But when running be gentle with the throttle until your running on gasoline, then goose it. A little Seafoam now in the gas tank would help keep it clean, A LITTLE.
remove the rag and button her up, make sure the air conduit is tight and no leaks, change the air filter if not done in a while.
With everything buttoned up now liberally clean the outside right side of the throttle area with that cleaner but be stingy on using it. Let dry then spray a little WD40 onto the bearings and pins and spring, just a bit
The cleaner will remove grime, the WD40 will displace water and lubricate.
As to the IAC, use Carb cleaner, wrap the valve with a rag to hold the chemical nar the valve, let sit, respray, blow out with compressed air, make sure it is dry, re install. Check out the hoses for carbon, if any spray with cleaner until wet, test it, examine until all carbon is gone, reassemble.
The EGR is a bit easier to work your magic, at warm up, at idle, take a hammer and give it (EGR) a few light raps with the hammer, just enough to vibrate that round dish and if any carbon is in there it will be sucked into the motor, keep lightly hitting it, the idle may cough and fart if so the EGR is getting rid of crap, continue rapping that EGR until the idle returns to normal.
If the motor dies, open the throttle wide open engine off, then with 1/3 throttle open try starting, if it starts give it a few quick revs, the idle will come back to normal.
Get back to that EGR and hit it again, if idle stays the EGR is clean enough for idle control. Now maintain it.
The hitting will work sometime, and if you cannot clean the EGR that way you have no choice but to remove it, open it, clean it...or replace it. And if you are lax on servicing it time will cause you to buy another EGR.
The amount of PM is determined by time and distance and the amount of actual careful work that is done when doing the PM. Most guys that do actual work on their own vehicle do that job better than a professional, not because the pro is no good but the guy doing the work is doing something that he enjoys and it is his. As DIY many go further than what the pro would do. These PMs do make a difference and the work facing you is very dependent on the condition of the parts you are about to pull apart and clean.
Carbon is a tough material. It may not be removed with a single cleaning effort, how much is there and for how long will play a critical part in removing it. Be sure you do not reshape, chip, destroy the metal parts of the engine. You want to remove carbon build up. If your engine is carbon fouled using full strength Seafoam or any carb cleaner must be used with care and use a little at a time.
Carbon while being removed is an inactive substance with a very active fuel mixture. Removing carbon from an older vehicle must be done in a delicate no event manner by diluting Seafoam for example in a full tank of gas instead of sucking in a 1/2 bottle through a vacuum line. A 1/2 bottle with a full tank will remove the carbon build up over time as the tank empties and will not damage gaskets, seals or leave chunks of carbon particles around to block passages.
Be careful, be purposeful and take your time.
Engine off. Spray inside, open throttle to full and hold open, spray, then brush every surface including the throttle plate both sides. Spray agin, close throttle plate let sit for 5 minutes, come back re spray and look for more carbon especially where the throttle plates rests around the circumference.
Try opening and closing the throttle plate, do you feel sticking? You should not, but if you do re clean. When done the inside bore of the tunnel and the plate will be shiny and clean. The further down your intake throttle you can not brush clean but you can spray with cleaner let sit examine then put everything back and try to start the engine.
It will take a couple times to have enough fuel over power that chemical soup and carbon crap that would run down into the fire chambers. But when running be gentle with the throttle until your running on gasoline, then goose it. A little Seafoam now in the gas tank would help keep it clean, A LITTLE.
remove the rag and button her up, make sure the air conduit is tight and no leaks, change the air filter if not done in a while.
With everything buttoned up now liberally clean the outside right side of the throttle area with that cleaner but be stingy on using it. Let dry then spray a little WD40 onto the bearings and pins and spring, just a bit
The cleaner will remove grime, the WD40 will displace water and lubricate.
As to the IAC, use Carb cleaner, wrap the valve with a rag to hold the chemical nar the valve, let sit, respray, blow out with compressed air, make sure it is dry, re install. Check out the hoses for carbon, if any spray with cleaner until wet, test it, examine until all carbon is gone, reassemble.
The EGR is a bit easier to work your magic, at warm up, at idle, take a hammer and give it (EGR) a few light raps with the hammer, just enough to vibrate that round dish and if any carbon is in there it will be sucked into the motor, keep lightly hitting it, the idle may cough and fart if so the EGR is getting rid of crap, continue rapping that EGR until the idle returns to normal.
If the motor dies, open the throttle wide open engine off, then with 1/3 throttle open try starting, if it starts give it a few quick revs, the idle will come back to normal.
Get back to that EGR and hit it again, if idle stays the EGR is clean enough for idle control. Now maintain it.
The hitting will work sometime, and if you cannot clean the EGR that way you have no choice but to remove it, open it, clean it...or replace it. And if you are lax on servicing it time will cause you to buy another EGR.
The amount of PM is determined by time and distance and the amount of actual careful work that is done when doing the PM. Most guys that do actual work on their own vehicle do that job better than a professional, not because the pro is no good but the guy doing the work is doing something that he enjoys and it is his. As DIY many go further than what the pro would do. These PMs do make a difference and the work facing you is very dependent on the condition of the parts you are about to pull apart and clean.
Carbon is a tough material. It may not be removed with a single cleaning effort, how much is there and for how long will play a critical part in removing it. Be sure you do not reshape, chip, destroy the metal parts of the engine. You want to remove carbon build up. If your engine is carbon fouled using full strength Seafoam or any carb cleaner must be used with care and use a little at a time.
Carbon while being removed is an inactive substance with a very active fuel mixture. Removing carbon from an older vehicle must be done in a delicate no event manner by diluting Seafoam for example in a full tank of gas instead of sucking in a 1/2 bottle through a vacuum line. A 1/2 bottle with a full tank will remove the carbon build up over time as the tank empties and will not damage gaskets, seals or leave chunks of carbon particles around to block passages.
Be careful, be purposeful and take your time.