1997 QX4 Intermittant stalling at idle

[ianmacdon]

We have a 1997 QX4 with 200K on it, and it looks and drives like new. Lately ( for about 6 months ) it has been intermittantly stalling at red lights , or idle . I changed the wires plugs rotor and distributor cap. I also changed the air filter. Other than the stalling at idle, the truck works excellent. There are no error codes at all and the checkengine light is not on.
I am at my wits end, and my wife is getting concerned that sometimes it stalls going downhill and she may lose steering and brakes. The local mechanics have no idea . I am appealing to this forum for help that hopefully someone has seen this problem and knows exactly what it is.
Also, I cleaned the mass air flow sensor about a month ago using sensor cleaner, and the problem seemed to go away for about 3 weeks, then it came back, so i have no idea if the mass airflow sensor can be intermittant ?? Please, anyone, I need your comments. i will try anything.
Thanks:
Ian

[ianmacdon]

Today I removed the MAF again, and cleaned it with sensor cleaner. i must have sprayed half the can at it. I was confidant the truck would work good for a while, thinking it is an intermittant MAF, but now it works even worse and left my wife stranded in the parking lot , it now keeps stalling and is hard to start. I still have no idea ifthe MAF will cause all of this, and hate to spend a few hundred bucks for nothing., Has anyone ever had a bad maf ?
Thanks

[ianmacdon]

Update : It appears no one reading my posts has had this wierd problem, so I will update you as I go along. Last Sunday, I had a wicked time getting the QX4 to start. Not to mention that I cranked it so much I killed the battery, and it was an old battery so it wouldn't recover , so I had to make a Wal-Mart run with the other car to get a new battery.
After I got that fixed, my neighbor came over to see what I was doing and I showed him the maf, and I disconnected the connector and re-installed it, and then the truck started perfectly.....
I now think that my problem is either a bad connector or an intermittant connection inside the maf.There are no error codes.
I ordered a maf on ebay for about 100 bucks, it should be arriving next week. When I simply swap it out, I will see if the problem disappears, that wll eliminate the actual connector as the problem, but if it re-occurs, i will further investivatge the wiring within the connector. In hindsight, I should really check the wiring first to eliminate the maf, but my experience in troubleshooting electronics makes me think the connector is fine , and the intermittant is within the MAF. When the truck is running normally, I can literally tap on the maf sensor with my nuckles and cause it to begin misfiring and stalling.
I will keep you all posted when I put the maf in.

[ianmacdon]

Well guys, I finally got the MAF which I bought on eBay, and I installed it last night. The QX4 works great ....but, because the problem was sooo intermittant I still didn't trust the maf so I decided to test it for a few days. Then I decided to take the old one to work, where I have access to many troubleshooting aids, as I am am Electronic Tech in the HealthCare field.
First I checked the resistance of the visible elements, and they were both perfect at 20 OHMS, then I decided to check the resistance of the pins on the connector, and I found them very odd...in the meg-ohm range, which I though was strange, and it was not constant.
I couldn't fathom there was anything other than 3 wires inside the sensor, so I put the sensor in the vice, crimped the case and the top popped off.
Inside the sensor there is a very complex circuit, covered in a silicone based moisture pervention semi-liquid.
I then took out the surgical microscope ( which I also have for troubleshooting ) and examined the PC board under high magnification, and low and behold, there it was, a broken wire, not much bigger than a human hair. It was literally laying on the tab, not connected, which explained the intermittant matter of the problem, and which also explained when I tapped on it with my nuckle, it seemed to work for a short time.
WOW. I was so amazed at finding this, I now know the problem is fixed and the SUV isn't going to stall anymore.


I really hope this information proves useful to others in the future.
Ian

[ianmacdon]

I see no one commented on my stalling problem, so i guess that an intermittant mass airflow sensor on a 1997 QX4 is pretty rare. It was a bad solder joint inside the maf . Oh well, I really hope this information is useful to others anyway. Bye