QX4 engine stumbling

[Scott L]

Greetings...

I've got a 2001 QX4 with ~140,000 miles. About eight months ago it "stumbled" for the first time, going down the freeway. The stumbling feels like a 90% loss of power while running over a washboard, as if it's running out of gas or running on two cylinders. It lasts for 5-10 seconds then all is well again. Since the initial time on the freeway, it happens intermittently, sometimes every day, sometimes not for a week or two. The most frequent time is when the engine is started cold (and not yet driving); or when I've gone a few miles, stopped for 30-45 minutes, and then started up again. It rarely happens on the freeway, and it never happens once the car is full warmed up. Service engine light always comes on.

After the initial time, I got a complete tune-up including new plugs. When it happened a week or two later, I returned to the mechanic and the service code said there was a faulty ignition coil. Replaced that and same problem returned a week later, different cylinder. I decided to live with it, and for the last six months the problem comes and goes for no apparent reason. At one point the engine service light went off on its own, but then returned the next time it happened.

I needed to get an emissions test done, so took it to a different mechanic to just clear the codes. He said the codes indicated a catalytic converter issue and ignition issue, but at this point I'm reluctant to throw more money down the drain. In the meantime, the problem didn't return before I passed the emissions test, but did a day later.

If anyone has thoughts or suggestions on what the problem is and how I might best proceed, I'd love to hear them.

[CanuckQx4]

I had a similar engine power loss problem and mine was resolved with new spark plugs or replacing #1 ignition coil.

The #1 coil (fornt of your car, passenger side) is the only ignition coil that is different than the other 5. When I was changing my plugs because I thought that may be the problem, I noticed my #1 coil pack was very poor condition looking and didnt seem as solid as the others. To my surprise the #1 coil pack was only $70 at crappy tire.

So I changed that coil, and all my plugs, for $125 and my car ran like new again

Just a thought, check the plugs and that specific coil

[CanuckQx4]

Cleaning the MAF sensor if you havent already and possibly simply disconnecting the battery overnight to let the ECU reset may be a good idea.

[Scott L]

Thanks, Canuck. I did replace the #1 coil back when this began, with no help. The MAF sensor hasn't been cleaned, so that looks like a good suggestion. Thanks again.

[CanuckQx4]

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