engine miss at cruise

extech · Apr 14th, 2004, 09:39 PM

A while back I asked a question about what would make engine miss at cruise.
This would be on a 1997 nissan frontier 2.4l auto with OD.check engine light
pretty much stayed on all the time. At various times it would flash while I was driving. Through several responses I determined it was not flashing fault codes, but was flashing because the ecm was seeing miss fires.I checked what I could check with a limited amount of tools, consisting of a good multimeter. Checked the 02 sensor input and output. As the 02 sensors are heated I first checked for 12v supply, ok. Then checked to see of I had a variable voltage coming from the 02 sensor, it would read from 2.5v to 4.2. always flutchuating up and down. So I determined it to be good. I then removed egr checked for carbon build up, ok. Checked egr tube for obstructions, cracks etc, good. Removed dist cap, checked cap and rotor. good. installed new plugs and ohmed out plug wires., good.
Tonight I proceeded to remove breather housing. Using a stetescope, I listened to injectors one by one, they sound like they were working ok( listened for a solid clicking sound at the base of each injector). I disconnected each injector while engine was running, and checked for rpm drop. All good. I removed the ecm ( by taking the passenger seat out), that certainly is an engineering marvil. removed connectors checked for corrosion or bent pins. Looked good. Then I unhooked the egr vacume line and test drove. seemed to improved a little, but still not satisfied.
Last week lewisinc gave a me a trouble shooting tree for a pathfinder, but found the diagnostics to the the same only a little different, so didn't get anywhere there.
Then out of the blue, while test driving, the mil light went off and truck started to run good. So now I am in it up to my neck. If I don't find something soon, I think I might lose it.
So I have just one more question. Is the maf located on the side of the throttle body? and does It really cost 800.00 ?. Any responses greatly appreciated
Extech

jadcock · Apr 15th, 2004, 10:07 AM

I'd keep looking at the ignition system. At night, or in a dark garage, run the engine with the hood up and lightly mist the spark plug wires with a spray bottle. See if you get arcing or anything else. Even though the wires show good continuity, there may be small breaks in the insulation. Also check the boots carefully, and the old plugs for signs of arcing at the plug.

The MAF is integral to the throttle body on the KA24E engines. Look straight down the throttle body (from the front of the truck)...the "large" throttle bore will be to the right, and the very small MAF sensor bore (only 1/4 or 1/2") is on the left. I don't know the price, but I don't think it's available separately, since it's a part of the throttle body.

Good luck.

extech · Apr 16th, 2004, 06:34 PM

Quote:

Originally Posted by jadcock

I'd keep looking at the ignition system. At night, or in a dark garage, run the engine with the hood up and lightly mist the spark plug wires with a spray bottle. See if you get arcing or anything else. Even though the wires show good continuity, there may be small breaks in the insulation. Also check the boots carefully, and the old plugs for signs of arcing at the plug.

The MAF is integral to the throttle body on the KA24E engines. Look straight down the throttle body (from the front of the truck)...the "large" throttle bore will be to the right, and the very small MAF sensor bore (only 1/4 or 1/2") is on the left. I don't know the price, but I don't think it's available separately, since it's a part of the throttle body.

Good luck.

yep you are one hundred percent right. that explains why the maf wouldn't come out of the throttle body. However after going through what checks I mentioned in the prev post. The mil light went out and it started running like it should. for now anyway. I don't know what I fixed but maybe someday I will figure it out. thanks for the reply. as you know sometimes a bit of info here and there can help- a whole lot
Extech