Contour Enthusiasts Group Archives Forums General Troubleshooting Missing at low speed, high load

At the risk of getting hit by our resident search Nazis, I am going to start a post regarding a problem I have had for about 700 miles now with my '96 SE 2.5 ATX with 163,750 miles.

I first noticed a miss every so often when accelerating under high load at low RPM, about 1800-2000. It was just occasional, maybe once or twice in a 25 mile combined city/highway drive. It seemed to get worse over about the next 5 days, so I pulled out my trusty OBDII scan tool and discovered a P0174, bank 2 lean. Since there was no bank 1 error, I swapped out the bank 2 upstream sensor with a new Bosch #13115. I tested the car and cleared all the codes. Now after 1 week and 300 additional miles the miss has gotten worse. The are no new codes present.

I pulled four of the six plugs to do a general condition check and found the plugs to be very much white in appearance. Nearly paper white. The gap is up to about .062"-.064". As I recall when I installed them about 42,000 miles back (with new factory wires) I had set the gaps to .054".

The plugs I was given at the stealership are Motorcraft AGSF32FM. How do these differ from the AWSF32F plugs. Do you believe this is my problem? By the way, I installed a new Sorensen coil pack back about 2500 miles ago when my #2 coil quit firing.

As always, thanks for the help!

Sounds like the plugs could certainly be part of the problem. My stock plugs at under 50K had the ground electrodes scalloped like a spoon. Autolite double platinums, APP764 IIRC, should be your next plug.

You still seem to be running lean, so please also check the brake booster vac line, the PCV system, your air filter, the vac tube under the UIM (just behind the throttle body), and clean the MAF sensor.

Check your plugs after a week of running & if the above doesn't reveal positive results, check your other vac lines & the rigid lines on top of the UIM & thier elbows. They crack sometimes. Run for a week.

Still no joy? tighten the UIM bolts to the top of the specified range, BUT PLEASE NOTE THE RANGE IS IN INCH-POUNDS. If you over tighten them you risk stripping the aluminum head, so be firm but not forceful.

Does anyone out there have info on the Motorcraft model code? I really would like to know what the difference is between the AWSF 32F and AGSF 32FM plugs.

I do have some cracking in the hose under the UIM, it is on my immediate attention list.

Well, it only took about half of my sanity to sort this out, but I finally got to the root of my problem.

I replaced the plugs with new Autolite Double plats (they were worn to .060 gap), and replaced a marginal tube/hose running from the bank 2 valve cover to the accordian tube. The problem didn't go away, although the plugs helped considerably.

Yesterday I had about 130 miles of running to do in the region, and the morning started off with only a slight miss off idle when pulling away from stop lights. I was still not getting any OBDII codes. The problem got steadily worse all day, so I called a friend who is a tech at the local Ford dealership. He went on the Ford Oasis system to check for any new info and his advice was that 80 percent of the issues like the one I descibed to him are Mass Air Sensor failures, so I stopped and picked one up on the way home. I decided to check for codes one more time since the problem had gotten so bad. I finally got one, P0302! This is the same code I had when my coil pack failed a month ago!

I had a #2 plug wire from a set I replaced about 3 years ago still in the garage (sometimes it pays to be a pack rat). I put the old wire on and the problem went away! ARGHHHH!!! I took the new MAS back to the dealer this morning.

I just ordered an new set of Motorcraft wires, they will be in tomorrow. I will now have replaced the entire ignition system in one month's time.

I'll keep on repeating: I love my car, I love my car, I love...

O.K. gang, I replaced the plug wires. I now have a completely new ignition system (within the last couple of months). All problems have dissapeared and the car runs as well or better than I can ever remember it running. Great low end response now! I can even spin the 225/50-15's at a stop light now (about 1 to 1 1/2 revolutions) by stabbing the throttle off idle. Not bad for a 164,000 mile ATX with minimal mods.