View Full Version : Jerking and studdering under heavy load

09-18-2002, 03:45 PM
Under a heavy load (pedal close to the floor :D ) the bird has developed a studder or jerking. It's not mechanical thing (trany or bumps in the road, althow it feels like it's skipping over little bumps). I replaced the plugs and wires about a year ago (8.5mm and plat. plugs) It was running smoothly until now so they should be ok. When the engine is reved (car stopped) it is nice an smooth all the way up the range. I'l guessing it's in the power distribution some where. It kind of cuts out and then it picks up again and cut's out and picks up.....

When driving normaly (not mashing the pedal) you can't even tell something is wrong, drives very normaly.

Any input would be great. I'm sure this has happened to someone before.....


09-19-2002, 01:31 AM
does the car feel like it is cutting out under load? if so i had the same problem. i replaced the plugs and wires with ford parts and haven't had any problems since.

09-19-2002, 01:55 AM
Sorry I can't shed any light on this, but it is exactly the problem my 89 has...under almost all conditions the car drives normally, but occasionally under full boost or when I've got it almost floored going up a long incline, it will kind of jerk or cut in and out....

09-19-2002, 05:38 AM
i had the same problem with my 89. i too thought it was in the distribution because i had new plugs and wires as well. also at idle i could hear a misfire(after market exhaust). it turned out to be a blown head gasket. i knew it was a possibility but i didnt want to believe it.

09-19-2002, 09:07 AM
What brand of plugs did you put in? I made the mistake of installing a set of Bosch Dbl Plats a few years back. They were fine at idle, or just cruisin' around, but if you ever got on it a little more than "normal", the bird would studder, cough, and bog down. I now only use MotorCraft (when I can find them) or AutoLite (which I believe are the same as MotorCraft) Double Platinum.
Another thing to check, if you have recently done some work on the engine, check your wires. I had one wire on the drivers side get a little too close to the exhaust manifold after doing some engine work, and it eventually burned a little pin hole in the insulation. No problem at idle, or when cold, but under load with the engine at temp the wire would arc and the bird would misfire something terrible. Took me several days to track that one down.....

09-19-2002, 10:52 AM
Its definately your plugs and wires. Either they need replacing (did you use bosch)? One of the plug wire boots fell of the plug, or one of the wires is frayed

09-19-2002, 11:09 AM
The plugs I think (I'll have to look it up) are the Motorcraft Plat. ones and the wires are the Magnacore 8.5mm istalled about a year ago.

I don't hear any misfireings any time. It idle's very smoothly. It's a 93 with 99K KM (60K miles)

When I replaced the plugs and wires, I was very happy. Car was more responsive, got much better gas millage and overall better running (engine wise, anyway). I'll take a peek at the wires and plugs and see is anything is obvious.

Thanks everyone

09-19-2002, 12:25 PM
not so much the plugs, more the wires....

When I had my heads reworked, I drove it under boost for about 1000 or so mi. When I finally went WOT, it started bucking just as you stated. Freaked out, checked everything....just the number 6 plug wire boot not totally snapped on to the plug. Its always the simple things that make our cars run the worst.