View Full Version : Bucking Supercoupe, help PLEASE!!! (long)

12-12-2002, 09:42 PM
1990 automatic...

OK I have recently began driving my SC after sitting for about 1-1.5 years...

Before I put it back onthe road I had the bucking 2-3 times, but that was pretty close to before I took it off the road.

Well I began driving it again about 3 weeks ago 20miles to work (one way). I have just replaced motor mounts, plugs (not wires as they "looked" OK...and opened up the exhaust manifolds with a dremel at the collector.

I filled up at the Amoco (I hear its the best quality) last week and got about 260 off the tank and "thought" I felt the bucking once or twice but it only barely did it once... I filed up at same gas station yesterday and noticed it a few miles down the road...

Last night I felt it very violently a few times, and then today it done it at an idle at a stop sign just after leavingthe house before it got warmed up good. It did it a couple of times on the way to work...Then after work it happened very viloently for about a mile almost to the point that I contemplated stopping and having it towed... :mad:

But In made t to the gymn after pulling over for a second and cycling the ignition on and off a few times to run the fuel pump a little more...I was wondewring if the fuel pump going coudl cause this, but I don't think so. I have a fuel filter I'm about to put in it, ad hopefully this is it.

I don't think it's the cam sensor, as my tach is reading just fine.

The difference between my problem and other I did my search for, is that it happens to me under very slight acceleration and/or coasting, and at idle. But if I put it in neutral it seems to rev OK???

Seems to happen most around 40-45... I checked it out in each gear, and in first it is less noticable, but does happen under moderate acceleration. It is worse in other gears...

The first few times I thgouht it may have been tranny slipping tween 3-4, but if I put it in d, it still happened, so...and then the lighter buck (more of a miss??) in 1st

Most of the bucking I read about here seems to be under heavy acceleration/boost.

My only mods are removed air silencer, and that opened exhaust collector.

When doing the motor mounts, it had a rough idle at first, because the SC tube going into the SC top was leaking. I drove it around the block before I realized this, and the idle was rough the whole time, but under acceleration and driving there was no bucking...I coudl only tell it was idling rough.

After tightening that SC tube it was OK, and I drove it about a week without incident. (I used copper sealant on the tubes, as per a few posts I seen here.

Sorry for the novel, but wanted to be sure I covered all the bases...

I am heading to the driveway to replace the fuel filter (hopefully it's that simple) and check wires, connectors, and hosesl; then try that WD40 in that tube behind the SC trick...

I also read that this could be a sign of HGs going???? but the car hasn't been running hot at all, and this happens when still cold and after its warmed up so...any thoguhts on that would be appreciateed also.

Thanks alot guys, ya'll are THE MAN :cool:

When it does start to buck, I can apply more gas and it doesn't stop bucking, I can give it hell, and it stills bucks... it seems that I have to let it run it's course before it stops...

12-12-2002, 11:24 PM
Well, start with the fact that you only have the problem with the car in gear, so it may be the Transmission mount. But that would not explain the odd intermittent pattern of your problem.

So, next consider you're poor gas mileage. 260 miles on a tank is poor, so maybe its the o2 sensors.

I have not had an experience exactly like yours so I can only guess. Perhaps someone else can give you a better diagnosis.

However the trans mount is probably worth changing anyway. Its a job you can do in under an hour and the part is less than 50 dollars, it also only takes minimal tools.

One more thing, are you getting a check engine light? A fuel filter or pump problem will not cause a check engine light to the best of my knowledge.

good luck,

Scott Long
12-13-2002, 12:17 AM

12-13-2002, 02:04 AM
Well, changed the filter out and put some snake oil in the tank just for good measure (b12 chemtool at the Autozone guys sugestion). I usually don't use that sort of thing, but I figured what the hey...

Drove a few miles down the road at all speeds, and a few stops, slow downs and hard accelleration....didn't do it again. I guess time wil tell.

As far as the tranny mount, its OK. It appears "new" and I would assume it had been rebuilt soon beforeI got it, cuz it shifts pretty good, and fluid looked good when I change it.

Rechecked the wires and re-snugged them, connected and re-connected every connector I could get to. I noticed that the ground connector that connected next to the DIS module was badly corroded, so I scrapped it out and brussed of the prongs.
Could have also been a factor I guess, but with the other 20 grounds I doubt it.

Checked the SC/IC tubes and coudln't find evidence of leakage...

Wish it luck fellas.......

David Neibert
12-13-2002, 09:19 AM
I'm betting it's the Spark plug wires too. It doesn't matter how they look. You can damage stock wires just by changing the plugs.


2x 35th
12-13-2002, 02:14 PM
I have a 90 SC as well, and had the exact same symptoms. I changed my plugs and wires AND my cam sensor and haven't had a problem since.

I would recommend doing the Cam Sensor first, it's like a $45 part, and it's a cinch to swap in and out

Hope this helps
-Steve :)

12-13-2002, 11:02 PM
Look at the CID its the thing that looks like it was a distributor. If oil is on the cap it could be leaking out of the blower seal. If oil is under the cap the car will buck. You'll get a CID code if you scan the ECU.

My 90 did it and I had the tell the Dealer what to fix, yes I still shack my head about that!

I hope this helps.

12-14-2002, 12:52 AM
Same here. Had the bucking going on. Had some other work done (valve cover gaskets), and had the magnecor's and plugs done too while they had everything out of the way. No bucking now, much nicer to drive. More responsive. These were the original plugs/wires. Wires looked fine, but one was broken on the inside making sporadic contact, and of course weak when it did. SC keeps getting better and better. ;)

Running right and looking great. Time for the fun stuff. :D

FearThis SC
12-14-2002, 09:48 AM
Originally posted by JAFO
Running right and looking great. Time for the fun stuff. :D
What have you done thus far? I would suggest taking that drive down this way and get your exhaust done, before anything else.


12-14-2002, 10:49 AM
Nothing performance wise yet. The lady that owned the car before was good about oil changes etc, but didn't keep up with much else. I've done the upper/lower ball joints, motor mount, changed all fluids, thermostat, rebuild radiator, hoses, belts, plugs, wires, Eclipse CD, pair of Boston Accoustic speakers, new sub (speakers were blown, HU didn't work)...general stuff that needed to be caught up to date.
I'd like to do the exhaust with Magnaflows first, then ZR intake, gears and 5% pulley. Then carpet, floor mats--cosmetic things. Tranny mount & diff. bushings somewhere along the way, but it feels pretty good now.

12-15-2002, 02:16 PM
If none of that helps try this.....Look and see how much your harmonic balancer is moving....Mine did the EXACT same thing and I smoked the balancer. (The outter ring would move on the inner and screw up the timing, but only under load, not in neutral at first...then...well...it wouldnt start at all.) I am currently making the decision of keeping the car a getting a 1 piece or ordering a stock set from ford and selling the car.

Happy Hunting.

By the way can you let me know what you find at.....
[email protected]