FIXED: Bucking See Last Post

JoePolo

Registered User
So I’ll be driving along fine then all the sudden if it increase throttle the thing starts bucking. No matter what gear I pick, the severity changes with gear obviously. If I fight through it and slowly increase to full throttle it will go away but feels like it’s losing a cylinder. It’s a 90 SC 5 spd. It was parked since 2005. Had new plugs and wires like a month before it got put away in dry storage. Slowly getting worse and more frequent. All fluids changed and fuel filter changed. Fuel system/injector cleaner was added and new fuel (premium) obviously. I’m gonna get a coil pack due to the intermittentness of the problem (comes and goes). I know some of you have stored SCs for sometime or revived some after a long time. Thanks for the advice.
 
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Running the codes may shed light (and save from throwing money/parts at it) - you can also use the opportunity to do a 'cylinder balance' test to see if in fact one or more cylinders have seen better days.

But after 13 yrs. sitting, and since you got rid of the old fuel, I'd be worried about corrosion/grounds etc. and if the system is seeing at least 11.5 volts when running.

These cars hate sitting, and death by being parked is always a risk, I think. Might just need to have some spirited miles put on it.

Do the basics - confirm mice haven't made nests in the intake and squirrels haven't used the exhaust for a pantry ;)
 
Running the codes may shed light (and save from throwing money/parts at it) - you can also use the opportunity to do a 'cylinder balance' test to see if in fact one or more cylinders have seen better days.

But after 13 yrs. sitting, and since you got rid of the old fuel, I'd be worried about corrosion/grounds etc. and if the system is seeing at least 11.5 volts when running.

These cars hate sitting, and death by being parked is always a risk, I think. Might just need to have some spirited miles put on it.

Do the basics - confirm mice haven't made nests in the intake and squirrels haven't used the exhaust for a pantry ;)

The place it was stored there is 0 mice for sure but I’ll double check grounds etc. And will also double check voltage. I agree with the spirited drive thing it seems to do better after I give it to it. Haha
 
Was it run at all during that time? If not, stuck rings, injectors maybe.

Why did the plugs/wires get replaced? Was there an existing issue you were chasing back then?
 
Was it run at all during that time? If not, stuck rings, injectors maybe.

Why did the plugs/wires get replaced? Was there an existing issue you were chasing back then?

No didn’t get run at all. My head did go to fuel because of the clear up at full throttle.
No plugs and wires weren’t for an issue, I changed valve cover gasket and I was there so I did them, it was just routine maintenance.
 
I'd focus on the injectors, and wait on the coil. Problem is, if one or more is bad stuck, you might need to yank them and send them out to be checked/serviced. Even if they free up, they might not flow/spray correctly. Injector cleaner via the fuel tank can only do so much, and too much of it can supposedly raise hell w/catalytic converters.

I'd also check fuel pressure/delivery, and for vacuum leaks from dried out hoses.

Good luck.
 
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I'd focus on the injectors, and wait on the coil. Problem is, if one or more is bad stuck, you might need to yank them and send them out to be checked/serviced. Even if they free up, they might not flow/spray correctly. Injector cleaner via the fuel tank can only do so much, and too much of it can supposedly raise hell w/catalytic converters.

I'd also check for vacuum leaks from dried out hoses.

Good luck.

Thanks for the help. I’m definitely gonna look at fuel delivery now more seriously after this discussion.
 
I had the same problem. One of the spark plug wires was loose on the plug, making spark jump from wire to plug. That cyl would drop out under load only.Hope its that simple
 
I had the same problem. One of the spark plug wires was loose on the plug, making spark jump from wire to plug. That cyl would drop out under load only.Hope its that simple

Thanks will double check all plug wire connections.
 
Update: went to drive it today short trip, and the rack was dead, turned it off really quick at a light to see if it would work upon restart and I couldn’t even get it started again. So I sat for some time cranking, could hear the fuel pump cycling, and the tach flutters when I turned the ignition on. Finally got it running again and here’s my bucking, tach will bounce and like go to 0 every so often then be back then buck and flutter all around. Think I have a bad connection somewhere but where, I assume the tach signal for the gauge is probably the same as the ECU signal.
 
And the routing from coil to cylinder.. backfire is a big hint!
Don't fall for the:

1-2-3
6-5-4 misprint either. Its:

1-2-3
5-6-4

Mine doesn’t backfire at all though so think I’m safe on plug wire firing order, and everything I have is numbered and motorcraft or Ford. Crazy that they misprinted it.
 
Update 7/6/18

Swapped the DIS module today, with a fresh coat of Heat Sink Compound under it. Ran excellent when cold with perfect tach signal, until about one mile from my house (temp starting to rise into 1/4 gauge) tach fluttered two times at a stop light, made the turn and about another half mile down the road completely lost tach, and had major drive-ability issues. Had to limp it home. Cam sensor coming next, not seeing any frayed or damaged wire insulation.
 
Fixed

Swapped out the Cam Position sensor and also checked wiring for Crank sensor and all is good took on a little 5 mile drive and flogged it pretty hard. No issues. Tach works perfectly.
 
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