Bucking/Misfire

G

GatorGlassRon

Registered User
My car out of nowhere just started to misfire and buck very bad under any load.
It will start up every time and idle fine, but if you even sit in park and hold RPM's at 2000 or even 2500 it starts to misfire and buck like crazy....I can drive it but can barely touch the gas with out it popping and misfiring. Any help would be appreciated...
 
I'm not going to explain this because the search function is available to those who must know why... but.. replace your cam sensor. :cool:

OK. just unplug it first. If the problem clears up, then replace it. Do a search on "unplug cam sensor" for what to expect.
 
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I had a DIS module fail and cause the exact same symptoms, except it started misfiring, bucking, and backfiring around 3K under load. I always look at what is cheapest and easiest to test/replace first, and before doing a 4-hour tune-up on the thing, for the cost of a DIS module and cam sensor, and as easy as they are to change, I would do those first. Even if it doesn't fix the problem, they are both common parts to fail, and now you will have them to test or in case it fails in the future.
 
I did plugs/wires about 3 months ago. Used brand new ford wires and ngk plugs gapped at .35

Just changed the cam sensor about 30 min ago and no change. The only work I did was clean the air filter. It is a modified SC with a MPX and supporting hardware. Was running fine till I pulled it in my shop just to change out the air filter. Maybe the coil pack???
 
These coil packs rarely fail.

Could have tested the cam sensor by just unplugging it and seeing if the issues went away.

Ignition modules fail, but this doesn't seem to match the symptoms that closely. Still, could be the module.

I would think crank sensor is very possible. If that is involved, the harmonic damper might be broken. Good time to check that the crank pulley doesn't wobble and that the bolt in the center is still present and not broken.

The car needs both of those items to run.

Did you make sure that the PCV fresh air inlet tube is connected to the underside of the intake pipe? It's easy to forget hooking that back up, which lets unmetered air bypass the MAF.
 
Doubt it's the crank sensor...check to see if a plug wire got burnt or one of the plug wire boots is loose. It will be easier to see if you have a plug wire arcing if you look at the running motor in the dark. Also take a look at the portion of the wiring harness going down to the crank sensor that gets close to the supercharger belt. Seen a few SCs where the belt rubbed through the crank sensor harness and ran like you are describing.

David
 
What dave said. :) If it was running fine before the air filter change then I would say maybe a vacuum line, is the MAF now in backwards (assuming you have a CAI), or you disturbed a plug wire(s) and now it is leaking.
 
90sc35thann said:
What dave said. :) If it was running fine before the air filter change then I would say maybe a vacuum line, is the MAF now in backwards (assuming you have a CAI), or you disturbed a plug wire(s) and now it is leaking.
Click to expand...

Going off of what Rob mentioned above, make sure the MAF sensor lead is completely plugged into the MAF sensor. I had this problem and the car ran like absolute garbage for the 10 seconds it was running before i shut it off.
 
GatorGlassRon said:
I did plugs/wires about 3 months ago. Used brand new ford wires and ngk plugs gapped at .35

Just changed the cam sensor about 30 min ago and no change. The only work I did was clean the air filter. It is a modified SC with a MPX and supporting hardware. Was running fine till I pulled it in my shop just to change out the air filter. Maybe the coil pack???
Click to expand...

Gaps a bit narrow, but won't hurt overall. Be sure your plug boots clicked into place. If your hands didn't ache after attaching the wires... you probably didn't get them seated.. :D

My guess is its something at/around where you changed the air filter. MAF perhaps? MAF issues usually set a code. Also, coil packs rarely go bad. Kinda doubt its the crank sensor either. Thats usually a no-start and no-run.
 
I changed my plugs n wires...2 months later it was doing this same thing because a wire was stuck on the header.
 
I unplugged the mass air flow sensor and it cleared up. So I am guessing that the sensor is bad. Even though I only took off the air cleaner and not the tube with the mass air meter. I am going to try cleaning the sensor element first then buy the mass air sensor if it does not work.
 
No one has a mass air sensor in stock and will not be able to get a new one until next week. Found one at a bone yard this morning and cleaned it with mass air sensor cleaner and installed. Still same issue. Plug it in = running like crap, then I unplug it and runs smooth.
 
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