Car is bucking under load...need help..

89SCK@t

Registered User
Kinda long guys, sorry.

Ok, I was finally able to get my bird to pass emissions with an outstanding score. But the score made me uneasy. At idle i had 0% CO2 and 16 HC PPM and at 2500 "highway speed" i had .01% CO2 and 15 HC PPM. Not saying thats bad, but before I got my car tested, it was, and still is, bucking really bad.

The saturday before I got tested, I had highflow cats welded in and newer O2 sensors put in. The O2 sensors were from my XR7 with about 10K miles on em. The car started to act funny after I got back to base, and hasnt been running right since. I decided to unplug the O2 sensors yesterday, thinking that could be the problem, but alas, its not.

The only thing I changed within the last week is the Cats and O2 sensors. I did change the Oil and tranny oil, but that was after it started bucking.

I did check to see if was possibly the DIS or Coil, but it isnt either one of them. I havent changed the plugs or wires, I'm waiting for TBird88 to respond to my email for downtubes for the Kooks headers, and it will be done all at once.

The only problem is that the car wasnt doing this before I put the Cats or O2 sensors in. I was thinking that the Cats could be reversed. Is that a possibility? Could that be the cause of the problem? Any help is appreciated.

Thanks,
Stephen
 
When the car starts bucking like that shut the engine off and see if it restarts easy, if it acts like the engine is out of time by cranking over very hard the cam sensor is shot.
When you shut it off and if it acts like its really hard to turn over just turn the key off and then try again, eventually the comp will geuss right and the engine will fire right up. Thats a feature built into the comp so you dont get stranded if the cam sensor goes out. The comp will geuss right 1 in 3 times of a restart when the cam sensor fails or the wiring to it.:)
 
Thanks Mike 38SC. I dont know if its the cam sensor, I dont get a CE light or nothing.

To add to the description, when I do normal driving, there is no problem. When I start creating boost is when the bucking happens. I mean once the gauge goes past 0, a hair past it, it starts to buck and sound like a lawnmower at once. I hope i dont confuse anyone...when im accelerating normal, no boost, it sounds fine, but once the boost kicks in it sounds like a lawnmower, or a 2-cycle.

Any help is appreciated.

Thanks,
Stephen
 
How do you know the DIS and Coil are not the problem? If it sounds like its popping, MOST of the time there is a problem in the ignition. It could however be starving for fuel or air. Check your filters. Then check your IC tubes and make sure they were not moved. Did you jack with the EGR?
 
I agree, sounds like ignition,. dis, plugs, or wires.


`I have seen a clogged fuel filter do the same also.
 
Chris Walker - I did the plug wire pulling to see if there was any variance in the engine and there wasnt. Im not saying that it isnt, but I disagree on that fact. I am changing the DIS and Coil today, so I'll let you know on that one.

I am going to be changing the fuel pump and filter here in the next month, so if it the filter, then it will have to wait. Bills come first, then food, then car...*sigh* I need a second or third job.

thanks guys,
stephen
 
Stephen,

99.9% of the time bucking under a load is caused by spark plug wires, spark plugs or clogged fuel filter (in that order). The way you checked the wires is not going work, unless it's also missing with no load on the engine.

David
 
Dude, I didnt catch if your car was an auto or not... Get a buddie and soak the wires down with a spray bottle. Wait a minute and then put a load on the engine. Do it at nite and it will light up. If your gonna put new DIS on it. USE THE ONE FROM FORD. Trust me. I can not stress this enough. Dont waste your time on Auto Zone crap. I saw a low mile one on E-bay with the coil for like $50.00 (I think) two weeks ago. A fuel filter is A LOT cheaper then all the rest.
 
David Neibert - Yeah, its missing as its idling as well. just noticed it today.

Chris Walker - The DIS and Coil I got are from my XR7 that Im parting out. Low miles on both of em.

The only thing that is bothering me, is now Im starting to worry about why I saw 4 DIS and 3 Coils in the trunk when I bought the car...

stephen
 
Just do the stop and restart test I mentioned earlier it costs nothing and you dont even have to work on the car to do it.
When it bucks like that just shut it off and try to restart it, if it cranks hard shut off the ignition and try again. Keep doing that until the engine cranks right and starts up. Should the car act just as I described that proves the cam sensor is out. My sensor did'nt set a code either but thats what was bad and my car acted just like yours except I'm not sure about the restarting part because you havent tried it yet.
Could be something else but the test I described is easy to do and costs nothing yet it will either point the finger at the cam sensor or it will eliminate it as a suspect.:)
 
Figured it out

well not really, but I was assuming it was the DIS or the coil pack. So I replaced both of em, and used them from the dead cat. Some dielectric grease and the bird fired right up. boost is hitting 10lbs quick, and running like a champ. Now all i gotta do is replace the plugs, wires, crank sensor, cam sensor, and i should be good for a while. But one thing still worries me about the amount of DIS's I found throughout the car after I bought it. Everysingle one of them is a motorcraft dis, and they are all bad. I guess I'll find out soon enough...

Now I gotta figure out why I'm burning the stock clutch, when I'm at full boost in 2nd, 3rd, and 4th....:rolleyes:

stephen
 
maf

i had a car do the same thing with a maf sensor. you can usually look at them and see if it is broken. also, as mentioned above, fuel pump, fuel filter, air filter, dis box, wires, plugs, tps, injector.
 
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