Bucking Problems
 

I just added the following parts to the ol' stang over the (long) winter.

TFS heads (mildly ported)
Performer RPM intake
30 lb injectors
75mm bullet Pro-M (plastic, calibrated for the 30's )
F-cam
roller rockers
190lph pump
Adjustable FPR ( set to 44 psi)
Hedman shorty headers
gutted H-pipe ( smog pump eliminated )
Paxton supercharger @ 7psi

I had the supercharger and headers on last year and it worked great.
The problem I am having now is at cruising speed. It idles, accelerates and decelerates great but when I try to hold a steady speed it bucks terribly. If anybody has some tips as to what could be wrong they would be greatly appreciated.:confused:

Mine does this slightly at cruising. I can feel it, but it's not bad. Does your CE light come on? If it doesn't then that is very weird. Mine also hesitates, then surges sometimes when I'm just taking off in 2nd gear from a roll. I watch the A/F guage when it does this and it's reading totally lean.

Thanks for the reply Blue...

My check engine light doesn't come on. It takes off from a start fine, it just happens when I try to hold a steady speed, and it doesn't seem to matter what RPM its at.

Mine does it too at low rpm's......I was told that it was my F303 cam.

Well, the F cam is certainly no blower cam, but not knocking it either, but I feel that could be part of the problem, also, how old are your engine sensors? especially 02's! I have solved lots of bucking/surging problems just by replacing old sensors.

Run some real good gas and see if that helps, what cc chambers are on those heads?

I was told the f-cam was a decent blower cam by the shop that sold it to me:rolleyes: . Oh well its in there now. Has anyone solved the mystery as to why this cam has these characteristics? Is there anyway to fix or at least lessen the problem?
I run the best gas that I can get around this town and as far as the cc's on the heads...I don't have a clue. I should've checked them before I put them on.:o

I had the same problem two years ago. It turned out to be a new
air meter that was faulty from the start. As soon as I replaced it the problem went away. I assume that your air meter matches your injectors.

My first thought was the MAF too. I don't want to think about that as it took me 3 weeks to get this one!! (one of the perks of living in Canada ). The sheet the sensor came with says it is calibrated for 30lb injectors but who can say for sure if it didn't get damaged in shipping.
I'm going to check out a few other things before I send the MAF back to get checked.

Well, I checked my TPS, cleaned my IAC, adjusted the fuel pressure, installed new wires, cap, and rotor ( It needed them anyways )and checked for any place unmetered air could be getting into the system. The bucking is still there. It doesn't smell like its running rich, but it almost acts as if its loading up. Maybe I'll have to contact the shop that sold me the MAF and see if they can exchange it. Anybody else have any ideas??

I'm running the F-cam with a procharged 351 and have no problems with surging or off-idle stumbles. I had a problem with surging and bucking at 2nd gear accelerations and it turned out to be a bad FMU. I would check to see what your FP is doing under load/boost.

I'm not running an FMU as I thought I would have enough injector to go without. I will try re-installing the FMU tonight to see if it helps.
Thanks for the idea Tony.

Do you have a FP gauge that you can see when driving, if not, I would get one, it help to solve problems.

I re-installed the FMU lastnight and it improved things ALOT. Its still not perfect but at least its driveable now. I will have to get a guage I can see from inside the car like Tony suggested and maybe I can tune out the rest.
Thanks for your help guys.

The F-cam is a good blower cam by the way.

I think your fuel pressure is too high. Try lowering it.

Thanks for all the help guys,

I dropped the fuel pressure back to 39lbs when I re-installed the FMU and it was still bucking a bit. Today ( just got back from a week of holidays ) I bumped it back up to about 43lbs and the problem is pretty much gone now.