Hesitation when shifting gears hard....

[Aliate X]

Hesitation when shifting gears hard....**UPDATE** PROBLEM FIXED!!!

**UPDATE PROBLEM FIXED**, Solution at bottom of page.


This is a 93 5.0 LX, I have owned for almost 2 years.

First when I start the car up, no matter how warm it is, if it has been sitting for more than 5 minutes it, it sputters and hesitates extremely bad if I give it gas. When driving down the road if you floor it, the RPMs struggle to climb, they go at a constant rate but extremely slow. After a few mins of driving, the problem is gone.

Also, even after the problem has passed and I have been driving around, if I am on it and I shift hard, say from 1st to 2nd, 1st will pull hard, then you slam second and it just boggs down and does the same thing as before, RPMs struggle to climb at a constant rate, if you come off the gas for a few seconds and then floor it again, it pulls fine. This problem is really hard to track down, so far Ive replaced :

Fuel Filter
255lph Fuel Pump
BBK Adjustable Fuel Pressure Regulator
Cap
Wires
Rotor
Plugs
ECT sensor (the one near the lower intake, not on the TB)
TFI module

2 things that I think may be the problem are either bad O2 sensors or improperly installed AFPR. When I tried to change the fuel pressure, the furthest it would go down with the vac off would be aboue 37psi, any further and the screw would come out. This concerned me.

The second thing I think it is are my O2 sensors. I have not changed them in the 2 years I have had the car, and when I took them out, they had a white film on the upper part of the actual sensor.

I have been trying to find this problem forever and I would appriciate anyones help, thanks a lot.

To give you guys an idea of how bad my car is running, I took it to the track tonight, heres my best run.

R/T - .676
60' - 2.365
330 - 6.667
1/8 - 10.283
MPH - 67.78
1000 - 13.394
1/4 - 16.009
MPH - 86.24

=( Im not a bad driver, if I shifted too fast it would just bog until I came off the gas, this run was on 275 Nitto 555R's.

 

[wyominghotwheel]

it sounds like it may be your fuel pressure regulator..............what is your timing set to? hotwheels of insanemustangs.com

 

[Aliate X]

timing is around 15 degrees, is there any way that the BBK AFPR could have been installed incorrectly? Or may I have damaged the EGR when I was changing the AFPR?

 

[Aliate X]

ALSO, one or 2 of my rockers are ticking bad, would this cause any problems like I am having?

 

[HISSIN50]

Your O2's are not used at WOT, so if issues happen at WOT, the O2's are not necessarily involved.

I would be all over that fuel pressure issue and go from there.

Good luck.

 

[Aliate X]

What should i do with the fuel pressure?

 

[cjman15]

Check it?

 

[Aliate X]

Check it?

Like I said its at about 37 with vac off.

 

[vikingpower]

Hey, I had a serious problem with my 89, the fuse link lead from the battery for the fuel pump burned up and disintegrated a few months ago. You should check that and the rest of the wiring to the fuel pump. I also had to repair some of the wiring in the fuel pump/ tank sending unit harness when I put in my 255 pump.

 

[Aliate X]

UPDATE PROBLEM FIXED ---

Today I cleaned the MAF and my K&N. The MAF wires were basically wrapped in grease. The filter had huge spots of dirt/grease which Im sure contributed to the problem.

No more hesitation upon startup, no more bogging between gears or going from half to WOT. Nothing, not only that, but all around power is awesome, Im going to the track on wednesday Ill let you guys know what kinda improvements I see.

 

[HISSIN50]

If the problem arises again, I would reclean the MAF. You probably reoiled your air filter after cleaning it; oil can be slung off the element and back onto the MAF.

Good luck.

 

[Aliate X]

Thanks