Need Help on Misfire Problem.......

[Manewaymja2]

Hey guys bought a 1989 GT Mustang with some Mild Mods to engine and sent it to a dyno shop in Kentucky (a guy named Greg at Speedy Dyno to Tune the car for race fuel and Pump gas) Trying to get like at the 450RWHP area. But now he has come up with a problem. Let me explain as he told me and you guys see if you can shed some light on whats going on. Man he has had my car for about a month now and its driving me crazy with frustration. Help Please.

The Car Has: 302-.30 over, 8:1 compression, Hastings rings .17 top, .15 bottom, Tall Ford Racing valve covers-black, Edelbrock Performer RPM aluminum heads, 7/16 head studs w/ 1/2 spacers, Ford Motorsports 1:6 aluminum roller rocker arms, Hardened push rods, Comp roller cam
55 lb. injectors (Big enough Fuel System good for 700hp)
Mac gear drive timing,ProFlow mass air meter, 70mm throttle body
Ford idle air adjuster spacer, Milodon 7-quart oil pan with windage tray
GT-40 lower intake w/ Car tech upper (extruded/honed), High volume oil pump w/ hardened drive shaft, ProCharger P600 9-14 psi w/ 2-core intercooler
MSD 6 boost timing master ignition, MSD Blaster TFI coil
BBK adjustable fuel pressure regulator.
This is what he is experiencing and has done to try and rectify the problem in his own words:
Greg from Speedy here is a list of what we have swapped for the
testing of your car.
Had a weak/low exhaust temp from #3 cylinder. Tried new wire , new plugs
Adjusted valves on pass cylinder. While we had the valve cover off we swapped the #3 injector with the #1 injector. After reassembly of the #3 cly it was within 15 degrees of the other cylinder. Now when on the dyno @ steady state/ similiar to a drive down the road she runs fine below 3500 RPM when accerating above 3500 has a slight miss? that carries all the was to 5600 RPM.
Swapped out the following to try to get rid of the miss.
PCM with know good 1. New 6AL box, Dist module (new motorcraft), Complete dist with new motorcraft parts (module and pick up coil/stator) Ignition wire set, Cap, Rotor

All this time the fuel press is staying within desired range (36
idel climbs to 45 psi under WOT with 6lbs of boost)
The air fuel ratio is 14,25 @ cruise and 11.75 @ WOT. The only thing I could think is the cam is installed out of time??? We also did a clynider leak down on #4 &#3 cly they have 3-5% leakage which is well below the allowable 10
Any ideas are welcomed.
Thanks Greg

So as you guys can see im in need of some help, the Tunner cant even help me

 

[87GT40]

has he ran any cods yet. id start there. also could be a small vac leak. have him hook up a smoke machine to look for one. i assume he obviuosly has the timing set right.

 

[Manewaymja2]

No codes. He will ckeck 4 Vacum leaks. Timing set right.

Anyone else please i need all the help i can get here. Due to this problem my car is still siting there now over 3 weeks. Please Help me anyone

 

[HISSIN50]

If the car is sitting there, how can you work on it or check things? Or are you looking for things to suggest to your tuner?

Were plugs checked and swapped? How about the coil?

 

[Manewaymja2]

Hes doing the work and trying to find help 4 him, as you can see he has already done a few things to try and fix the problem.

 

[HISSIN50]

Did he check the plugs (to be sure they're not platinum and are gapped properly for the blower) or swap a new coil on?

 

[90mustangGT]

Lifter collapse, burnt valve?

A buddy of mine had a similar nightmare miss and it turned out to be a lifter collapse.

 

[Manewaymja2]

Lifter collapse? Sounds possible but will it only happen when the car reaches over 3000rpms? if so then why?
Thanks Allot

 

[1993SSP]

I just posted a thread before reading this one, I too have an annoying miss from 3500 on up. I have drove myself crazy trying to figure my problem out as well

Greg tuned my car, Great guy, knows his stuff and is top notch.

 

[Manewaymja2]

Thats good to know that Greg is a great Tuner. Just really need this slight miss resolved. I will have to wait and see if its the Lifter collapse. Still would like more conformation on the idea and if any other issues can cause this missfire on only one cylinder #3.

Thanks Matt

 

[90mustangGT]

I know that often a lifter that has failed will collapse at low rpm because of lower oil pressure but they can also collapse at a higher RPM due to the increased load as it has to move that pushrod much faster. So it may be a weak lifter, not totally collapsed. One thing to check for once the lifter is out is to be sure the oil passage to that lifter isn't clogged.

 

[Manewaymja2]

Thanks For all the Help please keep it coming. Need it all

 

[Manewaymja2]

Ok I havent heard from Greg as yet but he says he will check everything that was posted and that he also was thinking that if we went as far as to check the lifters he thought it would be a good idea to change all and swap in a cam that was made for Super Charged Motors (Not that a Comp Cam isnt already in the car, but we have no knowledge on this cam).

What do you guys think about that and any more ideas of why the Misfire would be on the #3 Cylinder only as i said in the first Post?

Thanks Matt

 

[HISSIN50]

What do you guys think about that and any more ideas of why the Misfire would be on the #3 Cylinder only as i said in the first Post?

I would bold this or make sure it's explicitly known in the first post. When I read it, I didn't know the misfire was known to only come from cylinder #3. I thought there was an issue with #3, it was fixed, but that a random misfire remained.

 

[Manewaymja2]

Yes the Problem has always been the #3 cylinder and still is even after trying to fix the issue. Need ideas as to what can cause this. so far he has checked what is mentioned in the first post and in the process of checking a lifter and thinking about the cam as well.