Sorry just venting, Im getting sick of it. I mean the car runs great when it wants to then just acts up. I cant seem to find the problem. First off its an 87' TPI motor w/ 5 speed. It is modified, But what i cant seem to understand is, When i gun it(track)(usually happens after 2nd-3rd) It starts to miss or just fall flat on its face. This just happened about a month ago, 2 days ago i thought it could of been a bad ignition coil(saw it leaking current), then i changed it and the problem still occurs, I figured it could be the knock sensor, retarding the timing excessively for some reason, But then i disconnected it and its still happening, What i dont understand is, The car idles beautifully(even when revved)but when i gun it at 2nd and once the RPM goes high it seems to missfire badly, Checked the fuel pressure and its a good 48psi. Dont see any vacuum leaks, so what could it be. 3 months ago i had a bad header gasket leak on the #8th cylinder and i ran it for about a week, Could this have burnt the valve and cause the problem? Could it be a small problem as the timing being off. I tried adjusting it. If timing was off, can a motor idle really well and missfire when gunned? Id appreciate any help and hopefully this problem can be fixed BTW its a MAF vehicle

 

I see one of two things happening here:
1.)Your fuel pressure fine at idle or cruising but is dropping off as the demand increases, as WOT speed runs.(Tape the gage to the windshield and run it.)(My pick...)
2.) "valve float". At high speeds with weak stock springs and especially with your roller cam, the springs allow the lifters to jump off the nose of the cam, only to be hit by it again on its way back up before the valve even seats. Bleeding cylinder pressure and missing and popping.(install good spring, there's a lot that fit w/o machining.
**Ignition probs are seen throught the entire rpm range most often, unless revving past 6500 or forced induction.

 

How is first and 4th gear?
Take it out on the highway and run in 4th gear from 1.5K up to 5.5K and let us know how it runs, if there is any hesitation, sputtering, etc.....

It can idle and rev perfect with TPS and timing problems since there isn't a load on the engine.

 

It has a high lift cam, the forgot the specs, but its a accel 74211 cam, and i do have their Double springs, I was thinking about valve float as well. One thing which im really thinking is the distributor itself, I mean its a Replacement from Autozone and its been replaced once already(about 5 months old) Motor itself has about 1,200 miles. On first gear its fine for the most part, SOMETIMES it use to missfire on first,Id rather not go up to 4th since when at 3rd it missfires really bad. There are time when i just gunn it(at second) and the car falls flat on its face and it makes a quick HSSSSSSSSS sound and the tires screetch as if i stomped on the brake, Thanx for the replies and help, if anything else comes to mind i appreciate it.

 

Well just checked the distributor and it is working including the ignition control module, I saw that #1 and #3 wires were completely burnt and was arcing through. I put in new wires, cleaned the rotor(minor carbon ) set the timing at 4 degrees BTDC. I tested it out and begged for it to stop it from hitting itself flat in the face, heres the result.

As i drove in first gear, notice a great deal of improvement in performance but once i hit second and gunned it problem was still there, Guess i can try mounting the fuel gauge and see what the PSI is at, What PSI would it be at at WOT? This is annoying and im tired

 

I'd advance the timing till you start to hear gas ping then back it off till it goes away.
Is your TPS set right? IAC clean and adjusted? Does the car run rich at idle? Big cam creates less vacuum at idle which makes the FP higher than normal.

 

74211 camshaft specs

Duration Lift Lobe Sep
Int / Exh Int / Exh

211/219 0.500/0.525 112

Your pressure looks ok. Stock is 45 psi I believe.

Get a scantool and warm the car up. Set it so the idle is at around 20-30 IAC counts after you clean it out. TPS should be around 0.54. Also you need to have the ignition on so you can read the TPS. It should have a nice clean sweep from foot off to mashing it. Timing should be set before all this at 6 deg.

 

TPS was adjusted about 6 months ago, IAC was cleaned as well. The car is VERY responsive, guess i should try to check it again, thanx guys

 

Just Tested the TPS and its at .60 v. I read that it should be between .54-.56, But this couldnt have been the problem, could it? I mean there were times when i launched on 1st and there were no problems. aagggggghhhh

 

For later cars it is 0.6 and for your year it is 0.54 v. Could it be bad injectors? Bad EPROM calibration?

If your fuel pressure is ok, next thing to check is the injectors. take them to some tech college and have them flow check them. That or find some injection service to flow them so you know if that is the problem. Next, if that does not cure it, you might need a new EPROM. Maybe at the time when it was ok, atmospheric conditions were ok but now it is not. Call up Lingenfelter because that is the designer of the cam. Also, if you have ruled out mechanical, try get hold of www.fasterproms.com and see if they think it is a chip issue.

 

Fuel pressure readings at idle are MEANINGLESS. You MUST know what the fuel pressure is at WOT, at high RPMs.

Personally, I duck tape the gague to the windshield (temporarily!) and make a few runs. If your motor is outrunning the fuel system it'll be obvious. Fuel pressure will nose-dive and the engine will immediately start to miss and hesitate.

I've been caught by fuel supply problems more than a few hundred times. Always KNOW if you have enough fuel pressure, NEVER assume.

 

Your right about checking the fuel pressure at WOT, Its just been very hectic. Right now im exhausted, so i guess tomorrow afternoon i'll lower the TPS to .54 and see what the fuel pressure is at, at WOT. As for the injectors guess u could say its a possibility, They are however 8 months old and from SVO ford injectors, Guess no harm in testing them out after the fuel pressure is tested. BTW whats a safe reading for the fuel Pressure at WOT? thanx