Fucking car isn't running right, and I'm at a loss....

I'll try to keep this cliff notes style, so it doesn't go on for EVER.


last year, the thunderbird never ran quite right..... same issues this year. I'll put the issues down, and then what we've tested.


Issues:

On throttle tip-in, car misfires. If you keep your foot in it, the misfire goes away, pulls like a raped ape until it builds 10PSI and misses all over the place, bad enough that you have to get out of the throttle completely. Fuel pressure at idle wavers rapidly back and forth about 1-1.5PSI. It also begins wavering right before the WOT stumble/miss. At a steady speed down the road, car will start misfiring. Plugs look lean, O2 sensor is whitish, narrowband A/F meter pegs full lean each time it misfires. it also seems to have lost a bit of vag at idle, as it used to read 19GH..... it now reads more like 15.

Tested:

Every power and ground from the battery to the EEC. All power wires are providing correct voltages, computer is reading sensors correct which in turn are actually reading correct. Fuel pressure is not steady, but set to a bit above factory. Compression is 150 across the board. All ignition parts are Brand New, all motorcraft. No change after they were installed. Turbo was re-sealed, so ther is no more leak there. Boost is set to factory levels. Everything from the air meter forward including all the intercooler connections have tested to 30PSI and there were NO leaks. No Vac leaks found. Swapped computers with a known good unit, no change. New cam was installed, shimmed correctly, and is quiet. NO leaks of any kind of fluid at this point.


By all means this should run like a new fucking car, but seeing as it wants to be a bitch, it doesnt. The ONLY and I mean the ONLY thing that hasn't been either replaced or swapped with a good part is the Fuel pump.


Do my symptoms above (Lean misses) seem like a weak pump to you guys? I'm rally almost ready to give up on this car and put it completely back to stock.

it could be. on the initial tip in, it its weak it could miss and missing at 10psi is also a give away, how much boost should it normally run? sounds like the fuel pump cant keep up. if its a stock pump, i would swap it and put in new plugs. i guess its possilbe it could be ignition related but with the fuel pressure jumping around, the fuel pump makes more sense.

Weird, cause my Cobra was doing the same thing down low after i added a bunch more boost. Like in 2nd gear when i would stab it at 2,000rpms. Turns out i needed to regap my plugs closer because of all the boost. Make sure you have the right kind of plugs as well. That's what i know from just tuning my car.

I would think plugs blowing out also, BUT it does it at constant speed also..... low boost. How are your injectors? I had one go bad in my Talon once. It took me forever to track down. Damn thing would sound like an air cooled VW under partial and full load. When the car got up to temp, it was only under big boost. Damn injector.....

$0.00002 says pump

Original pump.... how old is the car..... upped boost... I would think a new pump would be a good investment anyways:)

I went through this with the mazda, needed a bigger fuel pump. Replaced the pump and got one step colder plugs and gaped them about .008 closer than stock and no more problems.

^ yes. with more boost u need to make the gap a bit closer.

these are all good suggestions for sure. i hope you track it down soon man. you need to bring that thing out and unleash it on the unsuspecting.

Well, I just oredered a walbro 255lph High pressure fuel pump. Not to o bad a 106 shipped. I'm going to try swapping it out this next friday, and put new plugs gapped a bit closer.

It is the stock factory pump in the car afaik, so it would be almost 23 years old at this point. The stock pump is 88lph. The injectors were sent out by MA70TT very early last year to be flowed and cleaned, they are stock size which should support 300HP.

Today, i took the vac line off the regulator to see what the FP would do at idle.... the needle was still oscillating rapidly, but only 2PSI max. When i hooked the vac line back up, it started swinging wildly..... I noticed while my average vac is where it is supposed to be according to the cam guy, it also fluctuates rapidly. Now this could be because of some valve overlap with the new cam, but just to be sure I sent and e-mail out to the grinder.


Hopefully, i'll be able to drive it after the pump and plug swap.... it sure sounds bad ass when I rev it up... this turbo is LOUD compared to the stocker, especially through a straight pipe

vac should not "swing wildly" even with overlap it will be lower but not move around. you have something else wrong...... misfire or valvetrain issues cause this......

What kinda power are you looking at when it's done here?

Vac swings slightly, but I was talking about fuel pressure.

The cam grinder got back to me, and he says that my vac readings seem to be about right, and that what I'm seeing with the vac needle is normal. It fluctuates slightly and very rapidly, but its a small variation MAX of about 1-1.5 Hg. From doing some reading tonight online, it says that what I'm seeing is pretty normal.

The complete valvetrain seems okay. New HLA's Roller rockers and cam, all the springs are alright and strong, valves are sealing.

Terminator wrote:

What kinda power are you looking at when it's done here?

Well, after all is said and done, it should put down 300hp at the wheels, and a bit more than that in torque. Next year is going to be the fun time though..... since all I'm lacking is a bit of pocket porting on the head, my megasquirt and a set of injectors.


At that point, the engine should be done. My goal is no less than 500 at the wheels. Its been done with less mods than I have.


After that..... i want to find an older car. Possibly an older mustang or maybe even a dart if i can find one.

any misfire will show up as a lean misfire your pumping air and raw fuel into the exhaust it see the O2 and that shows lean no matter the reason it misfired. the fuel pressure swing while the vac is hooked up sounds normal if the vac has a swing since those at that point are connected. try a pump since it sounds like it needs it but im sure your pump is plenty for cruise and idle

Okay...


We changed plugs with some fresh Autolite 764s gapped to .028. When we had them out, we checked compression again since the tester we used last time was fubar.

Cyl 4: 155
Cyl 3: 150
Cyl 2: 145
Cyl 1: 145


Sound good?

Still didnt run right. SO, we put in my new Walbro 255lph HP. We gained 3PSI on the fuel pressure gauge when we went to the Walbro, without changing the fuel regulator setting. 45PSI Vac off. The idle was a bit smoother. We revved it in neutral pretty good to see if we could get it to miss. It was pretty smooth revving, but would break up when you let go of the throttle. All of a sudden, we lost a cyl. We shut the car off, and checked all the plug wires. We started it and we still were missing a cyl. On a hunch we started pulling injector wires. We got to the number 2 injector, and when we pulled the connector, NO CHANGE. We removed the fuel injector, and noticed that the PINTLE CAP WAS MELTED!!! We only pulled one other injector, (#1) and it looked normal. We put a good injector into it, and went for a drive.


Symptoms are greatly diminished, but it still is acting up. Throttle tip in still has a pretty good miss, but after that.... Holy cow! It built a full 15 PSI and pulled smooth and hard up to 5500RPMs. We only got it to miss ONE TIME in the upper rpms. It still breaks up a bit at steady cruise....but not nearly as bad.


Any Ideas now?

How the FUCK did I melt a pintle cap on an injector????!!!

Tusk wrote:

How are your injectors? I had one go bad in my Talon once. It took me forever to track down.

I'd be checking the rest of the injectors, not just two........

Tusk wrote:

Tusk wrote:

How are your injectors? I had one go bad in my Talon once. It took me forever to track down.

I'd be checking the rest of the injectors, not just two........

Sounds like a good idea to me too. Make sure there flow blanced as well. If you replaced 1 it might be a good idea just to replace all 4 any way.