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1999 3.0 SilFro
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Discussion Starter · #1 ·
BAD missing under load

WHAT IS IT!?!?

The problem began as a bad hesitation when taking off from a stop. It got worse, to the point that there were backfires coming up through the intake when starting out. But once you get going, it smooths out and runs fine.

Then it started bucking and missing and losing power on the highway. Fine at cruising speed, but a if I tried to accelerate without downshifting, it shakes and backfires and bucks. Over 3000 rpm's it is usually okay; the bucking only occurs below 3000 - hence if I downshift, it's fine.

It's gotten to the point now that I have to pretty much "launch" every time I take off from a stop. Rev to almost 3000 and slip the clutch, in order to keep it from pretty much dying. Sitting still and revving gets a healthy POP thru the intake.

I've done everything. New plugs, new wires, new fuel filter, 2 bottles of Techron over the last couple of months, and tonight I replaced the fuel pump. Still it acts like nothing has changed.

Checked the plug wire order, both on the coils and on the cylinders - no crosses. Gas mileage is about the same as it always has been. No CEL has lit, no matter how hard I try to make it throw one. It idles as smoothly as ever.

I am at a complete and total loss, and I'm sick of throwing money at this thing. What's left that could be bad? Somebody give me some ideas!
 

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1999 3.0 SilFro
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24,932 Posts
Discussion Starter · #5 ·
RE: BAD missing under load

I'm really thinking injector as well. Maybe stuck open or whatever. I'm going to the yard Saturday to get a set of injectors and a coil pack. See what happens...
 

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1999 3.0 SilFro
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24,932 Posts
Discussion Starter · #6 ·
RE: BAD missing under load

Looks like the fuel pressure regulator was the culprit this time. After unhooking the vacuum line to the FPR and sealing it off, the problem has entirely disappeared. I'll be replacing it tomorrow.

Now the question is - is it okay, for now, to drive around with the FPR not functioning, until I get the new one installed? Or should I plug the line back in and deal with the bucking? What's worse for the engine?
 

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Bennet...

What happened with this "solution" ? Did it just come back? Seems like every time you lift your hood and mess around it goes away for a bit. Could it be related to you resetting the PCM? Original programming is fine, but in relearning, it learns bad things and the problem comes back?

The mis-education of Bennett's ECU

Massiv.
 
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