1988 F150, 5.0L, 76K Miles on the clock, AOD, GT40 U/L Gasket matched intake, TIII Injectors,65mm TB, New Coil, wires, cap, dizzy, module, battery, pumps, filters, fluids.

Would a PCV grommet leak cause a small amount of hesitation off idle, and cause mild pinging when cruising above ~75MPH? I've been having to back off timing quite a bit to get it to stop, and have a decent power loss and drop in MPG (18 to 14 MPG now).

I have a new grommet for the GT40 style PCV, the old one feels like plastic, just wondering if this is the most likely culprit for the issue. Problem is I have to move the fuel rail to get the PCV valve and grommet out. Would like to know before I make that jump.

Also, if you've swapped the GT40 intake in, please chime in as to issues you encountered.

 

Spray some carb cleaner around the PCV with the engine idling, if the idle RPM picks up then you know you have a vacuum leak.

 

what rla said also works for finding vac leaks elsewhere.

 

I know it's leaking.
I'm asking if the leak is the cause for the issues.

 

ok, is it likely the cause? no. could it be? absolutely. if you know its bad, misewell get it over with. that eliminates it from the equation, and if it in fact is allowing massive amounts of air to come in without the computer knowing (airflow doesn't match tps reading) then it could be lean and pinging.


you could have a myriad of other problems contributing to your ping. spraying the carb cleaner on the pcv will shed some light on just how badly its leaking.

 

Everything else has been replaced or rebuilt.
It's the last thing I havent been able to do.

 

Bump. To the top.

 

Why? You already know you have a vacuum leak right? Fix what you know is wrong.

 

I would like more feedback on the original question.

 

All of your original questions have been answered.

you obviously aren't looking for feedback or answers, seeing as how "everything else has been rebuilt or replaced" rules out anything but the pcv to be the problem.

 

I am looking for more feedback for my questions. The more people reply, the better idea I have. Especially if they have had similar issues.

Thanks for the free bump!

 

The more brain cells you can coax into swimming in the same direction, the less you'll rely on others, who are relying on your novice "given information", to give feedback on simple diagnostic issues.

You're welcome.

 

Good advice, moving along now.
I'm still looking for people who've done GT40 U/L intake swaps on SD 5.0 trucks.
Wondering if it may now be an issue regarding the SD setup with a GT40 intake.

I'll revise the OP accordingly.

 

Does this thing have an EGR? If so, not enough EGR at cruise, and it'll ping, conversely, too much off-idle, it'll hesitate. One more thing to think about.

This isn't a mass-air-flow system, it's the older MAP thing, isn't it? Or not?

Duh, what? He's just asking for more feedback. That means he would like more people to chime in. Not an unreasonable request, given his questions.

 

Egr would be a Good start.

And as I have reread this thread many times, the replies were to fix the known problem with the PCV, and eliminate it as a known problem. Then, if further diagnosis was needed, to report back.

You don't keep filling a flat tire with air, when you see a screw stuck in it and think that changing the valve stem is the problem. Seeking knowledge isn't a problem, but NOT fixing a known problem and expecting a better outcome is failure.