Skippng Problem

Hey fellas, I'm posting this for my brother (CB900fer on the boards) since he has no internet access at Florida. I know he's frustrated with the problem, so any suggestions are greatly appreciated! Thanks guys!

"I have a 1988 Thunderbird TC with minor modifications (3" dp, gillis boost valve, and K&N pod).And also, my timing is set at 10-12 degrees. I've been having a problem with it for about the past month, and I cannot figure it out. (I'm at college in Pensacola, FL right now so I'm a little limited in what I can do).

Here's the problem: I was running it at about 18 psi of boost until, out of nowhere, it would start missing at 3-4000rpm. It would miss all the way up to 4000, then it would clear out as high as you wanted to rev (I only went to 5000). If I let off the throttle so the boost would fall, it would climb through 4000rpm fine, but as soon as the boost got above about 15 psi, it would cut out again. So I decided to set the boost at about 15psi (I only have the stock gauge to read by), took it for a drive and it was fine. A little later I had to set it down as low as 12 psi for it to run right.

I thought it might be the TFI, as I had problems with it this time last year. So I swapped a spare TFI I had (it is used, and it skips when it's cold; but it warms up and it's ok), and took it out and it seemed a little better. I could put boost up to about 15psi, but anything higher and it did the same thing as before.

Another note: during all of this, one night when I was out, my car died due to a burned ground wire on the alternator (the single one that bolts on to the backside). I believe the voltage regulator inside my alternator burned out so it fried the wire (the wire and stud glowed red hot when I turned any accessories on). So I bought a new alternator and it's all good. But something I'm noticing now, my tachometer is acting up like I'm having spikes in voltage or a short somewhere. Once in a while my tach bounces up a little, and it gets a little better when I turn accessories on. I don't know if it has anything to do with any of this.

I didn't notice the skipping problem until shortly after I got my last tank of gas; though I'm not sure, it may have been coincidence. Initially I was thinking maybe it was my fuel pump or fuel filter, but I'm not sure. I don't know of any electrical problems since I ran codes on it, but got nothing, not even a TFI/PIP. One opinion from a local Thunderbird guy in town here says possibly the FPR since winter fuel has more alcohol in it, so it needs more fuel to handle the boost. The only other thing I can think of is spark plugs, wires, and distributor, but they're only 1 year old.

I'm leaving Florida to go home to New York in three weeks and I would like to get it fixed before then, so any help would be greatly appreciated. Sorry for the long post, but I'm trying to be as descriptive as I can. Plus, this has been an ongoing process for about 3-4 weeks now. Thanks guys!
-Seth"

try new wires (especially if they are not motorcraft) and make sure your intercooler hoses are hooked up tight and dont have any tares in them. Id check the cap and rotor for wear if you are doin wires. I had plugs do that before even though they looked visually fine so try a new set of them too.

I've just been researching misfire and what not... 3000-4000 miss on these cars are usually due to faulty wires, like bang said.

I doubt its IC hoses... if those were bad the boost would cut out completey after it leaked, it wouldn't come back... but if you are going to have it off to change the plug wires, never hurts to look thoroughly!

Have you checked the fuel pressure for 1:1 with boost? Stock IHI setup should cut out at those RPMs, maybe that's why it clears up after that??

James

Fuel pressure tests couldnt hurt. I would check the VAM and TPS for electrical flat spots.

Otherwise wait until spring before coming back to NY. It's freezing here now.

Bill

My experience with high boost problems has been fuel delivery issues. If those are only mods, KN cone, Gillis, and 3" DP then there's only 1 major restriction left. Fuel Delivery. The stock pump was marginal at best in the stock system. Upgrading the pump to the Walbro 255 HP has been so far the single most rewarding and best move I have made. It fixed so many things and really woke the car up. Go ahead and do the fuel pressure tests if you want, but if its still stock pump I'd go ahead with the pump swap anyway or keep the boost at 10psi.

Just figured I'd let you guys know what's going on with the car. It was simply the spark plugs. He was running an old set of NGK TR5's if I recall. Put in a new set of Autolite 764's and she runs like new again! Thanks everyone!

classic !

after being around me for 5 yrs, my ex-GF would start helping me with diagnoses ..

first she would ask: 'is it getting power?'
then: 'make sure it has good plugs!'

first she would ask: 'is it getting power?'
then: 'make sure it has good plugs!'

Is she referring to car or a more personal issue ?


PonyBoy, glad the problem has been found. That's why I'm a proponent of recent/fresh tuneups as an early part of the problem solving process.