Unknown problem at high RPM

[TurboWarrior]

Hi everyone.

I rebuilt my engine from the ground up. Titan MHG, Lex AFM, RC 550s, Walbro Pump.

I have full hardpipes (Cooleeze) and Fully Elbow back 3" exhaust.

The car runs very well. Engine is so smooth that you can have beer bottles on top while its running. lol

Anyway. under boost. 75%-100% throttle. Id say above 3500 rpm. The car stars to jitter. It starts this in second gear and gets worse later on. Like a hesitation of some sort. It will still pull to redline but I can feel it a lot. Feels kinda like its starving for fuel or something? and it scares me. I don't know why it would do this. Its not fuel cut at least not any sort ive experienced. It just doesnt feel right.

Its only at 7lbs of boost. Im not turning it up until i figure this out. Any ideas?

 

[Nick M]

Check out your ignition wires and spark plugs.

 

[Dirgle]

You sure it is an engine problem and not a drive line under load problem?

 

[Guedo88]

mine does the same thing..idk what is wrong either..im also running stock boost.

 

[TurboWarrior]

ok im going to check my wires tomorrow. and someone mentioned on Supraforums that my timing could be off so ill be checking that as well. and yes it is only under load this happens. Ive rev'd the engine up to 4500 in my driveway and it seems smooth.

If I figure it out ill let you know what it was Guedo

 

[Dirgle]

While you're checking your wires crawl under your car and inspect the carrier bearing on the drive shaft. As in its early stages of wearing out it can cause odd vibrations when put under load. It's just a thought and it only takes a few extra minutes to check.

 

[TurboWarrior]

its worth a try. what do i do? see if there is play? turn it with my hands?

 

[Dirgle]

Basically, you got the idea. The center carrier bearing has a rubber insert that after time can breakdown and cause excessive play, thus allowing a slight wobble in the drive shaft.

 

[TurboWarrior]

ok today i changed the plugs, checked the timing. Both made no difference. It was off like 1 degree in timing.

I havent had a chance to jack the car to get underneath.

After checking the timing i noticed that the check engine light was flashing. Code 11. Momentary Power Interruption to ECU. Whats that mean?

And I pulled the vac line off the FPR while it was running. There was no noise. Im used to hearing loud air pressure when you take those lines off. There was nothing. Could it be my FPR?

 

[bountykilla0118]

Sounds like spark blow out how old are the wires? If they are new reduce the sprak plug gaps to 28 or so?

 

[TurboWarrior]

hm they are a few years old. not too many km. though i may have been a bit rough on them.

Right now i have the plugs gapped to .030. is there any danger in going to 0.028?

do you know if that fpr thing of mine is normal?

Just to let everyone know the J-tube is gone. Bypassed. and I have braided larger lines running to the rail from the FPD

 

[Adjuster]

I run iridum plugs, gapped at .28

This cures many 7MGTE's of the spark blow out that happens at high rpm, under boost.

Seen it "cured" a few times.

No problems with the smaller gap. It still lights off the air fuel mixture just fine in my opinion. And it's much better than the miss your getting just when you want the power the most.

New wires often do not hurt either. Even a set of wires that looks great, can have serious issues. (They are a wear item, and even the most expensive ones wear out.)

I've run Stock, NGK, Magnacore and Moroso.

In every case, the NEW set has been the best ones... LOL

 

[IJ.]

I had to pull mine back to 25 and still had an issue around torque peak so ended up advancing the timing a touch in that band to cure it.

 

[TurboWarrior]

ok well i had the injectors tested. They are 4cc out on 4 and 8 cc out on 2. I didnt test them before because i bought them from a respected person on the forum and the injectors only had 6k on them. but i should have done it i guess. 2 of them wont come back to normal so i guess i need new ones. They are RC injectors too.

 

[starscream5000]

Just for the record, what spark plugs were you previously using before you changed them, and what are you using now? Have you got around to checking the carrier bearing? You can do that faster than you can change out your plugs .

 

[TurboWarrior]

I have a stack of new plugs i always use the same. NGK 3300's.

No i haven't checked it yet. But i know theres something greater going on because the engine ran really rough after my first posts. It got so bad that it barely ran. Basically since i first posted the car went downhill the more it ran.

 

[TurboWarrior]

Well i think it was my fault not the person i bought them off of. Crap must have been in the rail that clogged them. Lucky the shop phoned back and after re-cleaning them they all shot back up to normal. So im reassembling the car tomorrow or the weekend. I'll let guys know what happens. Thanks for the help

 

[TurboWarrior]

I reinstalled everything and the car runs much better. Smooth through all rpm. But idles bad. Wants to die after you rev it. I found an exhaust leak between the elbow and turbo. Would that cause this problem?

 

[starscream5000]

I'd say that the o2 sensor is reading the extra air from the exhaust leak there, since that is very close the the sensor, probably making it run way rich, probably fouling out the plugs and making it want to die like you explained due to being loaded up on fuel. Get that fixed before you go driving around in it anymore .

 

[TurboWarrior]

Allllright im getting somewhere now

I readjusted the TPS, fixed the leak. The leak played a role in the idle problem im sure.

the car is running mint now. But hessitation is still there.

I found broken wires all exposed near the coil pack. Im soldering them together and getting rid of the harness. Hopefully this solves the problem