93 VR-4 engine sputtering - Mitsubishi Forum

3KVT · #1 09-10-2009, 04:02 PM

Hey all,
I have a 93 VR-4 that has had a rebuilt engine and transmission. Everything ran fine after the engine was rebuilt, until a couple months ago. I was racing a 95 GSX on the street and I noticed my engine started sputtering at high boost and high rpms. The boost level sank, while the engine sounded like it was running rich. I've talked to a few friends with VR-4's and they suggested I do a boost test. I found a small leak in my intercooler (It is dinged up from a wreck by the previous owner, but not enough to hurt functionality). The leak is small and it doesn't seem that it could be causing the drop in boost that I see when I floor the car. Anyone had a similar problem or have any suggestions as to what's wrong with my baby? Any help is greatly appreciated.

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Girly VR4 · #2 09-11-2009, 10:07 AM

I'd try spark plugs and wires too. Sputtering at high(er) rpm's usually is spark plug related if there are no other issues with the car.

Sebba · #3 09-11-2009, 11:41 AM

I also agree with the plugs and wires route. Check for corrosion on the contacts etc... any signs of arcing or rubber degradation.

If everything appears fine, be sure to check the gap.

Also don't use those iridium plugs, Mitsubishi turbo engines hate them for some reason. Good ole NGK is what you should be sporting.

3KVT · #4 09-12-2009, 10:08 AM

Thanks for the quick replies. She's in the shop for a while but will be back soon. I never even though to check my plugs/wires or the gap. Seems logical now that I think about it. Can you explain why 3/S's hate those iridium plugs? That's what I have in it now, so looks like I'll be buying a new set.

3KVT · #5 10-12-2009, 07:52 AM

Well, I got the wires and plugs replaced (Big thank you to Hans at Ground Zero Performance for seeing me and getting me in and out of his shop so quickly!!). The sputtering has improved drastically, but still persists. I found out that my rear turbo is going bad and starting to spit a little oil. Could that oil that's running in through my intake be causing the sputtering under heavy load/high boost levels? I thought it would just burn up, but can it cause these symptoms if the concentration is high enough? Also, my fuel system has 130K on it as well, should I consider looking at that? Maybe the pump or injectors just can't handle the high loads it used to. Any suggestions on where to go next would be greatly appreciated.