rb25 acting up.

[smoked240]

My RB recently started acting up while driving it hard. If I'm sitting and Rev it up fast or slow and hold it there is not problems. When I start to drive it and step it down it runs terrible and starts to cut out then go then cut out and it will keep doing it if I'm stepping it Down. Would anyone have an idea on what it could be?

It almost seems to me like its blowing the spark out. Could it need to be timed? Would anyone know the steps to time it? And what to advance it to? I tried it one day by following a guide and it didn't work out. Any help would be appreciated!

Its a 91 with rb25det. All stock but Freddy style intake manifold, large fmic and a Turbonetics bov.

[fliprayzin240sx]

If it uses to work fine before and suddenly started doing it, check the plugs first. Might just need some fresh plugs. If its stock, run some cheapy NGK BCPR7ES-11s and gap them down to .030.

[Kingtal0n]

Sounds like it could also be a maf cut, did your boost suddenly change? If the engine is all OEM, you should not be using more than about 9-10psi if you want it to live as a daily.

[Sileighty_85]

Like Flip said check/replace plugs, If no go clean MAFS and check for boost leaks. Inspect coupler close maybe one is torn and opens durring boost

Sounds like it could also be a maf cut, did your boost suddenly change? If the engine is all OEM, you should not be using more than about 9-10psi if you want it to live as a daily.

MAFS shouldnt be and issue on a stock turbo.
Stock turbo can hold 14psi.

[smoked240]

Alright thanks guys. Ill try them tomorrow and see how it goes. I'm only running 7lbs.

[Kingtal0n]

Like Flip said check/replace plugs, If no go clean MAFS and check for boost leaks. Inspect coupler close maybe one is torn and opens durring boost



MAFS shouldnt be and issue on a stock turbo.
Stock turbo can hold 14psi.

Depends on the RB25. If it is from a Laurel then the maf will not tolerate more than about 10psi.

also those turbochargers are known to fail in daily driver applications when pushed beyond 12psi~ which is why I said, to keep it below 10.

[Sileighty_85]

Depends on the RB25. If it is from a Laurel then the maf will not tolerate more than about 10psi.

also those turbochargers are known to fail in daily driver applications when pushed beyond 12psi~ which is why I said, to keep it below 10.

Never heard that before....

Interesting my RB25 is pushing 13-14 psi for over a year now with no issues.
As well as some friends i had rocking 14 on their RB20's and 25's.

[smoked240]

Depends on the RB25. If it is from a Laurel then the maf will not tolerate more than about 10psi.

also those turbochargers are known to fail in daily driver applications when pushed beyond 12psi~ which is why I said, to keep it below 10.

I believe the maf is the correct one from an r33. I have heard this a couple of times. Its kinda the luck of the draw. I can't push past 7lbs. The manual boost controller I have is useless.

I had a bad intake manifold leak and installed a cometic gasket now soo ill check that over.

[Sileighty_85]

Check Post #563

Its all the MAFS that RB25 Use
http://zilvia.net/f/engine-tech/90376-rb-faq-19.html#post3352955

[WhipsGoneWild.net]

hows ur A/F's? check for boost leaks! lol - i had a few issues with mine

[smoked240]

hows ur A/F's? check for boost leaks! lol - i had a few issues with mine

Not sure on my a/f. I have started a new project a couple months back,and being its somewhat winter I park my car. So I haven't got around to buying all the little odds and ends I wanted.

[smoked240]

Pulled my plugs, turns out there too hot and are gapped to. 040. And I think I found the problem. I noticed my fpr vacuum fell off and I think that's why it was cutting out. Ill check when I get the plugs tomorrow. Anyone recommend some good vacuum line? I use the black auto parts stuff and it just heats up and collapses. Thanks.

[Darius]

The vacuum line on the FPR is your problem. If it doesn't see boost, your fuel pressure will remain at 50 psi, which mean it will run lean under boost. You are lucky you weren't running more pressure because bad things could have happened.

[DDK]

I'm having some problems with my car spitting and sputtering if it goes past 10 psi... Runs like a charm up till then though. Using BCPR6es NGK plugs and gapped to .08 mm...

[Functiontheory]

Like darius said, it your for vacuum line. Not only are you not allowing the engine to increase the fuel pressure when boosting. But you Also will be leaking boost by there as well which is also causing your car to run like crap at high boost. Turbo cars are so sensitive to boost and the air that is being metered that then tiniest little pine hole can make a car run like crap. Ever since I Have had a turbo car the first thing I made was a boost leak tester. Cause most llikely if your just randomly starts running bad it's going to be a boost leak or something really stupid. Good luck I hope you get it fixed. And as for a vacuum line you just want to make sure you get one that is a snug fit, one that fits properly. My aeromotive for came with just a silicone vacuum hose and it works great.


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