R33 Gtr Miss

[big_tedman]

Hey guys,

have a 1995 R33 GTR that has developed a bad miss at low revs or cruising speed. under load it runs perfect, but try to cruise and it misses or taking off until it gets up to 3k rpm or higher in first then its fine. Occassionally it will start and die straight away or run perfect for a day or so before playing up again.

Have cleaned both and resoldered the primary AFM and replaced fuel pump.

Have search everywhere i can but no certain answers.

Any ideas what else to check or replace as its dangerous it cutting out power when we try to take off.

cheers

[scotty nm35]

I would be leaning towards the crank angle sensor or fuel pump. Has the pump been replaced with an aftermarket? If so did you run power from the battery through a relay and fuse?

[big_tedman]

Fuel pump replaced with a walbro, power connected using factory wiring, we didnt run a new power from the battery.

[scotty nm35]

we didnt run a new power from the battery.

Most likely this is your problem, at least it's an easy fault to remedy. There is a 'how to' in the tutorial section for running the direct power feed.

http://www.skylinesaustralia.com/forums/topic/91993-fuel-pump-direct-feed-rewire/page-15

[big_tedman]

why would an aftermarket pump need rewiring? its getting same power as standard and works perfect at high revs, just not at low?

would have thought they wouldnt draw much more power than standard?

[scotty nm35]

Walbro's don't like the low power the factory pump controller puts out at idle and cruise. Was it a 255 you installed?

I gave you a simple answer to your dilemma, now go wire a relay in and let us know how it runs afterwards.

[big_tedman]

will do

[big_tedman]

yes and a walbro 255. will rewire.

just on a side note, we had the same issues before we replaced the pump, hence why we replaced it. could be just a coincidence?

[Ben C34]

Then it's probably not the problem.

You should still rewire the pump but dont expect it to fix it.

[scotty nm35]

Perhaps the stock pump had failed, no surprise there... I know for a fact the Walbro's can cause poor running like this if running low voltage. Most aftermarket pumps can have similar issues.

I have had many customers buying them off me and telling me they are shit and wanting their money back, even after I explain they need full 14v. It's probably half the reason they got such a bad name. The twin 255's are running fine in my car 5 years later, with constant e85 use.

[big_tedman]

Just want to say thanks totally fixed the problem. So anyone with similar problems should make sure they do the wiring. Was suprised, but car runs best that it ever has. cheers mate.