Loss of power/stumbling?

[WowWee]

Under WOT in second, third and fourth gears my car seams to stumble. Full boost hits and it pulls well, then the car slows (still WOT), then pulls again, and slows again. Its like a lack of power to the wheels. I don't think its the clutch because when it stumbles the revs don't shoot up, it almost seems as though they slow down. Boost stays constant at 12psi, fuel pressure is normal, AFR's are at 11/12. The one thing that may be out of the ordinary, is the exhaust temp. During easy driving it is lower than 300 degrees, as soon as the stumbling starts it climbs quickly to 500+ degrees. Oh, and the exhaust temp probe is located in my test pipe. I would like to know what to check, as I
don't have the faintest idea of what it could be.

Thanks,

Scott

[Skym]

When cat gets hot, ECU protects engine by going into failsafe mode, so you can drive to the local Nissan. But sounds like there is no extra fuel being injected.

Clamp the cat temp sensor to side of exhaust with a intake hose clamp and plug the hole in cat elimination pipe (I guess you dudes call it a test pipe???). Then look at TPS, fuelsystem, as 11-12 A/F is quite lean for just 12psi. Should be around 11.6:1 or so at peak power with around 14psi.

Might be as simple as a blocked fuel filter. Or maybe a weak fuelpump. Test the fuel pressure between rail, fuelfilter, as that should give you idea if the fuelpump is on the way out or there's a clogged fuelfilter.

[go_n_low88]

When cat gets hot, ECU protects engine by going into failsafe mode, so you can drive to the local Nissan. But sounds like there is no extra fuel being injected.

Clamp the cat temp sensor to side of exhaust with a intake hose clamp and plug the hole in cat elimination pipe (I guess you dudes call it a test pipe???). Then look at TPS, fuelsystem, as 11-12 A/F is quite lean for just 12psi. Should be around 11.6:1 or so at peak power with around 14psi.

Might be as simple as a blocked fuel filter. Or maybe a weak fuelpump. Test the fuel pressure between rail, fuelfilter, as that should give you idea if the fuelpump is on the way out or there's a clogged fuelfilter.

When testing the fuel pressure, do you know what pressure we should be getting from our stock fuel pump?

cheers.

[WowWee]

I have been told 3 bar which is equivalent to 43 and a bit psi.

[go_n_low88]

43, excellent. I am ordering a new Tre 255LPH pump and installing if that is the case with my issue. My car just bogs all of a sudden and I can barely creep along. It then picks back up and I can accelerate away, and then it jerks back again to barely moving. I stop at a light and car stalls. I have changed oil, Cleaned MaF , Changed Plugs, changed fuel filter, cleaned injectors and running 94 octane, no turbo leaks. Anyone have suggestions? Do you guys still think this might be a MAF issue or fuel pump issue?

[go_n_low88]

I think I may have found the problem. I pulled the square lid off the Maf and the connections made me a little suspicious. I then grabbed the soldering iron and re-did the 4 connectors to the plug. Took the car out for about 20 mins and no bogging , sluggish or hesitation.

cheers,
Parrish

[MikeRWK]

was the car stumbling as you hit boost? like when the needle just starts to go form vacuum to boost on the gauge? my car seems to do this for a second, then hooks in good but then in the higher rpms it will do it again.