SHOP needs help with customers car

[jokergerm]

We are working on a 2001 pathfinder and it will not rev above 4200 RPM its like a rev limiter comes on, when accelerating on the the highway you floor it and it goes to about 4200 rpm and then slamms into 3rdf gear but you cant go any faster

We have checked the, MAF, TPS, New fuel filter, Fuel pressure and volume are good, Cats are not clogged.

Its been getting worse since we have had it at the shop today, If you pinch off the return line to the tank it gets a little better, so we are thinking maybe the fuel pressure regualtor is just stuck open and returning all the fuel to the tank. but we are not sure yet.

also you cannot get the car above 55 mph

Any advice would be great, we as a shop are stumped.

Also the only codes we get are both banks are lean, so we know we have a fuel delivery issue

Thanks

[Densetsu]

Never happened to me, but I found this while Googling around:

http://www.mombu.com/asian_car....html

After replacing the MAF, he reflashed the ECU with the latest firmware and claimed the problem went away.

I believe he's a member on this board as well (Chuck Tribolet), he may be able to answer additional questions on this.

[jokergerm]

We did not replace the maf, we checked it on the modis scope and it was fine.

[jokergerm]

On top of all of those problems, the car does not rev in nuetral either, it just bogs down, at the most you can get it to 2500 rpm but you have to feather it to get the RPM that high

Found this thread seems simalar, What goes bad in the distributors?

zerothread?id=405346
Modified by jokergerm at 7:20 PM 1/20/2010

[abadlovesong]

Does the engine run rough at all? And does the exhaust smell fuel rich?

I'm not sure how much help this will be, but my old car before getting the pathy had an issue where it would intermittently stall, engine would run rough, and RPMs would be limited to about 3000. It would not throw up a code all the time, that was intermittent as well.

What it ended up being was the MAP (Manifold Air Pressure) sensor and vacuum pump were bad, and would sense the air pressure dropping and would compensate by injecting more fuel into the engine, causing it to run rich and the rpms down b/c there wasn't enough air pressure to power the engine.

Now, i'm still pretty new with the VQ engine and i don't know that much about engines. So, i don't know if it has a vacuum pump (which i doubt it does b/c it was a 4cyl and probably needed one).

btw, is the check engine light on? can you read out a code at all?

[Chuck Tribolet]

Never happened to me, but I found this while Googling around:

http://www.mombu.com/asian_car....html

After replacing the MAF, he reflashed the ECU with the latest firmware and claimed the problem went away.

I believe he's a member on this board as well (Chuck Tribolet), he may be able to answer additional questions on this.

My symptoms were quite a bit different. I got a hesitation at 4000 RPM, then ittook off fine.