M35 With Issues

[stagea-and-skylines]

Hi all first time poster,

i have a 2002 m35 stagea car broke down the other night and when called the raa they said fuel issues most prob fuel pump took to mechanic who ran some tests and thought same prob so swapped the fuel pump but car still doing the exact same thing will idle fine but for some reason when you give it throttle is does nothing besides try and die the mechanic said for some reason the pump is only getting 1/4 of the voltage it should be and the injectors are dumping three times as much fuel as they should be, he has no idea why has been troubleshooting for a week now, any one else with this issue and how they fixed it ?

[Ben C34]

How did he establish fuel pump? Did he put a pressure gauge on it?

Also, 3 times the fuel is a weird statement, and unmeasurable. Time to take it somewhere who knows what they are doing.

[Ben C34]

And the obvious suggestion is run 12v directly to the pump and see what happens.

[stagea-and-skylines]

How did he establish fuel pump? Did he put a pressure gauge on it?

Also, 3 times the fuel is a weird statement, and unmeasurable. Time to take it somewhere who knows what they are doing.

[stagea-and-skylines]

Yes he put a pressure gauge on it, mechanic comes highly recommended as they are rotary and Japanese specialists.

[conan7772]

How did he establish fuel pump? Did he put a pressure gauge on it?

Also, 3 times the fuel is a weird statement, and unmeasurable. Time to take it somewhere who knows what they are doing.

+1, take it to someone who knows the car..

Both my mechanics have never seen a VQ25DET before.. and it's 14 years old

Don't rush into process of elimination.

[stagea-and-skylines]

Yeah only prob is the adelaide hills no one seem to know the VQ25DET so it's a learning process for them too I'm sure it'll get sorted just may take some time.

[conan7772]

might be a dumb suggestion, try a new fuse..

Edited September 16, 2015 by conan7772

[stagea-and-skylines]

Anything worth a shot at this stage Looking for any suggestion from anyone who may have had similar problem with the same car

[BoostdR]

Fuel pump runs lower voltage at idle to reduce noise and heat.

Symptoms sound like the Air Flow Meter could be stuffed. Unplug it and restart your car a couple of time so the ecu knows its unplugged and will enter limp home mode(won't allow revs much over 2,000rpm which is normal). If it then idles smoother the AFM sensor may need replacing. I replaced mine with a genuine Nissan item after my Chinese sensor lasted 4 days but others say the Chinese copies are more reliable. Maybe talk to scotty about which one he has had good reliability with. I'm sure he will chime in soon.

*a loose intercooler pipe or charge system leak will also give the similar symptoms as a blown AFM. So check them before buying a new sensor if limp home mode works.

Matt

Edited September 16, 2015 by BoostdR

[stagea-and-skylines]

So my mechanic has done everything listed here and more all is in working order accordi g ti scan tools abd such, yet car still the with same problem any other ideas

[scotty nm35]

He changed the AFM already?

Matt is on the money I suspect.

[stagea-and-skylines]

Trying to source one now but the afm is doing exactly what it's supposed to be doing according to my mechanic

[scotty nm35]

It's ferked, and the ecu has no way of telling it's ferked.

Scanners don't tell you the fault, they only tell you what the ECU thinks the fault might be, perhaps.

Edit, does it run the same if you unplug the AFM?

[stagea-and-skylines]

There are no fault codes coming up at all.

[stagea-and-skylines]

By the way he described to me when unplugged it goes into limp mode

[scotty nm35]

Does it drive the same in AFM limp mode?

If it idles fine, then it obviously isn't the fuel pump, slap a known good AFM element in there and try it out, it's the only way to rule the AFM from the equation. The AFM's rarely fail where the ECU actually throws a code in my experience, and I have changed literally hundreds of them.

Once it's sorted, get a new mechanic. I suspect he just wasted your time and money changing a perfectly good pump. Do you know what pump he put in there? it might need to be re-wired if it's an aftermarket Walbro or similar. They don't like that low voltage at idle/cruise (that all cars do these days.)

[stagea-and-skylines]

The pump he put in was a walbro pump yes, the mechanic has only ever dealt with upgrading parts on m35 stageas before so it all one big learning process unfortunately he never had one with this problem before like most mechanics I've spoken to before him

[stagea-and-skylines]

I don't know if it drives in limp mode at all as I haven't touched it since it went on a tow truck after it died on the side of the road

[BoostdR]

Check the cooler piping