Intermittent Limp Mode?

[super_joel7]

Any idea what would cause a car to go into limp mode after it gets warm then go from limp mode to normal with higher rev's and back and forth?

Also when in limp mode it will stall?

Tried new TPS sensor, no cigar.

[Skym]

It sounds like ECU is switching between knock maps, main maps. Knock maps are richer in parts of knock fuel map and ECU can pull timing.

Stalling can be due to airleak, faulty MAF, TPS, ignition module, CAS. Ignition module is different symptom wise, as engine won't start until ignition module cools down (wait roughly 10 minutes).

[super_joel7]

Thanks Skym. That makes sense.

[Skym]

Check for cause of knocking, like low fuel pressure (faulty fuelpump or clogged fuelfilter), low octane fuel (ECU switches to knock maps), if boost level is not high enough to make engine knock.

[super_joel7]

Well it has been going on for a little bit so I can rule gas out unless i have had a great deal of bad luck with bad gas but running 91 octane since the start. Boost level isnt very high at all and i recently changed the fuel filter.

How can i check if my fuel pump is going?

I read something on gtr australia about grounding a fuel pump wire to make it get its full load from the battery; their problems sounded similiar to mine.

[Skym]

My cars engine would knock on 95-96 octane fuel with stock maps. It ran without knocking on 98 octane. But our octane ratings downunder are different to northern hemisphere octane ratings. Run 94 octane if you can.

Check fuelpressure via plumbing in a fuel pressure gauge between hosing to fuel rail from fuelfilter. If you don't have a fuel pressure gauge, local mechanic, Nissan dealership or auto sparky (some auto sparky's can come to your house, as they are mobile) should have a fuel pressure gauge.

The voltage regulator (increases voltage as revs rise) for fuelpump can play up on R32. Most bypass regulator and run straight to battery which gives constant voltage. The only problem is pump is running at 100% all the time and can shorten lifespan of fuelpump.

Running fuel tank low (below 1/4 on stock fuel gauge) is what damages intank fuelpumps, as the fuel is used to cool the fuelpump. Intank fuelpump should be changed every 100,000kms and fuelfilter every 20,000kms or less as routine maintenance.

[super_joel7]

okay. I will check fuel pressure and go from there. Thanks again.

[cbileske]

how much fuel pressure should a GTR have?

[Skym]

Around 35.5psi at idle for RB20DET, RB26DETT.

[cbileske]

ok thanks, how much under about a bar of boost should it be?

[Skym]

From what I understand, if you increase base fuel rail pressure at idle, should also increase fuel rail pressure at 1 bar of boost, due to fuelpump increases flow of fuel to fuelrail as revs rise.

The FPR (Fuel Pressure Regulator) sits on end of fuel rail, where fuel returns to fueltank. By blocking return fuel line more via adjusting Nismo or similar FPR, base fuel pressure at idle should rise.

Like with RB20DET, some up base fuel rail pressure to I think was 44psi + fit say a 255 fuelpump or a Bosch 300 lph fuelpump to force more fuel through stock 259cc injectors. It can make stock 259cc injectors stretch to 370hp, when they usually max out at around 300hp with stock 135lph fuelpump, stock FPR.

[cbileske]

holy those injectors are running a little over there limit. I have a regulator but still havent put it on, I need a fitting to adapt it to the rail, I believe SARD makes them. a bolt on flage to hose type. Since I still have the stock fuel rail

[ChrisCheezer]

* i just copied this from another section. but i think it pertains to this problem

""
just fixed my stalling problem ...

Ok, First let me tell you MY problem.. to compare.
- r32 gtr
Cold start perfect, Driving after warm up Perfect, about 25 min after mixed driving, stop and go, and highway then, randomly the motor would start breaking up under any acceleration and soon after start stalling out at low RPM's, Shutting the car off ( wait a min.) and turning back on it would return to normal for about 2-5 min.. then stalling again.

after trying everything else... i cut open my MAF sensors, checked out the connection board inside, noticed gray/white residue around a few soldered connections. I simply touched each point untill the solder remelted. sealed it back up and seems great!
I had my first 45 min drive today!
Ill keep you guys updated if anything changes
"

[super_joel7]

All things to do with the maf have been checked. Exchanged other ones that were working on other cars and still the same thing. All maf wiring has been checked and rechecked. CAS changed out for a new one and no change. Fixed all air and boost leaks. New Fuel filter and fuel pump seems to be running fine. ( i still need to double check fuel pressure )

Have noticed that the problem only seems to happen after I run the car until it is warm. ( drive for 20 minutes ) then stop somewhere and turn the car off. Wait 10 minutes. After i turn the car back on and start to drive, the problems start happening.

I dont understand! The guys at the shop cant seem to figure it out either!

[DarkCaporaL]

Are you certain the car goes into limp mode and it's not an obnoxious missfire?

I re-read your first post and it sounds exactly like the missfire I had last year, fooled around with the coils and plugs and it fixed the problem.