Sam Mcgoo

iTrader: (1)

I'm after some help and ideas please guys.

Setup - Vortech 3.33 @ 8.5psi, PMAS, Kinetix SSV, Japspeed Decats, Invidia G200, AAM basic RFS, Walbro 255 and DW600cc injectors.

I'm getting a lean spot (16 - 17 AFR) between 3000 and 3500rpm while on part throttle. Seems to only happen between 0 and 10inHg Vac, never on boost.

This problem started after fitting PMAS, AAM basic RFS, Walbro 255, DW600cc injectors, ditching the SST and going to UpRev.

I have since put a brand new set of DW600's in. I have been back to the Tuner twice since and he has added more fuel in the relevant cells and reflashed the ECU.
On both occasions it appeared to cure the problem until after about 50 miles of driving when the problem comes back.

binder

iTrader: (8)

odd that the problem comes back but it sounds tune related.

Sam Mcgoo

iTrader: (1)

It is very strange. Its been tuned 3 times now buy a very well regarded tuner and each time its re-flashed it drives brilliantly for about 50 miles or so then something changes and gradually the lean spot comes back exactly as before.

If I reset the ecu by either disconnecting it or doing the pedal dance the issue is there straight away on the next drive.

binder

iTrader: (8)

hmm, i was going to say long term fuel trims are messing up but if you reset the ecu that wouldn't be it.

i would be talking with the tuner

Sam Mcgoo

iTrader: (1)

Yeah we have been discussing it for a while.
Today I unplugged all 4 o2 sensors just to see if it changed anything.
Strangely I didn't get any CEL. It ran pretty lean (15 - 16 afr) under part throttle acceleration (0 to 10inHg) up to 3500rpm then dropped to 13s and started to pull.

Plugged them back in again, lean spot back between 3000 and 3500rpm.

Tomorrow I'll be looking for a vac leak as the tuner says its a possibility especially around the plenum. I would be surprised if it was, as I get a good vacuum (20ish inHg) and the fact that the plenum has been off when changing the injectors and the problem occurs at identical revs every time without fail.

Could the Pmas Maf be the issue? He has said we can change it to the newer Uprev Maf to eliminate it but it would require a full re-map - which would be pricey for me. I'd like to eliminate cheaper thing first.

Any ideas?

binder

iTrader: (8)

well, what can happen with the leaks like that is they occur at a specific load and vac. Just because it doesn't happen at idle doesn't really mean it won't happen at some other rpm/load.

could be an issue with the maf. The thing is, the PMAS is the uprev maf. They are the same thing. HPX makes the PMAS which is what uprev sells.

Sam Mcgoo

iTrader: (1)

Thanks for your help

Finding a leak that happens at certain revs/load is gonna be a nightmare! How would I go about that?

Regarding the PMAS, I was told that there was a newer version of the MAF from Uprev?

djamps

iTrader: (1)

Does ECU reset make it 'OK' again. If so, it's the long term fuel trims. If they are getting out of whack every time it probably means your o2's aren't working right.

djamps

iTrader: (1)

Naw uprev has their 'own' maf now supposed to be much better than PMAS (it's also much more expensive).

But I doubt the MAF has anything to do with this... it's something f-ed up in his closed loop. Bad o2's or leak.

I'll put money the kinetix is leaking :P

Sam Mcgoo

iTrader: (1)

It doesn't appear to. I have reset using the peddle dance and unplugging the ECU and the problem is still there. Its only a re-flash that temporarily 'fixes' it.

I may try swapping out the o2's anyway.

Sam Mcgoo

iTrader: (1)

Thanks, I just hope it shows itself and I can find it if its a leak.

I've read a good method is to use an unlit butane torch and blow the gas around the joints listening for the rpm to raise a little. Makes sense but sounds dodgy.

djamps

iTrader: (1)

smoke test both exaust and intake

Sam Mcgoo

iTrader: (1)

Right, I haven't found anyone that can do a smoke test yet but I did use butane, carb cleaner and ether around all joints, gaskets etc and nothing showed up.

I have just plugged in an obdII reader and I'm getting differing voltages from the o2 sensors.

At idle - Bank 1 sensor 1 = 0.3v bank 1 sensor2 = 0.3v
Bank 2 sensor 1 = 0.6v bank 2 sensor2 = 0.3v

So looking like bank 2 sensor 2 is f*cked??

binder

iTrader: (8)

the sensor 2's mean nothing. They are for emissions do'nt adjust your fuel. the sensor 1's do the fuel trims.

If they are narrow bands then .3v difference could be significant since narrowbands only read from 0-1 volt

Sam Mcgoo

iTrader: (1)

I swapped out the suspect o2 sensor, done a ecu reset and done about 40 miles of driving - no change, the lean spot is still there exactly as before between 3k and 3.5k.

I'm gonna swap out the other sensor next just to check.

It's going back to the tuner for the new UpRev Maf and a remap this week to see if that cures it.

Before it goes I would like to eliminate any problems with the RFS by removing it.

As the UpRev was done with a base fuel pressure of 52 psi can I just remove the modded hanger and Walbro 255, fit the stock pump and hanger and disconnect/blank off the FPR ?
If I remove the cog belt to stay in vacuum would it be ok for a quick test to see if the lean spot has gone?

binder

iTrader: (8)

that doesn't sound like a fuel issue. I think you're chasing something into an area that wouldn't affect it. It would be very odd for a fuel problem to happen in a specific area in vac only. Unless it's the resonance some of us had with no dampers in an aftermarket fuel system then it's not the fuel system. The resonance problem on all of us has happened in the same 3 areas on the map.

Do you still have your stock fuel dampers?

Sam Mcgoo

iTrader: (1)

You could well be right, I was wondering about the damper issue and thats why I was asking about the fuel system. I do still have both stock dampers in place but saw that mx needed to add a third to cure the problem.

However, I have had a break-through today. I swapped out bank 1 o2 sensor 1 and it seemed to improve a little. I reset the ecu and went for a long drive of mixed driving. After about 50 miles it appeared to smooth right out.

I drove about another 30-40 miles and and it was smooth as silk so fingers crossed.

binder

iTrader: (8)

he wasn't on a stock system. If you still have a stock system in place with both dampers then that's not the issue. it's only an issue with you have high flow/high pressure systems with the dampers removed. He needed an additional damper because of the other aftermarket stuff. I have 2 dampers on mine and it fixed the problem.

If you didn't reset the ecu on the first sensor swap that could have been the issue....OR the one with low voltage as tested was the good one and the one with high voltage was the bad one.

It sounds like a fuel correction issue which points towards o2 sensors. I would say you have probably found the issue.

djamps

iTrader: (1)

Long story short this is incorrect statement. Lower o2's are used in certain conditions, as confirmed in the FSM, a master nissan mechanic I asked, and even my own logs and testing.

binder

iTrader: (8)

what? i have the manual and it says they are used for emissions only which does nothing for o2 control therefore "pointless" when tuning.