bogs and idle search

[mvs2]

Hi guys, picked up a new R32 sedan but I've noticed some issues.

6L of methnol was put in the tank to pass aircare while the tank was around 1/4 left. The car was bogging at regular cruise speed once in a while, the gas pedal would essentially go dead and the car would nearly stall ( on the way to the gas station ). I filled up with 91 octane ( to a 3/4 tank ) and for the day the car seemed fine.

The next day I felt the bog hit again at normal cruise speed and then it stalled out after bucking a few times. It took a few minutes before the car would fire up again and I managed to get up the road and home but not without having the same bogging issues.


I've given the car a good boot after I filled it up and it pulled hard without issues. There isn't any backfiring etc. Although the idle does search occassionally when downshifting. Normal idle is around 1200, itll drop down to 700 and surge back up to 1200 , drop then surge back up once or twice.



I was thinking maybe the fuel pump was on the way out ( aparently its a walbro ). Other than that from what I've been reading the likely culprit is the Maf?


Just wondering if anyone has any suggestions.

[Rides]

sorry to hear your car is going through this. Check out my threads, i've had this issue a year ago and finally resolved it. there are many suggestions from other members too. Hope it helps.

[mvs2]

Interesting, thanks for the heads up -- I checked out your thread and I'll get to cleaning the MAF after work. I hope that is what the problem is. I'm not sure what the CAS is but my money is on the MAF.

[specialedition]

As rides said theres a lot of different things that could be going on right now. My suggestion would be to change the fuel filter and run some injector cleaner for the time being see if theres any difference. If possible borrow a maf sensor from another member to narrow down your possibilities. My guess would be maf but could be something else aswell!

Goodluck

[mvs2]

Bought some MAF cleaner and hosed it down, reset the ecu in the process and filled up the ol gas tank. Car runs like a champ so far, no dipping idle no loss of power and no searching idle.

I'll keep you guys posted if the issue returns but I sure hope it stays fixed !


Thanks for the help guys, if there is every an issue -- clean the MAF :P

[Rides]

so happy to hear your back up and running. Best thing out of this is you at least narrowed it down to the mafs. If you bog again, check your connectors, because you have moved it while cleaning the mafs, therefore that could have fixed it too.

good luck man!

[mvs2]

Well I spoke too soon. After driving it for a few hours today without issue it died on me while pulling onto my street.

I did notice it was backfiring once in a while during a few slow shifts.

when it was dying the gas pedal did nothing

[Rblove26]

if it cleared up some from cleaning the maf, i would try and find a know good one (maybe borrowed like mentioned above). i had similar issue with my car, tried everything, both cleaned and re-soldered the maf but were only temporary fixes. borrowed my buddy's maf and car was running great .if it does come down to the maf, just replace it and dont waist as much time trying to save a crappy maf like i did.

also new fuel filter, check, re-gap or replace your plugs depending on condition and check for a vacuum leak wouldn't hurt

good luck

[Skym]

I did notice it was backfiring once in a while during a few slow shifts.

Popping sound (flames from exhaust) could mean ECU is adjusting to lean A/F ratio (via o2 sensor) by running engine rich. Sometimes it means o2 sensor is lazy / stuffed and o2 sensor makes ECU run engine rich longer.

6L of methnol was put in the tank to pass aircare while the tank was around 1/4 left. The car was bogging at regular cruise speed once in a while, the gas pedal would essentially go dead and the car would nearly stall ( on the way to the gas station ). I filled up with 91 octane ( to a 3/4 tank ) and for the day the car seemed fine.

Running methonal through non methonal compatible fuel system is probably going to do some damage to fuelpump, rubber hoses, injectors, etc. Also not tuning ECU to suit methonal probably will do some damage to engine due to running too lean. From what I understand, methonal needs a richer A/F ratio compared to pump gas. I would dispose of any gas from fueltank into a methonal compatible tank and inspect stock fueltank for damage, replace fuelpump, replace fuel hoses, replace injectors, etc. Or find a crashed car and use the fuel system off that car.

From my experience a failed MAF didn't cause stalling on my car, etc. It just made engine idle at 1500rpm when cold, warm and have MAF error code on ECU. Not saying it doesn't cause stalling, just never experienced it.

Also TPS, CAS, AACV are the other causes of engine stalling.

[Rides]

if there is no throttle response, i'm thinking it might be your CAS. When you say the gas peddle did nothing, does it drop all the way to the point of stalling? or does it pick back up? I'm thinking if the Mafs are acting up, it could just simply put you into limp mode, still allowing you to give throttle, but not rev over 2500rpm. Check the connections to the mafs to make sure they are still good. See if there is any corrosion to the connectors, that could be a sign of bad maf connections.

[mvs2]

Basically what happens is the RPM drops really low then goes back up and drops immediately again, natural reaction is to try and give it some gas but it just does nothing. After a few rpm drops it just stalls out.

After I cleaned the MAF my RPM stayed solid, after you give it some gas the rpm goes up and drops to 1100 or so where the car idles. Now when I touch the gas pedal the rpm goes up but it dips down to 700 - 800 rpm and goes back up to normal idle of 1100.

It does seem to be fuel related but what gets me is how inconsistent it is, I drove for about 20 minutes today and had no problems. Its almost like the car goes extremely rich or lean like SKYM said and then stalls. It fires up again about 20 seconds later. It just gets me on how random the issue is. I really need to get a FPR on there, would love to see what a wide band would be telling me.


This is why I don't think its fuel pump related or injector related. I'm not too sure what the CAS controls but from what I read I keep pointing my finger at the MAF :/

[Rides]

with mine, it would have no throttle response what so ever usually after 20 mins of driving perfectly. I had everything from plugs changed, to fuel filter, cleaning AAC. But at the end i found out it was my Cam Angle Sensor that was messed up. The CAS is the silver piece you see on the front of the timing belt cover. After changing that, my car didn't have anymore throttle dipping.

I know your frustration, and i hope someone on this forum can shed some light for you. I went through literally a year of hell and nervous driving it wondering if it was going to stall out or lose of throttle control.

[Skym]

Faulty CAS (faulty bearings inside) can make engine hard to start when cold, hot and can pull ignition timing by 1-2 degrees or so (what makes the engine feel lazy / flat). Also get CAS error code on ECU. From what I understand, CAS is used for timing of injecting fuel, base ignition timing figure (ECU adds ignition timing to this and fires sparkplug).

Idle up and down is probably the o2 sensor making ECU run engine richer or leaner (it did this on my car when o2 sensor failed). Also it does this when o2 sensor is lazy / faulty or when engine is running extremely lean due to intake manifold leak. If engine runs too rich and when combined with idle stabilisation playing with ignition timing it can make engine stall. Also running too thick oil can cause this idle instability.

If run engine on methonal it breaks down the oil as well (have to run methonal compatible oil). It's not as easy as just adding methonal to a fueltank. It's the same when running on E85 with E85 compatible oil, fuel lines, injectors, etc. I think Motul has E85 compatible oil.

[mvs2]

Going to put an FPR gauge on later tonite and see what happens. I really need to narrow it down. What blows me away is how the car fires up no problem cold, no problem hot and can run without error for quite some time before out of nowhere it just hits.

Car didn't stall on me today but the fuel seemed cut or something and there was no throttle response once again, the RPM would spike to 2000 then drop to 1500 and repeat over and over while the throttle had no response. I turned off the car it fired right back up and the idle stablized at 1k and off I went back home.

This is beyond frustrating. When I parked it at home and started it up again the idle dipped very low and barely kept running for a second.



Checked for engine codes - gave code 55 - no malfunction QQ

That certainly doesn't help lol

[Skym]

Engine runs richer when cold and o2 sensor is not used up until certain coolant temp (it's adjustable on ECU if have Nistune). o2 sensor doesn't show up as an error code. You have to hold engine at 2000rpm and note how quickly it changes from rich to lean and lean to rich via multimeter on o2 sensor plug or a oscillisoscope would make it alot easier to measure how quick it's switching. Also can datalog o2 sensor with Nistune via ECU which is similar to using a oscillioscope. Look at manual (RB25DE) for o2 sensor check procedure.

Also lean = revs rise and rich = revs drop. Also check AACV idle rpm vs ECU idle rpm calibration. They should both be set at I think was 650rpm (check white sticker under hood on passenger side that has idle rpm info).

That's what my cars engine did (reved up and down at idle by 1000rpm+ or so) when o2 sensor failed. Also it ran very rich and popped flames from exhaust on decel. But in your case it might be fuel related (still have some methonal in tank??) and need to run on a clean tank of gas to flush system out. But don't know if the methonal has done any damage to injectors (rubber seals), fuelpump, etc.