BM3 F80 Rough Idle on Pump Gas & Pump E85

[F80_Greg]

Hey guys, hope everyone had a great holiday season. Need some assistance, was wondering if possibly someone could take a look at my log on stage 2 OTS pump 91? I switched back to 91 pump gas (CA Gas Sucks i know) just to run a tank of gas through the system. I'm feeling a bit of idle roughness. Feels like a slight misfire like every about 20-30 seconds while idling. The 6 speed shift knob feels like it's vibrating a little more than it should at idle. It was like this after switching to e85 as well. After taping the gas pedal and letting off the car seems to hesitate a bit and go back to idle, rpm drops a little and feels rough, just isn't smooth as it should be. Spark plugs are NGK 97506 @ .020 gap and about 2k miles old. Have always ran Lucas Ethanol Stabilizer & conditioner on full e85. Car has full bolt ons as well including VRSF front mount intakes. Was thinking between 3 different possible issues that would cause a rough idle. Either the intakes, spark plugs or gap, and possible injector issues as I've heard many guys having issues after switching to full E85. And yes i have reached out to my tuner, just wanting to get any addition insight from a lot of you experienced guys on the s55 platform. Any assistance would be great. Thanks Guys

https://www.bootmod3.net/log?id=5ffd...729b6a974e9b37

https://datazap.me/u/f80greg/pump-ga...g=0&data=7

[TheMaster1971NL]

since I changed the spark plugs I have the same.

[TopJimmy]

Looking at both logs I see that all cylinders have the same timing, which means that the plugs and gap are probably good.

Your Bank2 Lambda seems to run a full digit less than Bank1 Lambda, so you may have an O2 sensor failing on the rear pipe (check BM3 for codes, even without CEL). When you tap the pedal the lambdas come closer together, which seems to be why the car does run but not idle so good. I also see this is causing the one STFT to run richer. I'm not a pro so we need your tuner to chime in for a real answer here.

Any chance that you recently had a fuel delivery problem not mentioned? I had a stuck injector when I went to E, which also caused a bit of fouling (fuel buildup) on my rear O2 sensor. I ran like crap right after replacing the injector and saw my Bank2 Lambda was off, but I was lucky that it burned clean after a few runs. I wouldn't try to burn yours clean without your tuner asking you to.

-Jimmy

[F80_Greg]

Originally Posted by TopJimmy

Looking at both logs I see that all cylinders have the same timing, which means that the plugs and gap are probably good.

Your Bank2 Lambda seems to run a full digit less than Bank1 Lambda, so you may have an O2 sensor failing on the rear pipe (check BM3 for codes, even without CEL). When you tap the pedal the lambdas come closer together, which seems to be why the car does run but not idle so good. I also see this is causing the one STFT to run richer. I'm not a pro so we need your tuner to chime in for a real answer here.

Any chance that you recently had a fuel delivery problem not mentioned? I had a stuck injector when I went to E, which also caused a bit of fouling (fuel buildup) on my rear O2 sensor. I ran like crap right after replacing the injector and saw my Bank2 Lambda was off, but I was lucky that it burned clean after a few runs. I wouldn't try to burn yours clean without your tuner asking you to.

-Jimmy

Thanks Jimmy, appreciate your insight here. This is what my tuner Paul said: Your Bank 1 and bank 2 AFR and fuel trims are very different from each other. This would indicate that you may have a leaky or defective fuel injector or bad O2 sensors.

[mystermykee]

I had the same issue. Shortly after I started throwing a CEL for upstream O2 sensor.

[TopJimmy]

Originally Posted by F80_Greg

Thanks Jimmy, appreciate your insight here. This is what my tuner Paul said: Your Bank 1 and bank 2 AFR and fuel trims are very different from each other. This would indicate that you may have a leaky or defective fuel injector or bad O2 sensors.

Glad to help. Paul's my tuner too. When my fuel injector stuck open the one STFT would be down at 0.7 and the other near 1.0.

I would look at the lower O2 sensors first.

[F80_Greg]

Originally Posted by mystermykee

I had the same issue. Shortly after I started throwing a CEL for upstream O2 sensor.

What modifications do you have, fuel, tune?

[F80_Greg]

Originally Posted by TopJimmy

Glad to help. Paul's my tuner too. When my fuel injector stuck open the one STFT would be down at 0.7 and the other near 1.0.

I would look at the lower O2 sensors first.

Thank you, what was the first step you did to determine the injector was in fact stuck? Same issue I'm having? By starting off with the rear o2 should i replace it first and check for idle issues as the first step in the process? Trying to start off with minor possibilities first and least expensive

[TopJimmy]

Here's what happened with the injector:

Injector stuck, a short chronicle... https://f80.bimmerpost.com/forums/sh....php?t=1783097

From reading stuff here I just knew that's what happened.

Yes, I'd swap in a new downstream O2 sensor. See if that fixes it. You could also read up good and check part numbers to see if you could swap the sensors front-to-back, but that's a lot of work for a test.

[mystermykee]

Originally Posted by F80_Greg

What modifications do you have, fuel, tune?

Catless DPs, custom E30 tune.

It was after 2 years though and 50k miles.

[F80_Greg]

Originally Posted by TopJimmy

Here's what happened with the injector:

Injector stuck, a short chronicle... https://f80.bimmerpost.com/forums/sh....php?t=1783097

From reading stuff here I just knew that's what happened.

Yes, I'd swap in a new downstream O2 sensor. See if that fixes it. You could also read up good and check part numbers to see if you could swap the sensors front-to-back, but that's a lot of work for a test.

You think it's a good idea to try some good injector cleaner in the tank?

[TopJimmy]

Originally Posted by F80_Greg

You think it's a good idea to try some good injector cleaner in the tank?

Once an injector sticks it's usually stuck open and you go through a tank of gas super quick, and need a foot on the pedal to stay running. I don't see that injector cleaner would hurt things, but doubt it would help either. I'd look at that O2 sensor first.
Possible part numbers (u check first):
11-78-7-848-486 and -487
They seem to be the two downstream sensors with different cable lengths (and connector color) for the short and long pipes.

[F80_Greg]

Originally Posted by TopJimmy

Once an injector sticks it's usually stuck open and you go through a tank of gas super quick, and need a foot on the pedal to stay running. I don't see that injector cleaner would hurt things, but doubt it would help either. I'd look at that O2 sensor first.
Possible part numbers (u check first):
11-78-7-848-486 and -487
They seem to be the two downstream sensors with different cable lengths (and connector color) for the short and long pipes.

Thank you I'll look into that. Idle isn't bad where i have to hold down the petal at all it holds idle fine. Just like every 20 seconds idle with drop a hair and feel like it's misfiring and go back to normal and do it again. I went back to stock tune and locked the dme, I'm thinking about taking it to my guy at the dealer to see if he can have a tech run some diagnostics. Hopefully they find something. He is most mod friendly so that shouldn't be an issue. Only thing is their system might pick up the preview tune flashes and red flag the car or something. My warranty just expired last month, maybe they can do a goodwill repair or something

[TopJimmy]

Even if flashed Back to stock and locked they will see the tune was there. The new software picks it up. I was just at the dealer last month and my mechanic told me all about it. It's the first thing BMW corporate looks for in a warranty request.

[F80_Greg]

Originally Posted by TopJimmy

Even if flashed Back to stock and locked they will see the tune was there. The new software picks it up. I was just at the dealer last month and my mechanic told me all about it. It's the first thing BMW corporate looks for in a warranty request.

I figured, but what's the worse that could happen my warranty is already expired lol

[F80_Greg]

Originally Posted by TopJimmy

Even if flashed Back to stock and locked they will see the tune was there. The new software picks it up. I was just at the dealer last month and my mechanic told me all about it. It's the first thing BMW corporate looks for in a warranty request.

I could always pull the plugs and check for fouling

[F80_Greg]

Bump!

Hi everyone, I'm still trying to hunt down my rough idle problem. I have tried a number of things to figure it out but no luck yet. I have tried pulling plugs to check for fouled plugs since i have a suspicion one or multiple injectors have gone bad from e85 use. Plugs look okay, i can upload pics. They are NGK 97506 with 2k miles on them. Car has 36k miles. Currently flashed back to stock tune and relocked dme with bm3 with 91 pump gas in the tank (best we have in CA). I have tried unplugging both MAF sensors, resetting adaptions, no difference. The exhaust does have more of a very slight gas smell, but i have catless down pipes mid pipe. I'm just got access to ISTA+ and playing around with it to try and pinpoint this problem. I'm new to ISTA so still learning. Does anyone know which tests to run? I have tried individually temporary disabling injectors in the software, but the idle roughness is affected the same with every injector being shut. Possible leaky or stuck injector? There are no errors or malfunctions in any modules such as the DME. Zero fault codes. I have screenshots of (rough running values) for all cylinders on ISTA along with (misfire values) and o2 sensor values. Problem is i don't know how to read these values as I'm new to ISTA. Any assistance would be appreciated! Thanks guys

[TopJimmy]

The plugs look pretty clean.

Is this a situation where one Lambda reads different at idle, but when you give some gas the Lambdas run equal?

[F80_Greg]

Originally Posted by TopJimmy

The plugs look pretty clean.

Is this a situation where one Lambda reads different at idle, but when you give some gas the Lambdas run equal?

Yes it's like that, think I'm going to order plugs, coils and all six Bosch eu6 injectors on fcp with lifetime replacements. Maybe i can get away with Just plugs and injectors. I'm trying to learn how to do injector testing on ISTA+ to narrow it down possibly. The last picture i attached shows misfire counts on basically all cylinders when tapping the gas pedal. It shakes and stumbles a bit then stabilizes. Still no codes

[TopJimmy]

It could also be the downstream O2 sensor on the one bank.

[F80_Greg]

Update: Issue solved for anyone who might be having similar issues. In my case, injector 4 & 6 seemed to have a partially stuck open issue. When pulling all injectors, the rest came out dry except for those two, they were dripping from the tips when pulled out. Seems like that was causing the rough idle issues. Ordered OE Bosch EU6 injectors from FCP because of their lifetime free replacement warranty. My injectors did not need to be coded for the record, the 3 digit numbers matched the oem injectors along with ISTA+

[lookitsapples]

Jeez, what's the best way to prevent this? Seems stuck injectors keep popping up when I read up about going full e85