LTFT increased over 10% after oil change (new E85 user)

[tracerit]

I was driving to Chick Fil A today and peered over at my OFT and noticed that LTFT was around 8%. Later noticed it over 10% on idle. I had normal fuel trims on my first full tank of E85 two weeks ago. I filled in my second full tank of E85 yesterday (and took it easy, under 3k, for first two miles) and performed an oil change this morning. So those two have been the only varying factors.

Here is my log: http://datazap.me/u/tracerit/new-ene...og=0&data=8-10

[steve99]

Originally Posted by tracerit

I was driving to Chick Fil A today and peered over at my OFT and noticed that LTFT was around 8%. Later noticed it over 10% on idle. I had normal fuel trims on my first full tank of E85 two weeks ago. I filled in my second full tank of E85 yesterday (and took it easy, under 3k, for first two miles) and performed an oil change this morning. So those two have been the only varying factors.

Here is my log: http://datazap.me/u/tracerit/new-ene...og=0&data=8-10

No exhaust leaks ??
Stock intake ??

If stock intake and no leaks, you may have just got some high ethanol content E85, that tune will have low trims with about E70-E75.

Try giving it a bit more time, say another 10 minutes or so driving, if still high positive trims see below

since the trims are mainly positive, ie ecu is adding fuel to correct lean condition it appears you have E85 that probably close to E85, if you add 3 or 4 litres (is that about a gallon ??) of petrol to a full tank of E85, will dilute the E level and will cause it to run richer and positive fuel trims will come down a bit.

[tracerit]

Originally Posted by steve99

No exhaust leaks ??
Stock intake ??

If stock intake and no leaks, you may have just got some high ethanol content E85, that tune will have low trims with about E70-E75.

since the trims are mainly positive, ie ecu is adding fuel to correct lean condition it appears you have E85 that probably close to E85, if you add 3 or 4 litres of petrol will dilute the E level and will cause it to run richer and positive fuel trims will come down a bit.

Intake I'm using the stock airbox with aftermarket filter and a Perrin inlet hose. Is that generally considered "stock" whereas CAI are "non stock"?

I don't believe there are any exhaust leaks, I've driven with no issues the last 1.5 years without modifying my exhaust setup in anyway. That will change when my OFH comes in though :P

Ah, I do recall adding 2oz of Lucas Ethanol Fuel COnditioner after filling up my second full tank of E85 yesterday.

Will try to add a gallon of gas tomorrow and see how the trims react. Thanks!

[dave-]

I had the same thing happen the last couple weeks. I switched back to 98 and found the same problem even with the stock tune. We found that the overpipe to frontpipe flange was poor/damaged and leaking. While addressing that, we also found that the stock header cat had completely disintegrated. I hadn't changed anything on the car in over 6 months so that isn't always a reason.

Since fixing the exhaust leak in the frontpipe, my trims have gone back to +/- 5%.

[tracerit]

i hope it's nothing mechanical. but i will check those parts later next week. Are these leaks easy to identify for a novice with just four jackstands?

here's an updated datalog from an hour ago. thte first four minutes are a drive to the gas station to f ill up 1 gallon of 91octane, then a few miles drive to Carls Jr and Mcdonalds.

http://datazap.me/u/tracerit/1gal-91gas?log=0&data=1

[dave-]

Originally Posted by tracerit

i hope it's nothing mechanical. but i will check those parts later next week. Are these leaks easy to identify for a novice with just four jackstands?

If you have the car up on stands and its safe, you could have another person give the car a few rev's while you're under the car and inspecting the various joints.

[Phantobe]

Originally Posted by tracerit

i hope it's nothing mechanical. but i will check those parts later next week. Are these leaks easy to identify for a novice with just four jackstands?

here's an updated datalog from an hour ago. thte first four minutes are a drive to the gas station to f ill up 1 gallon of 91octane, then a few miles drive to Carls Jr and Mcdonalds.

http://datazap.me/u/tracerit/1gal-91gas?log=0&data=1

Do you have any WOT Pulls? I think this would help in determining if there was a problem or not.

[tracerit]

This may sound silly but does WOT mean pedal to the floor or just max RPM? I"m only asking because I'd rather not floor it in say 3rd gear tonight since it just rained and i'm still a little sissy after losing control a month ago on a wet on ramp :/

[brianhj]

It means the throttle valve is fully open

[Phantobe]

Originally Posted by tracerit

This may sound silly but does WOT mean pedal to the floor or just max RPM? I"m only asking because I'd rather not floor it in say 3rd gear tonight since it just rained and i'm still a little sissy after losing control a month ago on a wet on ramp :/

No worries

WOT = Wide Open Throttle. Pedal to the floor.

Basically what you want to log is a 2nd or 3rd gear pull from about 2k RPM - Redline (7450 I think). The shorter your log the easier it is to analyze, you don't want to do a WOT pull then keep logging 5 minutes afterwards.

[tracerit]

http://datazap.me/u/tracerit/wot?log=0&data=1-2-10

just two very close WOTs tonight. Road was too wet so I figured I'd try another time.

[Phantobe]

Originally Posted by tracerit

http://datazap.me/u/tracerit/wot?log=0&data=1-2-10

just two very close WOTs tonight. Road was too wet so I figured I'd try another time.

On your WOT pull your AFR & fuel trims look good. I'd suggest doing a better pull tomorrow at 2k RPM, then pedal to the floor. You really only need to log from 2k rpm to redline, then pretty much stop logging. It looks like you didnt go WOT until about ~4k RPM.

It also looks like your fuel trims settled a bit below 10%.

Pretty much no FLKC or Knock Corr. as expected on E85, which is good. Everything looks to be in order.

[tracerit]

http://datazap.me/u/tracerit/wot-2nd...0&data=1-2-7-8

WOT twice in 2nd gear then 3rd gear. LTFT looks better now. Is the FLKC at +7000rpm a concern? It's -0.65 which is eerily close to -0.7 which steve99 mentioned should be investigated.

[steve99]

Originally Posted by tracerit

http://datazap.me/u/tracerit/wot-2nd...0&data=1-2-7-8

WOT twice in 2nd gear then 3rd gear. LTFT looks better now. Is the FLKC at +7000rpm a concern? It's -0.65 which is eerily close to -0.7 which steve99 mentioned should be investigated.

looks good now. that little bit of minor knock is not rearly a concern just pull 0.35 to 0.7 out of the timing around the load\rpm it occurrs if your rearly kean