Intermittent P2178 P2188

[nunzi]

Hello all,

I have been having a problem where the car stumbles a little when idling. The biggest problem is that it is intermittent. Most of the time (when the problem does occur) it idles poorly for a couple of seconds and then smooths out. Very rarely the car will stutter slightly under normal acceleration but it has not happened in a couple of months. It seems completely random as to when it happens. No noticeable problems when cruising/WOT. These problems started a couple months ago and I thought I traced it down to a MAF sensor that was not fully seated in the hole but it did not seem to fix anything. Car has an OTS by Freektune, CS CAI, HPFP, fully catless, stock catback, new sparkplugs (stock heat range). I could not find a boost leak last time I checked, I tested the purge valve solenoid, unplugged the MAF when it was acting up and no apparent change to engine smoothness. I have attached a log from when the car seemed to be running OK (datalog15) and a log from the final revision of the tune in February of this year (idle1). Unfortunately, I don't think I will be able to get a log from when the car is acting up because it is so random. I am out of ideas for what is going on and looking for any direction. Thank you!!!

 

[The_big_dill]

Hello all,

I have been having a problem where the car stumbles a little when idling. The biggest problem is that it is intermittent. Most of the time (when the problem does occur) it idles poorly for a couple of seconds and then smooths out. Very rarely the car will stutter slightly under normal acceleration but it has not happened in a couple of months. It seems completely random as to when it happens. No noticeable problems when cruising/WOT. These problems started a couple months ago and I thought I traced it down to a MAF sensor that was not fully seated in the hole but it did not seem to fix anything. Car has an OTS by Freektune, CS CAI, HPFP, fully catless, stock catback, new sparkplugs (stock heat range). I could not find a boost leak last time I checked, I tested the purge valve solenoid, unplugged the MAF when it was acting up and no apparent change to engine smoothness. I have attached a log from when the car seemed to be running OK (datalog15) and a log from the final revision of the tune in February of this year (idle1). Unfortunately, I don't think I will be able to get a log from when the car is acting up because it is so random. I am out of ideas for what is going on and looking for any direction. Thank you!!!

I sympathize with your frustration. I too have had an intermittent stutter/missfire at idle that I cannot put my finger on. Mine is pronounced at cold start idle though and I believe it is due to the VTCS delete.

Your logs show very healthy operation, although your first log shows long term fuel trims pulling a lot of fuel. Based on your second log, i take it that has been fixed?

 

[nunzi]

Sorry I should have been more clear. The first datalog, datalog15, is a log from about a week ago when the car was behaving OK with it slightly stumbling. The second datalog, idle1, was from final revision of my tune in February when the car was running really well. That's why I don't think it's the tune because I have not changed anything since then besides adding an OCC. I don't think an OCC would cause a problem that's intermittent, thought. Please correct if I am wrong. As I said before, I would appreciate any type of direction as I would rather not take my car to a shop.

 

[Greg Senge]

IMHO it seems to be a fueling type of problem... Your LTFT are wack in the datalog 15, maybe try to get a log just driving around and see if you can pick up something...In the mean time I would look for a crack in downpipe, a loose bolt or something before the primary 02. Maybe even try sourcing out a leak after the maf sensor on the intake or the EBCS hoses...Thats just my 2 cents

 

[The_big_dill]

IMHO it seems to be a fueling type of problem... Your LTFT are wack in the datalog 15, maybe try to get a log just driving around and see if you can pick up something...In the mean time I would look for a crack in downpipe, a loose bolt or something before the primary 02. Maybe even try sourcing out a leak after the maf sensor on the intake or the EBCS hoses...Thats just my 2 cents

His fuel trims were bad prior to the latest tune, the newer tune fixes that issue.

Sorry I should have been more clear. The first datalog, datalog15, is a log from about a week ago when the car was behaving OK with it slightly stumbling. The second datalog, idle1, was from final revision of my tune in February when the car was running really well. That's why I don't think it's the tune because I have not changed anything since then besides adding an OCC. I don't think an OCC would cause a problem that's intermittent, thought. Please correct if I am wrong. As I said before, I would appreciate any type of direction as I would rather not take my car to a shop.

If you plumb your OCC incorrectly, It can cause pressure issues in your crankcase which would result in many possible problems.

When you installed your OCC, did you take the intake manifold off the car to reach the PCV valve?

 

[nunzi]

First of all, thank you for the responses. A couple of things to clear up: there is no difference in the tune between those 2 datalogs, just one was taken in February and one was taken last week, my OCC was set up for the valve cover to the air intake because I noticed a small pool of oil in the turbo every time I would take the intake off. Keep in mind that it was not an alarming amount of oil but it was noticeable. I have cleaned the intake valves, replaced intake manifold gasket and throttle body gasket, and pcv valve. This problem was occuring before this, however, it seems like it is happening more frequently now.

IMHO it seems to be a fueling type of problem... Your LTFT are wack in the datalog 15, maybe try to get a log just driving around and see if you can pick up something...In the mean time I would look for a crack in downpipe, a loose bolt or something before the primary 02. Maybe even try sourcing out a leak after the maf sensor on the intake or the EBCS hoses...Thats just my 2 cents

I can get a log of just cruising around this weekend to see if anything is out of the ordinary there. When I did the downpipe, I replaced the downpipe gasket for safety. I also rounded off one nut on the stud so I had to replace that stud with some stud from autozone. Maybe that could be coming loose? I can check that this weekend too. One thing to add is that the problems do not seem to be at any given engine temperature.
Thank you guys!!

 

[The_big_dill]

The second datalog, idle1, was from final revision of my tune in February when the car was running really well.

This comment that you left was a bit deceiving, thanks for clarifying.

If it isn't a huge deal, remove the oil catch can lines and revert to what you had before.

 

[nunzi]

Update, car still running slightly bad at idle but is perfect when accelerating/cruising. I attached 2 datalogs, one at idle and one cruising, and the cruising one looks like it is running excellent (to my untrained eye). However, the idle one does not. I rerouted my OCC lines so it just goes from the valve cover to the intake now and seemingly no change. I checked the DP area (nuts, gasket) and found nothing out of the ordinary. When the car was cold, I stuck my hand back by the DP gasket to see if I could feel any leaks and could feel nothing. Not sure if I said this before but the MAF sensor o-ring was replaced because there was a tear in it. This was AFTER my tune but the car seemed to run about the same before and after the o-ring was replaced. I also changed out the boost tubes and BPV hose a couple of months ago but, again, the problem was occuring before and after.

 

[The_big_dill]

Update, car still running slightly bad at idle but is perfect when accelerating/cruising. I attached 2 datalogs, one at idle and one cruising, and the cruising one looks like it is running excellent (to my untrained eye). However, the idle one does not. I rerouted my OCC lines so it just goes from the valve cover to the intake now and seemingly no change. I checked the DP area (nuts, gasket) and found nothing out of the ordinary. When the car was cold, I stuck my hand back by the DP gasket to see if I could feel any leaks and could feel nothing. Not sure if I said this before but the MAF sensor o-ring was replaced because there was a tear in it. This was AFTER my tune but the car seemed to run about the same before and after the o-ring was replaced. I also changed out the boost tubes and BPV hose a couple of months ago but, again, the problem was occuring before and after.

So the tune was done with a MAF o-ring that was torn? How damaged was the oring?

Your fuel trims (for both idle and cruising) are showing that there is a lot of fuel being pulled from the system, which would be an appropriate reaction to tuning with a vacuum leak and then sealing it after the tune.

The ECU is managing this rather well since your AFRs are really good, but with those trims, your car will likely have an unsteady idle.

I don't know how it works with updating tunes, but See if you can get your tuner to update your MAF calibration.

 

[nunzi]

I will email the tuner and see what they have to say about a MAF calibration. The o-ring had a little tear in it. I am more concerned about the MAF being crooked while it was tuned. I also forgot I have a picture of the MAF setup when I was preparing for the tune. I attached it below. Looking at it now, that could definitely be a problem and cause a vacuum leak. I will keep you updated on the situation!

 

[Greg Senge]

I would agree with big dill, there is a lot of compensation from the ECU but its out of the normal zone ( SHFT & LTFT = + 10 or -10 is acceptable) definitely talk to the tuner and see if the maf cal is the problem, if not look for cracks in the exhaust system before primary o2 or do a boost leak test if you haven't already. Also check the gap on your plugs, that wont fix the fueling issue but it might be causing the stuttering and the fuel trims might be its own problem (MAF cal or leak), if the plug are fine I would assume its fueling issue or boost leak issue.

 

[nunzi]

So here are the updates: I spoke with my tuner and explained the problem ended up getting a retune. I was given a new base map and the car runs better and the datalogs looks better to me. This all happened today and I want to give the car a couple more days before I call it a fix. Either way, I am glad I got a retune since the possible leak at the MAF certainly does not help the car. Additionally, no CEL after my short drive and letting it idle for a couple minutes today! I attached a new datalog on what the idle looks like now.

 

[The_big_dill]

So here are the updates: I spoke with my tuner and explained the problem ended up getting a retune. I was given a new base map and the car runs better and the datalogs looks better to me. This all happened today and I want to give the car a couple more days before I call it a fix. Either way, I am glad I got a retune since the possible leak at the MAF certainly does not help the car. Additionally, no CEL after my short drive and letting it idle for a couple minutes today! I attached a new datalog on what the idle looks like now.

Glad to hear improvements. As you can already tell, both your LTFT and STFT are much closer to 0 - Thats a good thing. Keep us posted.