Goes mad lean+sputters on low throttle cruising

[pSimytSi]

So I've searched many posts for some kind of help but keep ending up empty headed.

I've been having this sputtering problem with my car for the past week or so. It's mainly happening when I'm holding a steady speed staying real light on the throttle. It'll be driving perfect, then all of a sudden it starts sputtering, my wideband a/f gauge jumps from 14ish to 3 Red - - - meaning it's over 18, the maximum my gauge can read. It's basically identicle to what it does when your deceling.

If I try just letting off the throttle for a second and getting back into it the sputtering just gets louder. The only 2 things that cure this is to engage the clutch and wait for the rpms to drop down to the idle level and then resume throttle as if it never happend. Or I can downshift and resume throttle as if it never happend.

So if I'm being easy on the throttle, holding a steady speed, it does this randomly about once or twice every half mile. When I'm running it hard, even from a stop it has never happened, it pulls hard all the way.

I know it has a shorted ISC(possibley some burnt ECU drivers), blown Fuel Pressure Solenoid, stock FPR, FIC 550's, 255lph pump, and a new set of NGK wires and plugs (700miles) and they look to be burning pretty good..

Can anyone offer information? I don't have a logger so I can't show any specifics. I beleive I can check my O2 and TPS sensors on the SAFC though, if that would help.

 

[motomattxxx]

Sounds like you should add some fuel to your low throttle settings to correct for your injector dead time.

 

[dsmgst16g]

im having the same problem. the guy i bought the car from said to increase the fuel pressure an that should eliminate the sputtering however i have not done this yet. but its just something to give thought

 

[knochgoon24]

Fix your ECU.

 

[JEFFREYCASTGSX]

That fuel pump is overrunning the stock FPR, and is most likely the cause.

 

[brownfinger]

I posted a similar question once. I got a response that it sounded like a bad MAF. That's when I remembered that I had swapped in a different (used) MAF while trying to diagnose a seperate issue. I put my original MAF back in, the problem went away. It was just like you describe: chugging and coughing at very light throttle while trying to drive like a normal person might. Try to borrow another MAF to check it.

 

[knochgoon24]

255 with a stock FPR is also a no-no
Fix that along with your ECU.

 

[Tucugs-t]

im having the same problem, but the only way i can make mine go away is by turning the car off and turning it back on...its weird, it only happens when i go over 70mph and i keep it there for a little bit...

 

[blackrosenova40]

Did you ever fix your problem, i am having the same problem, lean misfiring like crazy under light acceleration.

 

[dsm5062]

Did this ever get resolved?? I'm having the same issue with the light throttle cruising and acceleration stumble and wideband shoots to as far lean as it will read. And wouldn't overrunning the stock fpr with the walbro cause a rich condition,not the dipping lean??? I have been talking to jeff from DSMChips.com and we haven't been able to resolve it yet. I am also having to add fuel,about +16-18 on the safc to get it around 11:0 afr under boost with 560cc injectors and the chip with correction for them. I even put in brand new 680cc injectors and was having to add around +14 to get the a/f around 11:0. I am totally lost on what to check, I have swapped walbro's with new strainer,maf's,new fuel filter,tps. any help will be appreciated,I want to get my daily driver back

 

[DSM8ALL]

Are you running an open BOV? I've had similar problems with it being partially open at cruise and causing sputter and surge. Another question, are you running a 6 bolt swap in a 2g? The ecu can be causing a random misfire code and cutting cylinder fire. There is a pretty common fix for that problem.

 

[dsm5062]

I am running a recirculated rfl bov,and I do have a 6 bolt swap but the chip I have is supposed to correct the issue with the random misfire.

 

[DSM8ALL]

OK, if you have another MAF as brownfinger suggested, try swapping that. Also look at your MAF and see if any of the honeycomb is damaged, that will disrupt the air flow and can cause problems.

 

[nyTalonTsi]

A walbro 255 would be fine in most cases without an afpr, as long as its not rewired.

If you really think your ecu is taking a dump, pull it and check it out. Otherwise you don't want to be stranded.


I also agree with if you have a 6bolt, which judging by the pic in your profile you have a 1g head?



If so without link or keydiver you could be getting the random misfires when driving a while on a steady speed as you say you do.

 

[dsm5062]

I figured out the stumble but not the running lean part,the stumble was caused by the injector pins being swapped wrong. but I did a few pulls in it and it is still dipping into the 11's on the a/f with +16 on the safc. And Im getting some knock up high, which I know is fuel related because I was getting no knock when I swapped in the 680cc injectors. But...I was still having to add around +12-14 to get it in the 11's a/f.

 

[Tedbermejogst]

Did you get this figured out? I have the same EXACT problem