dsm gods needed, popping only at minimal throttle

[dsmoverboosted]

Well I have been trying to figure this out but I can't so I need some help from the dsm gods. I can acclerate great and everything but as soon as I go to shift or if I let off the gas it pops and sputters for a sec every single time. It does the same when I am accelerating but just when i first touch the gas and only for a sec. It doesent seem to be affecting performance at all like the car doesent bog, cut out or shake when it happens (if I didn't hear it I would have no idea its happening), it is basically more embarrasing than anything.

I have recently notaced that if i hold my foot on the gas just enough that i am still decelerating it will pop and sputter for the whole time i hold my foot there.

ahmen!

 

[donmagicjuan]

It can be difficult to diagnose that kind of problem because a number of things can cause similar symptoms. What have you done so far to try to isolate it? In your mod list you report a hacked aircan. You didn't alter the airflow sensor in that process, did you? Also, is your MBC tapped into your BOV line? Is your BOV vented or recirculated?

 

[dsmoverboosted]

Well the last time i remember the car not doing this is before i got my head rebuilt. right after the head job was finnished I had some problems with the car (sputtering and stuff)and found out my ecu was toast. I swapped it with another bad one and I finnally got a good one in yesterday and it never fixed it. So i guess it could be caused by me missing something re-installing the head but i dont know.

I have a brand new fuel filter, new walbro 190, I have checked for fuel coming out the rail and there is more than enough flowing. I installed some new 7es after the head rebuild and some new plugs before. I have also tried 2 different coil packs and power transistors with no change.

I do have a fray in the idle position switch wire going to the sensor could that cause it?

I have chopped up the can more than anything, I removed the lower honeycomb thats it. I have leaned the car out 1-2% with my safc with no change.

My mbc is running from the turbo elbow to the wastegate and no my bov is not venting

 

[donmagicjuan]

Well, if your problems mostly occur when the throttle is shut or very nearly shut, I would say the frayed wire to your idle position switch sounds a bit suspicious. Normally the ECU uses this input to cut off fuel to the engine upon deceleration. If this fuel cut is not happening, or if it's happening intermittently, it might cause the sputtering that you're describing. I would look into checking the continuity of the wiring to the connector. Regardless of what you find, however, I would still make repairs to the frayed portion of the wiring.

Since you have replaced the head recently, I would also recommend a compression test and a boost leak test for good measure if you haven't done them already.

 

[Defiant]

Check for exhaust leaks.

 

[dsmoverboosted]

Well, if your problems mostly occur when the throttle is shut or very nearly shut, I would say the frayed wire to your idle position switch sounds a bit suspicious. Normally the ECU uses this input to cut off fuel to the engine upon deceleration. If this fuel cut is not happening, or if it's happening intermittently, it might cause the sputtering that you're describing. I would look into checking the continuity of the wiring to the connector. Regardless of what you find, however, I would still make repairs to the frayed portion of the wiring.

Since you have replaced the head recently, I would also recommend a compression test and a boost leak test for good measure if you haven't done them already.

it doesent happen when the throttle is shut, only with a bit of throttle. When i let off the gas and engine brake my idc goes to a constant 0% and i get a steady tone from the exaust, ie no popping.

I have not done a compression test since the head rebuild but I get ton's of power and no smoke so i didn't see the point but if you figure it might help i could.

I have done a boost leak test and my tb shaft seal leaks a bit but it did that since i bought the car (before it did this), I know I need to fix it sometime but the system holds pressure for a while despite it and I just havent had the time latley to pull the tb apart. I am planning on doing it in the winter when i park the car.

Check for exhaust leaks.

How would I do this? If I leaned it out a bit more with the safc (of course watching knock) should it help if this was the issue since I'd be removing the unburnt fuel?

 

[95talon_in_ma]

I have chopped up the can more than anything, I removed the lower honeycomb thats it. I have leaned the car out 1-2% with my safc with no change.

I'd put that Honeycomb back in, at least to rule it out... They are touchy..

 

[dsmoverboosted]

I took the lower honeycomb out when i first bought the car and it didn't do this. Removing the lower honeycomb is a "free mod" and is ok as long as the big one is left alone.

I leaned it out some more with the safc to like -4% (stock injectors) and it is the same

 

[Defiant]

How would I do this?

Same as an intake test, except from the tailpipe.

 

[dsmoverboosted]

how would I clamp a boost tester to my exaust tip?