Sputtering popping on heavier acceleration

[flyingewok]

My answer is probably covered in other posts but i don't have the money right now to start replacing things that don't need to be. Hopefully someone will notice an obvious problem here.

Just put in a new maf sensor because i had one with lower and side honeycombs removed for years and it drives a million times better. No more safc adjustment for that. Reset safc to 0 all the way across board. Was running decent on an unknown fuel pump but with high fuel pressure (60 psi with hose removed) but couldn't accelerate in 3rd without running out of fuel, 1st and 2nd were good no sputtering. But i was also afraid to full boost because of fuel pump so i may have been going easy on it. Not 100% sure if it was fine at this point.

Just put in walbro 255 could only get fuel pressure down to 40 with hose attached (supposed to be 33) screw backed all the way out. Now there's enough fuel there for the higher gears but under higher boost i'm getting alot of sputtering/popping but it eventually pulls through it and accelerates. Happens around 4000ish but seems to be boost related because i can half throttle it and get a smooth acceleration. Smells like its running rich but safc says it's running leaner than with the older pump due to lower fuel pressure i'm assuming but still not too lean.

Only other issue is low compression in one cylinder 110-120 and 150 in all others. It's a piston ring, compression jumped up when oil added. Could 110 in one cylinder be causing this?

Any way to do a boost leak test with just a compressor on the intake system alone without buying that special adapter for the turbo inlet?

 

[Breezio69]

There is a few issues that jump out at me.

1 base fuel pressure is 43 at idle with the vacuum line removed

2 yes, the bad cylinder will cause it to run funny

3 the safc isnt a wideband and wont tell you values on the a/f ratio

4 sounds like you need new rings and a tune

5 to do a blt you at least need to cap off the turbo to test the system and put a shrader valve in the intercooler system somewhere. This also requires a gauge to read how fast boost is lost, if it holds any at all.. sure you can test the charge pipes by taking the coupler off at the throttle body and turbo and capping them, but for the cost of just doing that, plus your time and potential for leaks by pulling things apart, $28 doesnt sound too bad to just buy the correct tester. Thats my opinion on that.

Check one thing at a time, but it sounds like you already have your work cut out with a bad cylinder and tuning, or at least get the fuel pressure correct (dont know where 33 came from, or 60 for that matter).

 

[flyingewok]

There is a few issues that jump out at me.

1 base fuel pressure is 43 at idle with the vacuum line removed

2 yes, the bad cylinder will cause it to run funny

3 the safc isnt a wideband and wont tell you values on the a/f ratio

4 sounds like you need new rings and a tune

5 to do a blt you at least need to cap off the turbo to test the system and put a shrader valve in the intercooler system somewhere. This also requires a gauge to read how fast boost is lost, if it holds any at all.. sure you can test the charge pipes by taking the coupler off at the throttle body and turbo and capping them, but for the cost of just doing that, plus your time and potential for leaks by pulling things apart, $28 doesnt sound too bad to just buy the correct tester. Thats my opinion on that.

Check one thing at a time, but it sounds like you already have your work cut out with a bad cylinder and tuning, or at least get the fuel pressure correct (dont know where 33 came from, or 60 for that matter).

60 psi was where it was at after installing the walbro, not set there. May or may not have been that high with other pump but it was definitely not intentional. 33 psi is what the pressure should be with the hose attached to fpr. Fpr is 1:1 with boost pressure. 43 with line removed is 0 in Hg vacuum. With hose attached it should drop 20 in Hg=9.8 psi to around 33 or 34. I have 43 with removed but with it attached it won't go below 40.

As for using the safc i have the blue wire mod which hooks up to stock O2 sensor. I realize it's not a wideband but i'm just trying to get a driveable tune and it's worked so far for that. Voltage fluctuates like it should at idle and part throttle and WOT gives a decent number that i can compare to how the car feels, sounds, and drives . But my stock injectors are back in as well so there shouldn't really be a need for tuning unless my problem is fuel pressure that i have to compensate for.

As for the compression i've seen people on here say they have 120 across the board with no issues so my question is why would it cause it to sputter and pop only at certain times. Like i said it pulls through it so it runs at higher rpm and boost without the problem so that doesn't make sense to me. Yes i know i need to re ring it eventually but is that the problem here? If so can someone explain why.

 

[Breezio69]

Your compression needs to be within a certain percent of each other highest to lowest, a 40 psi drop is well beyond that...

I forgot the exact % it has to be within but I do know you fall out of the "normal" catagory.

When you start getting blow by you may as well be driving a metro, those were 3 cylinder motors

But look up the spec.

Also, I thought the blue wire mod was bad for the sensor in these cars?

 

[93AWDDSM]

pretty sure it's no more then 14psi difference per cylinder on compression test and 122 would be "service limit"

 

[flyingewok]

Your compression needs to be within a certain percent of each other highest to lowest, a 40 psi drop is well beyond that...

I forgot the exact % it has to be within but I do know you fall out of the "normal" catagory.

When you start getting blow by you may as well be driving a metro, those were 3 cylinder motors

But look up the spec.

Also, I thought the blue wire mod was bad for the sensor in these cars?

Crap, i was hoping it wasn't this. Don't really have the money for a rebuild kit now. I just dropped a bunch of money on this car and some other things that are breaking randomly in my life. Like my golf club randomly broke when i hit a ball in the water and i slammed it against a tree, jk, for no reason at all just broke

I don't know if the blue wire mod is bad or not but i've had it on there for 4-5 years and it's been ok. You just splice into the O2 wire at the ecu.

Thanks for the replies guys.