Sputtering in boost and Rough idle

[smills1840]

1999 GSX, stock everything except intake, NGR bov (recirc) and 3in exhaust (no cat). This is on the T25 with the BCS removed.



1. I have a rough idle. It fluctuates from 800-1200, and it also misses every few seconds. It's not bad enough to stall, and it doesn't fluctuate very fast. It just sort of wanders between 800-1200, and misses.



2. It sputters/hesitates in boost. Unfortunately, I don't have a boost gauge, wideband, or any sort of logging. So I don't know where exactly this starts. It is however consistently at 3/4 of the way up the factory "boost" gauge, in all gears. It's not as severe as fuel cut, but it just sputters. It continues to pull all the way to redline, but constantly sputters/hesitates the whole time.



Both of these problems simply showed up one day. I had recently installed my 3in downpipe, but it drove completely fine for at least a month before these problems started.



Solutions I've tried:

1. Multiple BLTs (Found leaks at injectors and BISS, replaced seals and oring. It also leaks at the TB and out the crank case vent tubes, but it's always done that, even before this problem started. I'm certainly not ruling these out, but I'm not sure how to fix the crank case leaks.)
   
   
   
2. Replaced spark plugs with BPR6ES gapped to .028".
   
   
   
3. Ran with MAF both connected and disconnected. Disconnecting the MAF only yielded the typical symptoms, so I reconnected it.
   

1. 
   

Doing these improved the symptoms very slightly, but the problems are definitely still there. I'm really at a loss.



I haven't tried new plug wires yet because I don't want to keep blindly throwing money at this issue.



Tomorrow I might try to do a BLT starting at the LICP so see if my turbo seals are bad, allowing pressure into the crank case. I'm not sure if this is an accurate test, but I read a thread where a wiseman suggested this.



Any input is much appreciated!

 

[smills1840]

Nobody has any input?

 

[chico904]

Have you checked your timing?

 

[smills1840]

Mechanical or ecu?

 

[chacedog1]

I had a similar problem and happened to be a crack in my Intake Pipe. make sure your clams are tight around maf and turbo compressor housing check the couplers for slices pre turbo and check the intake pipe or snorkel (which ever kind you have).

 

[smills1840]

I checked my plug wires in the dark last night and I could see a bunch of arcing. I ordered some new NGK wires so I'll report back if that was the issue.

 

[97_4g63t]

1999 GSX, stock everything except intake, NGR bov (recirc) and 3in exhaust (no cat). This is on the T25 with the BCS removed.



1. I have a rough idle. It fluctuates from 800-1200, and it also misses every few seconds. It's not bad enough to stall, and it doesn't fluctuate very fast. It just sort of wanders between 800-1200, and misses.



2. It sputters/hesitates in boost. Unfortunately, I don't have a boost gauge, wideband, or any sort of logging. So I don't know where exactly this starts. It is however consistently at 3/4 of the way up the factory "boost" gauge, in all gears. It's not as severe as fuel cut, but it just sputters. It continues to pull all the way to redline, but constantly sputters/hesitates the whole time.



Both of these problems simply showed up one day. I had recently installed my 3in downpipe, but it drove completely fine for at least a month before these problems started.



Solutions I've tried:

1. Multiple BLTs (Found leaks at injectors and BISS, replaced seals and oring. It also leaks at the TB and out the crank case vent tubes, but it's always done that, even before this problem started. I'm certainly not ruling these out, but I'm not sure how to fix the crank case leaks.)
   
   
   
2. Replaced spark plugs with BPR6ES gapped to .028".
   
   
   
3. Ran with MAF both connected and disconnected. Disconnecting the MAF only yielded the typical symptoms, so I reconnected it.
   

1. 
   

Doing these improved the symptoms very slightly, but the problems are definitely still there. I'm really at a loss.



I haven't tried new plug wires yet because I don't want to keep blindly throwing money at this issue.



Tomorrow I might try to do a BLT starting at the LICP so see if my turbo seals are bad, allowing pressure into the crank case. I'm not sure if this is an accurate test, but I read a thread where a wiseman suggested this.



Any input is much appreciated!

Have you checked your pcv? While doing a blt have it disconnected from the valve cover
And see if it leaks. I just went the cheap us plastics check valve route. I have a new fp black and it leaks during a blt. Doesn't mean your turbo is bad. Not saying this is gonna fix your problem just giving some advice on your crank case pressure.

 

[smills1840]

Changed out my spark plug wires with new ngk wires. The problem is fixed and the car runs perfectly.

 

[RLSchwabe]

Gratz on the resolution. Been sifting through the forums seeing if anything here matches the symptoms for my DSM. But awesome Glad a shop didn't charge you through the nose to do that. Hoping for the same!