studdering on boost

[larryd]

so when I was out last night trying to get LTFT and STFT values I was coming back and I jumped on the car. Unfortunately the car damn near died and stuttered really bad. I figured I just blew an IC pipe off again so I Pulled over to look at it.

I checked all the piping and every hose coupling is on what appears to be nice and tight. I get back in the car and I do a log to see whats happening when it stutters figuring maybe its detonating. I get it up to 4000 in 2nd gear and it happens again, really bad stutter before it takes off. I check the log and 0 knock count but barely any timing. Looks just like all my other logs. That means the car isnt detonating right??

So im thinking now either I have a really minute boost leak thats not visible or something is wrong with the spark on the car.

Im going to pressure test the intake system today and see if I can find any boost leaks but other then that and checking the plugs do you guys have any suggestions?

 

[NJGSX96]

Check the gap on the plugs and do that pressure test on the intake.

 

[larryd]

gap was set at .31 when I put them in unless it changed since then.. thats the right gap for 20lbs of boost right?

 

[Kevin Jewer]

You should be at .028 for 20 psi. In my case I was getting a weird stutter when boost hit, but then it would pull normaly to redline. Search the DSMlink archives with my name and "fuel cut" and you should get a bunch of posts from about a month ago between me and dave/tom. In the end a .026 gap cured my problem. Its a lot more complicated than that, but you'll find the rest in the DSMlink list Try it out, only takes a minute to change the gap.

 

[larryd]

ugh.. ok i wanted to change the plugs anyway but Ill try going with a lower gap.. thanks

 

[cmc]

It definitly sounds like an ignition issue. I had the same thing going on to my car. I would slam it down and BOG down. Low fuel, retarded timing. Had to change one coilpack.

 

[Violater101]

Define stuttering boost Kevin? Like just normal driving, say going like around 35mph, not really in boost, just cruising and the car wants to stutter (sorta feels like the car is pulling timing, but its not?? or do you mean when you actually get on it and the car wants to stutter and not go anywhere?

 

[rdrkt]

When I would get a huge stutter like that it could almost always be traced back to an ignition issue like spark plug or spark plug wire.

 

[Kevin Jewer]

My case was particularly difficult to diagnose. On my log, the ECU would actually cut IDC/IOT almost to 0 and I would get a single stumble that seemed to coincide with it. I thought I was hitting some kind of fuel cut, which should be impossible with DSMlink. And it did start after the cam install... After lots of debating, and constant communication with Dave and Thomas of dSMlink, I was about to give up. So I pulled te plugs just in case and checked the gap. About 31-32. So it seems that a few weeks with high boost and the cams the gap blew out a bit. Regapped to 026 (028 may well have worked too) and the problem went away. 031 should be fine for most people, but I guess I didnt consider dropping the gap with my current setup.

So it seems that even though there is no fuel cut programming in the DSMlink ECU, and misfire detection has been disabled by the DSMlink software/ECU, it was still sensing the misfire and cutting fuel as a result. Now occacionally when boost first comes up IOT (injector on time) is cut as TPS rises, but there is no stumble. As fas as I can tell this isnt all that uncommon with Green sized turbos.

 

[larryd]

is there a way to test the coil pack? I know I need new wires and plugs but I want to know if I need to replace the coil pack or not.

 

[NJGSX96]

You can test the resistance with a multimeter. You test the resistance at the primary coil and at the secondary coil. Secondary coil is where you plug the plugs wires into. Primary is the plug of the coil. The numbers are in the manual. i don't know them off hand. Something like 11-13.9 for the secondary I think, testing between 1&2 and 3&4. Check the manual.

 

[Violater101]

I have similar problems as described above and it all seemed to start happening after I installed new plugs and a 1st gen TB. I fairly certain that my TPS is not set properly because when I get out of boost in the High RPM range and just put the car in neutral, the RPM's drop well below the normal 750 (more like 300) and it will die if i don't give it gas, then it comes right back up. If i shift into neutral going around 2k RPM's, its fine.

As for my stuttering, I logged today and from what I can tell, havn't really had a chance to examine the log, but i'm not knocking. The car just feels like its cutting out or sputtering. I checked the IO and its around 2.xx ..dunno what it should be. Another reason why I believe my TPS is not right is because the car isn't idling at high rpm's like it should for very long ..this morning was fairly cool and it only started out idling around 1200. I also forgot to put the gasket back on the other sensor. Dunno what that would affect, perhaps let some air it? I'm not sure. Anyhow, this all started happening when I did the swap. I'm going to check the plugs tonight and see where they are gapped at since I run a Green also.

 

[sunflashx]

If the plugs are gapped too wide you will probably get a erratic missfire. If the coil pack is going you'll get a high rpm misfire that slowly gets worse and starts occuring lower in the rpm band as the coilpack dies.

[Edit]HAven't had a problem with plug wires yet, so I don't know what effect they'll have in the grand scheme of things. Each of my other problems occured independantly.[/edit]

I've experienced both.

 

[larryd]

well its only a stutter at 4000..once boost kicks in it kicks in harsh but it feels like the pedal cuts out basically at 4000 when the boost first starts to hit hard and it only does it from time to time.

 

[Violater101]

Mine stutters constantly at low rpms, not really getting on the gas though..i think its the gap on the plugs like they said.

 

[Kevin Jewer]

Your throttle body may have a bad ISC Voilator. TPS wont affect those things. For the stuttering, double check your gap since thats the last thing you did. Try a different gapping tool, preferably a feeler guage.

 

[Violater101]

The ISC was from my 2g tb ..i used both tps and ics, but i did forget to put that gasket back on that goes on before you put the ics on. What does that affect? I'm thinking its the gap. I did a log today and no knock or nothing.

 

[P8ntBalla]

quick question, i have the ngk bpr6es, what should i gap them at on 15 lbs from a t25?

 

[GVR4#1353]

Originally posted by larryd
is there a way to test the coil pack? I know I need new wires and plugs but I want to know if I need to replace the coil pack or not.

yeah its called pull the plug wires out with the plugs on them and watch for spark when you turn the car over

 

[swordfish]

I have had the same problem from gross over fueling.

jeff

 

[Silent2g]

jeff has a point.
happend on my 95 gsx when i was playin witht he fuel one night.

get a buddy to rid with you to watch the computer. knock. timing. fuel trims yadda yadda yadda
doing it yourself sucks.

 

[larryd]

I actually figured out what my problem was, just never replied cuz I feel like an idiot. Here goes..

DSMlink has stutter launch automatically enabled and mine was preset default to 4000 rpms. this is only supposed to stutter your car at 4000 when the car isnt moving, unfortunately since my speedo sensor broke my car doesnt think its moving and hits the stutter. Ive since increased the stutter to 7500 so Im fine for now until I can fix the speedo sensor.