[YoungBlood]

Alright guys, I'm getting a stutter under load, with high boost. Doesn't happen on stock, and hardly ever on stage 1, but stage 2 or higher, going up a hill I can make it happen, when the engine is under the most load, almost like a misfire, but no codes are being thrown. Found a lot of threads on this, with different solutions. My coils are all new, my plugs all have less than 10k on them, and looked good when I pulled them. This issue started about a week ago, and then I had a mosfet go out on me. Replaced them all, and no more misfire codes, but the stutter remains. My injectors seem fine, but those are the next step after walnut blasting.

So, who had this stutter/jerk/misfire?

Did walnut blasting fix it for you? If not, what did? I know my car needs it anyways, so I plan to get it done this week and report back, but I'm just looking for insight. Thanks!

[Sshec152]

It sounds like you have a misfire, which wont always throw a code. If you are tuned, it is possible you have auto clear on which could be the reason there are no codes. Do you have any logs?

[HooDat]

are you manual? could be the clutch slipping

[YoungBlood]

Originally Posted by Sshec152

It sounds like you have a misfire, which wont always throw a code. If you are tuned, it is possible you have auto clear on which could be the reason there are no codes. Do you have any logs?

Yes, MHD. I can pull some logs later today, and it will do it on stock tune and not throw codes, just far less often. I'm thinking the carbon build up is making me misfire..

Originally Posted by HooDat

are you manual? could be the clutch slipping

auto, and I can hear it backfire sometimes from the misfire, so I know it's not drivetrain related

[parksjm7]

I had this exact issue, although my symptoms came out on Stage 1 93 Oct. Do you also have a squeak on engine shutoff?

Both the hesitation /stutter and squeak on shutoff were corrected when I cleaned the MAP sensor on top of the intake manifold and TMAP sensor on the chargepipe with electrical part cleaner / MAF cleaner. Both were gunked with oil.

[YoungBlood]

Originally Posted by parksjm7

I had this exact issue, although my symptoms came out on Stage 1 93 Oct. Do you also have a squeak on engine shutoff?

Both the hesitation /stutter and squeak on shutoff were corrected when I cleaned the MAP sensor on top of the intake manifold and TMAP sensor on the chargepipe with electrical part cleaner / MAF cleaner. Both were gunked with oil.

Good to know, I'll clean those off as well, since I'll have everything apart. No squeak, but the stutter/ I guess you could call it a hesitation mid rpm range, are both there, but I can start a run at like 3k in second and floor it, and not get it, but rolling into boost, and under load up a hill it happens

[parksjm7]

Originally Posted by YoungBlood

Good to know, I'll clean those off as well, since I'll have everything apart. No squeak, but the stutter/ I guess you could call it a hesitation mid rpm range, are both there, but I can start a run at like 3k in second and floor it, and not get it, but rolling into boost, and under load up a hill it happens

Yeah, I was able to downshift and give it the beans no problem, it happened to me at 5th/6th gear right around 1900-2000 RPM or so, giving slight load /throttle on the engine to accelerate in that rpm range when I had four passengers or going up a hill where it would feel like a misfire but no codes were thrown and the engine skipped a few beats. I'm guessing that the two sensors weren't giving accurate air pressure readings to the DME resulting in incorrect air/fuel ratio or ignition timing leading to the stutter? Hopefully someone can confirm or debunk this.

[YoungBlood]

Seems like a good theory, gonna try to get this and cleaning the valves done Wednesday. Would a catch can help this at all?

[Miller335]

Sounds like my issue to a T. I describe it as a "thump/studder" as the RPM climb, usually did it at random WOT 2500-4000rpms.

At first it only happened on higher boost E85 map but not on pump gas.
Then my tank got low one day on pump gas flash and it started happening, filling my tank up again made it go away on pump.

Logs show lpfp was struggling it didnt really get below 50psi but it would dip and spike alot. Swapped out the stage 1 with walbro 255 with a stage 2 pump with walbro 450 and went back to e85 and no more studder/thump so far.

I think my factory pump was slowly dying

[YoungBlood]

Logs show my lpfp holding 65-70 psi consistent, so I don't think that's my issue, but I'll try topping off and seeing if there's a change

[jjbmuu]

I was gonna say sounds fuel or spark related, if the issue just started happening just drive until it gets worse and hopefully you get a code. Your issue sounds to me like a bad coil which can be possible with a new one even. If I get a misfire on my car rolling into boost when load is highest it's a coil pretty much nine times out of ten, have yet to ever over the past 40k miles or so had a misfire due to a bad plug or injector. Although I did replace an injector preventively once due to some cold start stumbling because it was leaky..

[YoungBlood]

Originally Posted by J.J4ck0wsk1

I was gonna say sounds fuel or spark related, if the issue just started happening just drive until it gets worse and hopefully you get a code. Your issue sounds to me like a bad coil which can be possible with a new one even. If I get a misfire on my car rolling into boost when load is highest it's a coil pretty much nine times out of ten, have yet to ever overvtge oast 40k miles or so had a misfire due to a bad plug or injector. Although I did replace an injector preventively once due to some cold start stumbling because it was leaky..

Well, to add to my story, I had a boost leak and was only making 13 psi for the last 2 months, running stage 2. Fixed the boost leak and this started happening, and I blew a MOSFET. Thought that would fix it but the issue persists. If the carbon cleaning doesn't fix my issue, then I'll do new plugs again, and new coils again, and then injectors of all else fails. Hopefully I have good news after the cleaning

[YoungBlood]

Well, update, cylinder 1 misfire AGAIN. New plugs and coils. If the walnut blast doesn't solve it, I guess injectors are the only other solution...

[Eurocraze]

vanos solenoids... clean them out too.. I tell you these things get overlooked, they are like thieves in the night...

[YoungBlood]

Misfire is now bad enough that I can't get on it with the stock tune even. Gonna swap coils around and see if it follows, it's still not throwing codes unless I really get on it, but it did throw one for cylinder 1 again, which just got a fresh coil.. So I also just picked up a set of NGK plugs, my OEM ones with 10k on them don't look the best, all whiteish, and the electrode is worn sort of triangular on 3/6. But, one of my coils crumbled/ stuck to the plug so I'm trying to dig all that rubber out so I can get to it. In other words no walnut blast today, but it will be this week, and I'll report back

[YoungBlood]

New plugs are in, walnut blast is set for Saturday. Ran a log, not a single timing correction. Did a few wot pulls, and a few low rpm boost loads, not stutter or misfire as of yet. I'm thinking when I killed a MOSFET, it took the ignition coil with it? I also put a new coil into the mix, and swapped a different one onto cylinder 1

[jjbmuu]

Originally Posted by YoungBlood

New plugs are in, walnut blast is set for Saturday. Ran a log, not a single timing correction. Did a few wot pulls, and a few low rpm boost loads, not stutter or misfire as of yet. I'm thinking when I killed a MOSFET, it took the ignition coil with it? I also put a new coil into the mix, and swapped a different one onto cylinder 1

Makes sense to me, did you inspect your intake valves to see how they look? Just remove a few things out of the way to where you can at least pull the manifold off enough to see most of if not all the valves.

[Eurocraze]

well that is good to hear then. grab some before and after walnut blasting pics if possible,

[YoungBlood]

Originally Posted by jjbmuu

Makes sense to me, did you inspect your intake valves to see how they look? Just remove a few things out of the way to where you can at least pull the manifold off enough to see most of if not all the valves.

I'm taking all of Saturday to do it, so I'll pull it off then. I'm sure they're bad though, 101k and it's never been done as far as I know.

Originally Posted by Eurocraze

well that is good to hear then. grab some before and after walnut blasting pics if possible,

will do!

[Eurocraze]

how did it all work out mate? you get that walnut blasting done?