Engine stutter

[Speedsicks]

I wanted to see if other people are experiencing this issue as well: When I'm going WOT from 2nd to 3rd gear and let out the clutch and punch it in 3rd, I always get a long (half second) stutter before it takes off. Also the other day on the freeway, I downshifted into 4th, was at about 4k RPMs and was riding it there for a good 10 seconds (so doesn't seem like a timing issue) and when I punched it, the same half second stutter and then bam - takes off. No audible knocking, and unfortunately I have no AP or DH to monitor now.

Any similar experiences or advice?

 

[m4tic]

yup... thats pretty much normal

 

[amillman2]

same thing here too.. i would describe it as more of a pause for me tho.

 

[i8urgti]

Don't flame for this noob suggestion, but this could be the delay of the turbo building boost. The delay could be the brief lag that all cars turbo cars experience, luckily we have less than others.

 

[Nigelo]

Hmmm, at the rpm's you describe there should be no 'stutter' at all (and maybe only the tiniest turbo lag after a shift, less than a second)

Although its almost a cliche with the disi engine, sounds more like a fuel pump issue.

 

[bova80]

its normal with this car. no way around it cause we have all been looking. you can either delay getting on it as quickly or get a cobb ap and flat foot shift.

although i don't think there should be any stutter when punching it in 4th, maybe lag but not stutter. is the stutter you experience make popping sounds like back fire? the ms6 runs rich.

 

[markspd6]

i have problems too.. but, only in third i figured it was fuel cut cuz the boost goes higher in 3rd.. so yeah this happens..

 

[Speedsicks]

It's not turbo lag, the engine actually cuts out for a split second. I was thinkin maybe fuel pump also, but i had no fuel pump issues when I was tuning with the AP, and my mods aren't anything that serious (CAI, TIP, Boost tubes, TMIC, BPV, TP, and CBE). When the AP was installed I didn't have this problem at all, so I'm leaning towards some part of the stock map being the problem.

Thanks for the feedback everyone

 

[Nigelo]

After reading your mod list --> fuel pump.

 

[markspd6]

yeah its the fuel pump either way.. the stock map just doenst wanna work without more gas.. and i imagine the cobb had compensated for this??

 

[Speedsicks]

I was minus the TMIC and the TP when I had the AP installed. It did eliminate that stutter completely. I'll probably pick another one up this summer when I've got some extra loot, but I was noticing a lot of heatsoak going on so I sold it to get the TMIC and the TP was just a cheap upgrade.

 

[Qwik6]

Mine used to do it to. There was no way to get around it and I felt like the enge was going to blow. Like bova said. only way to cancel it is a flat foot shift with AP. The shift is seemless with no stutter and holds around 8-10psi. I have lost races because of this stutter...

 

[Nigelo]

Flat shifting keeps the revs up. This keeps the cam shaft rotating at enough speed to keep the fuel pump pressure up and removes the cause of the stutter.

In 'normal' shifting when the revs fall as the clutch in engaged and accelerator released, the pressure drops off and the pump can't respond fast enough when the next gear is engaged and the throttle is depressed to WOT.

I hope this explanation/reason is correct, its my own guestimation

 

[Speedsicks]

It sounds correct, but what can be done to shorten the stutter? Maybe going 3/4 throttle instead of WOT until you're fully in gear?

 

[Nigelo]

Upgrade your fuel pump? I've an MS3, but I get exactly the same issues as you. It only arose once the air temps really dropped and I had a decat pipe and SRI. Once the weather got warmer it went away, until I got the car remapped and then it came back. Putting 1+1 together I guessed the pump couldnt cope. The dense air/more boost meant not enough fuel. ...and you've a lot of breathing mods on your car too!

My internals for the pump are on their way. Once they're fitted I'll be back and say if it sorted my problem.

 

[Mr. S6]

Engine Stutter

Greetings,

I've had the same issue, mine is more in the 2500 to 3000 RPM range. By using quality gas (Shell/Union 76) , the stutter seems to diminish quite a bit. If I use cheap gas (ARCO, Fastrip), I get a lot of it.

 

[cccpms6]

wasn't there some way that people got the stuter to go away? I sometimes get a significant stutter when shifting without letting go of gas completely. Correct me if I'm wrong but I've read before that by stretching the coil springs many of those who tried where able to get rid of the stutter. I haven't seen anybody bringing that up in a while.

 

[AWDRACER6]

I was asking about this a couple years ago...and ive searched every where and have found nothing! My car is soooo horrible! I just gave up. The springs thing didnt work for me. there is a how-to so u can try it and some people did have there problem fixed. As far as the fuel pump, i always think thats what the problem is but who knows. Where can i find an upgraded fuel pump? There are a bunch of posts about this and ive posted some so if u wanna look at more info on this look thru my post....Good luck...you will need it!!!

 

[Blendercloud]

CP-e makes an upgraded pump. It's pretty expensive unless you send them your stock one for the core charge.

 

[FORZDA 1]

CP-e makes an upgraded pump. It's pretty expensive unless you send them your stock one for the core charge.

Even with the core exchange, the CPE pump is incredibly expensive at ~$650 PLUS $325 core for an initial total of ~ $1k. If you can use hand tools without breaking things or dropping parts into the dirt you can replace the internals in your own pump for significantly less money. I put the KMD kit into my pump and it works perfectly.

The consequences for an installation error on the internals or the HPFP itself can be costly, but so can upping the boost on your car, so YMMV.

Here are a few options for getting your fuel pump up to "Speed".

http://www.kmdtuning.com/index.php?_a=viewProd&productId=1153

http://www.kmdtuning.com/index.php?_a=viewProd&productId=1153

These are the only viable kits I'm aware of. These internals kits and upgraded pumps can be purchased from a number of vendors.