Ruled out fuel system. Why is my car still stuttering!?

[marshall13]

Okay, my car has been doing this thing where when you are holding throttle at a steady speed, usually past 50mph, it will just start stuttering like all cylinders are firing at once repeatedly. I have gone through my fuel system and either fixed or replaced every part including adding the 255lph pump and AFPR since I thought the FP had a lot to do with it.

A steady fuel pressure did help but it still does the stuttering. I reset the MAFT to my injectors, replaced my GM MAF with a brand new 3" piece, put in new BPR7ES plugs and 8mm NGK wires, turned down the boost, everything I can think of but nothing is kicking it. It sputters and hesitates when you give it more than half throttle and it builds more than 4 psi like it's not getting fuel but the A/F reads around 12.4-11.3 when it starts.

Could the fuel tuning in my ECU be crapping out and the rest of the ECU functions be okay, or could the MAFT be the cause of this or maybe a mixture of both? Please help me. I have not seen anything already posted that looks even remotely like this problem.

 

[98gst14b]

Quite possibly a tuning problem, are you just tuning with a maft? And correct me if I'm wrong but doesnt that afr seem a little rich before you even build boost?

 

[marshall13]

yeah it idles at 14.6 and holds at about 14.5 when not in boost, but during acceleration it gets rich pretty quick. All I have to tune with is the MAFT right now. EPROM ECU but the guy that had it before me was drag racing. He had it set up to run 30psi on E85. Obviously, I am dealing with someone else's problems and have been since day one. I will mess with the MAFT a bit more and lean it out a hair to see if that helps. Where do you think I should be as far as A/F at, say, 3-5psi?

 

[kahl23]

Your profile says EPROM ECU, but does that mean you have a chip (keydriver etc) or DSMLink? What I might do is convert back to the stock 2g MAS and injectors and see if the problem still persists, or maybe find a friend who can lend you a 2g ECU for 20 minutes to see if that is the source of your troubles.

 

[marshall13]

I have no idea what is on the ECU as far as the chip is concerned. I have tried to contact the shop that did the tune but they don't like to relay info to people who end up with customers' cars. I don't have any friends who own a DSM in this state, either. I'm pretty alone at the moment. I would like to get a new chip that is a bit toned down anyway so I can drive it without worrying about what's going to happen next but still be able to take it out to the road course or autocross it every now and again. Do you know who does a good tune and doesn't cost an arm and a leg? Even if it doesn't fix the problem, at least I have that taken care of and can check one more thing off the suspect list.

 

[kahl23]

If you have an EPROM ECU and want a plug 'n play setup, look into Keydriver chips. They don't allow the same adjustability or functionality that DSMLink (or ECMLink, whatever) allows for, but by the same token they are ready to go as soon as they're installed. If you don't care about different tunes for race gas/pump gas then I'd say give them a call and see what they can do for you.

KEYDIVER Chips - DSM ECU Tuning

Hope that helps

 

[marshall13]

That helps a lot. I think this may be the route I go since DSMLink is a bit out of my price range at the moment.

 

[kahl23]

Glad I could help

 

[the_mork]

I had a very similar problem at one point that turned out to be bad compression on one cylinder. Luckily for me the problem was a cross-threaded spark plug but you may want to test just to be sure.

 

[Nicks2319]

This is caused by the random misfire code because you are 6bolt swapped. This is a very common problem with the swap. To fix it, you need to have dsmlink and check the "disable random misfire" option, or get a keydriver chip with this option. Here is more info for you:

http://www.dsmtuners.com/forums/newbie-forum/286962-random-misfire-w-6-bolt-swap.html
http://www.dsmtuners.com/forums/newbie-forum/271588-2g-6bolt-options-random-misfire.html

 

[marshall13]

Thanks again for all the help guys. I looked at the website given above and also got a message from Jeff at Keydiver. I'm really leaning towards them instead of DSMLink both for price and for my needs. I am toning the car down instead of trying to continue making 330 whp. I actually need to sell the car and get a four door since my second kid is due in July, but if the tune is what I want I may keep the car....... in any case, I would LOVE for this thing to run properly for just one day at this point. I think the income tax will get it for me. I will keep the profile updated as things change out and maybe write my thoughts about the tune when I get it. After the ECU, there is only a few small things left to do. Isn't it nice to see the light at the end of the tunnel?

 

[bling5tatus]

I don't understand why everyone thinks that part of troubleshooting a problem is recommending you "just get a dsmlink and click this check box"... Anyone worth their salt knows that throwing parts at an unknown cause for a problem is NOT the right way to troubleshoot.

I'm sick of it. DSMLink is highway robbery and everyone's like.... hell yeah, it will fix your problem.

Another good one is anytime a 2g guy has a problem everyone's like, "just swap a 6bolt block in there... that'll fix it."

What a joke. Fix the problem at the root, don't bandaid it with some hacked code to circumvent the error from showing.

 

[Nicks2319]

I don't understand why everyone thinks that part of troubleshooting a problem is recommending you "just get a dsmlink and click this check box"... Anyone worth their salt knows that throwing parts at an unknown cause for a problem is NOT the right way to troubleshoot.

I'm sick of it. DSMLink is highway robbery and everyone's like.... hell yeah, it will fix your problem.

Another good one is anytime a 2g guy has a problem everyone's like, "just swap a 6bolt block in there... that'll fix it."

What a joke. Fix the problem at the root, don't bandaid it with some hacked code to circumvent the error from showing.

The problem is the Random Misfire code which results from the 6bolt swap. The solution is to check that box to disable it. There is no better way to fix that problem. And for the price DSMlink is a hell of a deal. Look at the price of AEM EMS, and that isn't even specialized for dsm's.

 

[bling5tatus]

No, that is one of those newb method's of fixing car problems, what happens if you get random misfire on any other car that dsmlink doesn't work on, how would they fix it? They would adapt the proper component to the car and make it work w/o using a software hack. Not everyone is so rich that they can just afford to pay that much money for something to fix a simple problem.

p.s.... putting a 6bolt in a 2g is another newb fix, there is absolutely NOTHING wrong with 7bolt motors other then a bunch of whiners from back in the day hyping up the crank walk problem. I've seen car's w/ non oil squirter block CONSISTENTLY run low 11's.... and i'm sure they had more in them too, so I don't buy into all this rumors and balogna that is so prominent on this site.

 

[marshall13]

Well I am wanting a better tune for my car anyway and I can't afford DSMLink. I am going with the Keydiver chip and ECU. Whether it is a newb fix or not to check the box and make it go away is irrelevant. The fact of the matter is IT WORKS. Yeah, sure, any other vehicle might have to be done differently. But I'm sure some company out there has come up with some easier way to fix it. As for the 6-bolt swap, the car came with it. I know, and so do most DSMers, that the 7-bolt crankwalk issue is too played up as well. But I asked a question about a problem and it was answered. Please don't add your complaints about how often an easy answer gets thrown around. Those who were helpful, thank you. As for the whiners, keep it in a PM. Thread closed.

 

[redgst95]

Does the random misfire have a dtc code? A friend of mine is having a very similar problem his stutttering "misfire" happens only at 2500-3000 rpms, but we are still searching for a fix! he threw a code p1400 but it doesnt say what it is.