Need some expert advise

[koston33]

Mods dp, rp, spark plugs, ms cai, ap stage 2. So at wot I get bad stuttering. I have to left off to make it stop then continue. My fuel pressure does drop to like 900 when this happens. I also just threw a code P2097 Post Catalyst Fuel Trim System Too Rich. So do I need a fuel pump upgrade or is it possible to get a pro tune and even everything out?

 

[solidtrance]

Where are you located, and has it been cold when this happened? Could be at least part of the cause.

 

[koston33]

I live in Georgia but it started doing it before winter

 

[solidtrance]

I experienced something similar today and I have seen a few other threads with similar experiences. I am going to plug in my AP and datalog for a while to see if I can get a log when it happens. It was about 15 deg out when it happened, the car was all the way warmed up, I pulled away from a stop sign on the way to my house and the car fell flat on its face at about 4K in first gear hesitated for a sec and then started to pull hard again. I wasn't paying full attention at the time, so I didn't know if I was at full throttle. As soon as I got into 2nd I stopped the car, put it back into first and went WOT all the way through 3rd. The second time (when I know I was at WOT) there was no hesitation at all until I got to the top end of 3rd and then there was only a slight hesitation (maybe pulling some timing). In the past I have only been able to recreate this when I am at partial throttle (which is 99% of driving for me, lets face it, we rarely need all the power we have). I think the face that it only happens at partial throttle is what make this hard to track down. It would be easy to recreate if it was happening at WOT. I will let you know what I find in the logs if I can catch it again.

 

[MSMS3]

With fuel pressure dropping, it sounds like you need to upgrade the pump - it's a known issue form many with your state of mods. I've been fortunate that pressure is holding fine -- so far.

But before you order a pump or internals, could you answer a couple questions and check a couple things?

1. How many miles do you have on the car?

2. How many of those miles are on your present set of plugs?

3. What are the heat range of the plugs?

4. When did you last check gap?

5. At what rpm range during WOT does the stuttering happen? By this I mean is it at or near your sifit point, or does this happen earlier in the power band, and if so, where?

6. How much boost are you running on that tune, especially under load, say from 4,000 rpm to 5,000 rpm or so?

A couple things to check, depending on answers above:

1. Pull the plugs and look at them. If they are aftermarket plugs, especially if they are step colder, are they clean or are you getting some fouling? The center elecrode should be clean. You may see a little black soot around the very bottom of the threaded part and maybe the last couple threads. That's o.k., given how pig rich these engines run, especially under load, but the ground electrode itself and the center fine wire electrode should be clean. The insulation below the center electrode wire should be white, clean and have no crack or evidence of heat blisters. The ground strap in the area where the spark jumps to the center electrode should be clean and light gray color.

2. While looking at the plugs check the gap. With your mods, you want the gap to be about .026 to .028 on AP tune.

You may be experiencing something called "spark blow out" in which high boost can actually temporarily blow out the spark when you are under load at WOT, especially once you get into higher gears - third and above. A poor analogy would be like trying to light a cigarette lighter in a strong wind, but you get the idea. This seems to happen when boost is raised 2 psi or more over stock and when the gap opens up on the plugs to .035 or more.

If you have the right plugs, if they are clean and if they are gapped properly, then you might have a bad plug coil or wire causing a misfire. If not, then it sounds like you may be a candidate for a fuel pump upgrade or new upgraded internals.

 

[solidtrance]

With fuel pressure dropping, it sounds like you need to upgrade the pump - it's a known issue form many with your state of mods. I've been fortunate that pressure is holding fine -- so far.

But before you order a pump or internals, could you answer a couple questions and check a couple things?

1. How many miles do you have on the car?

2. How many of those miles are on your present set of plugs?

3. What are the heat range of the plugs?

4. When did you last check gap?

5. At what rpm range during WOT does the stuttering happen? By this I mean is it at or near your sifit point, or does this happen earlier in the power band, and if so, where?

6. How much boost are you running on that tune, especially under load, say from 4,000 rpm to 5,000 rpm or so?

1. 110K Miles
2. 2K
3. 1 Step Colder
4. Never (this may be the problem, if so I deserve this for being lazy on the day I installed them)
5. 3.5-5K when not WOT, 5+K when WOT and it is a much smaller hesitation. I have never felt it is 1st gear,a nd I think second is good too. I usually notice it in 3rd and I don't get to the top end of 4th unless I at the track so I am not sure about 4th 5th and 6th.
6. 17-18lbs

I didn't drive my wifes car this afternoon so I will have to get those logs some other time. I will keep this thread updated.

 

[spdjnke]

I say get yourself a Hypertech and go back to stock plug and call it a day, will drive reliabily without any hassles. I did 1step just for the hell of it, but will be going back to stock plugs also once spring rolls around.