fuel cut or what?

[1fast97gsx]

I finally launched my car again after the rebuild and new turbo and so on. I launched it at about 5k and rode the clutch till 6500. As soon as I was off the clutch the car suddenly jerked really hard a few times so I shifted. I hit the up arrow on my safc and the max rpm I hit was 7555. I'm positive I didn't hit a rev limiter, so the only other thing I can think of is fuel cut? It would do this last year as well during hard launches. ( I am now on a new motor, new trans, new turbo and so on.. )

I'm thinking that maybe the tach can't keep up anymore with how fast the car is really reving, so I'm reving too high. It doesn't seem like I should be having problems though.

I tried launching it again this time softer though and shifiting right away and I didn't have any problems. ( or tirespin ) The safc read that I only reved to 6600 that time.... I'd like to take it to at least 7k though. Am I correct in thinking fuel cut is the problem even though it only happens in 1st gear after a hard launch? ( right when the tires stop spinning actually )

 

[espinelli]

Does the same thing happen in other gears when taking it up to high RPM's?

 

[Black95TSIawd]

what other ECU mods do you have. I dont think an afc can remove the rev limiter. 7550 sounds about right. If you hit fuel cut, it woulda felt like hitting a brick wall especially launching the way you did and considering your mods.

 

[1fast97gsx]

thats the thing ... I have a "gforce ecu" ... but nobody knows what it is or what it does. I have made posts about it before but nobody seemed to know what it really is. It was on the car when I bought it and the guy doesn't know either .... I'm assuming it gets rid of fuel cut and the rev limiter but I really don't know what else it could do. I want to just ditch it and get a 1995 eprom ecu, but I haven't found 1 yet.

No it only happens in 1st gear on a hard launch with a hard slip .. otherwise I dont have any problems.

 

[1fast97gsx]

what other ECU mods do you have. I dont think an afc can remove the rev limiter. 7550 sounds about right. If you hit fuel cut, it woulda felt like hitting a brick wall especially launching the way you did and considering your mods.

No an safc can't remove the rev limiter, however a rev limiter won't make the car keep jerking forward and backwards really hard will it? I thought it just makes a loud sound and looses a lot of power and thats it .. no a loose power, gain power, loose power, gain power and so on.

 

[espinelli]

Its g-force engineering. I think those guys may have been one of the first groups to come out with a hacked ecu. Can you view or make changes, tweaks to that ecu? Probably preprogrammed I bet and if you can't make changes to it I would just start by $hit canning the ecu. Maybe the ecu can't handle the performance mods you've recently installed. Sounds like that maybe your problem.

 

[1fast97gsx]

I don't think I can make any changes to the ecu .. like I said I posted before about it and nobody seems to know anything about these things. It was installed on the car back in 1997 and the shop that did it ( TAD motorspors ) no longer does street cars and I can't even find their phone number anywhere.

 

[1fast97gsx]

update: took it for a drive today and launched it .. it did it agan and only around 6000 rpm on the tach too. It kinda does feel like I keep hitting a brick wall actually but how am I hitting fuel cut if that's what it is?!?! Maybe a bad coilpack? The only other thing I can think of maybe the clutch is misadjusted causing it to grab but as soon as it gets a little heated it'll just slip? I doubt it ... I'm still leaning towards the ecu idea since the car has a different clutch on it from last year and I doubt a coilpack would only misfire during a hard launch.

 

[1fast97gsx]

if its a coilpack not firing under a lot of load would I get a check engine light? I have a set of 1g packs I guess I'll try today since I'm supposed to run at the track today and I'd rather not embarass myself too bad.

 

[Black95TSIawd]

a long while ago when i first bought my car, it did the same thing after i installed my catback exhaust. What i did was, i checked all the connections on the coil pack from the plug wires. I found a lil dirt or dust go behind plug wire number one. I got that cleaned up with a vaccuum, checked my spark plugs, installed an mbc, and the popping went away. I would say, check coil pack and plugs, and wires. Go to a junkyard and pick a pack up for cheap. Its worth a try. Good luck.

 

[1fast97gsx]

well I have 1g packs at my house .. I guess I'll try those. Wouldn't a misfiring pack throw a check engine light?

Another thing worth mentioning: My logger is always disconnecting from the ecu as soon as I lay on the gas to do a datalog. Would this point to a bad ecu or are coilpacks still in the question?

 

[espinelli]

i'm stumped. give the coil packs a shot. i think if it were the coil packs you would be experiencing all sorts of other problems. i'll be happy to loan you out my stock ecu in a few weeks, after i get my dsmlink running. if you still have problems and you think its your ecu just let me know. i'll be happy to let you do some testing.

 

[1fast97gsx]

well thanks for the help, I will let you know if I need the ecu. I actaully should have a 95 eprom ecu on the way too if the guy accepted my offer on it so hopefully that will be here soon then. I guess I'll try the packs and hope thats all it is because I'm supposed to run at the track today with some friends. Maybe I'll just roll it off the line

 

[EVIL X]

My car has done that same thing two diff. times. the 1st time, the plug for the MAF wasnt connected all the way, causing it to buck real bad, and the 2nd time was the intake pipe where it connects to the turbo, was leaking around the clamp, causing unmetered air (so i think) to enter/exit and it jerked and felt like fuel cut as well. those are my 2 exp.

 

[1fast97gsx]

My car has done that same thing two diff. times. the 1st time, the plug for the MAF wasnt connected all the way, causing it to buck real bad, and the 2nd time was the intake pipe where it connects to the turbo, was leaking around the clamp, causing unmetered air (so i think) to enter/exit and it jerked and felt like fuel cut as well. those are my 2 exp.

Your car ran perfectly fine though unless you were under a hard launch as well? I'm pretty sure my plug is in all the way but I'll double check.

 

[EVIL X]

Its weird, but yes it ran well, it would idle a little sloppy, but it only ran funny at higher rpms....the plug looked like it was plugged in, but when i touched it, it almost fell off. so i pulled the plug off compeltly, made sure there wasnt dirt and shit in there, then put it back on tight. and it ran like a champ, then second time it happend, i have a Big28 so i still use that little rubber ring that goes on the cool side of turbo that comes with the stocker, i hope you know what i mean, and what had happened is i tightened my intake to tight around my turbo inlet and it smushed that rubber ring and it didnt allow a tight seal. so it wouldnt hurt the check, just trying to help ya is all

 

[1fast97gsx]

ok cool thanks for your input and ideas. I just changed the packs out and checked all the plugs so in a few minutes I'm going to go launch it and see what happens. *crosses fingers*