Background on car:

2004 G35 coupe
built motor, APS TT
UTEC w/ 650cc injectors, 1 step colder plugs

For the past couple of weeks I've been having a strange problem with my car. It all started after a weird event, I'm not sure if the two are related, but what happened was I was making a left hand turn and I 'blipped' the throttle a little. I thought that VDC was off, but it wasn't. The wheels spun a crazy amount and immediately after that my throttle was unresponsive. I let off the throttle and pushed it back down and it didn't seem like anything was happening. I did this a few more times and all of a sudden the car took off like nothing happened. I got to where I was going and I started Cypher and found that I had thrown two ABS/VDC codes (didn't record them, not sure what they were). I cleared them and everything seemed fine.

Now, every once in a while (1 in 25 or so), when I push the pedal down the car won't do anything. The RPMs slowly rise, but there is little, if any, acceleration. I can hold the pedal to the floor for 4-5 seconds and basically nothing happens. After about 5 seconds or so the car takes off like a scalded dog. I also have found that if I let off the pedal and immediately push it back down it takes off right away.

It has only been doing it when I went from cruising to WOT, but, today it did it after a 2-3 shift when I was getting on it a bit.

It seems like the throttle body is sticking, but I don't think that this is the case. The only other thing I can think is that the UTEC is messed up and thats what is causing the problem. I know that throttle body problems are common as are UTEC failures so those are my two suspects right now. I haven't been able to log accelerator pedal input Vs throttle body output Vs throttle body position, but that is my next test.

Anyone have any ideas?

 

Log as much as you can with the UTEC... Hopefully it will do its deed when your logging..

 

doesn't the UTEC only take over AFTER boost is reached, I thought It didn't do anything until that threshold is reached. if the hesitation happens right when you mash the pedal, the utec shouldn't be activated yet? no?

 

Yes, the UTEC hasn't 'taken control' of the car yet. I've watched the dashboard of the UTEC and everything looks good.

However, all the signals pass through the UTEC. I remember at ZdayZ at the Tail of the Dragon last year someone's UTEC failed and caused something similar to what I'm seeing, but theirs wasn't occasional, it was constant.

At this point, I think I would be better off logging with Cypher, but I'll make some logs of both and compare them. I don't drive the car very often, so it's not all that easy to log!

 

it sounds like a short term limp mode, i would first try to change the utec. then work my way around the issue changing parts.

good luck kevin..

 

That's what I initially thought, but like I said if I hold the pedal down for a few seconds (all the way to the floor) eventually the car will accererate. I'm not throwing any codes, besides the P300 random misfire code.

I just happen to have a brand new Utec sitting in my garage to try and get rid of the P300 code issue. It's just such a pain in the *** to pull the old one out and put the new one in!

 

Kevin, seen this before with the UTEC. I quick test, is to reflash your UTEC's firmware, and then reload your maps. It fixed the car we had an issue with a car on the dyno.

If not, then perhaps your UTEC or TB is acting up.

 

Logging with the UTEC and/or Cipher so you can see what is happening to the TPS value will help narrow the issue a bit (to see if UTEC is just not "seeing" the throttle change due to a TB or wiring issue or if it's not responding properly).

 

A quick test????

Damn my G35. Reflashing wouldn't be a big deal IF you didn't have to flip that switch on the top of the unit. To get to that switch I've got to pull the whole unit out of the car.

Thanks for the confirmation though that you've seen another UTEC do this. Like I said, I have another UTEC to install, but I haven't been able to find time to do so.

 

Kevin,

I'll let you know if I figure anything out. so far, I can't figure it out. TB has been replaced, and no luck there. also, reflashed the throttle.mot file on the UTEC and no difference. I'll keep trying.

the last resort will be to pull the utec and swap back in my stock injectors.....but it'll be hard to test WOT like that.