So I posted this over on my350z but maybe you guys might have some insight or input...


Ok so I have a built engine with the greddy kit running 509rwhp on high and 439rwhp on low boost...not very relevant but I'm running a decent amount of boost on my built engine.

When I got my car back from Sam at GTM it ran perfect...nothing wrong at all.

Fast forward about 5 months later since the retune.

Occasionally while driving I'll decide to downshift to get my rpms up (between 3k rpms-4k rpms) and when I do so my car will sound like it's hitting fuel cut. It sounds like a rapid backfire sound and my car stays put and won't accelerate at all until I let off the gas first. On other occasions I'll be going WOT for the entire gear and shift into the next gear and it will do the same...It will stutter and won't let me accelerate til I let off the gas again. I'm not a genious but it sounds almost like it's running really rich and won't accelerate. But it's odd since it's recently started doing this and my old tune never did this either. I had my car checked out by Sam a month ago and he noticed it too but said it's probably due to the E-manage Ultimate not being very good at tuning such incremental rpm's.

Anyway's it really irritates me that my car does this sort of hiccup because I've paid lots of $ and I think it's fair to expect a better engine than stock.

If you guys have any suggestions or advice please let me know. If Sam can't figure it out then I don't know what to do.

Thanks a lot,

-Anthony

 

I have seen this more and more recently on TT'ed cars (never on a Greddy before though) I doubt it has anything to do with the E-Man Ultim.

 

Odd. Do you know a potential problem or is it still a mystery?
And any reason behind it not being the EMU?

Thanks!

 

hmmm it really does sound like it's hitting a rev limiter when it shouldn't be.

what do your gauges tell you? what logging capability do you have?

fuel pump going bad resulting in fuel cut?

a faulty ecu connection? would hate to try to troubleshoot that... you could always consider just moving up to a utec and sell the EU. then you can log what's happening. I'm not aware of how good the EU is at logging.

 

So I took it out yesterday and today and checked the A/F gauge while doing so. A/F is pretty steady through 4th gear at around 10-10.6.
It seems to wind through gears without hesitation but it's when I downshift or upshift fast that makes it backfire or sound like it's hitting the rev limiter.

If I try to downshift into 2nd gear at about 3.5k rpms like I did today, it makes that backfire sound and doesn't let the car move until I let off the gas..and then I shift up a gear to prevent it from happening again.

I then took 2nd gear to 6.4k rpms and shifted into 3rd to keep accelerating and it did it again until I let off the gas. It seems like it's dumping way too much fuel or something.

I hope someone can help me out here. I'd hate to spend more money on the tune and better EMS if it's going to do the same thing. I'd hate to spend $3500 on the V-Pro just so it doesn't do it anymore...

-Anthony

 

was your EU installed by sam?

have you tried accelerating hard with slow and smooth upshifts and downshifts? if the AF readings are steady throughout with the above protocol, only thing i can think of is the knock system integrated via the EU which is stuttering your car.

 

get a utec it sounds like that will clear your problems

 

my mazdaspeed did this for a while after I put a unichip on it come to find out there was a problem with the wire harnes mainly the wire that was tapped into the cam angle sensor. unichip fixed it and I never had a problem after that. Are you getting any CEL's coming on when this happens? if so what are they? you may have a vac leak and it is more pronounced when you down shift like that which is making the ecu over compensate bye dumping fule and causing you to hit fule cut. with boosted cars it can be any number of things.

 

If you have the EU, I think you should have the ability to data log your a/f, ign and knock counts. If you can do that, you might get a much better idea of what's going on.

 

My Greddy TT did the same thing on the EU. I have the Utec now and it will still do it but futher up the rpm or boost range. Sharif from Forged said this was done on purpose by him to save the engine.

 

Yes Sam installed my EU.
I haven't logged it but Sam did a while ago...but it's gotten worse since he last checked it out. He said it was a small rich spot but now it seems to happen more often than not. He said he's gonna take a look at it and hopefully figure this thing out. I sure hope I don't have to live with it though.
A couple ppl on the other forum said it could be the plenty of things so I'll keep you guys updated.

 

Any updates?

 

No update besides the car runs like even more **** now. I can't even half throttle on the fwy in 5th without it hesitating. It's weird it b/c it happens sporadically but happens several times in a short 10 mile drive. I don't know what it is but it really irritates me and after spending all that money it should run great. I'll be contacting Sam to try n fix this problem. I really don't want to but I might end up going with the V-Pro.

 

I had a similar problem on my eclipse when I owned it. Seemed like when ever I hit a decent amount of boost it wouldn't go anywhere, and my exhaust sounded like a machine gun (sort of). Ended up changing plugs, and ignition wires and the problem went away. Just check them out you never know. Also, since your running rich for a such a long period of time I'll bet your plugs are all fouled out. Also, since it's getting worse that leads me to believe that it maybe your plugs.

 

As simple as it seems, that's a good point.