Ok, I've had my car upgraded with the EVT700 package now for about 6 weeks. Since the upgrade (from the EVT580) I have had issues with the car until it warms up to full driving temp. This is typically about 3-4 miles. These issues occur every single time I drive it. Once proper temps have been reached ALL issues disappear completely and the car is insane.

The issue that occurs: When I drive off from a stop the car will 'buck' and several loud 'thumps' will come from the engine compartment. If I apply more throttle the car will hesitate and then thump more. Another second will pass and I may let off the throttle a bit and the car will kind of go again. I sometimes shift to 2nd at that point and the 'thump' will occur again and I'll apply throttle slowly and the car will eventually get going. All of this takes about 5-6 seconds and will occur every time I take off from a stop until the engine heats up. The thumps are really loud and I have no idea what the hell they are. During the thumps there is no forward acceleration. I'm assuming no fuel.

I'm no mechanic but I'm assuming the car is in 'open-loop' mode at this point since the engine is still cold. What components might I look into (MAF, fuel pump, etc) that could produce these symptoms? Keep in mind that once the car warms up it runs beautifully. Like ripping up all four tires through 1st and 2nd gear awesome! I just can't stand driving it for 3-4 miles whenever the engine is cold. It's also frickin' dangerous!

Thanks in advance. And don't ask me to talk to EVOMS. They seem too busy with SEMA to email or call me or my local install shop back for now. I'm trying really hard to be understanding and I really want to brag about how awesome they are once this last issue gets taken care of.

 

Loose plug. Just a guess though.

 

Wouldn't that always be an issue even after the car warms up though?

 

Bad timing on start-up? I would not drive the car and get it to the tuner asap

 

It could be a clutch engagement issue from the bucking description. What happens when you disengage during bucking and then re-engage? Does it go away? If so, then that could be your problem.

 

The car received the EVT700 upgrade when I had a Clutch Masters Stage 3 w/ 8-puck. It was bucking at that time. I have just recently had a Sachs 2.5 put in and it still does it...so I don't think it is clutch related.

 

Possibly...if only the tuner (EVOMS) would call me back.

 

My stock clutch used to buck on occasion and I believe the OEM clutch is a Sachs if I'm not mistaken. I don't think the Sachs 2.5 is immune from bucking either. Once things heat up and expand, it seems to run normal. Flywheel?

 

This is definitely something for me to think about. But you say yours used to buck on occasion. Mine does it 100% of the time.

 

There is a problem with your tune. I had a very similar thing with a replacement 'tuned' ecu once.

 

I hear ya. Was hoping it was something my local shop could do. I'll have to wait until EVOMS can find the time to assist me. Until then I guess the car will just stay parked. Six weeks and counting...

 

Have you tried giving Alex at Sharkwerks a call? Six weeks is way too long just to get a reply! I'm still wondering is it really your tune? There must be many EVT700s running around. If was your tune, would there be more people with this issue? Why don't you just send in your ECU and have them reflash it? That should tell you whether it's tune related.

 

I did too. This would be my bet.

 

It hasn't been 6 weeks since I've heard from them. I apologize if I made it seem this way. I had the install done six weeks ago. One of their techs working on my tune got sick a few weeks after and I've had no luck in getting help since then. Not their fault someone got sick. I would assume they have more than one person that knows these cars though.

Anyway, it seems that every car is slightly different. Also, there can be slight variations in components needed for the upgrade (intercoolers, headers, VTG turbos, intake, gas, etc.). A few people have messaged me saying their EVT packages needed subsequent retunes to dial everything in.

 

can you datalog the car upon cold start ? that will tell you if its the tune or not.