I have an 03 G35 with a Vortech V2. The brain is a UTEC. What I'm having problems with is something no one wants to happen to them. Some times (most of time when I drive my car hard) when I turn off my car it has a hard time turning over within an hour or so after. After that randomly my car will not go over 3000RPM. It will accelerate seemingly fine until it gets to 3000RPM then it immediately loses all power and drops down a few hundred RPM back to normal acceleration until you reach 3000RPM again it does it all over again. Then after a few minutes of driving or turning off my car and starting it up again it goes away but to come back another time.

To clarify this a little more when I reach 3000RPM (sometimes) it will jerk back and not allow me to exceed that RPM. I think it has something to do with my tune. It hasn't done this the first 10,000 miles of FI with this tune. Before I go and take my car back to the shop (8 hours away one way) to get it looked at I'm seeing if anyone else has had this problem and has a fix for it. It's weird how sometimes it does it (the first 10 minutes) when my car has been just sitting for 8 hours and it does it when my car was driven hard.

I'm hoping someone has the answer and it's not....replace your ECU/get another tune/use a different piggyback or stand alone. Let me know from the ones who have heard of this problem and know how to fix it or have fixed this problem. It was tuned by Shariff so before I go and take it there I'm asking for anyone on here to help first. Thanks.

 

Well I'm thinking it could be my ignition system or possibly a fuel problem. But I believe it is unlikely because of the circumstances as in what is happening. It shouldn't be my coil packs because I have inspected them and they seem ok. The spark plugs only have 10,000 miles on them so it's not time to change them out yet. Although when I did the compression test the cylinders were all within a couple psi of eachother which is fine although it was at 145-150 psi which is just over recommended. Plus when I drive it for a lil while the problem goes away. So i'm thinking it's definately a computer issue and not a mechanical issue. Do you think it could be my timing chain because I have just over 100,000 miles, and it could be messing with the timing?

 

Since it has not done this for the first 10k of the tune, has anything at all changed or been altered at or around the time of this problem occuring? Even something that was minor and didn't think twice about?

Any CEL?

Check and make sure your 2 Cam Sensors + Crank Sensor are tight and have a secure connection to the harness. If you know how to pull them there is a test you can do on them to make sure they are working properly (Need Volt Meter).

Other than this problem which certainlly is a problem, when the car operates normally do you notice any other issues at all (Poor Throttle Reponse, Decrease in Power, Odd Noises, etc..)?

Chris

 

are the rpms bouncing a bit at 3000 or does it just drop?

 

Since it first happened nothing has been changed or altered. The only CEL I have had is the one I have always had since before the tune which is my downstream O2 sensor. I'll check the sensors tomorrow and look up the test I can do on them as well unless you mean a resistance check. The only other problem I have had in the past since the tune is overheating. It happened a lot last summer and I did a number of things to fix this problem without getting ***** deep.

I feel like it must be my ignition/timing either mechanical or electrical. But the weird thing is after a little while it goes away and it doesn't always do it. Sometimes I'll start the car after work and it will start up quicker than normal and when it does start up quicker it will act up like I described. Then I'll pull over and turn off the car then turn it back on and it starts normal and acts normal....lol. It's a nightmare.

 

I guess you could say it bounces there if I kept the throttle open but as soon as it acts up I let off the gas or change the gear.lol. It doesn't die or just drop down with no response. It acts as if I'm hitting redline if that helps.

 

from what you are saying sounds like a Fuel Pump problem. its either faulty or from your tune.
it also sounds like a timing/tuning problem as well. if timing is in retard it will procuce alot of heat..causing overheating.

i would deff pull spark plugs and read the tips to see whats going on...again a timing/fuel/tune issue can be seen if present.

10k miles is along time.. i would get that check out asap.

 

Def. sounds like a fuel delivery problem. Or maybe even limp mode. Def. pull codes, if you always have a CEL from your catalyst you'll never know what other codes you're throwing without scanning constantly.

 

Yeah I took into consideration that my timing could be off. But with my tune I have it set to slightly more advanced timing on my 2nd map with water/meth. But this happens in both my tuned maps. I also took out the spark plugs about a month ago and they are looking like I'm either running lean (which im not) or my timing is to advanced (which it can't be either). I also took into consideration that it could be a fuel problem although I have a 255 lph Walbro pump installed with the modification done to the pump housing so help with the swirl of the fuel feed (or so I was told). I was thinking it could possibly be going in lag mode and another friend in my car club said it sounded like it could be going in lag mode as well. The thing about that is why would it only go in lag mode temporarily?

One more thing I need to add is that it seems that if I rev my engine up past 3000rpm after I start it and before I put it in gear then it doesn't act up....confusing or what? I also notice a slight difference with the exhaust sound (at about 3000rpm when my car would lag) when I rev my engine up after I start my car. I'm suprised noone has had this issue yet....I also checked my CEL and it's not pulling anything up other than the O2 sensor.

Any more help will be greatly appreciated.

 

Crank sensor or cam sensor can cause this, but usually throw codes. Assuming you really aren't having any more specific codes, my bet is a fuel system issue. Tunes don't change over time.

 

You have PM. I used to have a very similar issue which was from a faulty piggy pack and when it got hot (from the super hot sun in Las Vegas) it would put my car into limp mode. Your issue is limp mode, but for some reason it isn't throwing a code it sounds like.

 

'limp mode' will always throw a code. If there truly aren't any codes then it's something else.

 

i would suggest again pulling those plugs. in 1 month alot can change. your plugs wont lie..i would trust those tips(combustion chamber) rather than a gauge down stream.

please take a pic of all 6 plugs to get a better diagnosis.

another suggestion is to check MAF sensor and TPS.

 

I'm going to get another diagnostic check and see if a code had came up again but the reason why I think it couldn't be limp mode is because the other day when I drove my car an hour in 80 degree weather I couldn't start my car up as in it would turn over then die. That can definately be from the spark plugs considering they were burned last time I checked. It seems to be getting worse.

If my sensors were going bad they will throw a signal. I will take out my plugs when I get the chance and take a picture because I have to send a picture to Ryan at forged as well to see what they think is going on and why after only 10000 miles.

 

Post pics of your plugs if you can. You'll learn more from reading the plugs than anything else. You mentioned 'burned' look that implies detonation and/or lean condition... get it to a shop asap before your engine adds a window to itself.