Hey folks,

I have a 2001 monte ss turbo'd by cartuning and just recently chipped 2 pistons because of too much boost, so I built the motor from scratch with forged pistons rods etc...

I finally got my motor together and I'm having some problems....

When the car runs into boost it misfires....

I can power brake it a build up to 5 pounds of boost and not get a misfire but when I'm going down the road and put a load on it and start building boost the car misfires....

What Ideas could you think that can be happening here...

I know this is a very generic question but I would like to hear comments from people to see if I can figure this out!

Thanks!

 

I would look at spark plug gap and condition of your wires. Plugs should be gapped at around .052 +/- .003.

More importantly you might also be running some KR if it is chipping pistons. I would get a Tuner like HP Tuners, DHP, or a scanner from LS1M to check the KR. If you do, the LS1M can't help that but you will know about it.

 

Yeah like 04 intimidator said its most likely a KR problem. You DEFINATELY want to invest in some form on scanner or tuner. I grabbed both the LSM1 and the DHP tuner. The LSM1 is easy and small to mount in the car and monitor your KR, 02's, etc. The tuner is good to have to tune for different seasons, or different octane, etc. I would be willing to bet you have the same problem I had with my cartuning kit. See, mine was a naturally aspirated (L-36) motor, which yours is too unless you replaced it with a L-67 motor. Soour compression is 9.4 to 1. Cartuning tunes their PCM's for the L-67 motors which is 8.5 to 1. So they use a more advanced ignition timing with their PCM's they send you because of the lower compression. Like I said, I'd be willing to bet thats your problem. Do yourself a favor and buy a DHP tuner and learn to tune your own car. I'm no expert but if you get one I can help you with what I have learned along the way with tuning. When I got my tuner Isaw 14 degrees of KR with the PCM cartuning gave me. (Your stock computer onlygoes to 15 degrees before things start breaking).Now I'm down to 2 degreesat14psi.I bet your 02's are close to 1000mv too.Runningrich?All you have to do with the tuner to start out, is tweak the timing, MAF frequency, maybe injector flow rate, and a few otherthings and you should be good to go until your comfortable experimenting with the tuner.[sm=gears.gif]


By the way, If you have 42 # Injectors I wouldn't go over 14-15 psi. Our stock fuel pump and 42 #injectors can't keep up with more than that. Then you'd go lean and break things too. Plus stock headgaskets can only handle about 15psi too.

 

Yeah 14* will definately kill a motor right quick. Really once you break 5* you are starting to get into the red zone. This is why I'm not opening it up as I get 7*. I've heard of plenty of people blowing the engines at 9* much less that 14*.

0* is the ultimate goal for KR.

I did not know this about Cartuning PCM's so before you do ANYTHING get a tuner. Completely forget the LS1M at this point and think HP Tuners or DHP.

Hopefully in 2 or 3 weeks I can give you my thoughts on the HP Tuner first hand and get a video on YouTube or on Keegans website.

- Keegan - not a word on my video deadline skillz. =D

 

Did the Forged pistons retain the same compression ratio as the stockers? If they brought compression up it's going to be really hard to keep a forced induction car from pinging/knocking with higher compression. Probably a stupid question, but have you tried actual (not for street usage) race fuel to see if that helps?

How long did the car sit while it was getting rebuilt.. was it long enough that you could have some bad gas? (old gas)

 

Haha, I promise I won't say a word :-X

We need to get you a digital camera, so that you can take some video clips...
And I would be MORE than happy to post stuff for you on the site. Just lemme know!

And I agree with what was said above. Buy a tuner. I am going to have to part with the 400 bucks for one, but in the long run, well worth the money, or, at least I hope so.

-Keegan

 

I got the camcorder, it is just a pain to convert over to digital. I need a camcorder with like a 20 gig drive in it. :P

 

Well, they make em out there... but mucho expensive...

Sorry.. didnt mean to post hijack..

-Keegan

 

Well I quit dealing with Cartuning because customer service stinks! You can't never get a hold of Kevin or nobody in there so I quit fooling with them. ZZP programmed my PCM this time and thats where I got all my parts from except for the rods and pistons...

Spark plug gap is .045 so I don't think I'n having a problem with that plus when I power brake it I can build up to 5 pounds before it starts spining the tires with NO misfire...

The compression was dropped 1 point therefore I don't have an "L36" anymore you could say... I'm runing 8.5:1...

I don't know how ZZP programs their PCM's but mine is runing really rich when it's misfiring, like there is a lot of black smoke coming out of the tailpipe but again it could be from the combustion not happening correctly...

I'm notrunning stock head gaskets... It hascometic MLS .065" so there is another drop on the compression because they're thicker than stock (0.045 I think)...

Now, I have a set of MSD spark plug wires and when I rebuilt it I noticed that on wire number six the spark plug side boot is broke so I taped it..... At first, I thought that thiscould be my problem but why would it be misfiring only when I'm driving it and not while I'm stopped and power braking it??? However, I got another set of wires on the way because I'm going to replace it anyways...

The car did not run for 3 and a half months because of the rebuild process and the tank was left almost empty before I parked it... And I just refilled the whole tank with brand new 93 octane fuel...

Other than that, the car idles perfect... It runs awesome and everything until I hit 1 psi... it misfires like crazy!

I appreciate all your comments, you guys are being really helpful!

Any more suggestions?

Thanks!

 

I have a great idea... I'll give you my M90, you give me your Turbo

Sorry, Other than buying a tuner, I can't suggest more.

-Keegan