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Discussion Starter · #1 ·
Hey all,

I just had my motor installed thurs and tried to tune it today. The my tuner uses the Predator Diablo Revolutions program. First, it was a b*tch to tune and it still runs rough down low. But, when in the mid and upper rpm band, the cylinders are randomly and repeatedly misfiring. When the MAF electrical connector is disconnected, wait for about 5 secs, then reconnected, the misfires go away and do not re-appear until the car is shut off and the process is started all over again. Any ideas?

BTW...car dyno'd at 643 rwhp and 540 rwtq.

thanks for your replies,
Jim
 

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Awesome numbers, Jim!!! I can't tell you what the issue is on your set-up, but I am sure that, once it is corrected....look out for even bigger numbers on the dyno :thumb: !!
 

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Sounds like a tuning issue.

My buddy has a similar setup with a Vortech T Trim with a 244/244 110LSA cam and has 0 drivability issues. His car went 8.90's the other night and makes closer to 800 RWHP.

http://www.ls1.com.au/forum/showthread.php?t=40079

If you disconnect the MAF you are forcing the car in SD mode. I'd look at getting the HP tuners 2/3 bar SD setup and getting the car tuned correctly.
 

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Awesome numbers :thumb: :thumb: I'd try another tuner :z:
 

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Discussion Starter · #5 ·
I spoke to charlie at A&A who tunes all of Andy's cars and he was baffled.
 

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So if I understand this correctly. You are running the engine, disconnecting the maf plug...running the car for 5 seonds and then reconnecting ..?

All with the car running?

Is this safe? (not a flame but a real question. I heard this before but wasn't sure what SD mode was ...

Anybody have any thoughts on this?

Sorry I don't know the answer to your question.
 

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Discussion Starter · #7 ·
JBsZ06 said:
So if I understand this correctly. You are running the engine, disconnecting the maf plug...running the car for 5 seonds and then reconnecting ..?

All with the car running?

Is this safe? (not a flame but a real question. I heard this before but wasn't sure what SD mode was ...

Anybody have any thoughts on this?

Sorry I don't know the answer to your question.
You are correct. The car is revved to about 4k rpms, misfires are being seen, the revs are brought down to about 2k and the MAF is unplugged, wait about 5 secs and reinstall the connector, rev the engine again to redline and no misfires are detected despite multiple revs all with the car running. Shut the car off, restart and the process has to start anew. Weird.

Jim
 

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I would check your plug wires especially if you have headers first. If they all check out as secure, I would just ask your tuner to edit that code out, because your cam is most likely causing the random multiple misfire code anyway. It's pretty normal for that code with a cam.
 

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Interestingly enough (and I'm not proud to admit it) I found out what the issue was...

First I had a drivers side header with a broken bellhousing bracket...(screwed my a/f by adding fuel b/c rear 02 sensors were reading a lean mixture.)

Then a few thousand miles latter...the passenger side let go...

Fixed that....but inbetween the two header Bullsh!t issues...

I had simply taken the quick route to removing and then re installing the air filter assembly...

Want to guess that I had a leak around the entrance to the MAF because I DIDN'T REINSTALL IT CORRECTLY! :lol:

I'm laughing because it took me disassembling the connection from the maf to the air filter to realize it.

Its my fault as I took the fast route the last time I cleaned the filter.

So I'm embarrassed to say...but will anyway...The answer was a simple one...A job I've done a hundred times...I was rushing one time and missed the basics.

Its all good now though...

Thanks guys.

The reason I mention all this is sometimes the answer is in the basics...maybe not my specific example...but sometimes an answer lies in going back over the basics that for sure we wouldn't have made a small error but did...

As Todd suggests...Check the wires..check the plugs

Fwiw..

JB
 

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Discussion Starter · #10 ·
wires and plugs checked and everything is ok. If it as something that was uninstalled correctly, wouldnt I get the 0300 all of the time, even when re-plugging in the MAF?

Todd, I didnt realize that code was common with a cam swap. Anyone else have this? It was crazy to watch the misfires rack up while watching the HP tuners program during a dyno run.
 

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Yes, I believe it to be common as well.

I have H/C and am waiting to get tune corrected and all the while it constantly throws the multiple misfire code!
Like others have said though, I had a rough running car after we installed the heads and it would only throw the code under hard acceleration thought we went over everything when we were putting her back together and a week later I found my #7 wire was burned and cracked all the way through at the boot right next to the header, the thing that was most annoying is that the wires were supposed to be the best on the market and withstand 600 degrees by them selves not to mention I even had cool socks on them :flaming: they only had 1K miles on them as well!

Good luck and hope your able to figure out the issue!
:cheers:
 

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How about tuning the missfire out. You are getting it because of the cam. there is a certain way to tune it so it will work and still detect a missfire when needed. I find what your doing with the MAF pretty weird and is only a bandaid. Hope this helps.

Rick
 

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Discussion Starter · #14 ·
I think the problem was the alternator was accidentaly mounted against the frame of the car, hard mounting the engine to the frame. I used Andy's additional alternator brackets to put more tension on the belt to prevent slippage but pulled it out too far.
 

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I am having an issue an low rpms the car running real rough and dieing. It seems when I chop the throttle it clears up for a while. I was thinking MAF or TPS. However I am not throwing any codes.
 

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Discussion Starter · #16 ·
Fritts said:
I am having an issue an low rpms the car running real rough and dieing. It seems when I chop the throttle it clears up for a while. I was thinking MAF or TPS. However I am not throwing any codes.
Sounds like it needs a tune. BTJMO
 

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Well arrived home after a 29 mile ride and the missing at low rpms showed back up. So bad it would not even start after it died. Fire up for a few seconds then go dead. I unplugged the MAF and plugged it back in now it runs like a top. I think the MAF is about to die, one on order it will be here Monday, if it fixes it I will post.......

Thanks
Mike
 
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