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Help me diagnose 408 problem

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Old 05-13-2007 | 10:33 PM
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Did you change injectors? If so, what size?

Might need the crank relearn procedure done on it as well.

Lurius - what part of Arlington are you in?
Old 05-14-2007 | 01:24 AM
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when i got my 408 in there i had to do a crank relearn and turn down my misfire sensitivity down. I know tuning software is expensive but its a cheap mod compaired to a motor.
Old 05-14-2007 | 01:30 AM
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Originally Posted by BigTex
Did you change injectors? If so, what size?

Might need the crank relearn procedure done on it as well.

Lurius - what part of Arlington are you in?
I did change out to the standard(non marine) 8.1L injectors, with plans to upgrade after the motor is mostly broken in, and well before I do any nitrous runs.

Charlie did tune for the injecots, but with the distance between us and me with no data logging software yet its hit or miss mostly.

I am in south Arlington, not far from 360 and I-20, and if you are familiar with this part of town, VERY close(like 1 mile or less) from TCC southeast campus off of 360.

-Lurius
Old 05-14-2007 | 02:55 AM
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ive seen your issue. if all of your plugs and etc are in good shape then it lies with teh tune. your cam isnt large at all for a 408. your cam was designed to go in a stock 346 so being in a 408 isnt really that bad.

take your truck back to your tuner and have him look over your tune, if it still has issues then take it to someoen that knows how to tune larger cams. my first tune i did for a Trex car i had that misfire code. made a few adjustments with a clear head and the codes and car ran great after that. as for how low and idle, i can get a trex to idle all day long around 850. most ppl cant even get them to idle under 1,000 rather alone 850rpms. a ms3 is a sligthly tamer cam with a higher lsa [110 vs 113] and being in a 408 the effect wont be nearly as bad as it would be in a 346.
Old 05-14-2007 | 05:34 PM
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I got my wideband in today from the PLX groupbuy, should be able to see if it is in fact running lean or if its just throwing that code for a bogus reason in a few days when i get around to installing it.

-Lurius
Old 05-15-2007 | 02:33 AM
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Any other ideas guys? I should get the wideband running by Thursday/Friday when the bungs come in the mail, will at least tell me if I am actually lean or if its just a code being thrown for some other reason. I am thinking of pulling the intake tomorrow to see if the grounds on back of head are alright.. I imagine that could cause misfiring if the grounds were loose.. I think the grounds to each head are from coil pack harness after all.

What is the likelyhood of the torque converter being an issue even with the vehicle dying when put into gear? If its very very unlikely then I think i'll be getting some tuning software before bothering with the tranny just yet.

-Lurius
Old 05-15-2007 | 10:54 AM
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its the tune!!! simple as that, the tuner didnt adjust it correctly for the large cam. without adjusting it some it will throw misfire codes its all i nthe settings. also with it not idling that is simple but involves a few steps

take it to someoen who can actually tune a large cam!! this is a very common problem
Old 05-15-2007 | 11:11 AM
  #18  
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Originally Posted by Lurius
Any other ideas guys? I should get the wideband running by Thursday/Friday when the bungs come in the mail, will at least tell me if I am actually lean or if its just a code being thrown for some other reason. I am thinking of pulling the intake tomorrow to see if the grounds on back of head are alright.. I imagine that could cause misfiring if the grounds were loose.. I think the grounds to each head are from coil pack harness after all.

What is the likelyhood of the torque converter being an issue even with the vehicle dying when put into gear? If its very very unlikely then I think i'll be getting some tuning software before bothering with the tranny just yet.

-Lurius

Nah. If the grounds were loose it wouldn't start -- don't start pulling parts. It really is the tune and you need to get some logging (install your wideband while you wait for the tuning stuff) done to help Wheatly out.
Old 05-15-2007 | 01:27 PM
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Well I know the tune is going to be off considering the circumstances(distance, tuning a new motor without being there in person, etc). I dident expect it to be perfect first time around. He has tuned plenty of decent sized cams, so its not a question of his ability. As for the misfiring, it is not that it is just saying its misfiring, I can tell it IS misfiring at low RPM range, would this be caused by the misfire codes being off?

-Lurius
Old 05-15-2007 | 11:36 PM
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HPTuners ordered, will be able to send him the logs now. Thanks guys, i'll have to get some more vids once I get her driving!

-Lurius
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