ECM Problem or Something else with LQ4 Swap?

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Jul 31, 2013 | 02:06 PM

geoff17

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ECM Problem or Something else with LQ4 Swap?

Ok I've done a ton of searches and still haven't really found an answer. I just finished up my lq4 swap into a foxbody mustang but can't get it to start. I'm using an 04 lq4 out of an express van with a 4l80e. I am running the stock ecm which has the blue and green connectors. I had a custom harness made for me by current performance wiring. Anyways I finally put some gas in the tank and filled up the rest of the fluids in it last night and primed the oil pump then put the fuel pump fuse back in and it started and ran for about 3-4 seconds then died. Thinking nothing of it I tried again and ran for about 1-2 seconds, and then anytime after that couldn't get it to start only try for split second every now and then. So I started to do some investigating and confirmed I had fuel pressure, then tried adjusting fuel pressure anywhere from 30-60psi. Still nothing. Pulled all the plugs, they looked fine. Grounded a plug while cranking and confirmed I have spark. Also put a light noid in the injector wiring and confirmed I have injector pulse. So I have air/fuel/spark but it won't run. Checked grounds, all seem fine. Even temporarily ran a ground from the drivers head to negative post of battery and no change. I have no way of reading the ecm since I have no software or even code reader. The ecm has a base tune it for my injectors and supposedly has the VATS disabled and also tuned to run without a MAF in SD. Anyone have any ideas on what else I should be looking for?
Thanks in advance for any help

Jul 31, 2013 | 02:38 PM

salemetro

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From: Salem/Keizer

Being that it initially ran for 3-4 seconds AND you have injector pulse and spark....it's pretty safe to assume that it's not VATS.

At a very minimum, you need to get a code reader and go from there. My guess is it's either running super-rich, or the maf was not tuned out correctly. You DO still have an IAT sensor in the system, correct???

Edit; Regarding fuel pressure...leave it as it should be....58psi

Jul 31, 2013 | 02:51 PM

Bowtie316

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From: KC KS

How long had the injecters set without fuel in them? They can gum up and stick on you.

Jul 31, 2013 | 02:58 PM

geoff17

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Injectors sat for a month or so in the motor but were brand new re-flowed ls3 injectors. I got them from my tuner and he tuned the ecm to run with these injectors, they are supposed to be 80# injectors. I'm kinda thinking the same thing as salemetro that the MAF may not have been tuned out correctly. And yes I have an IAT plugged into the harness.

Jul 31, 2013 | 03:03 PM

geoff17

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Another quick question, will the ecm throw a code for a problem even though the motor hasn't actually ran? Can it throw the code from just cranking but not starting? I'm really hoping it will throw some code to point me in the right direction.

Jul 31, 2013 | 03:26 PM

salemetro

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From: Salem/Keizer

Quote:

Originally Posted by geoff17

.... but were brand new re-flowed ls3 injectors....

Drilled/re-flowed is not anything I'd recommend. Granted, it's nothing I've ever personally used...but I've read enough about them to keep me away.

http://www.injectordynamics.com/WhosGettingDrilled.pdf

Quote:

Originally Posted by geoff17

Yes....and yes.

Last edited by salemetro; Jul 31, 2013 at 03:37 PM.