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Discussion Starter · #1 ·
So I have been having many issues with my engine not running properly lately. For the longest time I havent been able to figure it out (8 months). I will give the details about it if some of you want to try and give me advice, but I am now going to do the "Replace everything until it works" approach. :dollarsign::dollarsign: I have an LS2 engine with the 25t reluctor and have converted my harness to work with LS6 PCM using a conversion kit. I will agree that I should have probably just stuck with the LS2 computer, which I still have and can probably switch back to if needed.

I am just curious if anybody recommends anywhere to make a custom engine harness for the GTM. I want to replace mine which is used and slightly butchered for a new one. Thanks for any advice.

I also am hoping that buying ISIS, I can get rid of both of the fuse boxes. There is no need to keep them is there?

Now I still welcome anyone's advice so I will give you all the details.

First of all, a year ago the engine was working fine and it drove like a charm on our test drive. It has deteriorated slowly since then.

Symptoms

Takes about 4-5 tries to start.
1st and 2nd try just crank
3rd and 4th spits and sputters.
Once running, it runs terribly and stalls randomly.
Burns very rich, so rich I had to replace the Spark plugs and O2 sensors
Once running, response to giving it gas is sluggish
Once running for a while, it will start right up while its still hot.

History behind the car.

-I have no codes, but when I got my computer flashed they said they will remove the codes I will have with this car for me, so I am unsure if they removed anything that would make identifying this easier.

-New spark plugs and wires, O2 sensors
-Cleaned throttle body
-Crank sensor and coolant temperatures seem to be operating normally.
-MAF sensor cleaned and tested to be operating correctly
-Fuel pressure was perfect.
-Car has spark, air and fuel just probably not the right combination.
-I have cycled between two brand new batteries.
-Have done everything required for an LS6 to LS2 swap. (Probably didnt have to but somebody from FFR tech support told my buddy who is building this with me that it would be better.)

Tomorrow I am installing a new camshaft sensor to see if that changes anything.

If you would like I can post a video of it trying to start and the layout on the engine.

Also, if I am buying a new harness, should I just use the LS2 computer or stick with the LS6 and switch my pedals again. It really isnt much work if the harness is remade.

Thanks to anyone with any suggestions or advice. I really am open to anything. Thank you. :001_smile:
 

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Discussion Starter · #4 ·
I replaced the camshaft sensor and the fuel pump relay. At least I think it was the relay. (Number 35) I couldnt find my fuse lid.

I did manage to start it up after several tries and long cranks. I have a video, Its dark but you can hear me rev it up and it sounds like its about to die as soon as I punch the gas. It seems like it was running rich. But that could have just been all the unburned fuel from the previous cranks.
I dont understand why is hesitating, but at least I ruled out the fuel pump relay and the camshaft sensor.

Video will be up soon.
 

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Discussion Starter · #6 ·
Well just to let you guys know. I replaced the spark plugs for the 3rd time (they were black) Cleaned the throttle body, put some lucas in the fuel. Put 8 gallons of fuel in it and now its running. Maybe not the best but it is a lot better. I still plan on getting a new engine harness if anyone had suggestions.
 

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Derrick,

I got a custom engine harness for the GTM for an LS3 from SMC Performance. Shaun was very good to work with. Harness came lengthened to work in the GTM. Pretty much plug and play.

SMCPerformance.com

Good luck.

-Michael
 

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Derrick. We built a car and the engine had been sitting a while. We tried and tried to get it running. Turned out it would run on ether, so we put a bunch of injector cleaner in the fuel and eventually all of the injectors cleaned out. May not be your problem but odd things make odd problems. HTH, Richard.
 

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Discussion Starter · #9 ·
Derrick,

I got a custom engine harness for the GTM for an LS3 from SMC Performance. Shaun was very good to work with. Harness came lengthened to work in the GTM. Pretty much plug and play.

SMCPerformance.com

Good luck.

-Michael
Thanks, I will take a look at them.

Richard I think you are right about the injector cleaner.

I have a new problem though. Last night it started up and ran smoothly. Today when I came home, I started it up for about 5 minutes playing with my new OBD2 bluetooth reader. It ran fine. I turned it off briefly to look at something, and now when I start it up, it runs for 3 seconds and then dies. It is the same kind of symptoms you would see if your didnt disable vats. :sad:

I am fully recharging the battery even though it was at 13.4v when I tried starting it.
 

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You have to flash out VATS and the steering wheel interlock or it will do all kinds of stupid stuff. It took FFR years to do the steering wheel interlock, if they do it at all. I sent my computer to them three times and then finally to Road Rebel, who works for SMC and it was fine ever since. HTH, Richard.
 

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Discussion Starter · #11 ·
Its okay. its an old problem. The battery wasnt fully charged. I have had this problem before, even with 13V the battery has to be fully charged for the engine to start.

Its strange, because while the engine is running, I see 14V at the battery indicating the alternator is working.

I am using a yellowtop optima battery
 

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Its okay. its an old problem. The battery wasnt fully charged. I have had this problem before, even with 13V the battery has to be fully charged for the engine to start.

Its strange, because while the engine is running, I see 14V at the battery indicating the alternator is working.

I am using a yellowtop optima battery
I once had a similiar problem, finally found that the "new" cables I had bought were not making a good connection between the cooper cable and the ends that had been factory made,. Some how they had corroded between the cable and the crimped on end was not visible at all. Found the actual cause of the problem when I replaced the new cables and cut the other New ones apart to see what was happening. If you show good voltage but do not actually have it check the cable ends. Hope this helps someone.
 

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Discussion Starter · #13 ·
I once had a similiar problem, finally found that the "new" cables I had bought were not making a good connection between the cooper cable and the ends that had been factory made,. Some how they had corroded between the cable and the crimped on end was not visible at all. Found the actual cause of the problem when I replaced the new cables and cut the other New ones apart to see what was happening. If you show good voltage but do not actually have it check the cable ends. Hope this helps someone.

Well I decided to replace my electrical harness with ISIS and get a brand new engine harness. Hopefully by replacing all electrical components, I can fix my problems.

Thanks for the advice though. I will look for that.
 

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Discussion Starter · #16 ·
I wish you posted this a little earlier. I am going with current performance wiring. I will make sure I post my results.

And unfortunately I had someone else tune my car, so I dont have access to the tune. If I end up buying HP tuners I will send you what I have.
 
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