I am not sure what the issue is with my L motor swap into my 2002 Screw. A little bit of history, Truck originally had a 4.6L with a 4R70W trans. I swapped in a complete L motor out of a 2003 Lightning (Oil Pan to Intake to Intercooler) I kept the stock ECM and wiring harness and the 4R70W trans and did a soft rebuild, shift kit, and bought a heavy duty torque converter for the trans. I had to redo some of the original wiring harness to work with the new L motor (TPS sensor wire, and IAT Sensor Wire) I had to buy another flex plate that fit on the L Motor crank, and had the correct bolt pattern for the 4R70W converter. I have an XCal II tuner, and went to a reputable tuner to make sure everything would be OK with the original ECM. I put the stock tune back on the ECM before I started any of the swap. Once the motor was in, and everything in place, I cranked the truck. It started on a dime and everything was smooth. I took the truck to the tuner to have it dyno tuned, and thats when all the issues began. I drove it there, and once on the dyno, he was trying to change some of the shift points and limiters so he could begin tuning the truck, and right as he connected the tuner for the first time, something went wrong. When he tried to start the truck, the idle was horrible, and it would barely stay running. He worked on it for hours trying to diagnose the problem. I mean I drove the truck there, he checked over everything including fuel pressure, coils, voltages and could find nothing wrong. He continued to try and return the tune to stock, and that didn't help either. So I was stuck there for a long time. After about half a day of this, mysteriously the stock tune went back in, and the truck idled and ran OK. He attributed the issue to be with the ECM, because he could never find anything else wrong, he even thought maybe it was the exhaust clogging up, because I had brand new dual exhaust with hi flow cats and magnaflow muffs, but when we disconnected the exhaust to see how it acted with open manifolds, it did the exact same thing and wouldn't idle right, and wouldn't run right when giving it gas. So in the end we kept the truck in the stock tune and it would run right, he only got it to produce 330 hp on the dyno but said it was cutting out for some reason at higher (above 3000) RPM's. The truck was driveable, and at this time I REALLY needed it since it is my daily driver. Phew this is long..... OK, now after driving the truck for a long while I noticed that the cutting out (almost sounds like its hitting a rev limiter) gets worse when the temps are hotter outside. If I get on it while the temps are less than 72 degrees or so, it screams, and the cutting out is a whole lot less, and not until higher RPM's like around 4500 to 5K RPM's. As the temps warm up, the issue is worse and starts around the 3K mark. Any ideas as to what this may be caused by? I am ready to start delving back into this issue and wanted to see if anyone else has experienced anything like this on a L motor swap. Could this be caused by one of the sensors or something. I am blind now, and want to get my truck running right......Please Help

 

Only thing that I had in the past was with a chip that I had in a mustang that would not allow the car to start and would stall when it was hot outside with the chip in. With the chip out it ran great. Dont know if this helps but best thing i could think of. Do you know anyone with another ecu you could try?

 

No, I was trying to avoid having to buy another ECM just to try it, but I guess I'll see if I can find one. Another thing, I just had a rebuilt trans and a new converter put in this week, and it is running like shiat. I am not sure what the issue is, but I am going to check the TPS tomorrow and replace if necessary, then go forward with a new ECM. If this sounds familiar with anyone, please feel free to chime in.

 

You should not need another ECM. Most of us have started with 5.4 ECM vice 4.6 ECM. So I'm not sure if there is a diffrence between 4.6 ECM and 5.4 ECM. If you have a Wiring Shop Manaual you can check. I have one and will try to check tonight. As far as starting the truck, it should not have run correctly with the stock NA tune, the injectors and MAF were different. As far as engine harness goes you must have used your 4.6NA harness so the cutting was just to get the wires longer to reach new locations. Again others have done that with 5.4 NA harness with no problems. I used stock L/HD engine harness and plugged into NA chassis harness.

So I am surprised the engine ran correctly. Maybe sensors. Tune should take fuel/load maps from L and plug into NA ECM. L/HD does have 2 IAT's where NA has only one. The tuner must compensate for whichever one you are using. You can go either way.

 

Yes, I only had to lengthen the wires to reach the new locations for the TPS and the IAT sensor. I did use the stock wiring harness from the 4.6 because I kept the same stock transmission. I am really unsure as to why the truck went haywire when my tuner tried to change any of the parameters of the tune. Basically he had to take it back to the stock 4.6 tune just to get the truck to run the way it is running right now.

 

I still don't know how it ran good with 42 lb injectors and 90mm MA. Should have at least had a check engine light.

Would be interested in hearing how towing gors with that converter? Was looking at buying one myself, but stall speed bothers me.

 

i have a single odd question... what air filter element are you using? my truck absolutely would not run with the short "ebay" cone filter...

 

Cobrakit: I am using the stock lightning injectors with the stock lightning MAFS. I am also using the stock lightning fuel pumps as well. I had to rework the fuel pump system to go from single to dual. So I have the dual pumps in the tank.

Klitch: I am using the stock Lightning Air Box with a K&N element.

 

When you said stock tune was that for the natrually aspired or blown? The 42 lb injectors and 90 mm MAF should have caused you problems without a new tune.

Also, you could have gotten by with 1-255 pump. The L/HD dual pump combo (as I remember) uses 1 pump for low boost and the second kicks in at higher boost, ECM controls. And both were 155's.

 

cobra the way i understood it is he has less issues running the stock tune than he does with someones tuning?

do you know the history of the injectors?

can you get us the maf counts? they should be less than 200 at idle roughly if i remember

 

Yea, the stock tune was for the naturally aspirated 4.6L, actually now that I'm thinking about it, it was a hi-performance tune for the 4.6L that was tuned by Troyer. I guess to be honest, I am not even sure what tune ended up in the darn thing. I guess I should check it with the tuner when I get home.

[/QUOTE]Also, you could have gotten by with 1-255 pump. The L/HD dual pump combo (as I remember) uses 1 pump for low boost and the second kicks in at higher boost, ECM controls. And both were 155's.[/QUOTE]

As far as the pumps go, I do realize that the two pumps were separately controlled units on the stock L, but without spending an extra 300 bucks, I opted to just have both 155L pumps working together off of the same leads that I spliced together. While on the dyno, there were no fuel issues, the psi never dropped indicating that I didn't have enough fuel. So for now, I have to go with the two stockers.

 

What injectors did you have in the 4.6? Were they 19 lbs? If you were using a performance tune from Troyer I would call him and discuss the changes.


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