Code 41 Check engine light
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Senior User
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From: Garage Floor
Code 41 Check engine light
Little background on the truck, its an 88 F150 302 4x4 with 125k on the odometer. Has Longtubes, custom 3" single exhuast, Elec fan, sixliter tuneup and a recent MAF swap. Bought the truck with a cobra ECU running things and it didnt run quite right and got terrible gas mileage. Swapped it for the ECU in my 90 Mustang and she runs better than ever but is now throwin a code 41 in the CM part of the test and is trippin the check engine light. If I shut the truck off I can drive about 5-10 miles before it turns back on, shut it off and itll stay off again for about the same. I replaced the O2 sensor seein that it was the original and have taken care of a couple exhaust leaks which I was hoping would take care of it but it didnt. The truck runs awesome, but I feel it could get a little better mpg and with a lean code I wonder if the comp is dumpin more fuel than necessary. ANYways, any other ideas? Ive hunted for vac leaks and not really found anything but I will try a little harder tonight. Just lookin for a couple other reasons this may be happening.
Thanks guys!
Matt
Thanks guys!
Matt
Tuned
Joined: Jul 2006
Posts: 284
Likes: 6
From: Clover, SC
Code 41 is for a lean condition. It is possible that the ECU you have swapped in there has fuel tables for a larger fuel injector than the injectors that are in your truck now...therefore causing it to run lean.
You need to determine whether or not the vehicle the ECU came from has the same size injectors as your truck does. If they are different, then its not going to work.
You need to determine whether or not the vehicle the ECU came from has the same size injectors as your truck does. If they are different, then its not going to work.
Cargo Master
Joined: Jul 2009
Posts: 2,538
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From: Des Moines
Little background on the truck, its an 88 F150 302 4x4 with 125k on the odometer. Has Longtubes, custom 3" single exhuast, Elec fan, sixliter tuneup and a recent MAF swap. Bought the truck with a cobra ECU running things and it didnt run quite right and got terrible gas mileage. Swapped it for the ECU in my 90 Mustang and she runs better than ever but is now throwin a code 41 in the CM part of the test and is trippin the check engine light. If I shut the truck off I can drive about 5-10 miles before it turns back on, shut it off and itll stay off again for about the same. I replaced the O2 sensor seein that it was the original and have taken care of a couple exhaust leaks which I was hoping would take care of it but it didnt. The truck runs awesome, but I feel it could get a little better mpg and with a lean code I wonder if the comp is dumpin more fuel than necessary. ANYways, any other ideas? Ive hunted for vac leaks and not really found anything but I will try a little harder tonight. Just lookin for a couple other reasons this may be happening.
Thanks guys!
Matt
Thanks guys!
Matt
After the computer has been reset, you'll then need to take it on a 20-30 minute drive so the computer can do some re-calibrating. This drive should include as much steady, open throttle [highway] driving as possible. I don't know if it would affect it or not, but I don't use my cruise control when doing these drives.
So if you haven't already, try resetting the computer and take it on a drive.
Good luck.
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From: Garage Floor
Ok, couple findings and some info to clear things up.
1)A9L computer from a 90 mustang 302 with 19lbers which replaced a Cobra ECU setup for 24lbers so thats not it
2)I unplugged the batter while I swapped the O2 in which should cleared any codes and it popped back up, but again in CM.
3)EGR is removed with a plate on the intake
4) I took the upper and lower intake apart today to swap some gaskets in I had layin around and found the vac. connector to the fuel tank vent tank thing layin unconnected. THAT might explain a few of the stange things its been doin lately. Unfortunately I snapped two bolts off in the head and it took me bit to get em out so Im done for today. Ill get it put together tomorrow and see what happens!!! Thanks for the help guys, lets see whats up tomorrow!
Matt
1)A9L computer from a 90 mustang 302 with 19lbers which replaced a Cobra ECU setup for 24lbers so thats not it
2)I unplugged the batter while I swapped the O2 in which should cleared any codes and it popped back up, but again in CM.
3)EGR is removed with a plate on the intake
4) I took the upper and lower intake apart today to swap some gaskets in I had layin around and found the vac. connector to the fuel tank vent tank thing layin unconnected. THAT might explain a few of the stange things its been doin lately. Unfortunately I snapped two bolts off in the head and it took me bit to get em out so Im done for today. Ill get it put together tomorrow and see what happens!!! Thanks for the help guys, lets see whats up tomorrow!
Matt
Tuned
Joined: Jul 2006
Posts: 284
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From: Clover, SC
Um...what size injectors are in the engine in your truck? If they're 19lb'ers and you're running an ECM that came from a car that had 24lb'ers...then it WILL run lean. Fact. If it were the other way around...then you'd be running rich, but code 41 is for a lean condition. I'm fairly certain the problem is that the ECM you're running is programmed for larger injectors than you have.
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From: Garage Floor
I appreciate the help mechanic, but the FACT is that when I had the truck it had the cobra computer in it that was calibrated for 24lb injectors which was makin the truck run like junk and get terrible gas mileage. I took it out and put in an A9L outta my 90 coupe which is the stock 5.0 mustang computer which is set up for 19lnb injectors. So the 24lb computer is sitting on the bench and the 19lb injector computer is in the truck powering the 19lb injectors so all is square as far as the comp and the injectors is concerned.
With that said, I just finished puttin the new gaskets on and making sure all the vac leaks are taken care of and she seems to run really nice now. Just set the timing and am lettin the computer reset again before I take it for a drive...hopefully thats the end of that! Ill update shortly.
Matt
With that said, I just finished puttin the new gaskets on and making sure all the vac leaks are taken care of and she seems to run really nice now. Just set the timing and am lettin the computer reset again before I take it for a drive...hopefully thats the end of that! Ill update shortly.
Matt
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From: Garage Floor
FAIL...truck runs the same as before, which isnt a bad thing it runs great but still kickin up the check engine light just as before, about 10 minutes or so into the drive. If I drive shorter than that it wont come on and if I shut it down and start it back up it goes away for about 10 minutes and comes back on.
Matt
Matt
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Tuned
Joined: Jul 2006
Posts: 284
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From: Clover, SC
You still haven't said what size injectors are in your **** bro....the computer HAS to be calibrated per the injector size, if its not, it'll either run lean or rich. If you keep getting a code 41, your **** is running lean. Your fuel injector pulse width is too narrow for the size injectors you have, obviously.
I won't post in your thread anymore, good luck getting this fixed.
I won't post in your thread anymore, good luck getting this fixed.
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From: Garage Floor
Ive been foolin with Mustangs for years and also ran the 90 that this computer came out of with 30lb injectors, but only after a custom tune. I pulled the chip outta the computer mechanic so dont worry, its back to the factory fuel tables etc.
Back on topic, I got to thinkin bout the MAF meter and remember it bein kinda picky when I ran it in the Stang so I swapped it out this morning for a stock mustang meter and drove the long way to work...no check engine light. Doesnt mean anything really but I usually get the light every morning on the way so who knows. Ill take it for a longer drive and see if I can get it to trip later today.
Matt
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From: Garage Floor
The computer itself is actually whats calibrated for the injector tho. You can trick the ECU with a "calibrated" MAF meter but when you go get a custom tune they will tweak the computer for the injector size rather than the MAF. I ran my HCI 302 with 30lbers and a lightning MAF meter and will use the same meter on my 393 with 42lbers! All thanks to SCT and some time on the Dyno
Matt
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Yeah thats true , what i was tring to say was the computer will run what ever injecters you put in , but the air meter needs to be tuned for them & yes a computer tune is the best way , i used a meter calabrated for 30# injectors , then had a custom chip buned for the computer...now i don't have to screw with it everthing is set....Lew
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From: Garage Floor
Yeah theres a couple different ways to go about doin it and get the same results. Gettin a calibrated meter is great for people who dont wanna get tunes, but whats the point of doin big mods and injectors if you dont tune it to work to its full potential. Maybe I should just throw this sucker on the dyno and tune it for max efficiency and torque lol
Matt
Matt
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Thats what i would do , mine ran fine but after the tune it was much better , it cost me 600 , for the dyno time , but they set the air fuel ratio , changed the timing cure , elimanated the rev & speed limiters , adjusted the tourq converter , change the trans line pressure , set the idle , set all the shift points , when i got it back it had alot more low end than what it had before the tune , well worth the money....