Bad ECU?
03-22-2015, 12:08 AM
#1
Bad ECU?
Ok, im fed up and need help. I have recently rebuilt my 1990 f150 xlt lariat 302. The transmission locked up and and I went ahead and decided to rebuild the motor and tranny.
Well I have dumped a little over 5k into this truck, included in that is stepping up to a rv cam, flat top pistions, balanced crank, .03 over, replacing every single sensor on the thing, shorty headers (big mistake) with 3 inch exhaust back. New fuel injectors, new distributor, replaced relays, I mean the list goes on and on. But, the motor is stout none the less but running insanely rich, Im talking like 7mpg rich...
So what has been happening.. I will crank the truck in the morning to go to work, truck will crank good and idle will be low with engine light ON, going down the road after about 5 miles engine light will go OFF and engine will idle up to about 1100 rpm in park. If I turn the truck off and try to crank immediately I have to hold throttle wide open, when the engine busts off it will run super rough and black smoke for about a minute until it smooths back out. That was the start of it. Next problem was the truck wouldn't crank at all unless I unplugged fuel injector #5 and sometimes #6 as they are the easiest to get to while someone cranks the truck and holds the throttle wide open. I actually have to unplug them and crank until it starts bumping over and as soon as I plug them back in it will start. THEN just the other day it quit all together. I have fuel at the rail, 40 psi, I have spark all that good stuff but I just don't have anything. My code reader throwns codes like water temp sensor out of range, overdrive cancel light out of range, and one other non important code. So Im heavily leaning towards a bad ecu. What do yall think? Please and thank you! Any questions yall throw ill have an answer because I do know what im talking about im just fed up. I do not want to do anything but fix it. It means to much to me and I have to much money in it!
Well I have dumped a little over 5k into this truck, included in that is stepping up to a rv cam, flat top pistions, balanced crank, .03 over, replacing every single sensor on the thing, shorty headers (big mistake) with 3 inch exhaust back. New fuel injectors, new distributor, replaced relays, I mean the list goes on and on. But, the motor is stout none the less but running insanely rich, Im talking like 7mpg rich...
So what has been happening.. I will crank the truck in the morning to go to work, truck will crank good and idle will be low with engine light ON, going down the road after about 5 miles engine light will go OFF and engine will idle up to about 1100 rpm in park. If I turn the truck off and try to crank immediately I have to hold throttle wide open, when the engine busts off it will run super rough and black smoke for about a minute until it smooths back out. That was the start of it. Next problem was the truck wouldn't crank at all unless I unplugged fuel injector #5 and sometimes #6 as they are the easiest to get to while someone cranks the truck and holds the throttle wide open. I actually have to unplug them and crank until it starts bumping over and as soon as I plug them back in it will start. THEN just the other day it quit all together. I have fuel at the rail, 40 psi, I have spark all that good stuff but I just don't have anything. My code reader throwns codes like water temp sensor out of range, overdrive cancel light out of range, and one other non important code. So Im heavily leaning towards a bad ecu. What do yall think? Please and thank you! Any questions yall throw ill have an answer because I do know what im talking about im just fed up. I do not want to do anything but fix it. It means to much to me and I have to much money in it!
03-22-2015, 09:30 AM
#2
Water temp sensor not reading right will tell the ecu that the engine is cold and give it more fuel even though it's warm so that's a place to start, since you have a code.
Throttle position sensor - did you replace it ? If so, did you adjust it or just put it on ? However you went with that, you should test it. Search through my posts for 'testing the TPS' (4 or 5 weeks ago).
What did you do about the o2 sensor ? Wrong position, faulty or incorrect sensor can cause havoc with the fuel ratio.
Or maybe it's a bad ECU - or the ECU doesn't like the engine changes ? Or it's just 20 years old. I'd check the other 3 things first.
Throttle position sensor - did you replace it ? If so, did you adjust it or just put it on ? However you went with that, you should test it. Search through my posts for 'testing the TPS' (4 or 5 weeks ago).
What did you do about the o2 sensor ? Wrong position, faulty or incorrect sensor can cause havoc with the fuel ratio.
Or maybe it's a bad ECU - or the ECU doesn't like the engine changes ? Or it's just 20 years old. I'd check the other 3 things first.