Need EEC IV help!
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Need EEC IV help!
Hello, all. My wife was gifted her grandfather's '86 F150 about a year and a half ago just before he passed away. It came to us non-running on a flatbed. Long story short, we got it running and driving fairly nicely and we are in the process of fixing her up, but we are having trouble chasing down a few issues. The main issue we are dealing with is that the ignition timing is barely advancing at all as the engine speed increases. I set the base timing to 10 degrees btdc per the emission label, and in park with the engine revving it only advances maybe another 7 or 8 degrees, regardless of how much rpm i give it. It feels pretty doggy to drive also, and it responds well if I give it more base timing. Also, it occasionally pulls timing at idle once it is warm; the first time it did it, I thought it was going to stall and when I checked timing it was at zero degrees btdc. I tried to retrieve fault codes, but the reader we used could not communicate with the computer for whatever reason. Any ideas on where to look next? MAP sensor maybe? Bad computer?
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Yes, the SPOUT connector was removed. The engine is otherwise healthy; compression is 150-160 in all the cylinders and it starts right up and idles fairly smoothly. The part that kind of has me stumped is the fact that the EEC IV reader at O'reilly was not able to read any codes (or communicate at all) with the ECM. I know the EEC module uses various sensor inputs to determine correct ignition timing based on the tables programmed into it (or at least so I have read), which makes me suspect a sensor issue since it does advance the timing, just not nearly enough to make the engine happy. Is there any way to manually test the sensors or the computer to determine if they are functioning properly?
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Joined: Mar 2017
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From: Everton MO
Mechanical advance locked up? the base plus mechanical should give you the majority of your timing an the vac advance ads to it for part throttle cruising. sounds like a mechanical advance problem.
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It is similar, but this truck has electronic timing control and is regulated by the eec iv module. From what I understand, the module senses engine load via the MAP sensor, throttle position via the TPS, and engine rpm and uses these values to find the optimal ignition timing via a table or map that is programmed into it. It seems that either 1 or more of these sensor readings must be incorrect or the computer itself must faulty, but I don't know how to determine this for sure.
What I do know is that this truck would run a lot better with a proper timing curve; I would prefer to make this happen by repairing the eec iv, but we haven't ruled out ditching the eec and back-dating the truck to duraspark II. I have the parts in the garage to do this swap if we decide to go that route, but it would be kind of neat to keep the original engine management system intact.
What I do know is that this truck would run a lot better with a proper timing curve; I would prefer to make this happen by repairing the eec iv, but we haven't ruled out ditching the eec and back-dating the truck to duraspark II. I have the parts in the garage to do this swap if we decide to go that route, but it would be kind of neat to keep the original engine management system intact.
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From: Everton MO
thanks for correcting me of that, the 86 was the change over year i believe, feed back carbs and electronic timing came in that year. I would assume it uses a combination of crank position sensor, tach wire and knock sensor. someone will chime in knowing better
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For the 49 states [California was earlier], the change over date was 1984 for the 4.9L engine.
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From: Angier, NC
Kzooman,
May want to post this over in the 80 - 86 truck area as I know we have a few guys in there that can help you with the issue you are having.
https://www.ford-trucks.com/forums/forum37/
Good luck
Dave ----
May want to post this over in the 80 - 86 truck area as I know we have a few guys in there that can help you with the issue you are having.
https://www.ford-trucks.com/forums/forum37/
Good luck
Dave ----
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Joined: Nov 2002
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... From what I understand, the module senses engine load via the MAP sensor, throttle position via the TPS, and engine rpm and uses these values to find the optimal ignition timing via a table or map that is programmed into it. It seems that either 1 or more of these sensor readings must be incorrect or the computer itself must faulty, but I don't know how to determine this for sure.
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