Problems solved with 2.9L V6


earlyboomer

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Hi, I am a new member, and I bought an 86 Ranger 2.9L Rwd truck new in 86 and it has been a hobby since day one. This was the first year for EFI. I read the posts on fuel mileage going south and another where the engine idles poorly. My 2.9L got to the point of not idling very long before it would just quit, unless you were driving it. 2 or 3 years ago I found out about electrolytic capacitors going bad in the Computer (ECU) from a video on YouTube, so I changed them and that one repair changed the engine back to running like a clock. The 4 capacitors are, 3 - .O47 mfd versions and 1 -1 mfd capacitor. These capacitors are the couplers between various Integrated Circuits that control functions like timing advance etc., and when the caps start breaking down they cause problems. They are very small to work with, and to change out, so if you have no electronic experience, maybe you know a buddy that does, and check the videos on youtube. Now I have always used Full synthetic oil in this engine so I never had anything sticking like the lifters. and the engine has stayed clean inside. The engine has 190K on it and around 100K I installed a timing chain set and that really helped. when I had the oil pan off, it was nice and clean. I live in the Rustbelt and among other things it caused the flange between the exhaust header to rust and destroy the seal between the exhaust header and the catalytic converter which caused the manifold pressure signal to the ECU to be off and fixing that helped the running of the engine Any little thing can irritate these ECUs. These items are not in chronological order. They all affect the running and the gas mileage. Like others have said the oxygen sensor is important and another big item for gas mileage is to forget about using the OEM designed muffler. At one point I changed the Injectors at the time when the fuel pressure start leaking gasoline all over the garage and that got my attention. Lately I finally tried the small bottle, 5.5 ounces, of Lucas fuel injector cleaner and was really surprised how well it worked, the engine had a bit more pick up, right away and was instantly noticeable. I have some rust problem with the truck but the engine finally runs like new again. This truck has a 5 speed and one of those awful hydraulic clutches, but the engine does have one pain in the butt problem, those constant leaking valve covers. I made cover supports out of a .75" x .75" x .125" steel angle to go across the whole bottom edge of the valve covers but it didn't cure the problem completely, so I need to put new gaskets in again. When these engines are idling right they have a special sound and replacing the caps in the ECU brought that sound back. Now I get at least 17 to 18 miles per gallon in traffic , keeping up with traffic, and on the few days when the traffic was light and I could keep to the speed limit, I got around 30 miles to the gallon, believe it or not, and it really surprised the H--- out of me, I think a lot of that is because of the turbo muffler with less back pressure. I should have quit using the OEM mufflers years ago. This is a 30 year+ Ranger history lesson, hope some part of it helps someone.
 


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8thTon

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As an EE with over 30 years designing circuits, I can tell you that electrolytic caps are by far the shortest lifetime electronic components, especially with elevated temperature. However, the value of the caps you listed are generally too small to be electrolytics - perhaps the 1uF, but that value could be any number of construction types. I'd actually be surprised if they used any electrolytics at all, but it's possible I suppose. If you post pictures of the caps I can probably tell you what they are.
 

earlyboomer

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O.K., you got me, I have been hearing lately the electrolytic capacitors are causing problems in electronic equipment being manufactured today and these little caps in ECUs of 30 years ago are no doubt from a different era and I no doubt made an assumption that is in error. Most of my electronic experience was before they invented ICs, so you are probably the guy to help someone that needs to check into replacing the caps in their ECU. Believe me it made a very big difference into bringing my V6 engine back to running like it was suppose to. The original 3-.047s had a voltage rating of 16 volts and a 12 volt electrical system in a vehicle is really a 14 volt system so I think that was a bit tight and the original 1-mfd was about 4 times that voltage as I remember. I bought new caps from Mouser and I got help in picking good quality caps from a rep, but they were still not expensive and worth their weight in Gold for bringing the ECU back to life.
There are slick operators on the net changing these caps and selling ECUs as "rebuilt" for about $200. They use double sided boards even in these old ECUs and you need good eyes to be working on them and my eyes are 80 years old now. Thanks for the reply and comments.
 

8thTon

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O.K., you got me, I have been hearing lately the electrolytic capacitors are causing problems in electronic equipment being manufactured today and these little caps in ECUs of 30 years ago are no doubt from a different era and I no doubt made an assumption that is in error. Most of my electronic experience was before they invented ICs, so you are probably the guy to help someone that needs to check into replacing the caps in their ECU. Believe me it made a very big difference into bringing my V6 engine back to running like it was suppose to. The original 3-.047s had a voltage rating of 16 volts and a 12 volt electrical system in a vehicle is really a 14 volt system so I think that was a bit tight and the original 1-mfd was about 4 times that voltage as I remember. I bought new caps from Mouser and I got help in picking good quality caps from a rep, but they were still not expensive and worth their weight in Gold for bringing the ECU back to life.
There are slick operators on the net changing these caps and selling ECUs as "rebuilt" for about $200. They use double sided boards even in these old ECUs and you need good eyes to be working on them and my eyes are 80 years old now. Thanks for the reply and comments.
Good for you for rebuilding it! You are right that parts from Mouser and Digi-Key are pretty cheap, while you can pay big money for them elsewhere, or for rebuilt units. Parts fail, and maybe they were electrolytics - who knows, I've seen all manner of dumb design choices, especially when people are tying to save half a cent.
 

RobbieD

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That's good info, and it does make sense. Thanks for the post, and welcome!

Robbie
 

earlyboomer

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8th Ton, that is an idea, I do have the caps I took somewhere and I have a couple extra sets of the new ones I installed, and if I can find them, posting a picture should be a good idea. It also seems to me that capacitors are the components in a 30+ year old automotive computer would be the first ones to go bad. The ICs in my unit must still be fine from the result I got from changing the caps, it was just like I had installed a new computer.

Something else I just remembered reading about as far as ICs are concerned, have you heard about what is called a "whisker" problem with ICs? This is a problem where environmental extremists wanted lead removed from everything, even solder, and this caused "whiskers" to grow from one IC trace to the next trace, shorting out the IC. Maybe this did not happen yet 30 years ago and I wonder if it is still a problem?
 
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earlyboomer

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8th Ton, that is an idea, I do have the caps I took somewhere and I have a couple extra sets of the new ones I installed, and if I can find them, posting a picture should be a good idea. It also seems to me that capacitors are the components in a 30+ year old automotive computer would be the first ones to go bad. The ICs in my unit must still be fine from the result I got from changing the caps, it was just like I had installed a new computer.

Something else I just remembered reading about as far as ICs are concerned, have you heard about what is called a "whisker" problem with ICs? This is a problem where environmental extremists wanted lead removed from everything, even solder, and this caused "whiskers" to grow from one IC trace to the next trace, shorting out the ICs. Maybe this hadn't happened yet 30 years ago? Are "whiskers" still a problem today?
 

chickenranger88

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I haven't had the bad electrolytic capacitors on my Ranger yet, but I did on my Jeep. The symptoms on the 89 Jeep were took several minutes for the dash idiot lights to get to normal brightness and the engine to turn over. That was with a fully charged new battery. Same fix though, replacing the caps in the computer fixed it right up.
 


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