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2.9 Problems - runs rough when warmed up


Hanster

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I have 1986 Ranger 2.9L 4x4 manual. Recently after the engine has been running for a little bit it slowly progress's to barely running at all. When its cold I can do what ever I want, it runs really strong. Accelerates normal. But when warm it struggles to get above certain rpm's until barely running at all. Then after cooling completely down it runs really good for a certain amount of time. I'm stuck on what it could be and I don't really want to put the money into a mechanic fixing it.

A month ago it had running problems which turned out to be a faulty fuel pressure regulator. It was pushing 120psi. I've had that fixed now and now this is happening. The dealership also mentioned my egr needed a looking at, but could be giving false numbers because of the fuel pressure regulator. So I just had the regulator replaced. It ran good for a while until now.

I have within a year replaced the spark plugs, wires, cap and rotor, air filter.

I change the oil regularly.

I have noticed that the temp gauge never gets up to regular operating temperatures recently. I've also been getting lower than usual mpg's, i get near 14 right now and I used to be at 22-23.

And one of my recent drives when it acted up, for some reason I decided to look under the truck and my catalytic converter was glowing red hot. So that is working overtime, correct? I'm running extra rich? Might explain my recent mpg's.

I've leaning towards egr or a temperature sensor. Or maybe something with ignition because it has issues getting to higher rpm's when warm. Or a ground somewhere. Or maybe a cat conv that melted down. Or the fuel pressure regulator was misdiagnosed or installed wrong.

Any kind of incite would help a lot. Thank you.
 


jhammel85

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Did you say that you're cat was glowing red? When did you see this, after a long ride? Thats a definite sign of a clogged cat. Hate to say it man, because they are expensive.

But..if that doesnt help you, it sounds very much like a engine coolant sensor too. The sensor is cheap so if the cats do not totally fix you, hopefully that will:icon_thumby:

If you are running cool, thats most likely a thermostat thats stuck open. When I bought my truck, it did this. I changed the thermostat and found that the old one was stuck open...therefore making it run cool. If your truck is running cold then it'll give you crappy mileage.
 
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177CIOfPureLove

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Check those, but it could also be the oxygen sensor too....in my case it was...
 

Spitfire1975

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Read through this. I know there are a LOT of posts, but it is my attempt to work through the same issues (minus the red hot cats). http://www.therangerstation.com/forums/showthread.php?t=68618

Anyway, do your research in the tech pages and start testing all off your sensors. You can usually test for voltage and resistance to find out if something is out of wack. Make sure your timing is where it needs to be. I agree, though, that you are probably looking, at the least, at needing new O2 sensor(s) and by now probably cats.
 

Spitfire1975

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Check your compression and vacuum as well. Too much internal oil leakage can wreak havoc also.
 

Spitfire1975

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and you don't want to replace the cats if you have underlying problems that will clog them again.
 

Epixstar

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depending on your state if you have to do emmisions testing just rip the cats off
 

Hanster

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Thanks for the responses. I don't think my cat conv is the problem because everything is fine until the engine gets warm. Unless when the cat gets warmer it clogs, then unclogs when it cools down. But if it is the cat there is no way im replacing it, I would probably just take it off, they are really expensive. Mainly it means I'm running rich.

A while ago I tried replacing my o2 sensor and couldn't get it off.

Do you know where I can get table of resistance and voltage values of senors?

I'm trying to get my hands on a analog voltmeter so I can check codes on the computer. I only have a digital one. I can do that right?

I'm just really stumped on this because it runs good cold then bad warm. something that effects a warmed up engine.
 

Epixstar

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you will get bad millage too if its not fully warming up
 

Hanster

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Does a MAP sensor sound right? (manifold absolute pressure sensor) Because I replaced that and it seems to be running good now.
 

jhammel85

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Thats good, it very well could be. I'd still be concerned about the cat!

How'd you find that the MAP was bad?
 

Hanster

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I didn't really know. I've just been replacing/testing sensors as I find them. It was the 3rd one I came across. And it still seems to be the fix! And makes sense considering what it does. I'm not worried about the cat conv. I'm taking it out soon. Thanks everyone for all the help.
 

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Catalytic converters almost never go bad, and clearly yours isn't clogged, so there is no reason to take it out.
 

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