87 Running Like Crapola

[cedave]

I have an 87 2.9L V6, auto trans, 2wheel drive, dual tanks. I've changed the fuel pumps in the tank and the HP pump on the frame rail, changed fuel filter, the spark plugs and wires, changed the fuel pressure regulator (napa), changed the MAP sensor, changed oil & filter, changed air filter, but the truck still runs like crap, seems like it is missing real bad. It starts up just fine but has a rough idle and some times after idling for a couple minutes the rpms will slowly surge up and down then it will eventually die. It doesn't do this all the time though, some times it will just sit there with a rough idle and not die. When I try to rev the engine it will bog and hesitate and then eventually rev up. Has anyone out there experienced these symptoms? What do you recommend? I'm at my wits end with this thing. It used to run really good!!!!! Also, the truck had sat for several years before now, so i drained out all the old gas in the tank when i changed the in-tank fuel pump (the old pump was totally seized up). The inside of the tank looked very clean. Please Help!!

 

[pcollins]

Replace the IAC. pretty sure the 2.9s have one.

 

[Gary101386]

Replace the IAC. pretty sure the 2.9s have one.

my 89 has an IAC. i took it off and took it apart and cleaned the carbon off of it. it now runs alot smoother and RPM's idle lower too...

dont waste the $50, try cleaning yours...

 

[cedave]

OK, get this, cleanded the IAC and it seemed to help the up and down idle a bit but it was still missing really bad. So i pulled the plugs and did a compression test and discovered i had two dead cylinders (1 & 3). So I pulled the valve cover and found both intake push rods just laying there. Apparently when i was reving it up earlier in my other diagnostic attempts (before i changed the seized pump in the tank) i over revved it, floated the valves and it dropped the two push rods. Anyway, their not bent so i put them back in and adjusted the valves/rocker-arms. Put the thing all back together and now it runs fairly good, however, it still has a slight hesitation when accelerating and there is still a very slight miss (slightly rough idle) especially when it is idling down after reving it up. I noticed now that my brand new fuel pressure regulator (NAPA) is dripping fuel when i remove the vacuum line, so i guess i will have to return it. Hopefully that is what is causing the slightly rough idle. Do you guys have any other thoughts? This thing used to pur like a kitten.

 

[lost86broncoii]

I had a similar problem with my number 5 cylinder's push rod dropping, happened two years ago and it was causing rough idle and smoke from the exhaust i fixed then, any every thing's been great, but now its acting up again, i'm wondering about pulling the valve cover off again to check it once more. Does this happen alot to the 2.9? is it a sign something should be tightened or replace in the valves or rocker arms and what?

 

[86Ranger Nathan]

Try the TPS (Throttle Position Sensor). My '86 2.9L 2wd had the same symptoms and after 3 months of searching and several hundred dollars, I found that I only needed a $40 sensor and nothing but a phillips head screwdriver to change!

 

[freedom5]

OK, get this, cleanded the IAC and it seemed to help the up and down idle a bit but it was still missing really bad. So i pulled the plugs and did a compression test and discovered i had two dead cylinders (1 & 3). So I pulled the valve cover and found both intake push rods just laying there. Apparently when i was reving it up earlier in my other diagnostic attempts (before i changed the seized pump in the tank) i over revved it, floated the valves and it dropped the two push rods. Anyway, their not bent so i put them back in and adjusted the valves/rocker-arms. Put the thing all back together and now it runs fairly good, however, it still has a slight hesitation when accelerating and there is still a very slight miss (slightly rough idle) especially when it is idling down after reving it up. I noticed now that my brand new fuel pressure regulator (NAPA) is dripping fuel when i remove the vacuum line, so i guess i will have to return it. Hopefully that is what is causing the slightly rough idle. Do you guys have any other thoughts? This thing used to pur like a kitten.

Have you replaced the 02 sensor? this can cause all of the things you have described. I went through the same drill - replaced all of the sensors including the EGR. I finally found a split in the Egr tube and sealed it. that helped. also used fuel injector cleaner. Now it runs perfect.