I have an 86 Bronco II, V6-2.9 fuel injected, automatic Trans, 4WD with 70K miles on replacement engine. When the vehicle is started cold or prior to full operating temperature, it runs up to 1800 rpm for about 40 seconds, it will then slowly role back to 800 rpm and kill.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>

<o></o>

Restart the vehicle and it will run great for approximately 30-40 seconds, it will then drop out of high idle and dies again. <o></o>

<o></o>

Press the accelerator and it runs extremely rough and bogs out. <o></o>

<o></o>

If I continue to restart and play with the accelerator until it comes up to temp. It runs and idles great. <o></o>

<o></o>

This is what I have done up to this time;

<o></o>

1.) Replaced spark plugs, cap, rotor, & wires.

2.) Replaced fuel filter & air filter

3.) Replaced oxygen sensor.

4.) Removed catalytic convert and insured there is no excessive restriction.

5.) Replaced the fuel pump in the fuel tank.

6.) I took it to a local shop for a diagnosis he replaced the TPS and said I need a power break booster and a fuel pressure regulator, I replaced both those items.

7.) Replaced the air temp sensor.

8.) Replaced the coolant temp sensor.

9.) Checked fuel psi, manifold vacume, initial timing and spark advance all were within spec.

10.) Replaced the MAP, MAS and idle air sensor with used parts from a 88 Ranger

that runs fine, they made no difference, and I put the old ones back on. <o></o>

<o></o>



Where should I continue my quest to find the trouble?

<o></o>

 

I have an 86 Bronco II, V6-2.9 fuel injected, automatic Trans, 4WD with 70K miles on replacement engine. When the vehicle is started cold or prior to full operating temperature, it runs up to 1800 rpm for about 40 seconds, it will then slowly role back to 800 rpm and kill.fficeffice" /><O></O>

<O></O>

Restart the vehicle and it will run great for approximately 30-40 seconds, it will then drop out of high idle and dies again. <O></O>

<O></O>

Press the accelerator and it runs extremely rough and bogs out. <O></O>

<O></O>

If I continue to restart and play with the accelerator until it comes up to temp. It runs and idles great. <O></O>

<O></O>

This is what I have done up to this time;

<O></O>

1.) Replaced spark plugs, cap, rotor, & wires.

2.) Replaced fuel filter & air filter

3.) Replaced oxygen sensor.

4.) Removed catalytic convert and insured there is no excessive restriction.

5.) Replaced the fuel pump in the fuel tank.

6.) I took it to a local shop for a diagnosis he replaced the TPS and said I need a power break booster and a fuel pressure regulator, I replaced both those items.

7.) Replaced the air temp sensor.

8.) Replaced the coolant temp sensor.

9.) Checked fuel psi, manifold vacume, initial timing and spark advance all were within spec.

10.) Replaced the MAP, MAS and idle air sensor with used parts from a 88 Ranger

that runs fine, they made no difference, and I put the old ones back on. <O></O>

<O></O>



Where should I continue my quest to find the trouble?

<O></O>

 

I recall seeing a TSB for my '87 (I think it also applied to an '86) that attributed such behavior to a dirty throttle body/upper intake. You might try cleaning those good.

Any trouble codes in the computer? Your '86 likely doesn't have a CEL, so you have to take the initiative and pull codes to see if the computer is seeing a problem. I had similar symptoms from a bad O2 sensor, and I started the diagnosis by pulling codes. I know you've replaced the O2 sensor, but there's more to a code than just the sensor, and there are a lot of other parts of the engine management system that could be at fault.

 

no codes come now./THANKS !