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87 4.0 4X4 Auto Rough Idle No Acceleration

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Remove the distributor cap and cut a "window" into the side of the distributor cap at the #1 spark plug wire post . The "window" should be large enough to allow easy visual inspection of the position of the distributor rotor at the #1 spark plug wire post. Reinstall the distributor cap.

Install a ¾” wrench or socket onto the vibration damper retaining bolt. Rotate the engine in a clockwise direction until the #1 cylinder is at top dead center. Align the timing mark on the vibration damper with the "0" degree mark on the front cover timing scale. The tip of the distributor rotor should be near the #1 spark plug wire post.

Disconnect the distributor electrical connection. Remove the distributor holddown clamp, holddown bolt and distributor. Remove the distributor cap and rotor.

Place the distributor housing upside down in a soft jaw vise. Scribe a line 1/2 inch from the end of the distributor locating tab. Cut the distributor locating tab at the scribed line with a saw.


Remove any burrs and metal filings from the distributor. Reinstall rotor.

If necessary, using a flat blade screwdriver, turn the oil pump gear drive shaft until the slot is slightly past the 11 o'clock position. The oil pump gear drive shaft is accessible through the distributor mounting bore in the engine block.

Visually align the modified locating tab area of the distributor housing with the holddown clamp bolt hole.

Turn the rotor to the 4 o'clock position.

Lower the distributor into the engine block until it seats. The rotor should now be very close to the 5 o'clock position.

Reinstall the distributor cap with the cutout "window". Rotate the distributor housing until the trailing edge of the distributor rotor tip is just departing from the #1 spark plug wire post terminal .

Reinstall the distributor holddown clamp and bolt.. Reinspect the position of the rotor to the #1 spark plug wire post to insure that it has not moved.

Install the new distributor cap, reconnect the distributor electrical connections.

Revised 07/03/2012

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I did the distributor and tdc everything is sitting right. I double checked my spark plugs that I changed last month and they were all covered in carbon pretty bad. So I put in new champion coppers and it started up with more ease and seemed to have more power. I took it for a spin and it was a little better but couldn't really accel past 30 mph but no backfire issues. I took a look underneath at the exhaust and saw that the muffler had been scraped with a gash in it. Don't know when that happened.

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Unless it's been obviously dragged across something, the backfiring may have simply split your muffler. I accidentally switched a couple plug wires around in my dad's van when I was 15 and didn't realize it for a month or so, couldn't figure out why it was backfiring so much, and the muffler ballooned and split down the side.

Carbon fouled plugs means the engine's not getting hot enough. Assuming you're running the right plugs, and since the plugs didn't fix the situation, this is definitely a symptom.

How's your oil use? Got much blow-by?

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Just going over basic causes for excessive fouling. It could simply be that the engine isn't getting warmed up enough to burn off the carbon, but if not, then it could be running too rich (a little unusual in an injected engine, but still possible), or else the timing's too retarded, which would also cause backfiring, or you've got some other ignition system issue, or else you've got compression/oil burning issues, typically from bad rings. Oily spark plugs are pretty obvious though.

It seems like you've been over everything except the compression and maybe the fuel pretty fully, so that's why I was asking about it. If compression's off the table, it's likely the plugs are fouled because the engine's not running well enough to generate enough heat in them to burn them clean. Lots of short or low-speed trips and starting and shutting off quickly can also foul them for that reason. So the fouled plugs may or may not be a symptom of the problem.

I'd look into the fuel system a bit more (injectors in particular), but I'm not much of a mechanic, so that's about all I've got for you. Sorry...

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