92 Exoplorer Surges

[qquake2k]

Hello All,

I have a 92 Explorer XLT with, of course, the 4.0 V-6. It just started surging yesterday. It surges at idle, when it's in gear. Doesn't do it in park, but it seems to do it slightly in neutral. Also seems to do it worse in park than reverse. Runs great under acceleration, doesn't seem to have lost any power. But at idle, or when maintaining a constant speed on a level road, it surges. When you come to a stop, the idle goes below 500, surges up to about 1000, then goes up and down. When the idle goes low, the alternator stops charging. This morning, on the way to work, it seemed worse than yesterday when the weather was warmer (80's). The check engine light came on at one point, but went off when I accelerated.

I'm thinking a fuel problem. Fuel pressure regulator, maybe? I would just replace it to see if that's it, but I can't see the darn thing. Do you have to remove the upper intake manifold to get to it? Could it be just a bad vacuum hose to the regulator?

Any other ideas what it might be? It has about 175K miles on it. It's been a great truck, but I think it's starting to do the nickle and dime thing. I replaced the starter last weekend. Also, are there codes on a 92? I read somewhere that you can only use a code reader on 93 and newer. Is that true?

Thanks in advance for any and all suggestions and/or comments.

Jim
Northern California

 

[zwoobah]

mine was surging when I had a vacuum leak. check the vacuum manifold ("tree") for leaks. mist the area with ether while the truck is idling. if the idle goes up, you have a vac leak.

 

[Backin72]

There's a method of pulling the codes by using a paper clip and counting the flashes of the CEL. Use the search function to find the process.

A few years ago I had a surging problem. Had the vacuum checked and all was good. Turned out to be a bad PCM. PCM controls the idle speed. Replaced it and all was good.

 

[jeremyhilton]

I had this same issue and ended up replacing the Idle Control Unit and the MAF Sensor. After doing the Maf you want to disconnect the Neg batt terminal for a little while to reset the ECU. After doing both of those and driving it for a few days it hasn't done it since. I also heard that you can pull off the Idle Control Unit and clean it out with some carb cleaner but that didn't work for me.

Hope this helps,
Jeremy

 

[smtcapecod]

surging

Would a bad MAF through a fault code/CEL though?

I've had a surge for a while, done the IAC, done the leak check, done the fuel pressure regulator...don't want to do the MAF needlessly.

 

[qquake2k]

It was actually some corroded wires underneath the battery tray. Caused an intermittent short.