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I have a 1997 Explorer 4.0 “x” engine, 2 w/d, with 289,000 miles. It was running fine before I took on the project of replacing the valve cover gaskets this weekend. To access the covers, I needed to remove the intake plenum and decided to replace the plugs and wires since they were readily accessible. After putting everything back together, I started the vehicle up and it kept trying to stall out; normally it runs @ about 1200 rpm on a cold start. I checked to make sure I had connected all the vacuum lines, sensor connectors, and plug wire connections; nothing changed. I was able to get it warmed up and it started running a bit better so I took it for a test drive. Seemed to run normal; good acceleration, no over-heating but when I stopped to turn around, it did stall out again. After getting home, I pulled each plug wire off, thinking I may have a dead cylinder and checked the connections at the ignition coil pack but didn’t find anything. I sprayed the plenum and vacuum lines with map sensor cleaner to check for leaks but nothing happened. When I had the plenum off, I checked to make sure that the fuel injector connectors were secured. I’m not sure where to go from here; anybody have some ideas? Thanks in advance.
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DId you torque the plenum to spec? Also, perhaps the gasket should have been replaced when the plenum was removed. Not 100% sure, but just throwing it out…
-Karl
I did replace the plenum gaskets (it has the 3 individual pairs, not the 1 piece gasket) but no, didn’t torque to spec because I don’t have the manual for it.
Fyi…i found the torque specs on-line (15 – 18 ft/lbs) and found that they were pretty close to spec already. After torquing, I started the vehicle again and it still won’t idle correctly.
Hmmmm… Gotta go to the basics now…
Perhaps check for any pending codes.
Any chance something foreign got into the intake area?
Double and triple check the spark plug wires and ensure they are in the proper firing order.
Proper motorcraft spark plugs?-Karl
Actually the check engine light came on a day or so before working on this project but I didn’t have time to have it checked out and the vehicle seemed to run fine. After taking the plenum off, I covered up the holes while I was cleaning my parts. I’ll double check the firing order. Thanks.
Make sure you didn’t miss re-connecting an electrical connector. Make sure all the connectors that you touched are firmly mated and seated in their sockets and latched. Follow the vacuum hose diagram (found in the manual or sometimes under-hood sticker) and make sure some hoses didn’t get switched around and connected to the wrong ports during reassembly.
Didn’t see a reply to Karl’s question of which brand of plugs you put in this. It does make a difference.
If you unplug the MAF sensor, does this run better? Realize this will set a code doing so.
Actually, I found the problem with the help of a mechanic friend at work. I suspected that the IAC valve connector might be the problem because I couldn’t get it to click into place and it didn’t seem broken. He looked at it and noticed that the o-ring inside the connector had rolled over and maybe causing it not to snap into place. He pulled it out with a screwdriver and we saw that there was another o-ring behind it! He left it out and the plug snapped snugly into place. I started the vehicle up and it ran fine! He unplugged it after I turned it off and it started running roughly again; plugged it back in, ran fine. Problem seems to be solved. He reset the codes and so far they haven’t come back. That o-ring must have been in there the whole time I’ve owned the vehicle because I don’t remember putting a second one in there! Anyways, Explorer runs fine now; thanks for all the responses and suggestions.
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