I have a 92 Explorer 4x4 with about 79K miles on the engine. It has been pinging for over a year. I've had several mechanics look at it. The last one replaced the thermostat and it helped some. More recently the engine started running really rough when cold (chugging), but would be OK when it warmed up. Now it runs rough constantly, and I can smell unburnt fuel coming out of the exhaust. I've replaced the ignition wires and E-coil pack thinking I was having a sparking problem. It was a small improvement, but not much. It has no power now, and I have to be really careful about pulling out into traffic and get some speed up for hills. I would like to try to fix it myself, but my repair manual isn't much help. Does anybody have any ideas on what I should look at? Thanks.

Dan

 

If you are having this kind of problems with the engine running rough, there SHOULD be a check engine light set, with a fault code stored in the computer. Have you had the codes read and if so, what were they?
There are a couple of other areas to look at besides the ignition based on the sysmtoms you described. Pinging indicates lean running engine but the raw gasoline smell from exhaust indicates rich condition or misfiring cylinder(s)
1. Pinging issue...Can be caused by a lean running engine due to vacuum leak. Others have had problems with the lower intake bolts loosening up and causing air to be sucked in to the intake system. Check for loose, broken vacuum hoses, leaking power brake booster, leaking in general in and around the intake system. May need to relpace lower intake gaskets if tests show air leakage.
2. Raw gasoline smell.... Check the fuel pressure at the valve on the injector rails. Pressure should be 30-35 PSI with engine running and vacuum line connected to the regulator. Engine off and key on or engine running and vacuum line disconnected to the regulator should boost pressure to around 40 PSI. If presssure tests show higher pressure, replace fuel pressure regulator. (approx. $80 part)
3.. There are other sensors that could also be at fault causing some/all symptoms you mentioned but should set a fault code in the computer. I suggest you start out by running the self diagnostic tests and eliminate these possibilities first. Start with key on engine off self test of sensors and replace items as indicated. Always replace or trouble shoot only the first code given then re-run the entire test again only working on the first code given.
If you are unfamiliar with diagnostic setup/ running, you can consult Haynes manual for 91-95 Explorers and it has a good explanation of how to and code definitions. There have also been other posts for sites with info for running EEC-IV tests.
Hope this helps
Dialtone

 

Thanks. I just pulled the plugs and found #1 had a broken insulator on the center post. Could it be that simple?

Dan

 

That could explain your rough running, and raw gas smell, but probably not the pinging. Was it running hot before the thermostat was changed?

Winford

 

I just took it for a test ride, and it purrs like a kitten. I think I heard a few light pings, but the engine otherwise ran very well.
Prior to the thermostat replacement, it ran too cold. I had a mechanic look at the pinging problem twice. The first time they cleaned out carbon and replaced an oxygen sensor. It was quiet for a few weeks. Next, they cleaned it out again and replaced the thermostat, cleaned the MAF, and did a vacuum check. The vacuum check indicated no leak, and it has pinged a little less with the thermostat. The mechanic said a cold engine can throw off some of the sensors the computer uses to control things. I would like to replace the EGR valve myself, but I can't find the darn thing, even with a Chiltons manual and a picture.:-X11 It was cleaned out last year, but it is 10 years old and may be functional, but off a little and causing the problem. Any hints on recognizing an EGR? Does that sound like a reasonable idea?

Dan

 

91 and 92 explorers never had EGR valves. Thank god for that one! One less part to worry about.