I recently developed a problem with my 1993 Explorer 4.0L. I was cruising on the interstate at 75mph (the speed limit here) using cruise control. Suddenly, the truck began to lose speed. It downshifted to try to compensate, but continued to lose speed. I then override the cruise control, and give it some gas. I am now going 65mph, and have it floored, so I pull off at the nearest exit. I pull away from the stop sign at the base of the exit, and seem to have power back, but it is running REALLY rough. After sitting at a gas station a bit, it isn’t running nearly as rough at highway speeds, but some symptoms linger. It idles rough, and has some suction at the tailpipe (possible exhaust valve problem?). It knocks under load. It knocks at idle when started cold…but then only under load when warmed up. I tried to see if it was missing, all six cylinders have spark, but when I pull the #2 wire, there is no change in the way the engine runs. So I swap the #2 wire with another cylinder. There is no change in symptoms. (Symptoms are still the same, no change with #2 pulled). I put the wires back where the originally came from, and swapped spark plugs with another cylinder, (spark plug doesn’t appear to be fouled, and the swap yielded NO change in symptoms). It seems that the #2 cylinder is dead. A local mechanic says I need a new engine, but ran NO tests, NO compression test…he just listened to it. I haven’t done a compression test yet either (due to lack of time, experience, and the fact that I live 180 miles from where the truck is sitting).

Any suggestions?

Thanks.

Bruce

 

You can start by pulling the trouble codes. You can do it yourself. There is also a cylinder balance test you can perform:

http://www.dalidesign.com/hbook/eectest.html.

IMO, to condemn the engine without doing any diagnostics (a compression test at a minnimum) is not sound practice. Consider getting a second opinion from a shop which will actually do the proper testing.

 

At least run a compression test.
Is the #2 fuel injector firing?
A cylinder leak down test might be more telling than a simple compression test, a bad head gasket or a valve issue could cause a dead cylinder, but would only require the top end be rebuilt instead of the entire engine.

 

I know I can pull the codes myself. They didn't help...it is DEFINATELY not an EEC...sensor, emissions control systems etc, problem. I agree...I need to do a compression and leak down test. This is kind of difficult at this point, as my arms aren't 180 miles long Those will go a long way in helping diagnose...as MAY the codes (but don't expect too much there). Next time I'm out that way, I'll have tools with me and will check the #2 injector. But my biggest concern still remains the dull, low pitched knock. It is louder under the engine than above it. when I say dull, low pitched knock...I DON'T mean rattling or pinging...it is definately NOT sticky lifters, valve tap or a lean condition. IMO it sounds like a problem in the block...most likely a rod bearing. I KNOW it needs a new fuel pressure regulator...but that won't cause the type of knocking I'm hearing. There is also a LOT of blow-by, which is NEVER a re-assuring sign. As far as the head gasket is concerned...there is no loss of coolant, no water or "milkiness" in the oil, oil pressure and water temperature are running at the same level they've always been. Not once did the temperature go up or the oil pressure down. Eventually I'll tow it back with my Expy and have all the time in the world to look at it.

 

just found out that Wal-Mart lub shop messed up...put in 10W-40 rather than 5W-30....could this cause a serious problem?

 

HEY EVERYONE,

I recently developed a problem with my 93 XLT, Runs Rough only when its warm and been running for at least 30 mins or more, I will be cruising at 60-75 MPH and the engine sounds like its missing with not all cylinders firing. When I pull over, engine idles rough, almost shuts down, but doesn't. Once it cools off from interstate driving, it seems better. I have cleaned out the engine and fuel lines with b12 chemtool, and no difference showed. I am getting spark on all 6, oil pressure is fine. Alternator is new. It started when my car battery died once while parked at the airport, and on the way home from the lot it began this problem. Could this be a choked up catylitic converter?

 

You will want to check the Mass Air Flow (MAF) Sensor, between the vacuum box and the throttle. Everything you described here is what I also had and I swapped the MAF out and every last problem I had went away.