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

 

Can you check and see if it set any trouble codes?

 

I don't know if this is an EEC IV or an EEC V. if its a 5, then no, I can't check the codes.

 

EEC-V was introduced late in '95. '96 and later model years are federally mandated to use OBD-2 (EEC-V). EEC-IV was used from ~'84 to '95, so you have EEC-IV

 

Ok, then I'll check for codes next time I'm out that way. I forgot to mention, that the check engine light never lit, and yes, it does work.

 

You may have other problems but I have learned that even though the check engine light will come on if your gas cap is loose ($65 lesson) the computer can set a code and not trigger the light.

 

the gas cap is on...and that wouldn't cause knocking (that the mechanic thinks is a rod bearing) anyway. Nor would it make it run rough. All the computer codes are good for are sensor readback anyway...won't tell me a darn thing about valves, rods, bearings etc...for that mater, I can unplug a spark plug wire, and not get a CEL, or a code set. That's all emissions control stuff.

 

Have a compression test done by a competent mechanic. I'm betting its either a valve train issue or its in the block. A compression test and a leak down test can determine this. If #2 compression is low or non-existent, then a leak down test can tell you if its leaking through the valves or by the piston. If its through the valves you can usually hear the air coming out the exhuast or intake manifold. If its a the valves you can have reconditioned heads with new valves installed for ~$1000.00.

Good luck. I had 160,000 miles on my 93 this year when this started and it had no or little compression in 3 out of the 6 cylinders by the time I decided to get it looked at. Now it runs like new.

Tim

 

as I said, the truck is located 180 miles from where I live. I plan on compression testing and leak down testing. It's just the knocking that's bothering me...doesn't sound like valves...the knocking sounds louder if you're under the truck (like, say, uh, rod bearings) so, I'm just keeping my fingers crossed.

 

I'm experiencing the same problem with my '92 4.0L 180,000mi. Low speed surge and knocking under load at highway speed(appx 1700 rpm). Fuel and Outside temp don't seem to affect it. It's been occuring off and on for about 10,000mi, but just got more frequent. I've had a scan done and no codes show up. I was planning to pull my plugs next. I was also starting to suspect bearing problem, but now I think I'll check the compression first. Thanks

 

Did you do it yourself, go to a dealer, or other shop to have the heads removed and installed?

 

I have a 98 explorer with a 4.0 liter and am experiencing a bad knock under load. only 60,000 miles and it started lightly about 30,000 miles ago. I bought a obdII code reader and confirmed no codes, added engine flush and changed oil thought it got a little better at idle (quieted down a little) but still loud under acceleration. seems to be louder under front end of engine, if it was a rod bearing going bad would it not have come apart by now? took it to ford, first time all they could find was a bad cv joint. next day back at ford and they replaced two injectors and said that was the problem, back next day to tell them it was not fixed and got "don't know what to tell you".

could it be a injector bad? one other thought is could it be a one of the cat's partially blocked?
another thing I found was the crank position sensor is rubbing on the crank and I am thinking that this could be a problem. reading about it it says that it sends a signal to a computer that helps determine how the injector work, how much fuel and what not and when to inject. so I suppose that it could be injecting too much fuel out of sequence causing the knock. seems to be okay at idle if it was a rod it would continue to knock even at idle i would think....

thanks for the help
Joe

 

Just thought I would throw in a few pointers on Main, Rod, wrist pin sounds.
1. Main bearing Knock: Generally will not hear a bad main at idle, but under a torque load the main will start to knock. Quick test is to put in gear, hold the brake and apply some gas. As the engine loads up the main will start to knock and get louder the more torque is applied.
2. Rod bearings knock each time the cylinder(s) fires. Usually, you can distinguish it from a main by disabling the spark plug for the offending cylinder and the knock will subside somewhat. Keep in mind that there are 2 opposing cylinders sharing a rod journal on the crank, and when 1 bearing goes, the debris generally take both out together so you may need to disable 2 cylinders to supress the knock.
3. Wrist pins tend to make the most noise when engine is under a reverse load as in deceleration or engine braking, or when engine is decelerated from being reved up.
All above depend on the amount of damage present. If severe enough, any of the 3 will make lots of noise at almost any time in the run cycle.

I had an engine let loose that mimic-ed the symptoms you described. Cruising along just fine, then noticed speed dropping off no matter how much gas applied. When I finally pulled over to side of road and engine idled down, I heard the dreaded main/rod death rattles. Tried to slowly drive back to help but engine kept trying to seize up so finally shut it off and hitch-hiked to get a tow. Crank was toast and ended up with a rebuilt short block as a quick fix.
Dialtone

 

been running like this for quite a few miles now gradually getting louder, read a post about those engines timining chain and tensioners going bad. this could be a possibility also I suppose, what do you think?

 

Yeah, swap injectors and see if it affects problem. I had a Sable that the injectors started dying one at a time at about 145,000.