I dropped a posting the 4.0 engine forum a few weeks ago, but didn't get any suggestions. some interesting things have happend since then, and I'm hoping that someone has an idea or 2 with this new info. thanks in advance!

I had the heads pulled on my 93 explorer (4.0, 130k miles) and 2 valves fixed about 6 weeks ago. ever since I picked it up it hasn't been right, and it is getting a lot worse. it skips occasionally for no consistant reason (it'll skip warm or cold, driving 70 or 30 mph) and over the past 3 weeks or so has begun stalling out on me.

at first it would stall out only when the engine was warm, and the rpms were really low (like leaving a parking a parking lot after running in a store for somethign quick) but now it is stalling while I am driving. the other day (the last time I drove it) I left for work in the AM and the truck stalled when I hit the stop sign at the end of the road. it skipped a couple times on the way to work, and then on the way home it stalled out while I was on the highway, going 65 pmh. the RPMs dropped to zero for about 5 - 10 seconds (but it felt like a minute!) and then I saw the RMP gauge move a little. I then pumped the gas peddle a little and it turned back on! while still going 60 mph! it was pretty strange. then it ran fine for most of the ride home, until I got to my street. when I pulled up to a stop sign, it stalled out again. and it was difficult to get started again. I had to the turn the key like 8 times before it started.

when it first started skipping, I visually checked the plugs, wires, vacuum hoses, air filter and important connections. everything seemed ok except the connection to my MAF. one of the little clips were busted, but I was able to make it tight again with a tie wrap. I also cleaned a bunch of the connections to sensors with contact cleaner. didn't help. so then I replaced the crankshaft timing sensor, and took the MAF apart and cleaned it with contact cleaner. didn't help.

before I repalced the crankshaft timing sensor, I pulled the codes and saw that the MAf and ignition module had been acting irraticly. I haven't had a chance to pull the codes since the stalling the other day.

if anyone has any ideas, I woud really appreciate it! I am certainly running out of them.

thanks!

 

maybe your timeing is not set right or one of the spark plug wires at the coil pack got switched around so the spark timeing would be off or maybe new plugs and wires

 

thanks for your thoughts on my trucks problem. apprecaite it!

do you know if I can check/set the timing on this? I am under the impression that it can't be set or even checkec manually.

also, yes, I did check the position of the wires to ensure that he put them back in the right place. everything looked good. the plugs are new actually, and the wires are not that old, maybe 15k miles?

any other ideas?

 

You are correct in that it isn't possible to make adjustments to the timing. However, the timing can be checked to verify that the PCM is doing it's job correctly. You can check the base timing (at idle, SPOUT disconnected. should be 10° BTDC) and timing advance (part of KOER EEC-IV test, SPOUT connected. should be base + 20° = 30° BTDC). See any good manual or www.dalidesign.com/hbook/eectest.html for instructions on running EE-IV tests and timing checks.
The hardest part of checking the timing on the 4.0 is getting your timing light and face in a position to see the timing marks on the crankshaft pulley. Takes some creativity but can be done.
One hang-up I found on mine. The crankshaft pulley/harmonic balancer assembly is a multi-piece assembly. This can allow the timing marks on the pulley/balancer to rotate relative to the crankshaft, causing the timing marks to be off (on mine they are almost 180° off).

 

thanks mrshorty. I'll check those links out.



oh - one other interesting thing I forgot to mention - when I hit a pothole (usually when driving 55+ MPH) my RPMs will drop to nearly 0 for a second or 2 and then go back up to where they were like snothing happened. I've thought it was going to stall a couple times, but it hasn't (yet!). any idea what could cause this? I've looked for a loose wire, but havn't found anything.

again, thanks for your ideas-

 

it sounds like that you might have a bad connection somewarer in the ingition system or the fuel system

 

I just wanted to submit a quick note to thank you guys for the loose wire suggestion, and to close the loop for future people who may find this thread by searching for problems similiar to theirs.

sure enough it was a loose connection causing this behavior. I couldn't find it, and therefore changed/cleaned and inspected many sensors + connections before bringing the truck into a ford delaership. they found the problem after a couple hours.

I learned a few things by trying to figure it out myself and appreciate the ideas you guys gave me. hopefully I can return the favor someday. thanks-

 

Hi Green explorer,
What connection was loose? Because I also have a 93 ford explorer but did not do any engine work, my problem is that when there is humdity outside for some reason when Im driving sometimes it just dies out - Im able to start the engine again but the problem is still there.

 

If you're stalling when there's high humidity, it may be bad spark plug wires. THey may have several cracks in them and when there's enough moisture in the air they arc off to the block instead of flowing the current through to the plugs. You can check this pretty easy by getting a spray bottle of water and sprying lightly around the wires. It's easiest at night because you'll probably see the arcs and little blues flashes, but you should also be able to hear a little clicking noise when it does that. I had the same problem in the past.

 

Thanks for the tip Hongalo,
But I already replaced both the spark plugs and wires this past October, but I will check that anyway, you never know I just might have bad wires.