Dead Cylinder

[LukeDog3D]

Greetings

Scenario:

I have a '92 Sport. I have recently noticed a dead miss in my engine around 55 mph, when the tranny shifts to overdrive. I pulled all of the spark plugs, and found that one plug had damage. The electrode was gone, and a very small part of the plug was melted. (preignition symptoms). All of the other plugs look perfect.
I replaced all of the plugs and the truck ran fine for a few days. Now the truck is missing again, but none of the plugs are damaged (i pulled them out again). I replaced the coil pack today, but it didn't help. The plugs are sparking strong when I pull them out and leave them connected to a wire. I ran a compression test on each cylinder and found them all to read around 180. The guage went up smoothly for each cylinder, so I know no vavles are sticking, and my rings are fine.

My Question:

What is the cause of the dead cylinder? I am thinking that it must be the fuel injector for the cylinder that fried the plug. If that injector was going bad and causing a lean mixture in the affected cylinder, could that cause preignition and spark plug destruction?

Any help is appreciated. I did a search and gathered as much info as I could.

 

[Alec]

Good hypothesis, might want to try getting a new injector or injector set. A good shop can probably test it.

 

[SteveVB]

Well I would start with the Throttle Position Sensor(TPS) since you said it happens after OD kicks in the TPS may be sending a faulty signal cuasing the timing to advance- detonation results. The TPS controls just about everything and it is the first thing to check in my opinion. .

Fuel system would be next since you changed plugs, wire, and coil. Check the injector on that cylinder - resistance acroos the terminals is around 15ohms , you could also pull the wires see if anything changes while its running. Could be a fuel filter, or Fuel Pressure Regulator(FPR)

Did you check for vacuum leaks around that cylinder- a leak can cause a lean condition.

Good Luck

 

[tenikiwon]

Have you tried to replace the plug wires?

Helped in my Girlfriend's car, but her problem wasn't really a missing cyl.

It's also a cheap, quick, and recommended thing to do.

 

[LukeDog3D]

Yeah, the plug wires are pretty new; I know the plugs are sparking.

I forgot to mention that since I changed the plugs and the miss came back, the miss is now noticable at other speeds, not just 55. It will buck when idling or if I gas it a bit. I'll change the TPS anyway though, being that the one on there is the original and they aren't expensive.

Thanks for the replys fellas, your insights are appreciated greatly.

Edit: how do I check for vacuum leaks around the cylinder?

 

[mrboyle]

A lean miss will cause the plug to melt if the engine is run for a sustained period and the plug is allowed to get hot enough. I agree with you on the fuel injector. You might try having them cleaned. A lot of shops are equipped to run a special injector cleaner through the injectors without having to remove them. It will likely run around $75-$100 for the job, but it is a lot cheaper than replacing injectors.

 

[Maniak]

Do a compression check.. If you have a blown head gasket can run lean and run hot..

Our '92 had a bad ping problem and turned out the cracked heads weren't helping it...

If you do a compression test and find that cyl is low compared to others then you either have bad valves, head or head gasket.. to check the rings just squirt a little oil in the cyl, then do the test again.. if the compression comes up, its rings.. if not its the stuff above the pistons (head gasket, head, valves) or a hole in the piston (doubtful)...

This way you can rule out the really bad stuff..

~Mark

 

[Blockay Sockay]

I've got a 92' Sport that's doing the same thing. Do you have any updates to what's wrong and how to fix it?

 

[LukeDog3D]

I ended up having to change the spark plugs again...I had a cracked ceramic insulator on one of the plugs.

I still think the truck was running lean though. There had to be a cause for two spark plugs to fail back to back. The truck has been running good for a while now, but I did change quite a few parts before I found the cracked insulator.

Here is what I changed off the top of my head

-Fuel Injectors
-FPR
-Plug Wires
-Plugs
-TPS

My guess is that I either had a bad fuel injector or two, or the throttle position sensor was bad. This was causing certain cylinder(s) to run lean, heating the spark plugs to failure.

P.S. If you end up changing the injectors, look for a set on ebay. I picked up a good used set of 6 for 10 bucks.

 

[rikguy]

I had a miss about 2-3 months ago and a CEL reading said that their was a miss in cylinder #4. I had it checked out and the plug was bad (even though it didn't "look" bad) and the miss went away with a new plug. This week the miss was back and the CEL reading had the same results along with something about the EGR gases. I had new plugs and wires and EGR about 15 months ago. What could be causing this cylinder to be eating plugs ? I also had a mechanic check it out 2 months ago and he said the compression was fine.

 

[TPLYNCH]

Bad injector dumping too much (or too little) gas?

 

[LukeDog3D]

If I had to do it all over again, the first thing I'd do is check the resistance on the fuel injectors with a multimeter, like steveVB said.

 

[rikguy]

Aaarrgggg! My CEL is on again. Before I change the plug again I'll have the injector checked out. Could my IAC be causing this problem or contributing to it? It was noisy last summer. I cleaned it and then ended up removing the filter pad to stop the noise. It should be replaced but I don't know if it could be causing any other problems. The last CEL reading said a miss in #4 cylinder and something about EGR gases.

 

[fordby4]

I have a 92 xlt and the #5 cylinder I think is dead. Every sunday i go out and take out the spark plug for that cylinder and it is coroded. It always has oil on it and it burns a crust on it. The valve cover gaskets were shot and i replaced it thinking that was the problem but it is still happening and the engine feels like it is missing and it is very very sluggish. it seems like it has little power. Is there anything i can do?

 

[TPLYNCH]

Fordby4, your lower intake manifold bolts are loose and/or the head gasket is shot. Fouled #5 plug is the result. Try searching. There is lots of info on this board about the problem.

 

[fordby4]

If it was a bad head gasket wouldnt the engine overheat. By tightening the lower manifold bolts will that help with the performance of the explorer or is that another problem?