Sticky lifter???
 

I have a stock 302 Explorer motor. I bought it new from ford racing. It now has about 65,000 miles on it.
It backfires on the drivers side when cold but gets much better when the block comes up to temp. Even when warmed up it still sounds off on the drivers side.

3 of the plugs look fine. one is oily. (bad valve seal?)
Compresion on all four cylinders is 110 PSI
All 4 injectors read the proper resistance. ( I have not pulled them out to do any further testing)
I pulled the valve cover and to my untrained eye everything looks OK. Rockers, springs, push rods all apear to be OK. I ran it at idel with the cover off and all were getting oil and doing there nice little dance.

So I'm thinking a sticky lifter? Can I do more testing for this, or is there some magik oil additive that will free it up.

I run Casterol syntek blended oil and oil presure seems good. 30 psi more or less which is where this engine has been since new.

any help would be great.

Could be real simple, you have a defective spark plug, cracked ceramic, replace the plugs and see what happens. Dont ask how I know.

I don't think a lifter could cause a back fire out the exhaust pipe.

Bad distributor cap?

When did it start and what happened just prior to that?

you didn't mention a year, but a coil pack will cause that condition. the higher temps will fry plug wires quickly too, if the wires have over 20,000 on them. replace the wires and plugs. are you sure its oil on the plug and not just fouled due to lack of firing? compare ohm readings on the plug wires. is the one on the plug in question different?


fred

I have a question.

110 PSI sounds a bit low for a stocker, did you pull ALL plugs out prior to compression test?

Backfire out the exhaust will be overrich condition, leaking injector etc.

Thanks for the ideas.
It seems to have built up gradualy over the last few weeks.
I use this as a street car so I'm pretty tame with the gas pedal. ( I doubt I've abused the engine it that regard) It had a miss fire before this started to happen, A loose plug wire I believe.

Madmax: The bad plug could be a possibility. I replaced the plugs about a month ago so a bad one is possible. I'll put the old ones in and see if things change.

Olddog: a cap and rotor are cheap. I'll try that one first. Regarding a lifter and backfire, If the exhaust valve is not fully closed during the intake stroke I'd get raw fuel into the exhaust. That would "pop off" (backfire)at some point wouldn't it?

FWB: It is a single coil system off a 91 mustang. Wouldn't the backfire move around or at least happen on both sides of the motor? It is definatly only on the left side.

Gaz64: I may not have done the compression test correctly. I pulled 1 plug at a time and cranked it with the coil wire off. Each cyl would "pump up" to about 110psi. I only did this for the left side, assuming the right is OK.
A leaking injector is pretty high on my list too. About 10,000 miles ago I put on a new BBK intake and while I was at it I put in the newer 4 jet injectors (still the stock 19lbs) They were a set of re-conditioned ones that I got on-line. The nozels are very small so I run a can of injector cleaner through once or twice a season.

NEW SYMTEM: This morning the car started fine. After 30 seconds it began making a loud taping which cleared up after another 15 -20 seconds. I drove enough beaters in my youth to know what a rod bearing or wrist pin sound like. This was not evan close to that much noise, but loud enough to hear from the drivers seat with the hood down.

Compression should be checked with all plugs pulled out and throttle wide open.

I thought 110 psi was low, but I didn't know what the compression ratio is or the cam. I figured if they were all nearly the same, then there is most likely no issue with the engine mechanically.

I never heard of a lifter staying pumped up after an engine cooled off and was restarted. I don't know everything, so let's assume it is for a minute. If the exhaust valve is lifted on the intake stroke, it is going to suck exhaust into the cylinder, not push fuel into the exhaust. With unaccounted for exhaust in the cylinder EFI will assume the proper amount of air is in it, resulting in a rich charge. On the compression stroke, if the exhaust valve is still lifted, it would then push some of the air fuel mixture into the exhaust. This could cause the back fire in the exhaust.

However if the valve is staying lifted off the seat, it will melt fairly quick. The exhaust valves cool by toughing the seat in the head. Also the compression will test low on that cylinder if the valve is leaking. Also a valve issue should pretty much be constant and the same at all temps.

If the plugs, wires, cap, and rotor don't find the problem. Do another compression check the proper way and see if they are all the same or if one cylinder is lower than the rest.

My guess, at this point, is that one of the cylinders is not firing intermittently and the unburned air fuel charge is shoved into the exhaust and lighting off in there. I suspect an ignition issue.

Any updates?

I cracked a plug ceramic when removing. After weeks of compression testing, leak down testing, chasing everything under the sun, it was a bad spark plug. The cermic cracked and it would arc to the cylinder head.

It seems I have more problems than a 1 legged man in a butt kicking contest.

I replaced the cap & rotor. - No change.
After starting it up with replaced wires and plugs there was alot of noise from the exhaust header. I had a very thick gasket, a phenolic (sp?) type material in there. It was leaking badly. As I pulled the header off the gasket just fell apart in pieces. That has been replaced but not tested yet.

I will do a proper compresion test tonight (on all 8 cylinders if I can get to them) I'll post numbers tomorrow.

olddog- your help has been great in keeping me on track. You are correct about what would happen with the exhaust valve open on the intake stroke. I just didn't think about the fact that the intake air is sucked in and not forced in.

Madmax- When the plug was arcing did it make a ticking nose? Over the years I have had wires lay on the headers, melt and then arc to the header. I now recognize that sound. Either way I have 4 spare plugs in that side for now. I have looked at the plugs I pulled out and don't see anything wrong. Once the car is running well I will put the plugs back in and see if problem comes back.

One easy way to check for electrical/plug/wire problems is to wait until dark and open the hood and start up the car and let it run, then go look closely under the hood at the wire/wiring for the tell tale little blue arcs of electricity, dead give-away something is grounding out..........

If you have a plug wire that is grounding onto something it will show up immediatley.........

David

Ticking could be a bad lifter - but one thats collapsing as opposed to stuck open. If the exhaust valve does not open it will pop into the intake and run really poorly. On are occassion I have even had bad ones show up on the dyno on a new startup...

Well the good news is it's running much better. I replaced the exhaust manifold gasket on the left side. I'll wait until winter to do the right side unless it breaks up sooner.
I replaced all the wires on the left side and still have the older plugs in on that side. Dave & Max, you were right on about arcing. I have those foil covered heat sleeves on the wires for a couple of cylinders. Those wires are prone to hitting the headers. When I started it up there was arcing from the FOIL to the header. Moving the wire and the sleeve fixed that. I will put the new plugs back in 1 at a time to see if they are all OK.
I did re-do the compresion test. As oldguy instructed all plugs out and throtle held open. The block was cold. 5 cylinders were at 130 psi. 2 were at 120 psi. Cylinder no. 8 is only at 110.
For now I'm just going to drive it. If I have a great fall I'll get in another 750 miles before winter. I go through the car each winter and looking into whats going on with #8 will be on my list this year.

Thanks to all for the help, tips and education.

I tried the night techique, my ceramic was cracked right where it joins to the metal bottom. It was arcing in the recessed area of the head. In all honesty it is a surprise i found it. After numerous attempts I went by an engine rebuilder and he said without a doubt you have an ignition problem. I went home sitting in the lazy boy and out of no where I remember that I heard a pop while removing one of the plugs, sure enough one was black and if I tried to rotate the cermaic it had the slightest amount of movement. I broke in half and you could see where the spark had melted the ceramic while arcing to the plug.

I wouldn't worry about your cold cranking compression numbers, from high to low, it's 15% difference, generally speaking, 10 to 15% is acceptable.... DO pull all 8 plugs and DO hold the throttle wide open when testing, the butterfleis will all be open on the carb and it makes it easier and more uniform for the engine to draw in air...only thing I do differently is I start the engine first and let it run a minute or so to make sure the bearing are all full of oil before I begin cold cranking on it.....

Go back and "run" the compression test again, this time squirt 2 or 3 squirts of oil in the cylinder before cranking, if the compression goes up, then the rings are not sealing up, if the compression stays the same and is low, as in # 8 cylinder, then most likely one or both valves are where the compression leak is.... but with your numbers, I would just drive it and enjoy it and not worry about it.........

David