Why is my explored backfireing ?

[BigOne]

Your engine RPM's do not need to be increasing for a stretched cam chain to cause timing problems. The engine being under load is the key. The more torque one is producing the worse a stretched cam chain will show up.

I would still test the cam position sensor and if it is ok look into the possibility of a stretched chain. The mere fact you like to mash the brakes and the throttle will cause premature cam chain stretching.

 

[HH1]

hmm...well see we are all learning. I thought all vehicles had timing marks on the flywheels, so if it was a stretched timing chain you would see it with the light under load.
Could you put your 10second motor in it?

 

[SteveVB]

Injector check

I would have the injectors checked and cleaned. A leaking injector can cause some problems by putting fuel in the cylinder on the exhaust stroke.

Also if you have spark at idle by pulling the plugs, doesnt mean the coil is still performing at rpm with a load. Your symptoms show up under load conditions. You may want to take it and have someone run a diagnosis on it at load and road conditions. Still may be the coil.

 

[imq707s]

Thanks for the help guys. I thought that it might be an injector problem also. BigOne..... I don't usually power brake the motor, I just did that for testing. How can I test the coil packs?

 

[SteveVB]

A shop will have a scope they can hook it up to and check the systems. I had a coil pack go on my brothers car, it checked out fine with all of my at home diagnostics with a VOM, pulling the plugs etc- took it to the shop they scoped it and found the bad coil right away. Short answer; an osciliscope with someone who knows how to use it.

 

[punkbek3886]

i had the same problems w/ my 4.0 OHV. i changed the plug wires and it ran great for a week or so but then it started to stumble again. someone said that if the wires are installed crossing eachother they will arc and carbon paths will be burnt into them, ruining the wires. also, is it possible to clean the injectors yourself w/ cleaner and a brush?

 

[explorer4x493]

I'm right here w/ you guys. Backfiring when i get into high rpms. 105k on the truck. I am picking up new plugs and wires tomorrow though, but from the sound of it that wont help.....d@mn.

http://www.explorerforum.com/forums/showthread.php?threadid=69294&goto=newpost

This is what i started just recently. Tell me what you think if anybody sees this...

 

[Bryce]

Alright,

I've been trying to diagnose a problem like this on my '91 for close to a year now... When I read this thread it jumped out at me. This is a pretty good description of the symptoms my truck is having.

The problem definately shows up when the engine is under load... usually right around 2000 rpm. If I'm on the highway and the tranny is in 4th, when I gently press down on the gas it will first start to miss and eventually backfire a few times. I don't like to hear it backfire, so I either let up or floor it.

If I floor it, the tranny will kick into 2nd or 3rd and the engine runs much better at high rpm.

The engine idles nicely, and generally runs great at high rpm although I ALSO have noticed surging.

The weirdest thing about this problem is that every time I replace something, I think the problem is fixed because it goes away for a few weeks and then gradually reappears. This doesn't make sense at all.

I've replaced O2 sensors (a few times), wires, plugs, fuel filter, fuel pressure regulator.

Some of you were mentioning ignition coils... Last time I took it to a dealer, they replaced the coils. Again same thing. It got better for a little bit, but started running ****ty again in a week or so.

I haven't done the throttle position sensor yet. Has anyone tried this?

A side note about my truck... it has 270K miles on the engine. I know this a ridiculous amount, but there are really no other problems. All in all, it's in great shape. I'm tempted to think that it's the head gaskets (which I know leak a little). The valves have got to be pretty worn by now (but it idles so well).

If anyone has some insight into this problem... PLEASE offer advice.

 

[imq707s]

Bryce, that is the exact same thing that my 97 Mountaineer is doing..... the EXACT same. I put new wires on it and it seemed to help for about an week and then the problem came back. I cleaned the MAF sensor, but that didn't seem to help. New plugs didn't help either. I think the next thing I need to look at is the coils. Maybe one could be weak and when there is enough load on the motor at low rpms it might cause a plug not to fire a few times and then when it finally sparks it ignites all of the air/fuel mixtures that got blown into the exhaust and "bam" I get a backfire. Keep me posted if you find out what is causing your problem.

 

[Bryce]

The dealer thought my problem was the coil pack. They put a brand new one in... but the problem came back.

Like I said before... I still don't know if my throttle position sensor is working or not.

Could the computer be bad? My father's Dodge quit running while it was idling in the driveway and wouldn't fire again. Turned out the computer quit working right then and there.

Does anyone know if these symptoms could be caused by worn valves or old head gaskets?? Someone had a theory about a stretched timing chain. Does my OHV have a timing chain? I would imagine it does.

 

[imq707s]

Bryce, I'm almost 100% sure it's got to be some sort of ignition problem. If it was a timing chain, or head gasket problem it would do it all the time. I'm not sure about yours, buy my Mountaineer will run great for a week or two and then starts to backfire. I'm a dragracer, and I've built a ton of racing motors. The only thing that has ever caused a backfiring problem on my racing motors is either a very rich air/fuel mixture or a weak ignition system. I've checked all of the spark plugs and they all look fine, so I don't think the motor is runnign rich, so all I can think of is that it's a spark problem. Usually when a motor has a high load at low rpm, that's when you will notice a crappy ignition system. I'm not saying that it's not the computer, maybe something in the comptuer controlls how much power is going to the ignition. That's why I hate fuel injected computer controlled motors. The computer controlls everything, so it's really hard to track down problems. How are your spark plug wires? Sometimes under a heavy load the spark plug wires will short out and the spark will jump from the wire to anytyhing metal that they are close to instead of the spark plug. I replaced my wires but that only helped for a few days. I need to check my manual and see if there is a way for me to test all of my coils. Or maybe I need to change all of my plugs again, one might be bad????

 

[explorer4x493]

Mine feels like it's bogging out at very low rpm (around 1500-2000) and back fireing at high rpm (above 4000). Nothing in between though.

What do you guys think i should do? Just have it checked out see what somebody thinks or just start replacing stuff. I'm sure alot of things need to be replaced anyways, but i'm on a tight budget right now.

All in all i just want to get this d@mn thing fixed.

 

[imq707s]

Start with the basics. Have you tried replacing the wires and plugs. Also try cleaning the MAF sensor and replaceing the fuel filter. If that doesn't help, you're in the same boat as I am.

 

[machman706]

I'm having the same problem with the backfiring and the bogging down. I haven't driven the X for a week now. Starting to miss it, but atleast I have a 99 SHO to drive while its down. Has anyone tried looking at the fuel pump? I'm wondering about fuel pressure. It seems to me like its starving for fuel half the time and the other half like its flooding out. My gas milage has gone to the dogs since I've started having this problem about a month ago. Went away and now its back. I cleaned the maf and what not, checked plugs and all. I'm about ready to change the coil packs. I was going to change the coils the first time and it quite so I figured it was a frozen injector so I took the coils back to the parts store. Hope someone comes up with a fix quick, this is driving me nuts

 

[DTek]

Just because your Check Engine Light isn't on, doesn't mean that there are no stored codes. The PCM will still store codes. What might help is something called 'pending codes'. Get a scanner, or have it scanned, to help figure this out.

 

[machman706]

Well, I had the codes pulled on my X today and the dealer put coil packs on it. Well that didn't fix it. So I had him put the originals back on after a slight argument. I then took it to a local shop that pulled the codes once again and it showed that the #4 cylinder had a misfire. So its either my plug, or wire. I picked up the wires at the dealership (v8=$130). I'll put the plugs on to see if its the plug first, then check the wire if I see no difference. I'm going to do it myself to save money and hope that this fixes my problem.

 

[V8-X]

machman706 - Sounds similar to where my problem is located. Very similar problems as yours, which all started due to the CEL coming on and stating a bad #4 plug. Did change wires & plugs with motorcraft replacements, but this has not corrected the sluggishness, hesitation, stumble, or any of problems that have come along since the #4 plug went out. Hope the plugs and wires work for you, was no change for me. I'm on my 6th diagnosis shop, which no one has found my problem yet. Let us know if this is a fix!

 

[machman706]

I should also note that apparently the area I live in West Virginia, has been recieving contaminated gasoline. I changed the filter and drained the tank but it still had the problem. The gas had rust in it, and while I did see some rust in the filter and tank, it did not seem to make a difference. Ashland has stated that the problem is fixed and hopefully I will not get any more bad gas. Ashland sells to virtually everyone around here. I'm hoping now that the plug has fouled out and that this is my problem so that I can just change the plugs and take the wires back. I use fuel injector cleaner (X1R) once a month to keep the injectors clean. The filter seemed to do a good job at stopping the rust deposits as it all flowed from the intake side of the filter and clean looking gas flowed out of the exit side of the filter so hopefully the injectors are still clean. I will let you all know what I find out. Thanks V8-X

 

[explorer4x493]

Ya well I'm still screwed w/ my problem too...

 

[machman706]

Well, It was a PITA but I got the plug changed. I didn't realize how tight the compartment was there, so I ended up changing it by taking off the splash sheild in the wheel well. Is this how most of you change yours? Well after I replaced the plug, I started it up and checked to see how it ran. Drove it 15 miles plus 20 this morning and its running better than ever. Atleast for now, I hope the problem doesn't come back. I'm keeping the plug wires for a little longer before I return them to be on the safe side. The plug I removed wasn't too healthy looking. It had some serious carbon build up. I'm going to change the other plugs later, it was 15 degrees out last night. Well, I hope you all find your problem and that mine doesn't come back.