Help please! I have a backfire problem

Let me start off by telling you what I have. It is a 1991 Ranger with the 2.3 duel plug motor in it. It is a manual. I have done some mods to it which include, synthetic oil, NGK plugs, mustang header, free flowing air intake and filter, and electric fan. I have always taken good care of it and changed the oil, plugs, ect. I just changed the timing and serpentine belt about 20,000 miles ago.

Now here is my problem, my truck runs great with the exception of random backfires in the exhaust. I never had any problem out of this truck for the 160,000 miles I have driven it. I bought a new car last year and let my Ranger sit for a few months until the newness of my car wore off, when I started missing my Ranger, I pulled it out, cleaned it up and put some fresh gas in it. Well, I drove it around town about 5 miles each trip for a couple of days and then took it a little farther to a favorite hiking spot which is about 40 miles one way, it drove great and I rode it hard (you have to in order to get anywhere with these underpowered trucks) all the way there, I parked it for about three hours, on my way home, I made it about three miles before it backfired a couple times out the tailpipe which cut the truck off. It would start right back up and I would get another 50 feet to a mile and it would happen again, no real reason although it seems to do it more under load. If I push my clutch in and let off the gas while it backfires, it won't cut the truck off. I got home OK but had to baby it by doing 35 the whole way.

It will backfire randomly on some trips or not at all on others, I replaced the coil, did a tune up, changed the fuel filter, tried different gas, even checked the ignition control module on a tester at a parts store. Do you have any other suggestions? My friend wants to buy the truck but I won't sell it to him in this shape, I need to get it fixed soon. It seems to be more of an electrical problem with how random it is, but I checked or replaced just about every ignition part on the truck, I am hoping it is not a valve problem. Please help me get this problem fixed so I can sell it and buy a new Ranger.

Thanks for any help and sorry for the long winded post.

have you checked for vaccum leaks? you said you changed 'the coil' did you change one or both? also you might check the EGR valve out, when mine was stuck open it backfired like crazy.

Bryan22 said:

have you checked for vaccum leaks? you said you changed 'the coil' did you change one or both? also you might check the EGR valve out, when mine was stuck open it backfired like crazy.

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I am pretty sure I don't have any vacuum leaks, I put a vacuum guage on it and it holds strong vacuum consistanly with no fluctuations. Also, I blocked the EGR off when I installed my header. I did only change the one coil on the intake side, I did not figure that the exhuast side had anything to do with the truck running and was there only for emmissions. I have never changed those plugs or wires as they are very hard to get to.

I forgot to mention that my tach stopped working around the same time the backfires started, the problems may be unrelated but I am not sure. My truck only throws a CEL when the tach stopps, but not when it backfires. My tach will come back to life sometimes, not sure why, again another random problem but it doesn't work %65 of the time.

Check your camshaft timing belt. It sounds as if it has jumped a tooth.shady

shadetree said:

Check your camshaft timing belt. It sounds as if it has jumped a tooth.shady

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I just changed the belt about 10,000-20,000 miles ago and it still looks good. I would think if the timing was off, it would run differently and be a more common problem, it is very random. The truck runs great and as strong as it ever did otherwise, I also have no starting problems.

Backfire can be caused by a number of things...unfortunately, they are not that common from what I've read and most are actually due to timing being off...the belt may look good, but that doesn't mean the timing isn't set right...my truck idles fine when the timing is off, but as soon as I give it gas all kinds of things start happening...like the gurgling, chuggling, burping and smoke with flames...

However, you might want to read this article from wikipedia for some more insight...look under causes specifically and you may find the answer if it is not timing...

BACK Fire explained

I agree with the suggestion that you check your timing belt. And another thing to check, is the plugs.

fightinggoat15 said:

I have never changed those plugs or wires as they are very hard to get to.

I had a random backfiring symptom in my four-banger, and it was caused by a plug's center insulator being broken. The plugs are a little tough, but it's worth it to pull them for a look-see.

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fightinggoat15 said:

I am pretty sure I don't have any vacuum leaks, I put a vacuum guage on it and it holds strong vacuum consistanly with no fluctuations. Also, I blocked the EGR off when I installed my header. I did only change the one coil on the intake side, I did not figure that the exhuast side had anything to do with the truck running and was there only for emmissions. I have never changed those plugs or wires as they are very hard to get to.

I forgot to mention that my tach stopped working around the same time the backfires started, the problems may be unrelated but I am not sure. My truck only throws a CEL when the tach stopps, but not when it backfires. My tach will come back to life sometimes, not sure why, again another random problem but it doesn't work %65 of the time.

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actually the coil that fires the passenger side set is the primary coil. i'll bet thats the problem. also since the tach goes screwey with the backfiring, that almost surely points to ignition system, since thats what drives the tach.

I have changed the plugs and coil on the intake side (passenger side of truck), cannot really get to the other side and I believe it only fires on the exhaust stroke to make sure all the fuel has been burned, I don't think it has anything to do with how the truck runs. If I am wrong I hope someone will let me know, but I think they only did that for emissions. The tach wire might be hooked up to the driver side coil, not sure. The tach doesn't work %90 of the time, the backfire doesn't happen very often, only a few times on a long trip or not at all.

Just changed my coolant temperature sensor yesterday (a PITA to get to), my temp guage works now, but the truck still runs very cool, the temp will come up after long idleing with the fan off, but it never even gets to the middle of the guage. The motor does feel like it is hot though.

sounds like you need a t-stat. and i would change the stuuf on the left side of the engine. your coil pack, wires, plugs, could be shorting out. one of the wires might be chaffed just a little, enough to arc against something. i know its a total pita to get to. but its worth it to atleast rule it out as a possiblility

if you have a cracked header or downpipe im pretty sure it would cause backfire also, i would run seafoam through it to see if it clears it up at all if not id say its definitely an electrical prob.

I am going to change the thermostat and the plugs/wires on the drivers side today or tomorrow, I hope it will improve something. It will be hard for me to tell if it is fixed since I don't have any tags or insurance for and the problem only happens sometimes.

I did get a new 09' Ranger, they sure have come a long way engine wise, these four bangers are very peppy.

I have seen heat do some funny things to the ignition parts such as the module and coils and plugs. My truck would run perfectly and after a good 10-20 mile ride it would start misfiring, I took a guess at the ignition module and it fixed it. Just a thought.

fightinggoat15 said:

I am going to change the thermostat and the plugs/wires on the drivers side today or tomorrow, I hope it will improve something. It will be hard for me to tell if it is fixed since I don't have any tags or insurance for and the problem only happens sometimes.

I did get a new 09' Ranger, they sure have come a long way engine wise, these four bangers are very peppy.

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Congrats on the new truck...I've heard the Duratek engine puts out 134 hp stock...compared to 90-100 I'd say that is a big improvement...

Well I replaced the t-stat today and it still doesn't get up to operating temperature according to the stock gauge (already changed the temp sensor), I think it might be my gauge as the engine feels hot. Will change the plugs and wires on the exhaust side next week.

I am really lovin my new truck, they have made many improvements over the 91', odd thing is that the bed liner from my 91' fit my 09' that is quite a stretch in years to still fit perfectly.