Misfiring B2200

High everyone and thank you for this site.
I have a 1992 B2200 I purchased brand new back in 92 yes that is right I still drive this truck every day. I paid $10,500 for it right off the lot.

Just out of the blue it has started a sporadic carburetor backfire when I put a strain on the motor . Weird thing is it only does this on some days and some days it might backfire only a few times and some days it will do it at almost every hill or when strained. I changed the fuel filter no difference though.
So if someone knows the fix please post it . I would really appreciate it.
Thanks again.

Welcome, have you checked your spark plugs?

No I will though. It is so weird though like today the truck did not hardly spit up one time , I mean it did when i first started out of the subdivision and a few times here and there and a jolt here and there. I do not know man this one is really tricky, at least it is to me.

Pull the distributor cap and look inside the cap. May be an oil film inside the cap, allowing the spark to wonder.

I want write a novel but,I would think there is a air flow restriction.I would remove and clean the egr valve for one.I would also remove the pair tube hoses and remove and check the filters in the housing for the pair tube hose's.Lastly your truck has a pre-cat convertor just below the exhaust manifold which has screens inside that can get clogged up with carbon and reduce air flow and may need to be removed and cleaned.Btw how old is your cat convertor as this is a major part of air flow and maybe blocked up with crap.My premise maybe wrong in thought however these items play a very important part in the exhaust side and can create a variety of problems like your issue right now.I say all this as I have owned my truck since brand new for 28 years.

Thank you for the advise, i plan on popping the hood this weekend and giving it a look.

I bought my b2200 new in 1992 too. I have never replace the cat , this had not come to mind I keeping thinking timing is off, but I would think if it where timing it would be a constant backfire more so from the exhaust than the carburetor. Thanks for the advise, any more info is appreciated.

Ok I own a 1992 B2200 5 speed over drive.
Perhaps someone could explain o me as to why dealers and some specialty parts are sooooo darn expensive . Especially dealers item parts. Here is an example , As much as it hurt my pocket book, I spent $20.00 for the upper boot Part number UB3964491 , $22.00 for the middle boot part number UB4164490 , The lower boot needed replacing too , however , I could bring myself to spend a whopping $45.00 for a small piece of rubber only an inch or so in circumference . (This is what I am talking about $45.00 for something that in my opinion only cost no more than $5.00 to manufacturer ) This again in my opinion should be against the law. It makes me so angry for anything to be such a rip off. So I went online to see if anyone had a cheap fix for this small rubber boot. I read if I remove the damaged boot , clean it up and make sure it is free from oil and grease. Then use silicone to join the broken pieces together that would work as a permanent fix.
This was 2 years ago.
So last week I decided to check the bottom shifter boot (the small circular one that sits on the trany) , and sure enough it had broken apart again.
This was not what really made me angry, As I stated earlier , I had spent good money on the middle and top dust boots from the Mazda dealer mind ya , ya know "Genuine Mazda Parts" , yeah right. The middle boot has a huge tear in it. The boot is just as clean as when I installed it 2 years ago no grease or oil to weaken the rubber. I just do not get it . I have had this truck since it was new in 1992 , the original boot lasted for more than 18 years or so. So if I spent good money on what is supposed to be "genuine" , then why did this boot fail ? I already know what some people are saying reading this, Daaa It probably is genuine , but was manufactured back when your line of trucks where manufactured therefore it is been sitting in a warehouse aging just like your original ,thus ,causing the rubber to dry through the years , decades.
Here is where I need an experts help.
If all the dealers have the same ancient parts that deteriorating sitting in a warehouse it would be ludicrous for me to spend good money for the same problem.
Soooooo , here is the ten million dollar question ,does anyone know where I can purchase fresh rubber boots ? Of course I checked eBay , but I only GOD knows how long these have been sitting and if the quality of the rubber is any thicker than a piece of paper.
Also , my outside window door trim has grown to be hard as a rock. The trusty dealer wants an arm and a leg.
Manufacturer Mazda UB4159821A
A cool $54.00 each. (wow) .
I sure would give big thanks to someone who can assist.
Thanks to all .
Thanks for this forum to share our thoughts.

I would enclose pictures, but I have not figured out how to do it.

If your window trim does not affect how the truck runs, and you don't want to pay dealer prices, and you can't find a replacement part in the junk yard..... Leave it alone until it falls off, then see if a body shop can get you one cheaper. Good luck.

Ok thanks