Looking for experienced guess or idea

Ok so this is not XJ nor moto related, but I need my favorite forum to help me with this. BTW I asked about this on two Toyota forums over a week ago and can't get any response even though the threads had over 150 views! ahem...they suck.

I am looking at buying an old Toyota 2wd truck(74 longbed). It has the 18R motor which is a 2.0L 4cylinder, single carb, SOHC, standard Japanese motor for a 70's truck. The truck is in really decent shape for it's age, but the motor has an issue. Here's the details:

-Starts right up and idles fine after about 1 minute of high idle
-Everything is basically stock, but old
-When you gas it, it will rev up but then it lets out a quiet backfire
-Has fair power until it's under load and then it starts the popping and loses most power
-Was able to climb a hill in first, fairly well in second, not so much in third
-Believe it has sat for a while (around 1 or 2 years since the PO passed away) and probably has old gas
-Sounds like the backfire is coming from either the carb or the exhaust manifold (not the tailpipe)
-no smoke, no dieseling, no dying
-I don't think any real maintenance has been done since it was parked a while ago

Ok so anyone run into something like this before? What's your best guess on this, and do you think the motor should be put out to pasture or can it be rejuvenated?

Thanks to all who can try and steer me in the right direction.

 

old gas and clogged fuel filter

 

Old gas , fuel filter . The carb will most likley need to come off and get rebuilt. Do a compression test to see if there are any engine problems. A tune up will also help, plugs, cap and rotor, maybe plug wires. If it has pionts they will need checking too.

 

Thanks fellas, this is what I was leaning to as the likely cause-thinking it was bad fuel, not enough fuel, screwy ignition, or dirty carb. My only concern was that it could be more like a cracked manifold, burnt valve, etc.

I can't tell how much effort the seller (son-in-law) has put into the truck, but it doesn't seem like he cares for it too much. He's a Chevy guy and doesn't even like Fords so you know how he feels about those damn foreigners! I think he just hasn't even tried to do anything to it. But the old man clearly cared for the truck a lot based on the condition the rest of the truck is in-I will check the compression and go from there.

Oh yea and thanks again for being 1000% more helpful than the 'experts' over in the Toyota forums. No wonder people are always amazed when they come here and get timely helpful advice.

 

The symptoms could also be those of a tight or burnt valve; a lot of older Japanese motors didn't have automatically/hydraulically-adjusted valves. European motors as well, for that matter. My daughter has a '98 Escort with the "Zetec" motor in it, and it has guess what--- shim over bucket adjusted valves just like our bikes.

If you get good compression numbers, then you're probably safe to proceed; but as old as it is, I wouldn't buy it without a compression test first (unless you're looking to buy into a rebuild.) While you've got the plugs out to do the compression test, examine them carefully; you may be able to learn quite a bit about the motor.

 

flush and replace fuel, put a new fuel filter on, oil and filter change, rebuild carb, and full tune up. You can't kill those engines.

dave f

 

Also check the vacuum hoses. I believe that motor had vacuum advance on it. If so if the hose to the distributor is leaking it will not advance the timing properly as the rpms climb, ie: engine under load. If any of the vacuum lines are stiff, then they are dry and cracking, replace them.