Instant Complete loss of power b2000 86

Hello all,

New to this forum and had a question on a 1986 b2000. I was driving just fine and my truck lost almost all power. Would run but not rev high at all. I can drive it 5mph max in 1st gear and nothing else. The truck has 77k on it from original owner and he never had any major work done on it (including timing belt). Would a timing belt do this? Thanks for any help you could give.

As an update....I looked over the engine and took the airfilter cover off after changing the distributor cap, plugs, wires and rotor. I started it off and the engine ran great. I decided to make sure and drove it around the road briefly. It ran better than new, so I went back to the drive way and put the air filter and cover on, it stalled. The truck runs like garbage with the cover on and great with it off. Any ideas? I checked for anything obvious but didnt see anything out of the ordinary. I spend a couple hours looking, tightening the carb down and checking vaccum hoses.

Help?

I smell a vacuum leak.These trucks have a vacuum advance on the dist.It may be that when u put the cover on the air cleaner that the truck is running way too rich and bogs down.If the dist.advance isnt working would cause the same symptoms.When u open up the air cleaner more o2 goesinto the carb and the truck leans out and runs a bit better. Check vacuum hoses for leaks,especially the one that goes from carb to dist.Also check the sight glass on the drivers side of the carb and make sure u can see gas up to the sight line on the glass.Also be sure the PCV valve on top of the engine is not plugged up.BJ

Thank you very much for the reply. Someone outside of the forum suggested the distributor advance as well but I havent had time to check it yet. I really appreciate the advice/thoughts. I will let you know what happens.

Ok. I checked the vacuum advance and changed it and it had no effect, it still stalls when I put the air cover on. I did notice that there is moisture being blown in by the lower tube that comes from the assembly that is on the front of the air filter chamber. What does that do? Does it have a name? It has tubes going down toward the exhaust maifold, I am assuming that the water (no smell) is causing the carb to pull in more of the moisture when the cover is on and causing it to stall and have no power. Where can the moisture be coming from and would anyone have any idea how I can recify my problem?

Thanks in advance.

Your symptoms look like you are running extremely reach because of some sort of blockage on intake side. Try to remove the air filter, and put cover back. See how it behaves. If it helps, replace air filter. If it does not, look for any kind of blockage before air filter. Could be rag, or dead rat, or whatever:wink:

Thanks for the reply, I have checked the entire air intake related to the air filter housing and the hose to the grill. There is no blockage, I thought the same thing, mouse nest or something. Someone suggested it may be the warm air intake off of the exhaust maifold stuck which would restrict airflow and when I was checking for blockage I saw it in there, but with the engine off. I have rain up here today but I was gonna check for that and any information I could find on the reed valve unit on the front of the air filter assembley, which also has steel lines running down toward the exaust manifold.

This whole thing is weird. It is directly related to the cover on the air assembly and It runs like garbage with the cover on (with or without the filter). If I leave the cover off it runs fantastic all around. I agree that it's starved for air but I cannot find out why. The only thing abnormal is the tablespoon worth of water build up if I run the motor for ten minutes. The water is coming from the lower pipe on the reed assembly inside of the air filter compartment. Most people I have spoken with seem to think it's just condesation because I also have water coming from the exhaust pipe, probably a few tablespoons in the same amount of time.

Again, thanks for the reply.

Can you post pics of your air filter housing and cover? This might help.
Water is definitely a condensation, and it is because of blockage, too. Because it creates higher than usual vaccum, and lower than usual temps. It should go away if we find and fix the original problem.
And some kind of blockage is definitely the thing to look for, I strongly believe all of your symptoms fit the description.

Thanks again. I will get some pictures and post them (once I find out how hehe, it shouldn't be too hard). We have rain for a couple days but I will do.

Thanks.

The reed valve assembly on the front of the air cleaner box exists mainly as a polution control device.The assembly routes air into the exhaust system via the three pipes in front of the second cat to lower the amount of pollutants emitted by the truck.The condensate u see is because warm air is seeping back into the air box from the hot exhaust.In the snorkle in front of ur air cleaner there is a flapper valve that is controlled by a bimetal spring.It is supposed to be closed and let warm air from the manifold into the carb for warmup puposes.When truck gets warm the valve is suppposed to open and let cool air in from the snorkle.with the truck cold,take the plastic piece off the snorkle and shine a flashlite up into the snorkle.The flap should be closed.Do same thing with truck warm and it should be open.BJ

Bump.One other thought.Since ur engine is basically an air pump,if ur having trouble getting the engine to run correctly with the proper filter and air cover installed,u may have a plugged catalytic convertter on the exhaust side.Mazdas are notorious for the cat right under the manifold plugging up because the sorry Nikki carb runs rich anyway.Just a thought.BJ

Bump.One other thought.Since ur engine is basically an air pump,if ur having trouble getting the engine to run correctly with the proper filter and air cover installed,u may have a plugged catalytic convertter on the exhaust side.Mazdas are notorious for the cat right under the manifold plugging up because the sorry Nikki carb runs rich anyway.Just a thought.BJ

Interesting, how would I check the cat? You say this and I do remember an odd smell when it happened, originally I thought it was a timing belt slip. I couldn't quite place the smell. Would the engine run fine with the cat plugged? I would think it wouldn't.

The odd thing is that it runs perfect with the air cover off, I have driven it in 3 gears on the road. I put the cover on and it dies after a 30 second gasp and shake. I keep finding myself pondering the path of least resistance with this one, what would be the next easiest path for air if the cover is on? I swear the intended path is clear of any obstructions but I will recheck.

Thanks for the input. I will try to post pictures soon.

To check cat u will ned a muffler shop to unbolt the system right under the cat and visually check it.The only way that air can get into system with air cleaner on is thru the snorkle and the hot air riser mechanism attached to it, or somehow thru those three air lines that run into the air cleaner-but it is not supposed to run into the air cleaner but rather away from it into the exhaust.Something has to be plugged up somewhere.bJ

hello. pootz22
I just read the posts,and it looks to my like a bad reed valves at the exaust
air injection pipes.Those check valves, if bad,let exaust gas inlet in air filter
compartment, entering in carburator with cover on, with cover off it suck clean air and no problem.

hello. pootz22
I just read the posts,and it looks to my like a bad reed valves at the exaust
air injection pipes.Those check valves, if bad,let exaust gas inlet in air filter
compartment, entering in carburator with cover on, with cover off it suck clean air and no problem.


Thanks for the input, I had thought something like that, how would you fix the reed valves? Is this a whole unit replace or something you can buy new reed valves for?

I have several things I want to check based on input I have been graciously given (thank you):

1.) Warm air valve - is it stuck open while the engine is running limiting air flow through the neck of the air filter assmebly.

2.) Choke valve - Is it broken somehow where when the cover is put on the vaccum from the carb sucks it closed when the engine is running. I believe I already checked the valve but I have checked alot already and could have over looked.

3.) Reed valves - My thoughts on validating this would be either to disconnect the hoses leading the the valves or put a rubber stopper in the pipes inside the air assembley.

4.) Last and hopefully least likely is the CAT, I really hope this isnt it, and I also would think that the truck would run bad even with the cover off.

Again, thank you very much for the input. I will update when I get a chance to look at the truck with some daylight.

So, I got a chance to check things out. I checked the neck to the air filter assembley and all was clear. I disconnected the right most hose leading into the reed assembley and put the cover on, it worked! What does that hose do and how do I fix it? I drove the truck with the air cover on and the hose disconnected and it ran fine. I just wonder if I will pull dust and small particles into the carb with the hose disconnected.

Any thoughts?

Thanks in advance.

So, I got a chance to check things out. I checked the neck to the air filter assembley and all was clear. I disconnected the right most hose leading into the reed assembley and put the cover on, it worked! What does that hose do and how do I fix it? I drove the truck with the air cover on and the hose disconnected and it ran fine. I just wonder if I will pull dust and small particles into the carb with the hose disconnected.

Any thoughts?

Thanks in advance.
Did you plug the opening? I guess your engine just sucks air through this opening - means the normal way is still blocked:uhoh:

Did you plug the opening? I guess your engine just sucks air through this opening - means the normal way is still blocked:uhoh:


I did plug it with my hand when I had the cover on and there was no effect, it seems that the hose was blowing into the air assembley but I can't find anything on what it does exactly.

So in response, I would say that nothing is blocked but the hose or valve that is involved in that connection is not functioning properly. Someone lead me to believe that these three hoses work in conjunction with the exhaust by pulling clean air into the exhaust system somehow.

I did plug it with my hand when I had the cover on and there was no effect, it seems that the hose was blowing into the air assembley but I can't find anything on what it does exactly.

So in response, I would say that nothing is blocked but the hose or valve that is involved in that connection is not functioning properly. Someone lead me to believe that these three hoses work in conjunction with the exhaust by pulling clean air into the exhaust system somehow.
I don't really know the details of your particular engine. I found one drawing on the internet, and it is not really clear to me what those valved do. I would be glad for you if this fixes the problem, but I really doubt it does. Plug it more seriously and give it a test drive - I think this will tell you whether you found a reason or not.

What I suspect the true problem is (and I am not going to like) that the CAT is blocked and pushing exhaust back through the pipe/hose into the air intake. When I disconnected the hose it stopped the exhaust from getting into the air filter area. What doesn't make sense is that the engine should still run like garbage with all the back pressure but I am not exactly sure I understand the dual CAT system on these trucks. :banghead:

I think that was one of my posts-i.e. the cat was plugged-and I think u r correct.The first cat(called a pre-cat) is right under the exhaust manifold and covered by that cheesy bit of tin heat shield.The second one is right under the drivers feet and i bet that is the one that is plugged up.Replace it with a magnaflow hi-flow cat(about 45 bucks) and see if that doesnt cure ur ills.If the cat is plugged ,it does cause an increase in the back pressure which will eventually burn ur exhaust valves and then the engine goes.Since when u unplug the hose to the reed valve assembly,that causes a drop in back pressure and the truck runs better.To give u an example,my truck would not run over 75 mph.I changed the cat out,tuned it up and it now is able to do 95-100 mph.Makes a difference.:grinyes: BJ

Thanks for the advice, hopefully you weren't too put off that I disgarded your idea of the CAT but I really didnt want to deal with the exhaust in the northeast this time of year. With that said, I suspect that it is the second CAT causing the issue as the 2 right most reed valves hit the exhaust between the two CAT's.

I really appreciate everyone's input and thank all of you. I will post when I replace the CAT and the outcome.

Could you post the best vendor of the CAT you suggested for purchase please?

Thanks again.

As an update, I changed the rear CAT on my truck and it now runs normal. Thank you for all the help.

Great to hear that ur ride is back to normal.Be careful out there.BJ

Glad you fixed it :) And thanks for posting back