TH400 acting oddly

[DoubleDingo]

I know the caps are good, those were replaced when I got it. I definitely have some investigating to do. The vacuum leak at the choke can is not helping, that's why I linked the ports with tubing for the time being. I need more time in the day to unload the truck after work. Hoping to get a couple wheelbarrows full out of it tonight. Slow going with spreading the rock dust, compacting it then making sure it pitches the right way, or if it needs more material. Then repeat for the next section.

 

[da_raabi]

Would a bad torque converter cause all of this? What trans do you have?

 

[da_raabi]

Seems the majority here has nothing to provide on the subject, so I've been trying some research and getting mixed information. I just went to the Cliff Ruggles forums to see if there may be info there because I suspect this is a carburetor issue not a TH400 issue since the TH400 acts just fine when the truck is running properly. While there I saw a couple member's names from here over there. @fussfeld and @da_raabi I thought that was cool. There were a few threads on the hot air choke, and Cliff mentioned melting some lead into the vacuum passage of the hot air choke. I'm wondering if getting a split shot hot enough with a propane torch to make it more malleable and tapping it into that passage will be enough to seal it off?

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[DoubleDingo]

Would a bad torque converter cause all of this? What trans do you have?

I got the rock dust out of it last night. Drove it this morning and it runs better with the vacuum ports linked up with the tubing. It still stumbles a little but nothing like it did. This is a baffler for sure. When it stumbles, it's the engine, not the trans. Last weekend when I got back with the load of rock dust and was letting it idle with the hood up, you could see the engine rocking. Then I shut it off to go get the tool to adjust the air mixture. When I fired it back up it ran smooth with a minor stumble. Last night I needed to move it forward a couple feet and it started easier cold than it ever has since I've owned it. I'm telling you this is the goofiest thing I've ever encountered on a vehicle.

 

[DoubleDingo]

For the fun of it, when I pull the cap to check the weights, I will swap in an old cap, rotor, coil, plugs and wires that were operational when removed. Would it hurt anything to spray some wd40 on the weights? Not a lot, just a little spritz.

 

[da_raabi]

For the fun of it, when I pull the cap to check the weights, I will swap in an old cap, rotor, coil, plugs and wires that were operational when removed. Would it hurt anything to spray some wd40 on the weights? Not a lot, just a little spritz.

I've done the same without much issue. I need to replace my distributor because the weights are all rusty and I think they are sticking. All that does is give me some ping under WoT operations though.

Are you sure the fuel tank/system is all good to go? Are you sure all of the rubber fuel lines are good and not collapsed? I'm assuming you have been running ethanol gas in old-school fuel lines. There's a good chance they could be collapsing internally when the pump puts a vacuum on them to suck the fuel in. Most fuel hose is NOT ethanol resistant. I've got a thread around here somewhere detailing how I almost burned my truck to the ground for that reason...

Is sure sounds to me like something getting stuck/plugged somewhere in the fuel system.

 

[QBuff02]

For the fun of it, when I pull the cap to check the weights, I will swap in an old cap, rotor, coil, plugs and wires that were operational when removed. Would it hurt anything to spray some wd40 on the weights? Not a lot, just a little spritz.

You might find that the top end of the distributor is completely worn out. I had an issue with my truck where it would idle and carry on and run real good, but every once in awhile it would like "hiccup" and start running like complete crap. Put your foot into it and it would clean up and run good again. I went through everything on it trying to figure it out, finally decided to put the timing light back on it and see what was going on. needless to say, I found it would be sitting pretty at 12-14 degrees before at about 850-900 rpm and then put it into gear and all of a sudden the timing would go way late and be like 18-20 degrees after and the engine would hammer and shake and rattle. but if you bumped the throttle and got it revved back up just a little the timing would come back to where it needed to be and it would run fine, let it dip again and the engine would shake and rattle and carry on and the timing would be waaaaaay late again. Took the cap and rotor off the distributor to investigate and found the weights and bushings and pins completely SHOT. To the point that I felt it was just going to be better to put a new distributor into it. Especially with how cheap they are. Put new distributor in, got it timed and those problems pretty much disappeared.

 

[DoubleDingo]

I've done the same without much issue. I need to replace my distributor because the weights are all rusty and I think they are sticking. All that does is give me some ping under WoT operations though.

Are you sure the fuel tank/system is all good to go? Are you sure all of the rubber fuel lines are good and not collapsed? I'm assuming you have been running ethanol gas in old-school fuel lines. There's a good chance they could be collapsing internally when the pump puts a vacuum on them to suck the fuel in. Most fuel hose is NOT ethanol resistant. I've got a thread around here somewhere detailing how I almost burned my truck to the ground for that reason...

Is sure sounds to me like something getting stuck/plugged somewhere in the fuel system.

Not 100% sure. It is running a lot better after running tanks-full of fuel laced with lots of motor-purr fuel injection/carb cleaner. It's still a mystery why it'll sporadically creep in neutral while idling and act up while backing up. I have an extra vacuum gauge and I want to install it to see what the vacuum is like while I'm driving. This weekend I have some time to investigate some, so I'll report back what I find. I do remember your thread on the fuel lines. And I have not put new lines on at the tank. Pump, and elsewhere, yes, and it was the good stuff.

 

[DoubleDingo]

You might find that the top end of the distributor is completely worn out. I had an issue with my truck where it would idle and carry on and run real good, but every once in awhile it would like "hiccup" and start running like complete crap. Put your foot into it and it would clean up and run good again. I went through everything on it trying to figure it out, finally decided to put the timing light back on it and see what was going on. needless to say, I found it would be sitting pretty at 12-14 degrees before at about 850-900 rpm and then put it into gear and all of a sudden the timing would go way late and be like 18-20 degrees after and the engine would hammer and shake and rattle. but if you bumped the throttle and got it revved back up just a little the timing would come back to where it needed to be and it would run fine, let it dip again and the engine would shake and rattle and carry on and the timing would be waaaaaay late again. Took the cap and rotor off the distributor to investigate and found the weights and bushings and pins completely SHOT. To the point that I felt it was just going to be better to put a new distributor into it. Especially with how cheap they are. Put new distributor in, got it timed and those problems pretty much disappeared.

That's kind of what this is doing. It's a low mileage truck, but that doesn't mean the distributor isn't worn out.

 

[Frankenchevy]

The creeping in neutral thing is weird. Not to say there aren’t other problems, but that sounds like it can only be trans related. Have you thought about doing a drain and fill?

 

[DoubleDingo]

I have considered that, because I only did one drain and fill after I got the truck, so there is some of the old stuff still mixed in. The color is nice and red and doesn't smell burnt. The odd thing about the creeping is that it only does it when the engine acts up. When it's running smoothly the trans works perfectly, no creeping and backs up normal.

 

[da_raabi]

I have considered that, because I only did one drain and fill after I got the truck, so there is some of the old stuff still mixed in. The color is nice and red and doesn't smell burnt. The odd thing about the creeping is that it only does it when the engine acts up. When it's running smoothly the trans works perfectly, no creeping and backs up normal.

See this really point me back to the TC again. Think about it, if the TC is full of junk and getting itself out of balance and/or changing the stall speed, it could make it creep, and I would definitely think it would act up in reverse. I cannot think of anything engine related that would cause those two symptoms. Stalling/unstalling repeatedly would also make the engine buck like a **** one would think.

This might be a pain, but you could try unbolting the TC, slide it back into the trans so the engine is free, and fire her up. See if the problem persists. Maybe try plugging the modulator hose too. I'd be curious about the result of that test.

 

[DoubleDingo]

I can see that. But before I unbolt it like you mentioned, I'm going at it like it's a vacuum leak first, then the distributor, then the fuel lines, then the trans. It'll stumble even in park, but mostly while sitting at a light.

My plan of attack is to replace all the vacuum lines including the little check valves. Maybe the advance can. If I had a vacuum pump I could better diagnose a leak in the system, but I need to get inexpensive items right now, payday is a week out and mortgage & property taxes took all the money this week.

 

[DoubleDingo]

What are EFE TVS, SPARK TVS, EFE, TVS, TRC VLV?

This is my hose routing sticker.......

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[DoubleDingo]

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