Jrheingans

iTrader: (2)

Ok trying to make some progress on this beast so at least i can drive it around. It has the original engine rebuilt and original carb rebuilt with all smog equipment hooked up. All vacuum lines look to be in good condition or recently replaced. Engine runs perfect at idle and makes no strange noises or anything! Now i drive it in first gear- runs great. Go to second gear- runs great. go to third gear- runs great. Then as soon as i shift to fourth there is no power!! It will barely go 40mph and i cant even go fast enough to get it in 5th gear. What is this?Thanks Yall! Also if someone with an sr5 with tach could post a picture of the wiring that goes from the cab to the coil to make the tach work i would appreciate that.

zombie_stomp

Have you tried sucking/blowing on the vacuum advance diaphragms on the distributor?

Also last night I started rebuilding my carburetor and found one of the butterfly valves stuck closed... I'm very surprised it had the amount of power that it did, but instead had really terrible cold start and intermittent dying idle problems. Maybe something in your carburetor is gummed up. An easy thing to do without having to rebuild yet would be to clean it up from the outside in and also run a dose of fuel injector/carb cleaning fuel addititive. That stuff cleared up a rough idle on my '83.

Jrheingans

iTrader: (2)

No I havnt tried testing the vacuum on the distributor. I will do that tonight. However the carb has just been professionally rebuilt so I know it's not the carb itself...

Jrheingans

iTrader: (2)

Sucked and blew on hoses that go to distributor and the one closest to the radiator I can hear it pop in and out but can't hear anything on the one closest to the engine?

Jrheingans

iTrader: (2)

Could vacuum advance be my problem? What am i suppose to see/hear when i suck on the hoses?

enigmaT120

I do that test with the motor running and my timing light on the marks. Sucking on either hose should advance the timing, but to different degrees.

You can use a vacuum pump, like people use for bleeding brakes, to do the same thing. It will also make it obvious if the diaphragms aren't sealing and holding the vacuum.

Jrheingans

iTrader: (2)

Ok i have ruled out the vacuum advance. Going to try replacing air filter and see if that helps. If anyone has anymore ideas let me know

enigmaT120

So it has plenty of power in first and second? I was going to say it could be compression loss (was blown head gasket for me) but that affects the performance in any gear. Is the motor bogging down in the higher gears?

Jrheingans

iTrader: (2)

Engine is a fresh rebuild so I'm ruling out compression. And yes it seems to have pretty good low end power but no high end

gillesdetrail

iTrader: (1)

It doesn't make sense that you loose power in 4th and 5th gear, as nothing changes in the engine wether you are in 1st or 5th. Can you see a relation between power loss and rpm instead? Can you rev 2nd gear until 5000 rpms without problem? When you say no power what do you mean? does it pop and stumble and miss or does it just stop accelerating?

gillesdetrail

iTrader: (1)

If it is rpm related and not speed or gear related then I would definately make sure the mecanical (timing chain) timing is correct and also the distributor timing. A timing that is too advanced can make great low en torque but then can start detonating at higher rpm and it's really bad for the motor.

Jrheingans

iTrader: (2)

I'm almost banking on the distributor... That and the coil are the only not new things on the truck. I'm going to check to be sure timing is the issue and report back. I can rev in the first few gears and it will go as high as I want it. But in higher gears it acts like it's barely doing 1500rpm. Tach is currently not hooked up

g3bill2

Thinking carb also? could be the vacuum diaphram also. its an 81 4x4 and if never replaced most likely its leaking but could still idle fine. If so there pricey for a 4x4 so i rebuilt mine with diaphrams from a water control valve, couldn't pass smog without it fixed but didn't cause problems in high gears. Back to carb or something else??????

Jrheingans

iTrader: (2)

Thanks for the help! It could have something to do with the carb and I may just go with a weber eventually... I should have done more progress on it after the weekend.

zombie_stomp

I just rebuilt the carb on my '82 and it had a stuck secondary butterfly valve, and didn't even act up at higher speeds as bad as you're describing, which amazed me. It may not have anything to do with the carb, but I'd be curious to know if it had received a rebuild at the time the engine was rebuilt.

gillesdetrail

iTrader: (1)

I had the same symptoms on a car that jumped a tooth on the timing. Good power below 3000rpms but above it would ping and not rev. To help you further we need to make SURE if it is rpm related or speed related (unlikely).

g3bill2

U must be a young hot rodder? first thought when things cant be figured, get a weber,? Doesn't a '81 have a double row timing chain? thinking not so likely to jump and would have been some warning noise maybe. So when did this start or you bought it in this condition? If its a truly full rebuild should be no issues from the inside...unless the timing chain wasn't set correctly? u can check that.

When I bought my '82 it drove ok till i got out on a highway going into the wind, couldn't get over 35mph never mind 3rd and 4th gear, had to drive it home with an escort at 35mph on freeway and very slow on hills. Thinking boy this is the Shi%'s . I did as much as i could, checked timing, set valves new plugs, the regular stuff and I rebuilt the carb. i followed the directions contrary to the amarican mans thought pattern. Got it running and still had problems with lack of power even though it was better. Dont remember but something i did or didn't do in setting things right, think it was that high speed or fuel inrichment needle plus the secondary wouldn't open, its shaft was binding from lack of use maybe. I kept working it by hand many times and seemed better but still have to lube it once in a while even today plus get on it now and then with wot. The secondary wont open till the motor is well warmed up. Its been great now for over 10 years and haven't touched it since.
Might be right about the timing chain too. I got my 85 nissan from a guy that i found out later changed the chain by one or two teeth cause there was a bad piston. I dont remember it having much power on the freeway but was ok on streets. really got srewed on that one

Have to wonder why you eliminated the vacuum advance as being ok, sure you tested correct? Before spending tons of mony might just take it to a shop to test it? At my toyota dealer there a guy thats been there a long time and knows the older cars well so gives me pretty good free advice, u might try the same? good luck....

Jrheingans

iTrader: (2)

Jumped a tooth on the timing chain or on the distributor? I rotated timing mark on pulley to zero and checked my rotor and it was pointing toward the #4 plug... So if I rotated it again. It would be at the #1 plug which means I have it close at least to the right spot correct?

Jrheingans

iTrader: (2)

I wouldn't call myself a hot rodder I just want to restore this beast and have a reliable daily driver. I have been around engines my whole life but as far as timing goes in pretty new. I replaced the coil and had the same results so cool isn't the problem. Next step I was thinking was try moving distributor around and switching it out with another I have. Call Toyota dealer and they said it's too old so they won't touch it. Carb is rebuilt but I'm considering a weber just to rule out all vacum and fuel related possibilities. The search continues. I have seen a couple threads on here about exact same issues I have had but no one has posted that they fixed the problem!!

gillesdetrail

iTrader: (1)

For me it was a skipped tooth on a timing belt. I wish you could post a video so we could clearly see the symptoms. You can rule out a tooth on the distributor, as it will barely idle if even start if it isn't on correctly. Having your engine at top dead center and the rotor pointed at the No1 or 4 is not acurate enough to know if it skipped a tooth or not on the chain. I would go to a garage where they deal with older cars for them to help you. When it is fixed, you should report back on the results for others in the future!

This is a great way for you to learn about timing, go get yourself a timing light and check the correct procedure on how to check timing with the distributor and see if you can dial it in at around 5 btdc, if not you know the mecanical timing is off.