phychotron

Been trying to solve this problem that showed up after I installed some exhaust manifold gaskets that were non existent. I also ran about half a can of carb cleaner down the carb at the same time. I did a tune up a few weeks back and it was fine. But after the gaskets and carb cleaner its been running erratic. Surging up and down. I'm also having a misfire issue that's been there for awhile but seems to be much more prevalent now.

I've uploaded a few videos of the engine running and running seafoam down the carb to see if it helped. it seems to have done some good but not really fixed the problem. After shutting down and restarting its still a problem.

I've also replaced all the vacuum lines that I could find, as they were starting to age and crack and about half were loose (the other half had to be cut off). I did find one that was off but it didn't solve the problem.

Checked the compression, 160, 158, 150, 152.

It doesn't sound right but seems to have decent power when test driving it. at low speeds/throttle it surges like I'm feathering the clutch.

http://www.youtube.com/watch?v=2TTws...DagsDA6f7YjNDC

I'm using the Haynes manual to try and diagnose and fix the problem but its not the easiest of books to extract knowledge out of. Any help would be appreciated. I'm kind of at a loss.

L5wolvesf

Was it running well before this started happening? A lil more history since we have no idea what has been done, or not.
Surging between what RPMs roughly if no tach.

Did you check to see if the carb bolts are tight? How did you tune/time it if the idle is erratic?

phychotron

yes, the occasional misfire but not rough or surging. It was nice after the tune up so I went ahead and did the exhaust gaskets to finish it off.

It sounds different at idle but fine when driving it, other than at low throttle. Surging from 5-1100, or around 8-1400. I've been playing around with the idle speed on the carb to keep it from getting too low. Seems like it comes in waves of higher and lower.

The seafoam part 4 video shows the timing procedure. Its close to the mark and surges a little around it.

www.youtube.com/watch?v=u48jDpLgkUs&index=5&list=PLCoiVzWh29FPxukE DkMDagsDA6f7YjNDC

I checked the carb bolts and were all tight. Also sprayed carb cleaner around it to see but no change.

I bought it 2 years ago, put around 25k on it and have been replacing things as needed. I replaced the master cylinder/booster about a year ago and was considering checking that as a potential source of a leak but not sure how.

L5wolvesf

If you are very sure it isn't a vacuum line, then I would check the fuel filter and the pump pressure. I'm presuming it is the stock carb - correct?

phychotron

stock carb, new fuel filter. How would I check the pressure?

L5wolvesf

The search function here is your friend and easy to use.

I searched "fuel pressure test" and came up with several references to an item that MAY be your issue too - an idle fuel cutoff.
Disregard the numerous Weber postings in that search for your diagnosis BUT - how to test fuel pressure and flow MAY be in one of those too.

Let us know what you find or if you have a question based on an old post copy a link here so we can see what you're referring to.

phychotron

Message boards all have search function but rarely do they supply the exact information your looking for. you end up having to 'disregard the numerous .. postings'

To be honest I just don't have the time to read a bunch of irrelevant information about other peoples problems, and potential solutions of people speculating about what it could be, or threads that are never resolved. The top few results for the aforementioned search all have 5 pages.

Message boards don't present information readily-- they supply the human connection. The real search function on a message board are the regular uses who know the threads from memory.

Thanks, I'll try and find the procedure in the Haynes.

phychotron

Just an update. I drove it yesterday around the block and it was a lot nicer. Surging pretty much eliminated with a slight surge at idle occasionally. So today I adjusted the idle back down and set the timing and its running a bit nicer. In fact it sounded almost normal.

Now I'm trying to figure out if the noise I'm hearing is pinking or an exhaust leak I suspected I as going to have (because of the gasket rock auto sent me was not very proper looking). When I set the timing I retarded it a little to reduce any pinking. It ran fine across town but on the way back was a bit sluggish. it till got up to speed and running decent but a noticeable power loss when going up hill.

Its a problem I've had for awhile now, where sometimes it would just randomly run sluggish. In the past I mostly resolved it by putting the vacuum lines back on that had slipped off. I say mostly because it still happens occasionally but not as much power loss but still sluggish. It seems to go away when the engine is at higher rpm's and will stay at normal power for the remainder of the drive. Anyone know what might cause this?

its also not starting as easy as it normally does. Takes a little bit of cranking (2-5 seconds, compared to 0-2 optimal).

I think my carb is getting old and the smog stuff is starting to take its toll. I'm considering getting a Weber and De-Smog it. I considered rebuilding the carb but it seems very complicated compared to the one barrel I rebuilt 15 years ago. I also wanted to update the igniter with the GM-conversion and see if that helped with the misfire.

13Swords

I think you may be onto something about the carb. You say it's old but I'd be curious as to when it was rebuilt last. Your Seafoam treatment probably didn't help much; I suspect it loosened up some crud inside which is now at least partially blocking your idle circuit. That would account for the surging @ idle. As you've been driving it it may have partly cleared itself, but not completely. You also mention that it's pinging, which is a sign of a lean condition. A partially blocked idle circuit fits that bill as well; it's still a part of the whole fuel delivery metering, would explain lack of power on the hills.

If you have the in-tank electric fuel pump, it could also be your fuel pump resistor. Located in engine compartment on passenger side wheelwell, If you want to test it, it should measure no more than 1.4 Ohms cold & no more than 2 Ohms hot. No proper OEM replacements for this out there either. I just desoldered the old resistor & soldered in a new 20 watt aluminum cased power resistor rated for 1.4 Ohms. Works great.

I have a '78 2WD which is likely just like yours (mechanically) and I've been thru the mill with it on getting the fuel side sorted out, plus almost everything else. Although the Weber 32/36 would be nice, it costs too much for me to consider; Over $300 for a genuine kit. There are fakes on the market to watch out for too (beware ebay Weber Carbs coming from China). I ended up getting a pro rebuilt & tested stock carb from National Carburetors for $175 plus shipping. I looked yours up (http://www.nationalcarburetors.com/l...partnum=toy384) and it's currently $219.95. There's a $50 core charge that you get refunded to you when you send them your old carb. They replace every part subject to wear & flow test it. I'm very happy with mine. I have also completely desmogged the truck & just capped off the unused "smog stuff" vac ports on the carb without ill effect. Old school carb adjustments worked fine (idle speed, mixture). Power is good across the band & it gets on average 25/26 mpg around town if I keep my foot out of it.

One other thot because this is something I also went through, weird idle problems. Even when I got the new carb on I had inconsistant idle speeds that no carb adjustment would fix. Would be 800 then higher or lower at random after a rev & letting it settle back to idle position; different idle speed every time! It wasn't the carb. It turned out to be the throttle rod linkage in the engine bay, near the firewall. The rod end ball joints were worn, allowing too much "slop" in the linkage; it was also randomly binding up near idle position. You can't buy a new rod setup from Toyota (or aftermarket) anymore so I fabbed one up out of threaded rod & 2 new rod end ball joints from Dorman. Good as gold now, drops back to 800 rpm idle every time.

I hope this info is some help to you. Let me know if you have any questions. Like I said, I've been thru almost everything on my truck.