Dieseling + backfiring + rough/searching idle

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SinusoidalTendencies
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Re: Dieseling + backfiring + rough/searching idle

Post by SinusoidalTendencies » Tue Mar 19, 2019 9:54 pm

NWMO - I hadn't read that actually. Though had read about the carbon part on another post

Irowiki - they don't seem that complicated to me(descendant from a line of engineers), but rather fascinating actually. Though I don't know exactly everything about them yet. The only parts that seem to wear out is the valves, choke, and solenoids. If I had a machine shop I would probably just remake them.

Still interested in info on egr stuff, and brake booster.

I've really only been learning about cars for a few years at this point and this is my first experience having a carburetor to learn about. Might as well just assume I don't know very much as I appreciate learning how these things work in great detail
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Re: Dieseling + backfiring + rough/searching idle

Post by irowiki » Tue Mar 19, 2019 10:57 pm

The EGR is pretty much disconnect the two vacuum lines and cap them and see if it improves at all.

The brake booster will be a rather big line going from the booster to either the valve cover or the carb somewhere, I outlined it in blue, it has the white one way check valve on it (which sometimes snaps in half).
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SinusoidalTendencies
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Re: Dieseling + backfiring + rough/searching idle

Post by SinusoidalTendencies » Wed Mar 20, 2019 2:39 am

Interested in how the components work in the system as well
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TracDoc
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Re: Dieseling + backfiring + rough/searching idle

Post by TracDoc » Thu Mar 21, 2019 10:18 pm

SinusoidalTendencies,
One trick to preventing a AT car from dieseling is to shut is off while it is still in gear. The load on the engine usually keep the engine from dieseling. In addition, check the fuel level in the float bowl. The level should be in the middle of the sight glass.

If you have excess carbon on the tops of the pistons, you might want to look at how to do the old trick of adding small a amount of water to the carb while the vehicle is running. I have heard this works to remove carbon in the cylinders (valves and pistons). I am sure someone on YouTube has a video on it. Also, GM dealers used to sell a top engine cleaner that claimed to remove carbon. If I remember correctly, you would pour 2/3 to 3/4 of a can into the carb while the car was running and at about 1/4-1/3 of the can you would dump the rest in so that the car would stall. Then, let it sit for a while before starting it up and driving at highway speeds. Note: The GM cleaner process will cause lots of smoke out the tail pipe until all the cleaner is burned off.

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SinusoidalTendencies
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Re: Dieseling + backfiring + rough/searching idle

Post by SinusoidalTendencies » Fri Mar 22, 2019 5:25 pm

It's already smoking a lot when I start her up. Sooty grayish white.

Took the carb back off replaced that last hose I couldn't reach for the jet.
Took the egr and it's pipe off and cleaned em out a bit. They still had good flow. And valve seemed to work(I think, still felt sloppy like but held hose to my tongue).

Replaced the bigger hose for the actuator to egr & that breather hose that connects to the air filter box from the carb base as they seemed loose.

Inspected mixture screw. There was a small indented ring scored into the tip from being screwed in to tight in the past, but it wasn't to bad (I hope). Had it just slightly leaned out but put it back to spec.

Brake booster hose has one nic in it but doesn't appear to breach the mesh layer.

Didn't seem to solve the searching. Isn't dieseling as hard.

Exhaust leaks are killing me though. Might be most of my problems. I don't know.
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Petros
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Re: Dieseling + backfiring + rough/searching idle

Post by Petros » Sat Mar 23, 2019 5:27 pm

exhaust leaks should not affect the way it runs, but could affect the way your brain works from carbon monoxide poisoning, if it gets into the passenger compartment while you drive.

when the idle hunts or searches it means there is a vac leak somewhere. if it is not a gasket or leaky (or misrouted) vac line, it than could be a bad component with an internal leak. Almost every vac operated device will act like a vac leak if it is bad.

There are a series of simple tests in the FSM for each of the components. Run through the tests and see if you can find the bad one, unfortunately it still could be internally leaky, but function normally. So you also might see if the hunting stops when you disconnect each component as well, during your tests.

Also, it occurred to me that if you have a leaky AAP it would leak fuel into the intake manifold that could cause dieseling when you shut off the engine. so pull the vac line for the AAP and see if it has fuel in it. Or you can cap off both ends and drive it, see if that makes any difference.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
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SinusoidalTendencies
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Re: Dieseling + backfiring + rough/searching idle

Post by SinusoidalTendencies » Sun Mar 24, 2019 3:09 pm

If I remember correctly the actuator going to the egr failed during warm test phase.

Reports when I get to testing.

Put a half tank of regular gas in it to see what happened. It's searching/hunting further than before now.
Not sure why those would be related though.
The sounds of gas delivery within the carb are irregular and appear to match up with the searching......does that ring any bells?
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SinusoidalTendencies
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Re: Dieseling + backfiring + rough/searching idle

Post by SinusoidalTendencies » Sun Mar 24, 2019 3:55 pm

Page numbers for testing procedures would be splendid.

You can't use the section menu functions on a phone.

Between the 800 ish pages, lack of page numbers in the section listing and loading time. It's taken me days before finding a section.
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SinusoidalTendencies
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Re: Dieseling + backfiring + rough/searching idle

Post by SinusoidalTendencies » Mon Mar 25, 2019 3:34 pm

Found emissions testing. Though I already knew those where down in the em section.

Still looking for the rest of the component testing.

I know it probably seems silly. But every few pages I scroll through brings me to blank ones I have to wait for to load.

I can however see what page # I'm on when using the slider on the right (only quicker function available) but I still have to wait out loading times so page #'s is life right now.

Thanks
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Petros
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Re: Dieseling + backfiring + rough/searching idle

Post by Petros » Mon Mar 25, 2019 6:40 pm

you may have to go to the fuel system chapter.

much faster to scroll using a desk top with more memory, perhaps you can use one in your local library. just print out the pages you need for a few cents per page typically.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

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SinusoidalTendencies
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Re: Dieseling + backfiring + rough/searching idle

Post by SinusoidalTendencies » Mon Mar 25, 2019 11:58 pm

Perhaps by the time I'm done researching this I'll be able to post up a trouble shooting index guide for reference in the repair guide section
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SinusoidalTendencies
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Re: Dieseling + backfiring + rough/searching idle

Post by SinusoidalTendencies » Fri Mar 29, 2019 4:04 pm

Finally getting printing done at the Santa Cruz library. 15cents a page though. Luckily i found out you can do double sided to cut the cost in half since it's almost a good 100 pages. Hoping to post up a page # guide to go along with the trouble shooting pages for reference.

If this sounds good, where would you want it posted?
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SinusoidalTendencies
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Re: Dieseling + backfiring + rough/searching idle

Post by SinusoidalTendencies » Sat Mar 30, 2019 5:20 pm

The FSM does not state the specifications of ohms between the 2 carbon pins in the distributor cap.

Anyone know what it should be at?

The 44k ohms I measured seems really high compared to the 25k Max from the plug pins to the plug ends. Those where between 3 and 5k Ohm.

Picture of me pointing at them
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SinusoidalTendencies
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Re: Dieseling + backfiring + rough/searching idle

Post by SinusoidalTendencies » Sat Mar 30, 2019 5:27 pm

Also I found a little bit of oil at the bottom seam area. There obviously shouldn't be oil in the dizzy. Can it leak from the cam side as I suspect may be the case and possibly a good percentage of the issues I'm experiencing?
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Re: Dieseling + backfiring + rough/searching idle

Post by Petros » Sat Mar 30, 2019 9:33 pm

oil should not be getting into the distributor, usually the seal (an O-ring as I recall) lasts the life of the car unless the bearings get worn and sloppy (it wipes out the seals and allows oil leakage into the dizzy). check the side to side play in the distributor shaft, that will make it run crappy to too, it will cause irregular spark timing.

If there is an issue, the distributor can be rebuilt from off the shelf components. I highly advise against buying a rebuilt distributor assembly, most of them are crap right out of the box. Costly and a waste of money. You are better off getting a used factory distributor from a wrecking yard. of course if your coil and ignitor are good, no reason you could not put new bearings and a seal in it.

There is a thread in the repair guides section on rebuilding the distributor (it is also in the FSM).
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

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