Dieseling + backfiring + rough/searching idle

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SinusoidalTendencies
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My tercel:: 87 4wd wagon

Dieseling + backfiring + rough/searching idle

Post by SinusoidalTendencies » Mon Mar 18, 2019 4:24 am

History: purchased September 2018 . Still running
156k on odometer 3ac AT 4wd wagon 87(not sr5)
With Nevada classic vehicle plates
Main complaints where no power on inclines & sometimes hard to start.
Supposed carburetor rebuild (super dirty still, but was obviously messed with. Missing aap aluminum plunger spring so it didn't try to pop out when the top was cracked and the spring under the brass screw next to it was also missing). Needle was a springnless.
New belts (timing belt condition unknown..I guess I should check it)
New dizzy, plugs, wires

She has 159k on her today
I've rebuilt the carb(following the YouTube video and instruction sheet) but skipped a few things I didn't think needed attention at the time because they seemed to be working. Didn't touch/take apart any of the spindles (choke & flaps) or mechanisms on them, just cleaned with b12. Also didn't touch the mixture screw(even though the plug was already removed). Didn't touch sight glass(wasn't leaking so..)
Cleaned all holes with wire and b12. Replaced aap pump + it's diaphragm + needle. Cleaned the heck out of it, made sure everything moved (was dirtier on the outside). Made some makeshift springs from a lighter to fill in till I could find the right ones at a yard. Set the float and reassembled it. Cut off solenoids passed testing with solid clicks. Ran it, then cracked the top to make final float adjustments.

Still lacking power I investigated it's timing advance to discover the diaphragm was torn. Pulled a simpler 2 hole, 2 chamber diaphragm from an early 90s camery

It still lacked power... so I thought maybe it's old cat that never needed checking any more was clogged up when a friend said he didn't feel exhaust pressure out the back right away after start up....found out it wasn't the hard way, Dang it. Followed by finding out how much a crock of bull exhaust repair kits where.

In October I left Reno Nevada and limped my new wip to redding California where I found a Chevy Nova at pick n pull and acquired said missing springs. That shorter needle spring(grabbed the whole needle) and float since it was already set to the shorter spring. Grabbed the tvsv to while I was at it and it's different ebcv to try out.
Threw the new springs and needle + float in it just cracking the top, ran, then readjusted float accordingly.

Then off to Arcata, CA.
This is when some new things came to light.
Was able the finally weld up the exhaust. Discovered another severed(by rust) section by the hanger right before the rear axle and sloppily welded that together.
Then bought a timing light and multi-meter with a tach and a vacuum gauge and found I couldn't dial anything in very well. This started a cat and mouse game for a bit till I decided to check the mixture screw. In 6? Turns and back out 3.25 to spec (holy moly was it off)

And this is where the nightmare of trying to dial it in begins. I first try to follow the fsm procedure, only it still doesn't seem right after. So I start over and try a lean down method...but it's not working quite right either.
Various levels of dieseling and rough idle through this (didn't know what dieseling was then)
Not at all sure my harbor freight tach is working right at this point so I just do the thing by feel till it seems alright and isn't shutting off so rough.

- I forgot to mention I made a trip to Santa Cruz and back from redding before heading to Arcata.

So I start migrating south again to Santa Cruz and then onto San Luis Obispo where I picked up a friend to go to the Arizona gem fairs. It starts dieseling more noticeably while in Tuscon.
By the time we get back to San Luis Obispo (mid February) it's running on a good full rotation or 2 (I think)
I managed to make it back up to Santa Cruz where I'm familiar vending gems and jewelry on pacific ave to make some quick cash...

So here I've been messing around with it some more looking for where I can tighten her up. I found the last few manifold bolts loose and tightened them up. Those could of been slightly easier to get to. And found the carb studs where stripped. A good bike ride later I'm thinking I have my rough idle figured out with these new studs and nuts...nope

So I go to the beach and do some shwifty off roading for a nice parking spot...on an incline.
When I start her she won't hold an idle.
So I do some fancy footwork and get back to town.
Diesels hard
Turns out I forgot to get that hose under the egr actuator valve on the nipple to the egr...

I haven't cleaned the egr yet. And it doesn't look like anyone else has either.

Please tell me everything you know about causes for dieseling/engine run on and bad fluctuating idle. I really want to fix everything in this car but in order of importance as my budget comes and goes.

I'm learning and don't know a lot of terms so feel free to explain why.

I'm planing on looking at that egr and maybe rebuilding the carb again more thoroughly.

Bought a compression gauge so here's some #'s
They seem questionable from what I've been reading, but feel free to enlighten me
Dry/wet(oil)
1 : 150/180
2 : 155/183
3 : 145/165 (appears to have scorch marks outside plug hole)
4 : 140/173
Last edited by SinusoidalTendencies on Mon Mar 18, 2019 4:49 am, edited 1 time in total.
I don't always learn my lesson.
But when i do, it's the hard way.

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SinusoidalTendencies
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My tercel:: 87 4wd wagon

Re: Dieseling + backfiring + rough/searching idle

Post by SinusoidalTendencies » Mon Mar 18, 2019 4:31 am

Forgot that a new rust severing occurred about an inch after the last one I sloppily welded back together .. no welder so I sleeved it with some jb exhaust cement. That was before AZ. Seems the jb cement isn't holding as its leaking around the sleeve.
I don't always learn my lesson.
But when i do, it's the hard way.

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SinusoidalTendencies
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My tercel:: 87 4wd wagon

Re: Dieseling + backfiring + rough/searching idle

Post by SinusoidalTendencies » Mon Mar 18, 2019 9:30 pm

Sorry for making such a long post. Was just trying to include possibly pertinent information.

Took some videos of things.

Plug holes . Shows scorch marks on #3
https://youtu.be/TdKYKgdqsHE

Plugs condition
https://youtu.be/16vTrtToh8c

Warm up noises
https://youtu.be/4iIXiFLmL0w

Running temp noises
https://youtu.be/7RoH3tNujcU
I don't always learn my lesson.
But when i do, it's the hard way.

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SinusoidalTendencies
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Posts: 121
Joined: Thu Sep 06, 2018 12:06 pm
My tercel:: 87 4wd wagon

Re: Dieseling + backfiring + rough/searching idle

Post by SinusoidalTendencies » Mon Mar 18, 2019 9:37 pm

Also living out of the thing as I travel around, so my ability to garage her till its figured out is non existent.
I will be diving it daily while running around and pouring through posts like a chicken with its head cut off trying to figure this out with limited ability to find spots to park it long enough to do repairs.
I don't always learn my lesson.
But when i do, it's the hard way.

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NWMO
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Re: Dieseling + backfiring + rough/searching idle

Post by NWMO » Mon Mar 18, 2019 10:04 pm

ST,

Have you confirmed engine timing? Most like to run around 10 deg BTDC and that is with the vac line off the distributor advance and plugged. Sounds decent just idling.

Check for vacuum leaks on the myriad of vac lines?

Chris
Psalm 37:4 "Delight yourself in the Lord and he will give you the desires of your heart"

In remembrance of my friend ARCHINSTL:

T4WD augury?
"Oh, do not ask, 'What is it?' Let us go and make our visit."
T.S. Eliot - "The Love Song of J. Alfred Prufrock"

"Now and then we had a hope that, if we lived and were good, God would permit us to be pirates."
Mark Twain

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SinusoidalTendencies
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Posts: 121
Joined: Thu Sep 06, 2018 12:06 pm
My tercel:: 87 4wd wagon

Re: Dieseling + backfiring + rough/searching idle

Post by SinusoidalTendencies » Mon Mar 18, 2019 10:28 pm

Yes & yes. Forgot to include that I'd set it to 10°btdc without advance. 18 with advance. Replaced all vac lines with the smaller of the 2 available sizes that aren't exactly an 8th of an inch id and the ebcv lines with fuel line that was an 8th id.

Since the dieseling has been getting worse I retarded the timing a few degrees and am using premium gas
I don't always learn my lesson.
But when i do, it's the hard way.

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Petros
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Re: Dieseling + backfiring + rough/searching idle

Post by Petros » Tue Mar 19, 2019 12:47 am

sure sounds like there is a vac leak there somewhere. check all gaskets, hoses, and the vac operated components (including the power brake booster). occasionally the intake manifold has a crack that is hard to see that will also created a vac leak.

also, using your timing light, makes sure your centrifugal advance is working. the vac advance will not affect power output, but the mechanical (centrifugal) advance will. if it does not advance with RPM, usually you can lubricate it and work it free after you remove the distributor cap with penetrating oil. if that does not work you have to disassemble the distributor and clean up the mechanical advance mechanism to make sure it works properly, if not replace parts if necessary.

BTW, a bad vac advance can act like a vac leak. if it is bad, you can cap off both ends of the vac lines, and it will run fine. the vac advance is only there to improve part throttle efficiency (fuel economy) by advancing the spark on the leaner fuel air mixture (which burns slower). it does not affect max power output nor acceleration. And does not have a very big effect on fuel economy either.

The compression looks good btw, not bad for that many miles on the engine.

Sound like you are getting a lot of miles on it, despite these annoying problems.

Good luck.
'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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My tercel:: 87 4wd wagon

Re: Dieseling + backfiring + rough/searching idle

Post by SinusoidalTendencies » Tue Mar 19, 2019 2:55 am

I know you've all written these answers countless times, so I appreciate the patience here.

Dizzy is the newest thing in the car aside from the spark plugs. I've inspected it thoroughly out of the car. Painstakingly aligned it's #1 to tdc with room on the advance side to get just a little above 10 deg.(took a couple tries) was the only spot where you got an appropriate range from 0-10

The vacuum advance diaphragm is from a camery. Pulled and tested it. 2 port & chamber, just no second hac port on the lower chamber. Advance curve inspected visually with timing light.

I've replaced almost every vac line I believe. And will continue to double check them religiously as I have been.

I feel that it is progressing in severity. Both the searching and dieseling. Some how feel that this would narrow it down to things able to get progressively worse without being able to spot visually, like carbon build up. Though it's low miles has me thinking of other potentialities

Basically I've already been searching all of this in the forums for months. Doing my best to really learn why things work the way they do. Handle all the basic first likely suspects..(advance, vacuum leaks, dizzy advance mechanism, timing, carb rebuild & cleaning, pcv valve is new with grommet)..

Curious about the egr & actuator. I tested them per the fsm method and if I remember correctly they failed halfway into it. But I moved on as I had no idea what to do about it.
I don't always learn my lesson.
But when i do, it's the hard way.

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NWMO
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Re: Dieseling + backfiring + rough/searching idle

Post by NWMO » Tue Mar 19, 2019 9:06 am

ST,

I haven't read that it is a problem with these cars, but your description reminds me of an experience after rebuilding a 300 CI inline six Ford engine. I was still learning, but had the basics down and experienced similar challenges to what you are describing after getting it back together. I finally figured out the two part harmonic balancer was allowing the outside portion (with the timing marks) to rotate around the inner portion of the balancer, so timing with a light, etc. was a waste of time. You might set No. 1 TDC and confirm your timing mark.

Chris
Psalm 37:4 "Delight yourself in the Lord and he will give you the desires of your heart"

In remembrance of my friend ARCHINSTL:

T4WD augury?
"Oh, do not ask, 'What is it?' Let us go and make our visit."
T.S. Eliot - "The Love Song of J. Alfred Prufrock"

"Now and then we had a hope that, if we lived and were good, God would permit us to be pirates."
Mark Twain

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irowiki
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Re: Dieseling + backfiring + rough/searching idle

Post by irowiki » Tue Mar 19, 2019 1:02 pm

I would swap to a known good carb if you haven't already. I had a tercel that would run like crap, diesel, not idle, backfire, etc, and a "new" carb fixed her right up!

Also could try bypassing the EGR by disconnecting the vacuum line and capping it.

Could also bypass the AAP I never had that work right in any Tercel even after replacing the diaphragm!
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SinusoidalTendencies
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Re: Dieseling + backfiring + rough/searching idle

Post by SinusoidalTendencies » Tue Mar 19, 2019 1:21 pm

Wish I had the money for a new carb. Thing seems to be in pretty good condition though. Aap works, just a dab a oil (think it was a thinner oil).

Anyone near Santa Cruz with One I could try?

If I drive it very far at this point it diesels hard.. thought I threw a rod first time it did it. Was only driving about 3 miles in heavy traffic
I don't always learn my lesson.
But when i do, it's the hard way.

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NWMO
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Re: Dieseling + backfiring + rough/searching idle

Post by NWMO » Tue Mar 19, 2019 1:36 pm

ST,

I assume you have seen this already, but thought I would share for future folks that search this problem:

From Wiki-
Potential causes
Dieseling can occur for several reasons:

Built-up carbon in the ignition chamber can glow red after the engine is off, providing a mechanism for igniting unburnt fuel. Such a thing can happen when the engine runs very rich, depositing unspent fuel and particles on the pistons and valves. Similarly, rough metal regions within the piston chamber can cause this same problem, since they can glow red. It has also been suggested that an improperly rated spark plug can retain heat and cause the same problem.
A carburetor that does not completely close can contribute to running once the engine is off, since the extra fuel and oxygen mixture can combust easily in the warm piston chamber. Similarly, hot vaporized oil gases from the engine crankcase can provide ample fuel for dieseling.
Incorrect timing.
An engine that runs too hot or too lean may produce an environment conducive to allowing unspent fuel to burn.
An idle speed that is too fast can leave the engine with too much angular momentum upon shutdown, raising the chances that the engine can turn over and burn more fuel and lock itself into a cycle of continuous running.
Another potential "run on" problem after an ignition has been turned off can be attributed to an inlet valve(s) that are not sealing fully allowing the piston motion to pull a fuel mixture in when technically the valve is shut.

Chris
Psalm 37:4 "Delight yourself in the Lord and he will give you the desires of your heart"

In remembrance of my friend ARCHINSTL:

T4WD augury?
"Oh, do not ask, 'What is it?' Let us go and make our visit."
T.S. Eliot - "The Love Song of J. Alfred Prufrock"

"Now and then we had a hope that, if we lived and were good, God would permit us to be pirates."
Mark Twain

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irowiki
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Re: Dieseling + backfiring + rough/searching idle

Post by irowiki » Tue Mar 19, 2019 2:21 pm

SinusoidalTendencies wrote:
Tue Mar 19, 2019 1:21 pm
Wish I had the money for a new carb.

By "new" I mean "junkyard used" as there are no more new ones!

http://www.car-part.com/cgi-bin/search. ... ge=1&iKey=
Former Tercel Enthusiast (not a practical family car anymore but they still have a place in my heart)

Site administrator, if something is broken, PM me!

81 Coachmen RV, 70k miles
95 Camry Wagon, 153k miles
04 Camry Sedan, 250k miles

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SinusoidalTendencies
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Re: Dieseling + backfiring + rough/searching idle

Post by SinusoidalTendencies » Tue Mar 19, 2019 3:58 pm

Still looking to hear some stuff about the egr & it's actuator valve. As well as what that brake booster valve is and where.

About to go over the carb with a fine tooth comb and a rebuild kit on hand. Hoping I don't need the kit since I've already rebuilt it and still have all the extras from the last one.

Hopefully the pipe nut to the egr isn't a pita as I want to try cleaning it. Was the actuator that failed testing though.
I don't always learn my lesson.
But when i do, it's the hard way.

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irowiki
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Re: Dieseling + backfiring + rough/searching idle

Post by irowiki » Tue Mar 19, 2019 4:58 pm

Yeah but the carb would just be worn out. They are very complicated devices!
Former Tercel Enthusiast (not a practical family car anymore but they still have a place in my heart)

Site administrator, if something is broken, PM me!

81 Coachmen RV, 70k miles
95 Camry Wagon, 153k miles
04 Camry Sedan, 250k miles

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