car bucking at 2Krpm. Distributor cutting out?

[trailerparkzero]

Howdy y'all
I got the car all up and running again. I like to thank the forum and its gifted members for that. I bought a new carb and was having vac issues after I installed it and when I went to check the bolts that secure the intake to the exhaust manifold I snapped one off. After removing both exhaust manifolds I found that it was leaking on the underside of the manifolds. (1st thing a member told me to check ) I'm thinking both intake and exhaust was leaking as I could see carbon residues. Its weird becuse none of the bolts were loose. They all were so frozen even with lots of penetrating oil they all seamed like they were going to snap on the way out. I got it all back together and after getting all the vac lines routed correctly and disabling the AC kick up switch and removing it from tvac system it's running great.
In the past two days it will missfire at 2K rpms but it's intermittent. It's hardly noticeable if your accelerating quickly but it your going slow the car will buck like the engine just stopped working. It's fine before and past 2k but for some reason that seems to be the UN-sweet spot.
I was thinking it has to be the dizzy. I cant think of what else would cause it to only happen at 2K. I just went to the pick a part today that had a 50% off sale and picked up a spare dizzy and alternator for under $40. I going to swap it as a fist shot but I searched the forum and didn't see anything like this so I'd figure I'd ask around.

[TURTCEL]

Check your switch A on the passenger side fender well (black plug)...next to switch B (green plug). My car did the same thing. I had to plug my vacuum line off going to switch A (fuel cut solenoid) which activates between 1800 and 2300 RPMs. Give it a shot for diagnosis sake.

Peace

[dlb]

does it happen when the engine is cold, warming, and warmed up, or just one or two of those? does it happen in all gears? if you got a new used dizzy for such a good price, you could definitely throw that in to try it. while you're at it, you should replace the o-ring on the dizzy. they get old and brittle and are one of the common sources of oil leaks.

i would also check the carb float level, and all the vacuum diaphragms. there is the choke opener, choke breaker, throttle positioner, vacuum advance, that's all i can think of but i might be missing one or two. put a clean hose on each one and suck. you should not be able to suck air through. if you can, the diaphragm is ruptured and the source of a vac leak.

[4wdchico]

does it happen when the engine is cold, warming, and warmed up, or just one or two of those?

Dang, DLB, you have come a long ways! The above is a very important question.

To the OP: disconnect the vac line from the EVAP purge solenoid and plug it. Sometimes this can totally cure the issue that you are describing.

[trailerparkzero]

Oh look a new post before i finshed typing! EVAP purge solenoid? never heard of it, is that the VSV or the outer vent control valve.

I tested the vac switches after I got home from work. Switch A was open when when the engine was off and B was closed. When it was warm and running A was closed and B was open.
I decided to plug the vac line to SW A and try to get it to miss and I couldn't. I will drive it it to work tomorrow and see if i can get it to act up if not I will plug it back in and see what happens.


dIb, I don't ever recall having it happen when it was cold. Only warming and warmed. it has been most noticeable in 2nd gear. My carb is new so I hope all the diaphragms on it are fine. I will double check my EGR, EGR modifier and the vac advance diaphragms tomorrow.
I really want to try and figure this out before Friday as my sister just moved to San louis Obispo from the eastcoast and I what to check it out . its a 5 hour drive so I don't really wnat to drive my car with any issues.

As a side note and I don't think it has anything to do with this but does anybody know what the jet is for between the choke breaker and the carb? its the light blue line shown here: http://www.tercel4wd.com/download/file. ... &mode=view I removed this when I swapped to a different base for that did not have the hook up and lost it. Also I would love it if somebody could take a picture of the drivers side of the carb that shows correct routing. That section of vac diagram is confusing.

Thanks guys, I will not give up on this car!

[dlb]

Dang, DLB, you have come a long ways!

thanks marshall! that actually means a lot to me.

incidentally, i've been helping a forum member set up the stock tercel EGR with a weber carb to try to pass emissions with it. i think it's a great idea, and figured you'd be interested in it as well with your emissions training. here's the latest on it, trying to stop the EGR from opening on idle.

https://tercel4wd.com/forums/viewtopic.php?f=4&t=9409

Oh look a new post before i finshed typing! EVAP purge solenoid? never heard of it, is that the VSV or the outer vent control valve.

it will be the hose that has 'purge' in raised letters at its base on the charcoal can. i believe it's the one that goes to the VSV but am not positive.

As a side note and I don't think it has anything to do with this but does anybody know what the jet is for between the choke breaker and the carb?

the jet simply slows the vacuum applied to the choke breaker so that its action is slightly delayed. i'm not sure but i don't imagine it's crucial. i would just grab one from a junkyard the next time you see one.

Also I would love it if somebody could take a picture of the drivers side of the carb that shows correct routing. That section of vac diagram is confusing.

i find pics to be confusing because it's impossible to trace the vac lines through them. i have found this colour-coded vac diagram to be pretty easy to follow, although the sticker on the underside of the hood is usually the best bet.

http://tercel4wd.com/download/file.php? ... &mode=view

[4wdchico]

The hose that I am talking about runs from the EVAP purge solenoid on top of the EVAP carbon canister to the passenger rear corner of the carb. The EVAP purge solenoid is easy to recognize as it is the only thing on top of the EVAP carbon canister that has electrical control wires going to it.

[trailerparkzero]

Its still cutting out with vac SW A removed. I plugged it back in andplugged the canister purge line from the cab and the solenoid and it did not change anything. I checked most diaphragms and everything is good. I will swap the dizzy tonight but I have bigger issues now. see below.

I got really discouraged with the car today and I will have to cancel my trip. My rear passenger side brake was dragging when I bought the car. I switched shoes and the wheel cylinder and it didn't fix the issue. I redid it with new shoes since I cooked the first, then I sanded the back plate nearly smooth as there was pitting from when the car sat along time and put a new drum. I drove it a couple times after the fix and felt that the drum was cold but After I drove the car today I checked it just for the sake of it and it was hot and the other side was cold WTF! what else could it be? I hate doing things twice, thrice is even worse! I developed tendonitis from biking to work, work and working and this car. I'm not suppose to strain my arm for the next two weeks so I really shouldn't work on my car.

[rer233]

Did you check to see if the parking brake cable is hanging up?

[dlb]

don't get discouraged about the dragging brake. it's a simple system with few components so it's pretty easy to rule stuff out. my first guess for dragging brakes is a frozen park brake cable. they're about $30 new. easiest way to test that is to block the wheel on the ok side, jack up the offending corner,and pull the wheel and drum off. now look at the arm the park brake cable attaches to and take note of it's precise position, even mark backing plate behind it if you need to. then release the park brake and see if the arm and park brake cable have moved. if they haven't, that's your problem.

for replacing said cables, i have a few tips. first, use a wire brush to clean dirt off of the holders that fasten the cable to the body of the car and then spray penetrant on the tiny bolts and let them sit for a while before attempting to undo them. they're just little 10 mm bolts and are exposed to lots of water, salt, etc, so they are always badly rusted. next, when you put a wrench or ratchet on those little bolts, bounce the tool with mild to moderate force rather than putting a ton of weight on it right away. being so small and rusted, they shear off easily. if that happens, you can always drill the old bolt out and tap new threads in but it's easiest to just get them out in one piece in the first place.

for removing and installing the front end of the brake cable, i have found it easiest to undo the nuts from the park brake inside the car and pull the front portion down underneath the car. it's easier to work on it that way. otherwise you're fighting rusty, dirty parts right above your face, getting it in your eyes, and trying to work around the rear driveshaft. once it's on the ground you can easily tap the rusted stuff apart.

once you get the brakes sorted and you're back on to the bucking, i would also check the o2 sensor. there is a test for it in the FSM as well. i am confident that the problem is in the carb or the emissions system so it's just a matter of working through each component, carefully and systematically.

have you checked the AAP? i know you said your carb is new but stranger things have happened. the AAP enriches the fuel mixture when cold but it's supposed to stop doing so once warmed up. if it's broken, it leaks fuel all the time and often causes poor running when warm. it's just another part of the carb/emission system so like i said, just work through each system using the tests in the FSM and you'll find it.

good luck, keep us posted.

[Petros]

make sure the shoes return back to their retracted position, several things can cause this, likely is a rusty parking brake cable (a quick fix is to spray penetrating oil down the parking brake cable sleeve). the other is a hanging up wheel cylinder, a hanging up adjuster, or a bad flex hose. when the hose breaks down internally it can act like a one way valve, allows the brake to work, but they stay "on", not allow the pressuer to be released. I would suspect if this happens in the rear however, it would affect both rear brakes.

The cutting out could also be the EVBT (? not sure of acronym). There are two vac lines that go to the base of the carb from the passenger side fender, next to the emission control device. they control the mixture by bleeding air into the carb at various driving conditions, if it malfunctions it will act like a vac leak that only occurs at about 2000 rpm. the easy test (and fix) is to pull the vac line from the rear servo and cap it. There are two electrically controlled servos that allow the mixture to be control with the vac lines. there was a recent thread on this topic started by Tercle.

[dlb]

The cutting out could also be the EVBT (? not sure of acronym). There are two vac lines that go to the base of the carb from the passenger side fender, next to the emission control device. they control the mixture by bleeding air into the carb at various driving conditions, if it malfunctions it will act like a vac leak that only occurs at about 2000 rpm. the easy test (and fix) is to pull the vac line from the rear servo and cap it. There are two electrically controlled servos that allow the mixture to be control with the vac lines. there was a recent thread on this topic started by Tercle.

EBCV - carb feedback system

[trailerparkzero]

My EBCV measures 14ohms which is 1 ohm too high. I guess uts really close. Can a defective EBCV cause problems at idle too. Sometimes the ilde is right on then sometimes the car is about to die.

I took a look at the brakes. I' should of mentioned that I replaced the cable on the sticky side already. Everything looked good and I took both drums off today and they expand and retract the same. The flex hoses don't look so bad but who knows what they look like inside. At 8 bucks a peice from the zone I think its worth a shot. Unless a bent axle could be causing this. When I had both wheels off the ground and spun the tire I could here a little contact happing once every revolution. I drove around after inspecting everything and the drums were evenly cool like they should be.
again,thanks for the help I just might make it up to SLO this weekend!

[dlb]

that's really odd about the sticking brake. a delaminating flex hose is a possibility. to test that, jack up the rear end and make sure both wheels spin freely. then get in the car and pump the brakes hard 4 or 5 times. go back and see if the wheels still spin freely. if one side doesn't, it's likely the flex hose.

don't forget to test all the different things everyone has suggested here so far, like petros suggestion of disabling the EBCV to see if bucking goes away, plus all the emission tests i mentioned that are in the FSM. be methodical and thorough and you will find the source of the problem.

[trailerparkzero]

The brakes didn't drag at all on the way to work today. I wonder if the star adjustment wheel is causing this. Maybe anti-seize is not good enough for lube. I pumped the brakes when I had it up last night and they were fine afterward but I did not pump them that hard. I will try that when I get home from work.

I made some progress on the vac leak. I drove to work with the EBCV disabled and it still was cutting out. I found well trouble shooting on my lunch break if you hold the throttle at 2K the engine will surge from 1600 to 2200 rpm at about 20 to 30 revs per min. No matter what I unplugged this was happening. vac switches, ebcv pluged off/ unplugged, charcoal canister blocked off unplugged, o2 sensor. I unplugged the green connector to the carb and the problem went away. Now i'm thinking I have something miswired or my ECU "computer" is toast.

Another thing, I guess I really have a 84 not an 85. My title says 85 but the stamp inside the door says 84. I guessing because the car was made in 84 but not sold till 85. When I ordered my carb I told them it was for an 85 and since my colors don't match up to the FSM I think my problem is in the wiring somewhere. I remember reading something about this on the forum once, I will try and find it.