Running VERY Rough After Head Gasket Job

[vcp]

UPDATE
Well it's running better after my mechanic spent some more time with it, but still not right at anything above 60 km/h - it bucks, low power especially uphill, I seem to have to shift earlier to prevent high rpms, etc.

I checked the vacuum hoses yesterday. Not sure I did a very good job but couldn't find anything obvious.

Also tried reattaching the vacuum hose he sealed off to the distributor (as well as the hose that takes heat from the exhaust manifold to the air cleaner) and drove it with them attached and unattached a few times. Seems to run smoother uphill (less bucking) with them both reattached. I know, doesn't really make sense, but ...

Haven't gone into the distributor yet as I'm afraid of doing something that would just complicate finding the solution. And just checked and looks like I still have oil leaks, maybe from the front of the head gasket (that we replaced!) or the seal around the timing belt cover.

Was running so sweet on the highway before this job. Kinda bummed out. But not giving up!

[dlb]

checking the mechanical advance on the distributor is very easy, only requires removing 3 screws to get the distributor cap off. then you can see the rotor so give it a counter clockwise twist and see what it does.

[vcp]

Thanks! Will have a go. (Important to unhook the battery first?)

[dlb]

nope, no need to disconnect the battery.

[Petros]

you do not have to unhook the battery, just make sure the ignition is off and not in the run position.

head gasket is not likely leaking oil, that would be the valve cover gasket (easy fix) or perhaps the front front seal; both cam (likely replaced with the head gasket job) or from main crank seal. Upper cam seal is easy to reach and replace, the lower one is a lot more effort, but easier than a head gasket job. the lower front seal is also more common to leak. It could also be leaking from the oil pressure sender behind the alternator on the side of the block.

finding a vacuum leak is easy, use Gumout brand of carb cleaner and with the engine running, squirt short burst of it at various places around the intake system and all the vac lines. When it hits the leak it will suck it in and cause the engine to speed up a bit, than slow down. Other brands will slow the engine down. You can test it by spraying a bit down the carb to see how the engine responds, if it speeds up than you look for a place where the engine speeds up when you spray it at one spot. If it slows down when you squirt a puff down the carb, than you look for a place that slows the engine down when you spurt it at one place.

If you can find no vac leak it likely is spark timing related, so check that spark advance. BTW, it is not unusual to damage the TVSV valve when removing the head. It will form a vac leak it the housing is cracked or damaged. This is the valve on the coolant outlet on the front of the head with all the vac lines going to it (usually it is black). so check that for vac leaks as well.

[vcp]

Thanks!

Another thought I just has about the other problem- we replaced the fuel tank last fall and twice since then I've had gas coming back out of the filler tube on a hot day. It is also much harder to fill the tank because the pump often shuts off even after a few seconds, and when I take the filler cap off it often makes a vacuum 'pop'.

I'm sure I'm light years off, but is it possible I have a vacuum problem going back all the way to the tank / vent hose / charcoal canister??

[dlb]

your problem with the gas tank sounds like a plugged charcoal canister, or even the vent line to it. that should be fixed at some point but it's probably not related to your rough running issue.

[vcp]

Yeah, I figured. Wishful thinking

[Petros]

that kind of thing happens if the lines to the vac canister are mixed around. in the service manual it shows the proper routing of each of the lines. Might be worth a check.

If they were that way before the head gasket and you had no trouble, I doubt that would cause it.

I have replaced lots and lots of Tercel head gaskets, and never had this kind of problem after doing it. something got mixed around or messed up during the head gasket changed most likely. It is possible, but unlikely, that something failed or gave way right at the same time as the head gasket job. These kind of things happen very rarely but when they do they are very frustrating to find and fix. I would keep checking over everything that might get disturbed with the head gasket change. When all else fails, than consider the less likely causes.

[vcp]

Thanks, Petros. I really appreciate your input and experience. And for what it's worth, I feel the exact same way - almost certainly something that got mixed up during the head gasket job.

[vcp]

Thanks again P, dbl and all for your insights! I took off the Dis cap and tried to turn the rotor counter-clockwise (at least I think it's the rotor! Black wedge in the pics below, yes?) and it doesn't turn more than maybe an 1/8 of an inch. Didn't want to turn it too hard in case that's not the thing to do. Doesn't really turn clockwise either.

Distributor 1.jpg

Distributor 2.jpg

[dlb]

yes, that's the rotor. you should be able to turn it about 1/4" or so at the tip, and then it should snap back when you let it go. does it do that?

[vcp]

Will have to check again (back together now so I can drive it) but not sure it moves that far. Seemed like it hardly moved at all.

[Petros]

it should move about 10 to 12 degrees, which is about 3/8" I would guess at the tip of the rotor. It should not be hard to move, but it is spring loaded so you will be pushing against the spring. And it should come back when you release it.

It will not harm a think to spray light lubricant under the plate, and to pull the rotor off and soak the felt under the rotor cap (at least I think there is a felt oil reservoir there, most cars used to have them and I thought I remember seeing one on the Tercel too).

You will not harm anything by pushing hard on it, at worst you might break off the plastic rotor and those are easy to replace. Usually if they are rusty or gummed up you will be able to force it to move through its travel but it will not return; force to the end of its movement and release it. Push it lightly back to see if returned all the way or not. spary the light lubricating oil on the mechanism (under the plate that holds the pick-up), and down inside the shaft, and force it back and forth until it moves freely.

This is usually all that needs to be done to free it up. No need to take it apart past removing the cap and rotor.

[vcp]

Figured it would be easier to show you how the rotor's moving Video here: http://youtu.be/3DvWAjW-kak. It does move, but there is no spring-back action at all.

And if you're interested, you can listen to a short audio recording of the motor at idle here: https://youtu.be/Drg6S-jbPaw
Pretty rough, huh? (The intermittent rattling is a loose catalytic converter.)