Frustrated with poor running Tercel today

[xirdneh]

An old fellow (80 or so) asked me to help get his Tercel running better (it was poor) and I said I'd give it a try.
On the test drive it was idling rough and surging at slower speeds. When I stepped on the gas it tried to rev up a little but quickly switched to a reverse rev (felt like timing was retarded). Feathering the gas allowed it to increase rpms. Once the rpms increased the carb's secondary kicked in and it revved right up. The engine sounded good at the high rpms.
Back at the lower speeds it ran very poorly.
I brought the #1 piston to the top of its stroke and saw that the timing mark lined up at zero on the pully. I pulled the dist cap and the rotor was pointing in the right direction. The distributor cap and rotor, plugs and plug wires were new. Compression was 160-170 average. The ends of the plugs looked nice (tan).
I replaced the carb with one that worked well in my car. Same problems no change, so just to be sure I tried a re-built carb with no luck either.
I switched the distributor with a spare I had lying around. Still no change.
I replaced the plugs. Still no change.
I noticed he had installed a new fuel filter and added another fuel filter near the fuel pump.
With engine running I put some propane to the vac hoses and all around carb and manifolds (no change in rpm)
I double checked the routing of the vac lines (they were fine)
Checked timing with light (that was Ok too)
The only thing i did not check was the cam to pulley timing mark align but the old fellow had everything else hooked up right so I assume he installed the new timing belt correctly.(he assured me that he had)
I finally gave up. It's drivable in the state it's in but thats typical for these cars. They get you there no matter how crappy they run.
I'm frustrated mosly because nothing I tried made one damn bit of difference.

[blade]

maby it just has bad gass in it.

[takza]

Could be the dist is off a tooth...if all else fails move it around some? Big vac leak?

[Petros]

That acts like a vacuum leak. IT is not in the carb or lines, so it could be one of the components that are vac run, or off the vac system. I would check all of those systems, including the power brake booster.

My other thought it was fuel starvation at low speed, but unless the fuel pump/filter combo is causing that, it seems unlikely since you already swapped out the carb.

Good luck

[xirdneh]

That acts like a vacuum leak. I would check all of those systems, including the power brake booster.

the brakes were acting kind of odd
I will have to check the booster

[Petros]

I bought a Tecel4wd last summer cheap, it ran like crap. I found nine vac leaks, but still ran underpowered. I swapped the carb, which helped but was underpowered still. I found the brake booster was a massive vac leak. fixed the issue.

[takza]

That acts like a vacuum leak. I would check all of those systems, including the power brake booster.

the brakes were acting kind of odd
I will have to check the booster

Those vac boosters have a valve in them that can sometimes be freed up by spraying some WD40 into the vac opening of the booster...worked on my truck where it was pulling too much vac at one time...espec starting up cold and at idle...has been OK since.

[xirdneh]

Blocked brake booster vac line and blocked EGR hole on intake manifold.
still no change
wondering abt fuel pump and clogged CAT now

[4wdchico]

Blocked brake booster vac line and blocked EGR hole on intake manifold.
still no change
wondering abt fuel pump and clogged CAT now

If you can lay your hands on vac/fuel pump tester you can diagnose both issues you suspect quite handily.

Diagnosis using vac guage: http://www.secondchancegarage.com/public/186.cfm

[sdoan]

My first thought was bad accelerator pump but swapping carbs would probably take care of the that.

But you might check this - if the connections to the carb fuel cut solenoids are switched it will create a vacuum leak at idle and low rpm.

And I had nearly identical symptoms when I failed to reconnect the vacuum hose from the base of the car to the white valve under the air clearer OR the hose from the base of the carb to the valve cover aft of the PSV valve. Broken hose or stuck valve?

Other thoughts - stuck PCV valve, air leak from the charcoal canister (the soft large diameter hose sometimes melts through), reversed vacuum adv lines.

Did the poor running start when the old guy replaced the timing belt?

Good luck - Let us know what you find.

[xirdneh]

he had removed the charcoal cannister and plugged the port at carb

the fuel cut solenoids when not working have only affected idle (in my experiences)
they did not cause that "falling flat its face" during acceleration thing

that white valve under the air cleaner housing
that has fallen off on several cars
i know that one well

i will have him check the PVC valve

i will have to ask him when the problem started
i think he said the engine has been the way it is since installing it and did the timing belt after that
but will have to ask him to be sure