Engine problem

[Daddou]

Hello,

I have a toyota tercel, year 86, motor type 3A, this car made 230 miles kilometers. I did a complete revision of the motor since he/it lost the power. The problem now it is that after 500 kilometers the motor lost the power again, the mechanic while examining the Spark plugs
it notices that two of them are plugged by a deposit crotchet of carbon, the two others function normally. If someone, can help me to find the problem.

[otter63]

Can you post photos of the spark plugs?

Also, the results of dry and wet compression tests would be good to know.

[Daddou]

Thank you, So I will post the photo of sprak plug later to give you mor idea about the problem, but I think it is a problem related to the vacuum hose and and adjustment of carburetor. To put evry vacuum hose in his place I need the diagram that gives me an idea how to do this, this diagram is under the hood but it is not clear seen the age of the car, diagram isn't clear is erased, where I can found this for my model,My model is a canadian model with 3A engine type.

[ARCHINSTL]

Daddou -
Check out this Autozone site:
http://www.autozone.com/servlet/UiBroke ... epairGuide
It has a lot of information (sometimes better than the FSM), including the vacuum diagrams you need for the Canadian version.
I would also suggest a Search of this board; there were just recently posts with pix of spark plugs.
Tom M.

[Petros]

i do not think improper routing of the vacume lines would cause two spark plugs to fowl, nor would it cause it to run good for 500 kilometer, and then suddendly fail.

I had to take my engine appart 4 times after a rebuild because I kept burning exhaust valves and fouling plugs. It would run good for a few weeks or months, and then lose power. Compression test of engine showed leaking valves, plus (unrelated) I had high oil consumption.

After last exhaust valve replacemtn I advanced the spark timing to 10-12 deg BTDC (vs. factory 5 BTDC) and so far have not had the problem (yet). The advanced timing improves performance because more of the air/fuel mixture is burned during the power stroke, and less burning fuel goes out during the exhaust stoke. When some of the fuel is still burning when the exhaust valve opens, it makes the exhaust valve hotter casing valve damage. Advancing the spark lowers exhaust gas temp since more is burned during the power stroke, giving better performance.

I also had trouble getting the piston rings to seat properly, using permium or chromed rings, which resulted in high oil consumption and fouled plugs. Finally on 4th rebuild did new hone with heated block (less distortion in the bore when the block is heated) and put in quality plain iron rings. Now no oil consumption, no plug fouling.

Peter

[Typrus]

I've read a few "interesting" ring seating procedures recently. Several involve high-grit abrasives and 3-in-one oil applied to the cylinder walls followed by starter cranking for several revs then cleaning it up. Breaks down the glazing on the walls and gives the rings more of a catch apparently. Scares the crap out of me, but apparently diesel people have been doing it for a long time. No, we're not talking running sand down the intake, rather doing it with the head off and no power through the engine other than starter rotation.

Why the heck would your valves burn? Sure you're not running too lean or too small a valve lash? Factory is 8 and 12... Wouldn't do much smaller than .0075 and .0115 personally.... Intake and Exhaust respectively by the way.

You sure you torqued the head correctly? Its possible that improper torque could have blow the head gasket between 2 neighboring cylinders.

[keith]

The best way I've found to quickly break in an engine is ten 30-50 full throttle runs in high gear. It seats the rings and bearings fast. As for exhaust valves, if you grind them, they burn. I always replace them, they're cheap enough. Intakes are ok to grind.

[Typrus]

Hey keith.. Is there any way you'd recommend to get better flow past the exh. valve? I don't really want to be pulling the head every few thousand miles if thats the fate of a 3-angle'd exhaust valve.

You really have to pay attention to torque's, specs for gaps, order of assembly... The FSM IS available for DL you know.

[keith]

I might have been a little out of date with that statement. When I was your age, a three angle valve job was good for 30k if you were lucky, but then a regular valve job was only good for 60-100k, if you were lucky. Few engines went over 100k miles and an overhaul only added 20-30k more. Todays engines last so much longer. A triple angle valve job won't last as long as a double angle, but today, that is still a long time. Do start with new exhaust valves though and just do the inner and outer most angles only.

[Typrus]

Oh, I'm going all-new valving.
I wouldn't even try to grind valves myself. I'll have the pros do it.

[Petros]

Typrus,

I have also heard of people using the cleanser "bon Ami" down the intake to seat rings. Plain rings and proper finish honing seems to work fine (I will not trust a machine shop to do this again either). Putting abrasives in the engine is too scary for me too. Pulling these engines appart to get to the rings is pretty easy, all i need is a new head and pan gasket, I know that will work and not damage anything of the new parts.

I have never had problems with valves before, espl. since the Japanise usually use pretty good material on them (unlike the US makers). I checked and double checked the valve lash, at build-up, at the head re-torque, both hot and cold. I doubt it is too lean since I did not alter the carb at all, ran the same carb before overhaul just fine for 180k miles. Though I have seen totally stock 3a engines that dropped a value head (and promply trashed the engine). Perhaps it is a function of the emission controls, running lean is some conditions, and the 5 deg BTDC retarded timing condition. New valves are not too costly, if I knew it would be such a problem (and that new exh. valves would solve it) I would have just bought four new ones. But then I might then have just burned the new valves too.

And yes I did torque the head correctly (also lessons hard learned when I was much younger), I have a very precise procedure I learned working for a fully sponsored factory racing team. Aluminum heads are sensitive to proper torquing. Though a failed head gasket would not damage the valves, you can not reach the high combustion temps that would causes it.

It is likely a combination of the new higher compresion ratio, the performance cam shaft, the better breathing from the improve porting, and the timing and factory carb. It appears the advanced timing solved it, so far. I also just got 32 mpg on a trip up to the mountains to go skiing It has never ran so good!

Peter

[Daddou]

Hello,

First of all since it is the first time that I use this forum I don't manage to put the photos of spark plug on the website. Thank you for the different answers, but I don't manage to get a clear idea to act and solve the problem. Some of you said it is problem spark timing and exhaust valves. However if its true why that, affect two speak plug only, and not all of them. Before making another engine rebuilt and replacing the exhaust valves, we must eliminate other causes. Way is not a problem of carburetor that gives a bad mixture of air and fuel in the two first cylinders and what’s the problem to make carburettor give a bad mixture in the two cylinders only. I add a new element to you, I feel HC odors in exhaust gases.