Toyota Corona 1.8L Liftback

RONALD MICHAEL CARSON

MEMBER
TOYOTA

I am maintaining my aunt's Toyota Corona 1.8L liftback (3T engine). The year of manufacture for the car is 1981. The mileage of the car is approximately 147,000 miles.
Recently, three of the four cylinders are firing correctly, cylinder no. 4 is firing very weakly. When I pull out the spark plug cable from the no. 4 cylinder, there is very little change in the engine idling speed. However, if any other spark plug cable is pulled, there is a noticeable difference in the engine idling.
I have done the following:
Top overhaul and replaced all eight valves,
Swap the spark plug with a new one(problem still there),
Serviced the carb,
Swap spark plug cables between nos three and four(problem still there),
Changed the ignition coil (Nil fix),
Spark plugs cleaned, regapped and swapped (between nos 3 and 4 - problem still there).
Is there anything else I need to do to correct this problem?
Thanking you in advance and Happy New Year.
Best Regards,
Ron

3 Replies

GARFIELD

MECHANIC
197 POSTS

Since you said that you have moved plug wires and plugs and the problem is staying with Nr 4. You did not state whether you change the cap and rotor. Since you have change the coil, I would look at the distributor cap. I think you may have a bad terminal on nr 4. It possibly may be the ignition module is bad too but the cap is much cheaper than buying an ignition module. Good luck

Gary

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Saturday, December 30th, 2006 AT 6:47 AM

RONALD MICHAEL CARSON

MEMBER
3 POSTS

Hi Gary,
Many thank for your advice. I did that this morning, bought a new set of cables and a new cap. The problem is still there.
Regards,
Ron

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Sunday, December 31st, 2006 AT 4:41 AM

RONALD MICHAEL CARSON

MEMBER
3 POSTS

Hi Guys,
I managed to find what is causing the erratic engine idling speed. The brake booster was leaking internally.
It was mentioned when I brought the car to a friend. He did ask about the performance of the brake application. I told him there was no difference. However, he did everything else. Got home, I rechecked the valves gaps and compression. Both were good. So, I checked the hoses to the booster. Disconnected the hoses, thumbed the ends, and the engine idles beautifully. Release the thumb, and the idle went erratic again. Did that on all the connections to make sure that there is no leak. When I refitted the hose to the booster, the engine idling went erratic again.
So, if you come across a problem like this, you may not need to do a top overhaul. You can trouble shoot the brake system first. All is could be is a leak in the system!
Ron.

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Tuesday, January 2nd, 2007 AT 6:43 PM