85 corolla hesitation problem

Hi folks.

I have an '85 Corolla sedan with the 4a-lc engine,carburetor and manual trans.It has high miles but is in generally good shape,except that it has a momentary hesitation/miss problem at the end of the warm up period.
It always starts great and recovers from this miss after about 2 minutes of faltering.It has been ongoing for 5 YEARS, believe it or not, and I have not been able to tune it out or even properly diagnose it.
I have taken it to two mechanics.The first was a Toyota Service center.They replaced the advance unit in the distributor,which did not remedy the problem.They were lousy,so I did not go back to them.I drove the car for several more years til I parked it for about a year.
Now,I have put the car back on the road for my teenage son,and took it to my mechanic to have the problem diagnosed and fixed.He found it had a bad head gasket or cracked head(compression and leak down tests)which was letting coolant into the 4th cylinder and fouling it out.He also found hydrocarbons in the cooling system with his emissions sniffer.
I took the head off, and he was right.It had a rupture in the head gasket on that cylinder.The valves looked great for the mileage,so I replaced the gasket and bolted it back together.
Today,I smogged the car successfully,and he retested the coolant system for hydrocarbons,which tested negative.The engine compression is even at 160.I have replaced the plugs,distributor cap and rotor,plug wires,air filter,fuel fliter,checked the timing.A while back I checked the air gap for the igniter.
All this...and the hesitation problem still persists!
It seems like the choke it sticking and then popping open after the warm up,but on inspecting seems to be working properly.It seems a bit like igntion,but I have replaced most everything associated with that.
The car runs great otherwise,has average oil consumption for its age,and still gets great mileage.
CAN ANYBODY OFFER ME SUGGESTIONS ON WHAT TO LOOK AT TO FIX THIS PROBLEM?
It is a California car,and has all the related smog equipment in good working order.
Would love to hear from you sleuths that crave a good challenge diagnostically.Get back to me,please!

What about the ignition coil? This has caused misfiring and hesitation in my Toyota Van. Replaced it and the problem went away. They're heat sensative too. So you may notice the problem get worse as the engine warms up.

Hi.Thanks for the response!I have never replaced the coil,and the car has 207,000 miles on it.I will look at the manual and see if there is a way to test it.Would a coil work intermittently like that and not just fail outright?Guess so...
Time was when I would just replace parts I was suspicious of on the good guess that it would fix the problem.What with parts prices now-a-days a guy could go bankrupt doing that!
What year Toyota are you referring to?And how much should I expect to pay for a new coil?
Thanks again,Bob

I have a 1984 Toyota Van. Your car uses the same exact coil. They're only good for about 200,000 miles. Then they wear out. They'll be intermittent. Don't even bother testing it. By the time they're 200,000 miles old, the main contact gets very corroded. A new coil is about $35. That's the lowest price I've seen. It may cost more. I'm using a Niehoff Ignition brand coil. I did use one from NAPA, but it only lasted me 6 months. I'm not having any problems with the Niehoff Ignition brand.

Hey KCG 795,
I think you may be onto something here!I stopped by Napa on the way home and priced a new coil from them at $78.00. I'm going to call other sources this weekend.
I see from the Toyota shop manual that the coil is in the distributor. Where did you get this other brand coil from?
Thanks for getting back to me.Bob.

I got mine from Schucks. In your area, the store may be called Kragen or Checker. The website is www.partsamerica.com.

Hi again. Yes,Kragen has the part in stock and it is $54.00.That is a lot less than the NAPA part.I am going to give it a try.At the cars age,and having replaced most everything else(except the igniter) it makes sense.
Do cars with an internal coil also have a condenser,like the old 'point' systems had?Or is that something that went out years ago?And what exactly DID a condenser do?
Yours has been my only response.I appreciate it;even if it does not work,I am planning on keeping this car going until the rings fail,so it is worth spending the money.
I'll report back twomorrow if it had any effect.
Thanks again,Bob B.

Well, they don't have the points system. They do have some sort of "igniter." Then there's the "pickup" and the "reluctor." The reluctor looks kind of like a star. Each point on that is for each cylinder. The pickup basically detects when one of those points of the star go passed it so it'll determine when to fire. This is the early version of electronic ignition.

Here's the pickup.

http://www.partsamerica.com/product_images/img/nie/mp207.jpg

And the stator.

http://www.partsamerica.com/product_images/img/nie/mp211.jpg

You've probably seen the stator below the rotor. These items last a long time too.

Then the igniter. It could either be outside the distributor if you have electronic spark advanced, or ESA for short. It may be located by the air filter box and will look like this. http://www.partsamerica.com/product_images/img/nie/tp215.jpg

Or if you have vacuum advanced, the igniter will be under the distributor cap and look like this.

http://www.partsamerica.com/product_images/img/nie/tp187.jpg

So, that's a basic idea how the 1980s Toyota ignition system works. Good luck.

Thanks for the info.You are either one very well informed shade-tree mechanic or a pro.And that is a cool source for car parts.Can I order parts from them or is that a wholesale only outfit?
Bob B.

It's basically just an auto parts store. But I think you can order the parts. I tried ordering from them before and had a hell of a time trying to do so. So I just said "screw it" and went to the store and got it myself.

I'm just a shade-tree mechanic. My Toyota gave me its share of problems too, including a blown headgasket, which I had to study the repair manual and fix it myself. Also had to replace the fuel pump out in the street at my aunt and uncle's place where I broke down. But hey. A lot of shit wears out after 200,000 miles. But since my engine's rebuilt and a lot of the vital parts have been replaced, I haven't had a problem since.

Hello AF Enthusiast!
I worked all day yesterday to track down this problem.I tested all the components in the distributor for voltage and resistance and things looked o.k.Then I went and bought a new ignition coil.The old one tested o.k.,but it was time for a new one,like you said...
I road tested the car three times during the day.With the old ignition coil in the morning,the car hesitated as usual.With the new coil,I detected no faltering,but the car was warm,and that is not when the problem usually happens.
Yesterday was real cold and rainy here(we actually got a little snow in the higher elevations) Lastly ,I let the car sit for 5 hours til the evening,so it was well cooled off,and took it on a long drive to San Luis Obispo, a round trip of 56 miles,which includes going over the Cuesta Grade,an elevation gain of 1500 feet in about 3 1/2 miles.
There was no problem with hesitation after start-up,and the car drove up the grade in fourth with the speed increasing to 65 by the top,in the pouring rain.
I say that is a pretty good indicator of engine health---high speed in high gear on a steep incline.So that went well.I was happy.
I took it out this morning,after a cold night,and did a 15 minute run down the freeway.It did seem to hesitate ever so slightly at 4 to 5 minutes out,but I was in 5th gear going 70,and the speed never dropped below 65.It was greatly diminished and barely noticeable.After 6 minutes,it was perfect.
So,I have to say the car is running well...better than it has for the last 5 years ,anyways.I put new tires on it last week,and it rolls along like a newer car now.
I have looked over the repair manual for anything that might indicate the carburetor and its many smog related components,and that is confusing stuff.There are fuel-cut solenoids and choke kick-downs and various vaccum switches that could effect acceleration at that point in the warm-up.
It almost takes a smog technician to understand that stuff,though the manual does say what the intented purpose of each component is.I would need a tach and hand vaccum pump to test that stuff properly.
That is why I took the car to professionals! But I think as time goes by there are fewer guys who understand 1980's carburetor smog-related equipment.
Now-a-days techs are trained in fuel injection and let computers send them a code to diagnose problems.Back before the state required smog equipment,I could take apart a carburetor and rebuild it fine.Not now.
Of course,those were highly polluting vehicles,and they needed to go the way of the dinosaur,or we'd all be suffocating on fumes by now!
So that is it for now.We're going to drive the car for a while and see how it goes. Thanks for your help,and keep on truckin'!
Bob B.

Glad that worked out good. Yeah, sounds like it's rebuild time for the carburetor. My van has EFI. I went ahead and had the injectors rebuilt as I was replacing the headgasket. Only carburetors I've messed with was on lawnmowers. But fuel injection is definently a lot easier to maintain. If fuel injection has a problem, it's usually something simple as a sensor.