Was wondering if I could get some help with my Tercel. (12-Valve, 1.5L, Automatic)

Symptoms:

Random check engine light occurrences, followed by stalling. But the stalling only happens if you come to a stop (or maybe a rolling stop) and then try to accelerate again. IT WONT STALL IF YOUR JUST SITTING AT THE LIGHT OR LET OFF THE BRAKE AND JUST LET THE CAR ROLL FORWARD AT A COUPLE MPH'S. In other words, after the check engine light, any load on the engine will cause it to stall.

If your on the freeway (during this condition), it will never die. But it will have a lag between throttle and acceleration. And if your going a long distance, it will eventually go away and continue normal performance.

Lastly, regarding the symptoms. This condition will not happen in the Winter or otherwise cold, and/or dry weather. (Wisconsin)

What I've Tried:

Initially, I jumped on the internet and did some research that pointed to the "ignitor / ignition module" that sits on the firewall. So I got a used one and switched them out. No difference. So I returned the used one and put the old one back in.

Second, I went back to the basics and just replaced the spark plugs, plug wires, distributor cap and rotor. This seemed to clear up the problem ... for about 6 weeks.

Now the car is doing the same thing again. I replaced the ignition coil and there was no difference.

So what should I do next?
What kind of testing can I do?
Has anyone heard of this in Toyotas?

Also, forgot to ask. If no body has any ideas, does anyone know of a good Toyota forum for this question?

I know there probably not a huge following for this 82 bhp car, but there's gotta be some knowleadge out there, right?

GoldÐiamond;152619225 said:

Also, forgot to ask. If no body has any ideas, does anyone know of a good Toyota forum for this question?

I know there probably not a huge following for this 82 bhp car, but there's gotta be some knowleadge out there, right?

Click to expand...

This would be a lot easier if I was there.

Use this OBD1 code retrieval procedure here, and let me know what code(s) you might retrieve. If we are lucky, the code could be saved on the ECU even if the check engine light is not always illuminated.

Let me know what you find.

How's your front (likely only) O2 sensor?

Code says "Engine Coolant Temperature"

Haynes Manual says either:

Coolant Temperature Sensor
Coolant Temperature Sensor Wiring
ECU

I don't have an ohms-meter to test it.

You can usually get by with one of those Harbor Freight volt meters. They work in a pinch.

I'd of course start with the wiring. Trace it from the sensor to the firewall, then find where it comes into the firewall and into the ecu.

I'm usually against just throwing money at a car if I'm not sure that's the problem, but you could just replace it http://www.carparts.com/details/Toy...92toyotatercel19921996faew0133-16368531296512

Looks like a pretty cheap part.

Yeah, its $15 at O'Reilly Auto near my house. That's cheaper than an ohm-meter, so I might just try it.

And yeah, I don't usually like throwing parts at my daily drivers. I am even a little pissed I wasted $40 on an ignition coil. I don't think the parts store accepts returns of electronic stuff.

GoldÐiamond;152621421 said:

Yeah, its $15 at O'Reilly Auto near my house. That's cheaper than an ohm-meter, so I might just try it.

And yeah, I don't usually like throwing parts at my daily drivers. I am even a little pissed I wasted $40 on an ignition coil. I don't think the parts store accepts returns of electronic stuff.

Click to expand...

Great work retrieving the codes. You should get a multimeter because they really come in handy. Do not just throw parts at your car. Checking the codes on the car is a STEP in getting the car fixed. The guys telling you to throw parts at your car did not even know how to check the codes, and now that they THINK that they know what is wrong, they are telling you what to buy and where. It is most LIKELY your coolant temperature sensor. But a real mechanic would not go about buying and installing it without making sure it is the problem. The guys that are trying to help are not mechanics, I on the other hand, am. Please try to realize that the concise posts as to what you should do next are an indicator of the true knowledge the writer holds.

Now the next step is to check out the coolant level in the car. Just to be absolutely sure that the car has never overheated. Where did the temperature needle sit while the car was running and warmed up?

If the coolant level checks out fine, then go on to check the coolant temperature sensor harness connector pins. Make sure they are not corroded, loose, or dirty. Make sure the wires that go to the harness connector are well insulated, as to eliminate any chance of shorts.

If the wiring to the coolant temperature sensor harness connector, and pins, are fine. Then you will need and multimeter to check the rest, and I am starting in order of ease, and consumption of time.

First: The coolant temperature sensor: Check the values while the car is cold(Between 50-80 degrees ambient) by back-probing the harness connector. The sensor should read between 2200-2700 ohms while cold. Then run the car until it gets to normal operating temperature, or when you feel it has, sense the coolant gauge on your gauge cluster might not be too accurate without a properly functioning coolant temperature sensor/circuit. When fully warmed up, back-probe the coolant temperature sensor once again. This time it should read between 280-350 ohms while fully warmed up. If this is not the case, stop here and replace your coolant temperature sensor because that is your problem.

Let me know if you find that the coolant temperature sensor is functioning. We will then go on to check the wiring, and pins at the ECU.

Tony

So I tested the coolant temp sensor as you suggested. The resistance fell within specified range when cold, but was a different story when hot. Per the Haynes manual, for easier testing, I removed the sensor and plugged the hole and tested the probe in the a pot of boiling water. (roughly 200 degrees) Under this condition the resistance jumped all over the place and when it finally settled down it fell outside of the specified range, around 750 ohms.

Then I tested a new sensor the same way. It too tested good when cold. But when testing in the water, each time a dipped it in the water for a while it tested lower and lower ohms as it got hotter until it was within specified parameters.

So I replaced the sensor, plugged it snugly back in and filled the coolant back up. (spilled some during sensor removal) I drove it around a while. It was raining so I figured it was a good time to test - since the problem mostly occurred during humid conditions.

The check engine light never came on, and didn't stall during the 10 minute test drive. The real test will be on the ride to work tomorrow, but I think it was a success!

So we can't yet put the [RESOLVED] stamp on this thread, but I have a feeling I'll be able to within the next couple of days.

So thanks a lot, 91-gsx, looks like I will have only wasted the $40 on the ignition coil + some frustration.

GoldÐiamond;152621989 said:

So I tested the coolant temp sensor as you suggested. The resistance fell within specified range when cold, but was a different story when hot. Per the Haynes manual, for easier testing, I removed the sensor and plugged the hole and tested the probe in the a pot of boiling water. (roughly 200 degrees) Under this condition the resistance jumped all over the place and when it finally settled down it fell outside of the specified range, around 750 ohms.

Then I tested a new sensor the same way. It too tested good when cold. But when testing in the water, each time a dipped it in the water for a while it tested lower and lower ohms as it got hotter until it was within specified parameters.

So I replaced the sensor, plugged it snugly back in and filled the coolant back up. (spilled some during sensor removal) I drove it around a while. It was raining so I figured it was a good time to test - since the problem mostly occurred during humid conditions.

The check engine light never came on, and didn't stall during the 10 minute test drive. The real test will be on the ride to work tomorrow, but I think it was a success!

So we can't yet put the [RESOLVED] stamp on this thread, but I have a feeling I'll be able to within the next couple of days.

So thanks a lot, 91-gsx, looks like I will have only wasted the $40 on the ignition coil + some frustration.

Click to expand...

The boiling pot of water idea is great, very good thinking. It is a good method for checking thermostat function as well. I believe that you found the problem. Those are definitely signs of a malfunctioning coolant temperature sensor. I look forward to the [RESOLVED] stamp on this thread.

Great work!

No problem. Glad I could help.

Tony

GoldÐiamond;152628509 said:

resolved

Click to expand...

Great work you did. Learned a lot from your post

Thanks.

I was doing a bit more reading and I guess simple engines like that (and most foreign 80s and 90s cars) really come down to a hand full of sensors and switches that are the cause of most mysterious problems.