Torque converter lock up problem

[Landscaper]

Noticed my 93 3.1 lumina keeps cycling back and forth between lock up. At times it will stay locked at lower rpm but others it cycles back and forth for no apparent load change. Not sure if it applies to this but I'm also getting low coolant sensor and o2 sensor codes. Coolant is full. Car also stalls sometimes when leaving a standstill

[Schurkey]

Connect a scan tool, look at the data stream.

ANYTHING that makes the engine run bad is likely to screw with the converter clutch.

When was the last time you performed a complete tune-up--plugs, testing plug wires, verify cranking compression pressure, fuel filter, fuel pressure test, air filter, and all the rest?

[Landscaper]

Schurkey.....just bought the car 2 weeks ago so I'm just starting to try and get the kinks worked out. The guy I bought it off of kept decent care of it and a lot of the sensors are new.  I'm working part time in a garage but haven't had time to look closely at her. I appreciate the suggestions and info and will check those things asap

[pitzel]

What engine/transmission?  

At what RPMs are we talking about here?  Have you driven one of these before, there is a regime between about 1500 and 1700rpm or so that it can bounce in and out of lockup with very little in terms of load changes.

A coolant level indicator on the dash is typically not even routed into the ECU, but if it shows a coolant code and there's obviously coolant in it, then I'd definitely be looking towards the coolant temperature sensor and/or the fan relays.

O2 sensor, unless you know its been changed, its like a $10-$15 part, just one of them, easy enough to change out.  If you think you're going to keep the car and not get rid of it next week, I'd just go ahead and toss one in.  I only get 60-80k miles out of 'em before there's substantial degradation in performance that hits you fuel-economy-wise.

Malfunction of the coolant temperature sensor is probably diagnosable by finding its resistance when cold with a ohmmeter, and verifying against a temperature chart.   Lock-up is ECU-commanded even on the 4T60, and certainly on the 4T60-E, and if the coolant temperature is reading abnormally low by the ECU, it logically follows that it may very well not command lockup or have weird behavour.  

 

[55trucker]

A failing o2 sensor can cause the convert lockup to be erratic, the PCM will no longer be able to constantly keep the fuel system in closed loop, closed loop is necessary for lock up.

Map sensor failure can cause a stalling issue, the PCM cannot properly control air/fuel ratio if it cannot properly know what the ambient air pressure is.

If the PCM coolant temp sensor (not the gauge) is out of calibration the same can occur as the o2 situation.

[Landscaper]

Hey everyone 

It's a 93 lumina 3.1 liter 4t60e. The guy I bought it off of had changed the coolant sensor but it is still showing low coolant and tripping a code. I'm thinking a loose connection maybe? Perhaps a bad sensor out of the box? As far as the rpm it does it in the 50 to 55 mph range. I don't go any faster than that due to my insurance discount. I'm definitely going to change the O2 and MAO sensors. Any suggestions as to why it is still tripping a coolant light with a new sensor?

[55trucker]

more information is needed.......what code/s?

If one does not have a scanner or code reader any stored codes can be interpreted with a simple paperclip.

Remove the diagnostic port cover (under the driver kneepad,) slip one end of the paperclip into the upper right pin opening & the pin opening directly to it's left.

Key on (do not start), the system is now in diagnostic mode (you should hear the fans come on), the service engine light will light up ..then flash a Code 12...*that's a single flash ..a pause then 2 more flashes ..12.

any stored codes will flash up afterwards in the same manner.......example..Code 44 ..o2 sensor lean situation...4 flashes ..a pause 4 more flashes. 

If there are multiple codes stored they will flash one after the other so watch for the breaks in between (write them down).

The ECM coolant temp sensor does not have a light, if what you're seeing in the cluster is the coolant sensor LEVEL lamp coming on that is not ECM related and will not set a code.

If the lamp stays on even with a fresh sensor installed I'd start looking at harness issues. 

Let us know what you find.......

[Landscaper]

Hey everyone 

It's a 93 lumina 3.1 liter 4t60e. The guy I bought it off of had changed the coolant sensor but it is still showing low coolant and tripping a code. I'm thinking a loose connection maybe? Perhaps a bad sensor out of the box? As far as the rpm it does it in the 50 to 55 mph range. I don't go any faster than that due to my insurance discount. I'm definitely going to change the O2 and MAO sensors. Any suggestions as to why it is still tripping a coolant light with a new sensor?

[Landscaper]

So I ran the diagnostic paper clip...if I found the right list of codes heres what I have....

Code 15 coolant temp sensor low temp indicated 

Code 23 manifold air temperature low temp indicated 

Code 35 idle speed control circuit 

This is making sense now as I've noticed that the temperature gauge only reads about a quarter way past the C. So I'm figuring that someone put a cold stat in it or it's stuck open....hence she's running too cold.

As for the idle speed I noticed today that my idle got a bit erratic a few times and she stalled leaving a stop 3 times. So does it have an idle controller? I gotta fix that as I'm afraid she will leave me stalled pulling into traffic. Any help appreciated 

[55trucker]

That code 23 is for the IAT intake air temp, the sensor is inside the airbox, that works hand in hand with the MAP sensor to establish the proper barometric pressure & the temp of the ambient air, necessary for proper air/fuel mixture.

The sensor may just be filthy, or needs replacing.

Code 15 is the ECM coolant temp sensor, that code explains the torque converter lockup situation.

Code 35 will set if the idle rpm is out of range for more than 50 secs.... 200 rpm above or below the commanded norm.

 

Edited February 20, 2020 by 55trucker

[Landscaper]

Thanks trucker I am going to clean that sensor or replace if necessary.  I think also the o2 just for good measure and a fresh thermostat and gasket to see if she functions well with the proper I'm assuming 195 degree stat. I understand why the idle tripped a code as you say it was off idle over a certain amount of time but do you think temperature has anything to do with that? Vacuum leak maybe?

[mfewtrail]

Get yourself a multimeter, unplug the intake and coolant sensors, then measure the resistance across the terminals(one multimeter lead to each of the two terminals on the sensors. An auto-ranging multimeter will be simpler to use if you've never used one before. I can recommend a cheap one if need be.). Go here to see resistance values related to the sensors/codes you have: https://www.w-body.com/oldsite/ecm-codes.html The resistance values don't have to be exact, but should be close to those ranges at the specified temperatures.  Failed coolant temp + iat sensors can cause the idle code and stalling as they change the idle air control valve position, fueling, etc. based on the information they report.  Converter lockup is also based on coolant temperature, so a false cold temperature can cause lockup issues. Since your actual coolant gauge is reading low(this is a sending unit in the rear of the cylinder head separate from the actual coolant temp sensor the engine uses), I would try to verify the temperature of the engine because you could very well have a stuck open thermostat in addition to the other problems. A stuck open thermostat that won't allow the engine to reach proper temps will also cause lockup problems. I believe threshold coolant temperature for lockup to occur is somewhere around 130F.

 

As for the "low coolant light," more often than not those sensors(located on the side of the radiator) get corroded or just fail completely. If you unplug the harness connected to the sensor, the light will go out. Unplugging the harness until you decide to replace the sensor will not hurt anything as it's just for the warning indicator light on the instrument panel. Some people have success restoring those to normal operation by cleaning them, so that might be worth a shot. If not, replace it if you want...or just leave the harness unplugged and actually check your coolant level at a regular interval.

 

Engine coolant temperature sensor - this is located in the lower intake manifold just below the thermostat area on your 3.1. That manifold air temp sensor is going to be the "intake air temperature" sensor and is located in the rear of the air filter housing. Besides checking resistance, measure voltage on the harness for each sensor. One lead to each terminal and you should read 5 volts. Carefully touch the terminals on the harness, do not try to stick the multimeter leads inside the terminals or you'll spread them and cause problems. If necessary, have an assistant hold the harness for you while you very lightly touch those terminals to measure voltage.

 

 

Edited February 20, 2020 by mfewtrail

[vipmiller803]

On 2/17/2020 at 9:21 PM, Landscaper said:

a lot of the sensors are new.

14 hours ago, Landscaper said:

I am going to clean that sensor or replace if necessary.  I think also the o2 just for good measure

 

Come on... don't be a parts changer. Test, test, and test some more.

CTS and IAT can both play tricks on fuel trims so the stalling and the TCC might both be just symptoms.

@mfewtrail is putting you on the right path. Before replacing any of those, make sure you're diagnosing.

Do you have an IR thermometer at the shop? Check if the thermostat is really stuck before replacing it.

Do you have access to a scan tool with live data? You can put a substitutive value for both the IAT and CTS to check wiring integrity quickly.

Never throw parts based on codes alone.

[Landscaper]

My friend bill has a scan tool for OBD 1 and a meter. I'll work my way over there this weekend  and try to test these sensors

[Landscaper]

So turns out I had 5 volts to everything...IAT worked ok after a cleaning.  Replaced the CTS and thermostat as I already had them. My real problem was a vacuum leak at the throttle body...also my IAC was improperly seated due to a broken bolt which I fixed. It's running much better but I also discovered both colling fans were always running.  After disabling them to test she ran better than ever. They're stock relays so I assume I need to test those out and replace them if necessary or get to the real root of continuous run. If I'm correct one cuts in on high temp and one when A/C is on?

Thanks for all the help guys

[Landscaper]

On 2/17/2020 at 7:34 PM, Schurkey said:

Connect a scan tool, look at the data stream.

ANYTHING that makes the engine run bad is likely to screw with the converter clutch.

When was the last time you performed a complete tune-up--plugs, testing plug wires, verify cranking compression pressure, fuel filter, fuel pressure test, air filter, and all the rest?

Turns out that all these problems were caused by really bad plugs and plug wires. I dont think the back ones were ever changed. They were gapped over 100 thousandths for sure.