Chrysler Repair: 90 lebaron engine misses, coolant temperature sensor, 1990 chrysler lebaron

Question
Hi My car is a regular 1990 Chrysler Lebaron Thats got a 3.0 V6 under the hood. Every time the car sits and cools down all the way and I get back in to go some where the whole car will get to a certain temp and start jerking. Some times are worse than others. But when it gets warmed up to the actuall running temp its fine. I have noticed that when it does this the dash will go hay wire. And after it stops jerking the dash will be fine. I have also noticed that the positive post on the battery is broke. I could probably pull it out if i wanted. Not sure if that could cause that or not. Anyway all general tune ups have just been done. Thanx for your time.                           Nick

Answer
Hi Nick,
I noticed that you had questioned Pete Lacey about your temperature sensitive miss and the fact that changing the battery didn't help. Nonetheless, a loose battery post at sometime in the future probably would have caused the battery to fail due to an internal "open" connection.
I doubt that a tune up will improve the situation, because that usually means just replacing the spark plugs and looking at the emission system hoses, which is always relevant but not generally associated with your current symptoms. But if the plugs have gone 25,000 miles it would be prudent to replace them.
Because of the temperature dependence of the miss you might want to take a look at the coolant temperature sensor which controls the fuel mixture as the engine warms up. It is located adjacent to the thermostat housing (where the fat hose from the top of the radiator attaches to the engine) and has a two wire connector. It should read 7,000 to 13,000 ohm across the terminals when the engine is cold and then as it warm the resistance should drop gradually to 700 to 1,000 ohms when the engine reaches 200F. So by measuring the resistance as the engine warms you might find a glitch in the sensor that is causing the mixture to go wrong temporarily, when the engine starts to miss.
On the general problem of a miss without codes, let me add the answer I gave recently for that situation:
"When it is intermittant for such a short time it may not set a fault code, or the fault code be something that is not codeable. You may have to let this progress a little further until it refuses to start and then check for spark (carry a spare plug, pull one of the plug wires carefully by the insulator not the wire, and then insert the plug and hold the threaded edge against the cylinder head while a helper cranks the engine and you watch for spark to last for 5 seconds, 1-2 seconds, or not at all during a 5 second crank). Also, note whether the fuel pump makes its sound for about 1 second when you turn the ignition to run. And of course read for codes again. It might be the ignition switch if flakey, and this can happen if you have a very heavy set of keys that weighs on the switch. Try jiggling the key when it happens or to try and provoke it to happen. Those are the ideas I have at the moment. Please let me know what you learn or it this isn't clear. It sounds like one of the solid state (hall effect) sensors on the cam or crank shaft is beginning to breakdown because this is often the first sign of that, but it is not prudent to throw parts at the problem; the alternative of getting a diagnosis is to be preferred."
Good luck with your search.
Roland











Hi Nick,
A loose battery post could certainly cause an intermittant electrical power supply to the engine controller and the spark plug circuit (and the insturment cluster) so my inclination would be to trade-in the old battery for a new one. It might even have some warranty left which will reduce the cost of a new one.
If you don't want to opt for that without further proof you might want to see if the engine controller has seen such an intermittant power situation or some other cause of the miss that occurs (what you called a "jerk"). The controller can recognize faults and store its observations as coded numbers in its memory which you can access via the ignition switch. The code for the battery supply fault is 12. Try using the ignition key: turn it "on-off-on-off-on" and leave it "on" (doing this quickly, no longer than 5 seconds). By "on" I mean just the normal position when the engine is running, not the cranking position. The 'check engine'light will remain on when you leave the key in the "on" position with the engine still not running. But then watch the 'check engine' light to begin flashing, then pause, flashing, pause, etc. Count the number of flashes before each pause and keep track of the numbers. Repeat the readout and verify the counts are correct. Then group them in pairs in the order that they came out, thus forming two digit numbers. You may notice that the pause is shorter between the digits of a given number, and longer between the numbers themselves. Then send me a 'follow-up' question telling me the results of your readout. By the way, 55 will be the last number (two groups of 5 flashes each) and that is the code for "end of readout".
I have the troubleshooting manual for the 3.0L engines and we can look up the possibilities of what is wrong based upon what fault codes you show. There is also an essay on fault codes at the site:
http://www.allpar.com/fix/codes.html
which gives the meaning of the code numbers. But then you need to get specific info for what exactly might be the diagnostic tests or parts to replace to complete the repair. Let me know the codes and I can give you some direction.
Roland