QuestionHi,
We recently purchased a 1994 Chrysler LHS with 147,000 miles on it in excellent condition. A few days ago, I started the car, let it run a few minutes and backed out of my driveway. The car stalled and I wasn't able to get it to start again. It acts like it wants to turn over, but doesn't. I have read similar stories like mine on your website and printer out the spark test and engine code tests. As far as spark, my husband says sometimes it has it and sometimes it doesn't. We then did the code test and the code we got was 12 35 55. Our engine size is 3.5L. Can you suggest anything else we might try to get the car running? Sincerely, Brenda
AnswerHi Brenda,
I would try to ascertain first whether the 12v supply to the spark coil is present or not. You will need a voltmeter or a neon glow light. If you unplug the 4-wire plug to the spark coil you will notice that the pins are arranged in a square and that there is an indentation on one side of the plug. Direct your attention to the two terminals on the far side of the plug from that indentation. One of those two terminals has 12v on it when you are cranking the engine, if the spark-generation circuit is ok. So put your voltmeter leads between one of those two pins and the engine head or - post of the battery (ground) and have your spouse crank the starter to see if you get 12v when you first turn the ignition switch to the "run" position and that should last for about a second, and then use the starter for 5 second and see if the 12v returns and is sustained for as long as you crank it. If you don't see that sort of a voltage response, then try the other pin on the far side of the plug from the indent the same way. If you get that voltage response then we know that the spark-generating signals are ok. If not, then more likely the crank sensor has gone bad and needs to be replaced. Such a failing sensor would work sometimes, fail, work again etc until it quits completely. If you do get that voltage response, then you could check the coil pack. The resistance between the complimentary contact for where you observed 12v and each of the other 3 contacts of the coil pack socket should read 0.45 to 0.65 ohms. And the resistance between each pair of towers into which the spark wires are plugged should be between 7 and 16,000 ohms. If that passes then you should have spark reliably when you are cranking it.
Now let's consider the mixture and assume that the ignition system is ok One possibility is that the temp sensor is not accurate but not so bad as to cause a code (it should read 7 to 13,000 ohms when the engine is cold; it is located next to the thermostat housing on the top of the engine where the upper radiator hose attaches), and with the manifold absolute pressure sensor you would need a voltmeter to access whether it isn't working properly. So let us set aside those until we 'exhaust' the other possibility and you let me know if you have access to a volt-ohm meter.
I have another idea, one of my favorites when bad idle or refusal to start rears its ugly head. I would take a look at the exhaust gas recirculation valve which is located behind the engine near the air intake throttle valve. It is mounted in a pipe that runs between passenger side exhaust manifold and the air intake manifold. The valve is mounted horizontally and has a valve stem between its round vacuum actuator top and the body of the valve attached to the pipe, inside the flange that connects the two parts. The stem has a slot into which you can insert the tip of a flat-bladed screwdriver so as to lever the stem back and forth against spring action which should move freely and close tightly. If the stem seems to be sticky so that stem doesn't close all the way by spring action, then you can try spraying some penetrating solvent like WED-40 on the valve stem to free-up its motion.
If the valve is sticking slightly ajar it will make for a rough idle and or not start such as you describe because the mixture is too dilute. It is one of the most common causes of this symptom. So see if you can find the valve and check/lubricate the stem. To check it in motion you can rev the engine from idle to 2500 rpm and back to idle and watch to see if the valve stem moves freely in both directions to the extreme open and closed positions. It may be that the interior of the valve is cruddy so that might require that it be unbolted from the pipe where it it attached and cleaned. But chances are good it will only be a sticky stem. Feel free to write back with the results and other questions you might have.
The 12 code is very common and just means that at some point in the recent past the battery was disconnected from the engine controller (or a cable was removed from the battery). If that hasn't occurred recently then check to be sure the cables are firmly attached to the battery. The 35 codes means there is a problem in the circuit between the fan relay(s) and the radiator fan motor(s). But that would not prevent the car from starting. If you notice that the fans aren't coming on when you ask for AC or when the temp gauge on the dash pushes toward "H" then there is a problem with the wiring, or the relay(s). But that would not prevent starting. The 55 code just means "end of readout" so that you will always see.
So look at the spark coil plug and the spark coil pack resistances, and check the egr valve and let me know the results.
Roland
