QuestionI just bought a 93 concord with a 3.5 liter V6 it has 187,000 miles but runs good. My problem just happened on a day when the outside temps where 12 degrees or lower the car acts as if it's not getting spark. I can smell gas so I believe it's getting there. The first time I didn't what to run my battery down and thought it was froze up so i moved it to a heated shop and let it set for a couple of hours with a charger on. It was still hard to start but started. The next time I just kept on trying to start it and it finally started without any re-warming and then ran perfect. This has happened every time the temp is below 20. In normal or warm weather it starts and runs perfect. I ran the codes on it and had a 12 (disconnected Bat) and 52 ( O2 sensor). I checked prices and it goes for 40-70 dollars. I guess my question is could it be the O2 sensor in cold temps then once it is started it operates perfect? or is there something else?
AnswerHi Rick,
I doubt the problem is a temperature dependent spark situation because if there was no driver siganl for the spark coil there would be a code set for that. Of course the coil itself could be temperature dependent, so the first thing to do is to pull one of the plug connecter caps and insert an old plug into and hold the threaded shell of the plug against the cylinder head while an helper cranks the engine for 5 seconds while you observe whether or not you have spark for 5 seconds, 2 seconds, or not at all.
If you have it for 5 seconds then that is normal. Otherwise let me know.
The O2 sensor may indeed by bad, check its wires and plug connector, but that will have nothing to do with a cold start problem because the sensor doesn't come into play until the engine is warmed up. Before that point the controller has preset parameters and no feedback is accepted from the O2 sensor.
I would first check the coolant temp sensor whose resistance changes with the temperature of the coolant near the thermostat housing manifold which is where the sensor is located. So just follow the top radiator hose to the engine, and next to hemispherical manifold to which it attaches you will see an electical plug attached to a small sensor that is screwed in the cylinder head/manifold. The wires to the plug are black/light blue and tan/black. Gently lift the retaining tab to release the plug from the sensor. Then measure the resistance across the terminals of the plug. At 70F it should be 7,000-13,000 ohms, and it should rise even more as the temperature drops possibly to the range of 25,000-30,000 ohms. When the engine is warmed up it should read 700-1,000 ohms. If it is not doing anything similar to that, then you need a new sensor. That is the proximate sensor that is needed to provide the correct mixture to start a cold engine.
You may have excessive water in the gas tank so adding a can of dipersant as per the instructions might clear that if it were a contributory factor.
As with any starting problems, a check for disconnected vacuum hoses that are attached or traceable to the intake manifold is also in order. Ust the underhood sticker as a roadmap for the hoses.
Another possibility is that the EGR valve is slightly ajar which will prevent the proper mixture for starting. So take a look at that valve, particularly its stem, and use a flat blade screwdrive to lever the valve open and shut against internal spring resistance. A spray of the stem with WD-40 would help to improve its movement.
There are two O2 sensors so you may want to try and read the voltage signals from each to see which one is off-value, once you get the starting problem resolved.
Let me know how these suggestions work out.
Roland
