QuestionQUESTION: Hello Roland,
I previously wrote about an intermittent start problem with my 1993 5thAve. My mechanic diagnosed a bad computer and changed the module. Since then, the intermittent problem returned after a 100 mile trip in the vehicle. The car would not start after sitting overnight, but if the neg. battery cable was disconnected and reconnected it would start up and the car would run fine for the day. This rapidly progressed (before I had a chance to check the EGR valve as suggested) to a need to disconnect the battery each time and reconnect to start. After a couple of times the car would not start at all. It had been a cold night, so I removed the battery and recharged it, I even had it tested at the local parts store...they claimed the battery was fine. The battery charger I used indicated it was fully charged. The voltmeter reading for the battery was ~10.5V. The car had absolutely no juice though with the battery reinstalled. The check engine light will not even come on...if you turn on the ignition you can see some popping at the positive terminal of the battery and small wisp of smoke. What could have caused this new addition to my starting problem?
ANSWER: Hi Lisa,
If the battery read 10.5 volts when it was installed in the car sitting unused, and it truly was fully charged then you have dead short of some sort that is draining it really fast. Put it on the charger again and see what it reads after a few hours of charging. It should read around 13-14 volts unhooked up. You will need to use an ohmmeter to check for the load resistance that the battery "sees" when it is hooked up. It should be more than 100 ohms. If not, then you have to diagnose where the short is. Let me know if you have an ohmmeter for this purpose. Are you sure you aren't hooking up the cables backwards?
Roland
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QUESTION: Roland, I think I have fixed the charging problem...the repair had put a new cable on and it wasn't making great contact with the old battery post that has been scraped/cleaned so many times...I think the battery wasn't actually charging fully because of this. Anyway, I have been working on my original problem with this vehicle and wanted to get a little more info. The car won't intermittently won't start when cold...usually happens when the car has been driving long periods that previous day. It takes a long time for the temp gauge to move off of cold, though the heater works fine even when it reads cold. I also noted that the engine temp will be in the midrange around town, but drop all the way to cold when driving on the highway. I expected it would cool some with increased airflow, but was surprised that it read that cold. Once off the highway is when the car begins to run much rougher and loses power, though it never dies. It seems to be able to compensate until the car is shut off and then it won't restart. Using the key method, and when it was in the mechanic's shop, there were no codes registered on the computer. When the car won't start however, you can't check for codes because the check engine light won't come on at this time...the check gages light comes on instead...is this because the ASR has been triggered? I know the bulb works fine, since if I disconnect the battery (I assume this resets the computer), then the check engine light will work, but gives no codes (except 12, 55, as expected). The car will generally start if you go through this procedure (battery disconnect). I think the car is running rich though, poor fuel economy and black soot on tail pipe and muffler. I checked the EGR valve as you suggested, it appears to open and close appropriately, though I can't rule out a problem with the valve reseated...if the car is running that rich the valve seat may gunk up quickly? You also suggested checking the resistance of the coolant sensor, but I'm pretty new at this, so not really sure how to do this since the sensor is tucked tightly under the DIS coil pack...so I'm not sure how to access the wires without removing some of the parts around it...do you have any advice this or is it easiest to just replace the sensor (<$20). And does any of this new detail about the computer shutdown help (I thought I read somewhere that the loss of the check engine light indicated the computer was not getting power - perhaps an auto safety relay symptom.) As always I appreciate your advice...I have really struggled to find a mechanic locally to help me figure this out so I'm trying to learn what I can!!
Thanks again!!
Lisa
AnswerHi Lisa,
I would measure the coolant temp sensor resistance when the engine is cold and when warmed up fully. It is next to the thermostat housing which is connected to the top radiator hose. You might do well to change the thermostat by removing that housing and putting in a new thermostat. It appears that it is opening at too low a temperature.
Finally, I would try to move the EGR valve stem when the engine is warmed up to verify that it seats fully by the closing action of the internal spring. You should be able to feel that position with the screwdriver.
Let me know the results of you measurement of that resistance.
I can't be sure about why no check engine light at times, except that it is possible that there is an intermittent in the ignition switch contact that passes the power on to the PCM. So try jiggling the ignition key/lock cylinder to try and get it to light up. Other than a continuing voltage connection problem with the battery I can't figure anyother reason.
