Why would a 1997 Astro not start when it rains?

Answer 1

I dealt with this problem on a 1999 Astro for almost a year. I replaced the rotor, cap wires, ignition control module, and the crank shaft sensor. I finally figured out that it was a defective ignition coil (would arc out in wet or humid weather. Pretty easy to change. Only costs about $50.

AnswerI am guessing the car (van) runs fine when it is not raining?

Things that it �Could� be (this is not a complete list):

• Bad, Cracked, or Cheap distributor cap.
• Contaminated MAF sensor
• Bad O2 sensor(s)
• Bad or Cheap spark plugs
• Bad or Cheap plug wires

Explanation: A bad or cracked distributor cap would allow moisture to get into the cap, normally this causes backfiring � but not always. It also interferes with the rest of the spark circuit � the wires and plugs are basically the same thing, from the excess water in the air. The OBDII system does not use a BARO sensor to determine air density or humidity, it uses a learned routine from the MAF, MAP, and O2 sensors to determine the figure.

This is the exact problem that I have with my current 1997 van. I have 20 years experience at working on cars, am ASAE certified for computer electronics, and I still do not know �yet.�

In My Situation: There is no backfiring, and there are no trouble codes present. The O2 sensors have been replaced and there is no apparent contamination of the MAF sensor. The distributor cap has been replaced (twice) the second time it was coated with an electrical sealer(outside only), and sealer (electrical RTV) was placed at the base; the Coil and internal components of the distributor have been replaced as well. That does not mean that these things are not bad in your situation, but if they are not you are in for a long diagnostic in finding the trouble.

UpdateThere seems to be a chance that rain can run into the Air Temperature Sender on the air intake hose. If there is no seal or a bad seal on the hood it allows water to run down the inside of the fire wall. The placement of the sensor is right in line with a leak of this nature, and it points up so that it can catch water. This sensor is a simple resistor that reacts to temperature, so any change in resistance (like conductivity of water) changes its readings.

Location: The air intake hose is approximately 4� in diam. And runs from the air intake box (where the air filter is) to the intake manifold, this hose also houses the MAF sensor. On this hose just under the firewall is a small plug with 2 wires (the plug should point up) and this is the ATS.

Solution: I would NOT suggest using any form of sealer on this sensor, or the plug. It could make it impossible to replace or interfere with its function. I would NOT suggest trying to �turn� the hose; First it may crack as it is now formed because of age and heat, Second, it could adversely affect the MAF sensor. We placed a small piece of rubber weather-stripping on the firewall just to the right of the Windshield wiper motor. Purchase a small amount of 3/8 inch automotive weather-stripping and some weather-strip adhesive from your local parts house. Use a green scrubbing pad (that you would use for dishes) and lightly scrub that area with a grease fighting dishwashing soap. Thoroughly dry the area, then cut and glue the weather-strip to deflect water away from this sensor. I have not had this problem since doing this.

New Info from another owner- I own a 2002 GMC Safari and found that my catalytic converters were clogged and this is what was causing it to be very sluggish and I could not go much over 35-45MPH. This may have also contributed to hard starting. I did replace my spark plugs, rotor, wires and caps (what a nightmare) and starting was a little easier (and this was before the catalytic converter replacement.