Questions and Answers

Mazda MPV Runs Rough Until Warm Q. Vincent, Please help, I've already spent over $500.00 based on dealer troubleshooting work and I still have the same problem. Thanks in advance for your expert help! 1992 Mazda MPV 3.0 liter V-6 Automatic transmission 150,000 miles

The problem is that when you first start the car, it acts like it wants to stall. Runs very rough until it warms up. I can get it to go by punching the accelerator. After it warms up, it runs fine.

I replaced all typical tune up parts possible such plugs, wires, distributor cap and rotor, fuel and air filters, etc. The old plugs looked like they may have been getting hot but the dealer didn't think it was a major issue.

The dealer said my problem with the BAC valve which I ordered and replaced at almost $500.00 for the part. That didn't fix the problem, so the dealer said throw some more injector cleaner in and see what happens. I did but it made no difference.

Where else should I be looking? I don't want to take it to the dealer again because they are charging me $75.00 per hour for bad or incorrect information. Please help!

Thanks!

A. The first thing I would do is check the Engine coolant Temperature Sensor. This sounds very much like it is bad. With a scan tool the CTS should be displaying the same temperature as the ambient air temperature, plus or minus 2°.

Another way to check it, although not as accurate as the scan tool, is to measure it's resistance. Here is what it's supposed to read.

Temperature	Resistance (K ohms)
-20°C (-4°F)	14.5 - 17.8
20° (68°F)	2.2 - 2.7
40°C (104°F)	1.0 - 1.3
60°C (140°F)	0.5 - 0.7
80°C (176°F)	0.28 - 0.35