2000 Mountaineer dies after 2 hours

[ChuckinCO]

This problem has persisted each summer since purchase of the car.

When the outside temperature reaches 80-90 degrees and we have been driving for around 2 hours, the engine begins to lose power, surges and eventually dies. The check engine light comes on with ODB codes for one or both cylinder banks being too lean. The light remains on until reset.

If let to sit 30 miutes to overnight, it starts fine and runs great.

We have replaced the Mass Flow Sensor, air filter, fuel filter and the problem remains. The only other indication, related or not, is that the engine temperature indicator sometimes reads cold even after an hour of running.

Any suggestions short of waiting for cooler weather and dumping the car?

[taillight]

First pull any trouble codes and fix them first. Then put a fuel pressure guage on and tape the guage to the windshield and go for a ride and watch the guage when the engine starts to have problems.

[ChuckinCO]

Thanks Tailight!

The ODB codes are P0171, P0174 (Fuel system lean, Bank 1 or 2).

One possibility that has been raised is that the Barometric pressure setting in the Keep Alive Memory (KAM) has been reset when the battery was disconnected. It then defaulted to the sea-level setting not the high-altitude DENVER setting.

Is there a way to access the Keep Alive Memory to reload the high altitude settings or change those settings?

C

[shorod]

Welcome to the forum, ChuckinCO!

I think the person suggesting that the KAM and barometric pressure setting could be the issue is thinking back to the OBD-I system. This concern should not be a problem with the more advanced OBD-II system that your 2000 model year uses. OBD-I was completely phased out for the 1996 model year for all cars and gasoline light trucks sold in the US.

I agree with taillight that monitoring the fuel pressure when the problem starts is a good one. Also, you may want to explore the coolant temp issue more as well. There should be a sensor that the PCM uses for timing, air-fuel ratio, etc. along with a sender for the instrument panel gauge. If they are both reading the same, then you may have an air pocket in the cooling system.

-Rod

[taillight]

You could also get a scan tool with record and get the live data when the problem happens. So have both a fuel pressure guage and scan tool on at the same time.

[ChuckinCO]

When the mass flow sensor was replaced, the check engine light was reset, and although the problem reoccurred, the check engine did not illuminate. Recently, just after refilling the gas tank, the check engine again came on. I immediately checked the gas cap, but it was secure. I took it to Checker Auto (free ODB scans), and their ODB scanner indicates a 1132/1152 oxygen sensor out of range.

However, the check engine decided to reset and went out while driving, but the vehicle is untrustworthy.

I guess the next stop is the dealer and $100 to diagnose.

BTW - I own a Jeep Cherokee with 365,000 miles on it and it has seen the dealer once. My Hummer H3 runs like a top and never lets me down. Unless I can resolve this problem, my wife says, it's the last Ford she'll own.

Chuck