Cavalier hard to start

[alliedmotors]

Two in a row this past week with the same problem. When climbing a steep pass, the car switches to gasoline and the CEL comes on. 1st car has a leaking LPR. 2nd car is ok, CEL was read (P 1202) and cleared. Fuel economy recovered but is also hard to start now, but ran find on CNG before it threw a code.

According to GM, P1202 is "Gas Mass Sensor Circuit Low Frequency".

This seems common, yet all the threads in the archive are unsolved.

[CNG MOTORS]

Re: Cavalier hard to start

Welcome to my world. This will be a somewhat common thing with repairs before you can retail the cars.

[siai47]

Re: Cavalier hard to start

Most likely the expensive GMS is dying. There are some threads on this site about poor solder connections and cleaning that might help. The service manual says to check the connections to the stepper motor (which is the smaller 2 pin plug on the GMS). I would remove both connectors, check the pins and make sure there is no corrosion in either. The main connector has a small red colored clip underneath it that needs to be removed before the connector can be pulled out of the socket. The fact that it works at all is the good news.

[alliedmotors]

Re: Cavalier hard to start

Most likely the expensive GMS is dying. There are some threads on this site about poor solder connections and cleaning that might help. The service manual says to check the connections to the stepper motor (which is the smaller 2 pin plug on the GMS). I would remove both connectors, check the pins and make sure there is no corrosion in either. The main connector has a small red colored clip underneath it that needs to be removed before the connector can be pulled out of the socket. The fact that it works at all is the good news.

The second car seems to have resolved itself and fuel economy has improved. Even though I cleared the CEL with a scanner, it seems as though the code may have still been in memory for a while. Anyway, it starts up fine. I did notice that I didn't get a 100% fill until last night, and it runs much better now.

The first car still has the same problem, but at least that's attributed to a leaking LPR. I finally did find a source, but it too the better part of a week and several calls to IMPCO to get a good distributor. They explained that many are focused on propane and not CNG. So I did order some kits, thanks for the part #.