Hello my name is Kenny,

My father-in-law has a 1996 Monte Carlo with a 3.1. It has recently had a new gas tank installed due to the original having a hole in it.

Last week he complained of the car spitting and sputtering (low speeds 15-20 mph) and a lack of power coming up the hill to his home and it had the check engine light on. I scanned the code and found it to be P0300 (Random Misfire). I started the car and it ran fine. I test drove it on the interstate and on a back country roads at low speeds, it ran fine. I shut the light off and left it at that.

On Thursday August 4th I drove him to a doctor’s appointment from this doctor’s appointment we drove to the emissions inspection station. The car passed emissions. From the emissions stations we drove to the local mall I had the car shut off maybe 15 minutes while in the mall and it restarted with no problems. It ran fine to and from the appointments but it did throw a check engine light about ¾ of the way back to his house. The total mileage for the trip was around 70 miles. I didn’t bother to check the code since it was a long afternoon. After I had dropped the car and my father-in-law off he says he went to start the car and it would not start, it would just click. So that evening as I prepare to go and take a look at the car my wife tells me never mind the car started for him, okay.

So on Saturday August 6th at approx 2:30pm my wife calls me and tells me she on the way to pick her mother up at the grocery store because the car shut on her father as he was driving down the hill at their house to pick her mother up. So I say okay when I get home I’ll grab the tow rope and pull him up to his house. By the time I got home at approx 4:30pm she says he got it running and drove it up the hill. He did say once again when it shut off and he tried to restart it that it just went click.

I go in that evening and the car fires right up. Here is what I have for codes P0171 System Too Lean (Bank 1), P0300 Random Misfire Detected, P0705 Transmission Range Sensor Circuit (PRNDL Input), P1870 Trans Component Slipping. I also checked the alternator and am getting about 14.19 out of it. I do notice the shift lever seems to be off somewhat, for example when shifting into drive from park the lever doesn’t have the firm engagement into drive and shows on the indicator in the dash it’s between N and D, but car lurches forward into drive. But, if you shift down to 2 and then back into D it seems to engage more “sternly”.

Sorry for the long post but wanted to get as much detail as possible. Where do I start to troubleshoot? As it is now the car will start and drive. I plan on taking it for a couple of days to try to track down the issue.

Are these codes related to a common issue or are the P0705 & P1870 one issue and the P0171 & P0300 another issue.

Could the Neutral Safety Switch / Range Sensor on the trans be bad causing the car to shut down?

Thanks,
Kenny

 

Not sure about the NSS causing a shut down. I know it will start in gear if it's faulty. Your issue is likely coming from the misfire...which could be anything. Ignition control module, crank sensor and MAF sensor come to mind.

 

So I have an update. I went to the in-laws house to pick the car up to bring it to my house to troubleshoot. This is about a 6 mile ride, a short drive thru town, a little stint on the highway, and a country road drive. The car ran fine until I got to the top of the hill on the road I live on and it sorta of hesitated/bog down.

Anyways I got into my driveway and left it running while I monitored some of the sensors. After a few minutes it started to run rough and eventually shutdown. I tried to restart it but no luck. I checked for spark and had spark at each cyclinder. It was getting dark so I decided to wrap it up. After about 20-25 minutes I tried once more to start it and it fired right up.

I didn't get a chance to check fuel pressure. What should I see for fuel pressure? How can I check the fuel pressure regulator?

Also forgot before it died in the driveway the engine would rev high when I gave it a little throttle.

Thanks,
Kenny

 

Fuel pressure should be around 35-40 psi at idle IIRC. To check the FPR, pull the vacuum line off and see if it is wet / or if it smells of gas. Check for vacuum leaks too.

 

Nighthawk,

I got around to checking the fuel pressure. According to my gauge with the key on and the motor off I get about 14 PSI. With the key on and engine on it goes to about 16 PSI setting in the drive way idling. Is it possible for these engines to even run with that low a pressure. Also I noticed as it set and idled that when the pressure dropped the motor "blubbered". I plan on pulling the filter and changing it before new fuel pump.

Thanks,
Kenny