Help with Bucking/Backfiring wont run Malibu 3.1L

[atxjax]

Need help trying to troubleshoot my friends car. It's a 97 Chevy Malibu. 3.1L V6, Auto with 197K miles. Yep....197K

He told me it was running fine until one day it started to stumble and runs really rough like some cylinders were missing and it cut off inthe middle of rush hour traffic. Managed to turn it back on and and limp it home. It's been sitting in his driveway for a while now.

When you attempt to start it, it will run for about 4 or 5 seconds very roughly then cuts off. try it again and it just does the same thing.

It had the check engine light on at some point before it was parked but being how the battery drained out and it sat for a while the codes are not present anymore. I checked with my OBD2 scanner and nothing. Here is what I know so far.

1. Has spark. I checked with a inline spark checker on each cylinder.
2. Fuel pressure is right at between 42-44 PSI and holds steady after key is off ( pressure regulator is good )

Not sure what else to check from here since I have no codes to go by and I can't get them to set because we drained the battery again trying to do so.



Crank position sensor maybe or Mass Airflow sensor?

[robertisaar]

MAF sensor would make sense...

either crank sensor going bad shouldn't allow running for a few seconds and then dying.... just doesn't jive. it should also trip a code instantly.

[atxjax]

When I do manage to get it started it runs like total crap. I mean really really rough like its only on a few cylinders.

[robertisaar]

certainly does sound like a skewed/dead MAF...

when it's running, get a screwdriver and tap against the MAF using the handle... if it starts acting different because of it, that is a guarantee that it's an issue.

[atxjax]

I really hope it is the MAF. it looks like the crank position sensor is a bitch to get out.

[robertisaar]

I really hope it is the MAF. it looks like the crank position sensor is a bitch to get out.

i don't know about 3100 N-cars, but it's not that bad on a 3100 W... that being said, the MAF is about 10,000 times easier, so yeah, good luck.

[bszopi]

With that high of mileage, when was the last time things like the spark plugs or fuel filter were changed? Just because you have good pressure at the rail doesn't mean you are getting good flow to the injectors. And fouled plugs may work initially, but not be able to maintain spark once they start getting used for longer periods of time. If its been an unknown time, or even awhile since any of those have been changed, it might be good preventative maintenance to do it as well.

3x sensor is mainly a pain due to the tranny blocking good access to it.

[atxjax]

I don't think it neve rhas had its fuel filter changed. I will do that first thing. Then if the problem still happens I will move on to cleaning the MAF, if the problem still persists then I will disconnect the MAF and try to run it to see if it changes.

[jeffreylane]

I may be wrong, but I thought that the maf sensor did not come into play until the engine had been running a few minutes. Not sure about the 97, but the problem sounds real familiar. Sounds like an ignition control module problem to me.

[atxjax]

So in open loop mode it should start and run until warm then all the sensors kick in?

I'll check out the ignition control module your talking about. I wish I had a donor car to swap parts around with.

[robertisaar]

I may be wrong, but I thought that the maf sensor did not come into play until the engine had been running a few minutes. Not sure about the 97, but the problem sounds real familiar. Sounds like an ignition control module problem to me.

you're thinking of the O2 sensor. the MAF is active as soon as the motor starts turning.

[atxjax]

I am getting constant spark on each cylinder but I wont rule out the ICM. First ting is first and i will change out the fuel filter.

[jeffreylane]

yeah, changing the fuel filter as well as cleaning the maf can only help. When mine started messing up, I started off by cleaning the maf and changing the fuel filter. I was amazed at how dirty the maf sensor was.