I have a 2000 Discover II with 122,000 miles, got codes to replace MAF and Bank 2 sensor 1 when it could not pass Mass. inspection. Since doing that work now she coughs and sputters badly when cold. Have to pull over and rev the engine up to 3.5 or so before it smooths out. After that she runs well.
Any thoughts?
THanks

 

after you rev it it runs fine, or after 3500rpm as in above that it runs fine, but below still rough?

did you replace the MAF or o2 sensor? should be the passenger side o2 precat (upstream) position.

do you have a check engine light currently?

if not, do you have access to an obd reader to watch the MAF and o2 data streams?


id start simple first and check the connections at the MAF and o2 sensors again... and as rovermastertech showed me, follow the maf wire back to see if it is squished, crushed or otherwise abrased by clips or other components of the motor to see if its cut off or grounded somewhere causing incorrect low voltage readings.

pull the air filter box off and visually inspect the airbox for grease, grime, excess first etc... a sign there and it might mean a dirty MAF, check that next reguardless. the metal "pin" that sticks down the middle inside the maf should be clean. dont touch it with anyhting, but if it looks sheened over with crud use small amounts of MAF cleaner, just use VERY little aerosol pressure from the can, these are very sensitive components... dont drown it, but more importantly dont send too much force on it from the can as it can push/bend out the pin etc.

other then that itlll depend on if you have any codes. the maf and o2s control the fueling, and that will cause missfires and rough running that seems to imporve with rpm, but continue soon after.

does it do it cold as well? while cold the computer uses a preprogrammed fuel trim in whats called open loop where it ignores data from the o2 sensors. if it runs fine cold and only gets worse as it warms up, you can attribute somewhat that the o2s are definatly involved and its not an ignition problem somewhere.

 

Thanks for the post. I did replace MAF and the bank 2 sensor 1, passenger front.
If I drive it a little bit a mile or two and it warms up a bit it is fine. As long as it is warm it runs well, just if you **** it off for a while you have to go through the same issues again.
Even at idle or low rpms it is fine after a few minutes, problem is only when it is cold.
Will look through your suggestions this weekend and see if I can get lucky.