Cold start misfires plus rich condition *fixed* but why?

willSienna2000

Hi Scotty,

I just fixed and issue with my 2000 Toyota Sienna with 118k miles. I bought the car a year ago from the original owner with 114k. The car ran 40% lean with a vacuum leak(P0171) and cold misfires (NOCODE). 6 months ago I fixed the vacuum leak by reorienting the throttle body gasket. Gas milage improved from 15 to 20 mpg city.

Cold starts still caused misfires. When I put it in gear the extra resistance would make the engine misfire about 15-30 times. It ran fine after warming up, but 5-10% rich. I smelled gas when I removed an ignition coil, so I decided to change the plugs.

 Just now, I did the following work:
(1) Changed the old NGK single tip plugs for new NGK twin tip plugs. 
(2) Replaced the PCV valve and grommet. 
(3) Rerouted the three back plug wires to the ignition coils on the front bank. 

For the spark plug wiring, the rear bank is 1 3 5, and the front bank is 2 4 6. The Haynes manual says to connect plugs 2-to-5, 4-to-1, and 6-to-3.  This is how I wired them and it is definitely running better than before.

Looking at how they where, I thought that the wires were connected 2-to-5, 4-to-3, and 6-to-1, but would that even run at all?  I drove the car pretty much fine that way for 4k miles over a year (except for the cold misfires). 

I am wondering which thing fixed the problem? Any ideas? 

Thanks,
Will

Comments (1)
No. 1-1
Scotty Kilmer
Scotty Kilmer

Editor

How will run a few put the plugs slightly wrong order. Go to auto zone making print you out how it is supposed to be but if it's not that lot of times the fuel injectors need cleaning or fuel filter is clogged