I have about 12-1300 miles on my 2003 400i auto, I have done the tranny trick and muffler mod, rejetted it last year and my plug was the correct color, and it ran great last year, and except for a minor glitch this year has been running good this year also, until this weekend, as long as i cruised at lower revs (about 30 mph or lower) it ran good, but as soon as I had to pin it or put it under load (going up a hill, or in mud) it would sputter something fierce and would backfire when slowing down from any speed pretty much, thought it was maybe lean so I played with the choke to give it a bit more fuel, no difference, my first thoughts were water in the gas or a bad plug, but I didnt have a spare so I couldnt change it. The dealer did adjust my valves after break in, and told me that the intake was a bit to tight at the time so they adjusted it accordingly. I also checked the oil to make sure it wasnt full of water but it wasnt. So has anyone had this problem and can anyone offer some suggestions? I havent checked anything out yet except the oil. Oh yea and it was tricky to start unless I put in into neutral.

 

Hey doober
I can tell you one thing if you have read my post latly after I fix the cat i will be reversing the tranny trick. Mine did that once over the winter and. I don't know if the two are conected but just in case pull your head cover and take a look at the cam [the two craddles] and see what they look like? Just in case [img]i/expressions/face-icon-small-wink.gif[/img]

 

Yea Anton I read your post, that sucks man, but I cant see the tranny thing causing it. what were some other symptoms of your problems?

 

Not much, the ride before I could hear a ticking sound thought it might be the vavles? And overall a small drop in top end speed. That would be it, now my dealer said that most guys would run them untill it was too late as I was able to pull it out wash it go down the road blow dry[img]i/expressions/face-icon-small-happy.gif[/img] and drive it back in. he asked me to check the pistion on it because most probably the tick sound was the piston hitting the valves. I hope not, all and all I should be ok as far as a new piston go's. will have to inspect it.
I will change to a syntetic oil. for sure

 

doober, my 400 backfires and acts similar to that. It backfires and lacks a little topend speed. It usually happens when I forget to take the choke off and take off down the trail.

So you might want to check your choke and the starter valve? in the carb. I think the carb also has a low speed and a high speed jet so one of those could be plugged with something.

 

I am going to pull off the float bowl and check that, and while I am at it will check the jets inside, but cant do anything till friday. Thanks for the responses. When I did have it at the dealer a while ago they found a fly inside the carb?? How it got there is still a mystery to me[img]i/expressions/face-icon-small-confused.gif[/img]