Misshift Causing Rough Idle

I have a 95 BMW 325ic with the 2.5L.

Today as I was getting onto the highway and the two lanes were merging I gunned it and shifted from 3rd to 4th (or what I thought was 4th). I either didn't get all the way in and grinded gears or somehow shifted into 2nd and redlined it bad. I got that jerk forward that you get when you shift into too low of a gear and grinding sound.

After that I noticed a BAD idle problem that would sometimes kill. I drove the rest of the way home and after awhile it seemed to get better but not quite to how it normally idles. I had no problems driving, just idling.

I am hoping this was just it reacting to the poor shift/redline and it will calm down after it sits and cools or whatever it needs to do. Anyone else ever experience this problem? And what should I expect and check on?


Thanks.

It wouldn't stumble while idling after an over-rev if you hadn't damaged something. My guess is that you may have bent a valve.

Ah, fun. What's the cost to get that done? Also the cost of doing it myself and how hard would it be?

i would do a compression test first to see if the numbers are off. i would do a static (engine cranking speed), as well as running (you can do this, just don't run it more than a few seconds to get the compression readings).

hint: the 1st sweep of a static compression *should* be = to the running compression number.

another test that you could do would be to do a leakdown test, but you would need compressed air and the leakdown manifold. you could probably wind up renting these from somewhere if needed.


of course there are always potential unseen damages that may be uncovered upon removal of the head, but in general, figure at least the cost of a headgasket.

additional funds will be needed for a valve tool, which is going to be a bit different than the ones used for 'conventional' ohv engines. bmw, as well as many other newer designs have the valves recessed rather deep, so the foot of the spring compressor will need to be specific to the design application.

then there's the valve seat/face fitment that will need to be remachined, and i'd be hard pressed to find a machine shop that would only do the valve(s) that were bent. they usually do them all.



df

What am I looking at for price?

I just took it out for a short drive. It's been a few hours. I noticed no idling problems at all but I did smell gas. I don't know if that helps with diagnosis.

no, not really....

where is the fuel coming from??

as for price, probably in the neighborhood of 1500-2000 depending upon labor rate and parts, less if you are capable of repairing it yourself. there's really no way to give an accurate price, which is why they are called 'estimates'. like i said before, there could be hidden damage that may not be seen until the head comes off.

do a compression check at least and see ifthe numbers are wonky from each other. if so, then it looksl ike you'll be looking to get the motor ripped apart or find a replacement unit to drop in there.




df

Well, I'm going to have to take it in and get it looked at then but if it were a bent valve, wouldn't it not get any better after sitting? I sure hope I didn't mess it up as bad as you are speculating.

jtruell, you are about to find out why they call that a "money shift".

It's unlikely the problem is gone. Test it like df and ZeGerman said.

Sad. Most cars I've driven will push hard to keep you out of too low of a gear. This isn't they case on the 3 series?

i have driven cars with bent valves that would probably have been overlooked had it not been for the pcm recognizing a variation in the crank speed and flagging a po300, po302, and a po304. hooking a vacuum guage to it verified an intake fluctuation that pointed toward a burnt valve. off idle it ran great.

the tech that had 'fixed it' had just finished putting a cam seal in on the intake camshaft. (i know this because i diagnosed the leak, but was buy fixing a different car when it came back the following week). he came up to me and asked if i had noticed the check engine light was on in the car when i was looking for the oil leak, and had hinted that he wanted me to say 'yes'.

i knew something was up when he asked me this as he had been trying to set the timing belt and couldn't quite 'get it right', and wanted my help to hold the sprokets in place (v6 dohc). he apparently did not know we had the engine specific cam tools to lock the cam sprockets in place to get the timing correct. i showed him the tool kit and he had the thing back together in a matter of a few minutes. thisis when he asked about the cel...

once he got the head off i took it to the parts tank and filled the combustion chambers. with the cams out, only the #6 cylinder held fluid. there were no other visible indicators of bent valves observed during the inspection.

so, yeah, a bent valve can be ever so slight. but it won't 'go away'. it'll simply be more difficult to detect under certain circumstances.


what would i suggest at this point?? you could get it checked out, or you could do a compression check and vacuum guage check to see if there is something going wrong yourself, or, you could simply drive it until it falls apart....




df

I am going to get it checked for sure. I don't want this to be the little thing that slowly kills my BMW. But I am hoping it is something simple like flooded injectors like I am hearing from some other people. Thanks for the input. I am keeping my fingers crossed. Hopefully, I have avoided the "Money Shift" (by the way, awesome term).

ummm....yeah, ok...no such thing as 'flooded injectors'. they're simply a metering device. my money is on the money shift.



df

I'll let you know what the diagnosis says.

Good luck!

Thanks, I'm gonna need it!

Well, took it in today. They looked at it and noticed the spark pulls the dealer put in were ****. They said they are good for about a few months and then go to ****. They put in new ones and the car runs much better. They also noticed the gasket may be bad and if the problem comes back they will look into that and run more test. But for now it seems much better.