rough idle and rough drive

[ahalfacre5]

ugh.... I started up the car this morning and it idles like poop. took off down the road and it lurched back and forth. got to my friends house and pulled off (starting from the fan back) 4 plug wires because it was missing, and while the car was running I plug then back in one by one.. and it ran just the same with the plug wires off as it did on. the spark plugs are brand new. I do know I need a valve cover gasket but it isn't leaking bad enough to not drive. so my question... whats wrong? what needs to be replaced? and how much am I looking at for parts?

thanks in advance - adam

[dnguyen1963]

There are thousands of threads on rough idle and all of them points to vacuum leaks. Please spend a couple of minutes searching the forum before posting the same question. Thanks.

[ahalfacre5]

There are thousands of threads on rough idle and all of them points to vacuum leaks. Please spend a couple of minutes searching the forum before posting the same question. Thanks.

thanks but the problem is not a vacuum leak. its something with ignition but im not sure what which is why I posted my question.

[ahalfacre5]

its actually a m20 1987 325is

[dnguyen1963]

thanks but the problem is not a vacuum leak. its something with ignition but im not sure what which is why I posted my question.

From the description of your valve cover gasket I am sure that it is due to vacuum leaks. Please have a smoke test perform on your car before you spend money on unnecessary parts.

[ahalfacre5]

From the description of your valve cover gasket I am sure that it is due to vacuum leaks. Please have a smoke test perform on your car before you spend money on unnecessary parts.

I stand corrected.
I appologize for the blunt reply. But my question is, how (because I know little about BMW's ) does a vacuum leak cause 4 or more cylandirs to misfire?

[jlevie]

A intake leak can cause all of the cylinders to misfire.

[dnguyen1963]

No apologies required, but if you do not take care of the vacuum leaks you will be chasing these problems forever.

[ahalfacre5]

car wouldnt start this morning >_<

im sorry in advance for this because it may get confusing. but i was looking around today and the spark plug wire for the spark plug closest to the pasengers seat (farthest to the back) had a loop of rubbery looking thing with a wire attached that ran down to near the diagnostic check. it connected to... something (it had three plugs in a little case looking thing). i have no clue what. but it was on the drivers side. anyway the rubber that wrapped around that plug wire had almost completetly broken. I have no clue what this is called, or what it does (my guess is a timing signal), but that would explain it right?

[Ceeker]

yup..you're right...timing signal is picked up from cyl 6. if that thingy is broken -that is your problem. replace ign wire 6 and you should be good to go! or just changed the entire ign wire set. Easier if you have a spare set then the unclip the plastic surround and run another through it. it's a bit of a pain in the ass but possible.

since you mentioned the valve cover gasket being iffy. spend the 5-10 bucks and buy a new one as added measure.

[ahalfacre5]

yup..you're right...timing signal is picked up from cyl 6. if that thingy is broken -that is your problem. replace ign wire 6 and you should be good to go! or just changed the entire ign wire set. Easier if you have a spare set then the unclip the plastic surround and run another through it. it's a bit of a pain in the ass but possible.

since you mentioned the valve cover gasket being iffy. spend the 5-10 bucks and buy a new one as added measure.

where is the cheapest place to get a set? or at least the one wire? i cant find it on rock auto jegs or autopartswarehouse.com. for under $100 (the wire plug set or single wire not the gasket)

[ahalfacre5]

so i unplugged the plus sensor from the car... turned over but god is it running rough.. still only firing on about two or three plugs... and btw i checked the distributor cap and it looks good... so i should be right in thinking that once i replace the pulse sensor, it should run fine right?

[Beach Bum]

I'm having the same type of issue: Sudden onset of all-cylinder misfire, popping, no power. I have checked for vacuum leaks by spraying an unlit propane torch around all vacuum lines and the valve cover with no change in idle, meaning no vacuum leaks. I'm going to attempt to limp the car home today and swap out the coil with some of the one's I have sitting around to see what that does. I did a TB/WP job about a month ago with a new rotor/cap so that's out of the question. I need to get a gauge on the fuel rail to check pressure too.

The kind of vacuum leak it would take to make the car do this anywhere but idle would be clearly audible.

[Beach Bum]

Figured out my issue. Signal wire off the #6 spark plug wire is a bit loose. I need to hit it with some contact cleaner when I get home. A new wire set is on the list.

[Beach Bum]

New wire set is going in today, I will post a trip report tomorrow.

This morning the car was still cutting ignition occasionally over bumps. I noticed that the tach would drop when the ignition would cut. After some reading I discovered that the tach signal comes off the coil. I'm pretty sure that the coil trigger is the CPS(Crank) and has nothing to do whatever that signal wire off the #6 does (EDIT: It seems it's a fuel injection sequencer). I'm pretty sure this has to be the CPS, but the wire set on there is old as hell anyway so hey why not?

Like I said, trip report tomorrow.