Need some ideas about my idling problem

[Gaston]

My '95 318ti has 127k miles. It has always run fine but a month ago it started
starting up with a rough idle in the mornings, so I performed some maintenance:

New spark plugs (the old ones looked normal)
New fuel filter
Replace PCV-to-valve-cover hose which had a cut in it
Cleaned off the air filter

I thought the hose was it but the idle is still very rough every other time I start
it up. Recently it even had it miss as I accelerated on the highway. Something
is not right, yet it is an intermittent problem. Any ideas? What should I check next?

[Mallard]

it may be a sensor issue, but you will need to get the car fault read to see that

Also look around the engine for split air hoses. With the engine running, spray some carb cleaner around the engine. If the revs raise, then there is some kind of air leak

are there any unusual lamps lit on the intruments?

[Gaston]

Originally Posted by Mallard

are there any unusual lamps lit on the intruments?

Nope

[bbbmw]

Might be your plug wires.

[themightyquinn]

Gaston I have the same problem. The first start up of the day after she's been sitting, the idle will be really wonky. The other day it was so rough the car was shaking side to side for about a minute. Then it settles down to normal. I feel like every now and then I get a rough "blip" at idle once she's calmed down to normal. Could that be a missfire?

I've done plugs, wires, oil, fuel/air filters, and O2 sensors. She also seems down on power a little. My gas mileage has gone to sh*t as well...down on average 5-10 from normal.

Anyone have any insight for Gaston and me?

[Xenocide]

I had the same problem. My intake boot had a 2" hole in it, couldn't even tell until i took it off because it was right at an inside bend.

[lpcapital]

Could be several things, so here's some thoughts?

1) remove the ICV and clean it (along with the idle bypass in the TB). Use some carb cleaner or similar (I used Seafoam Deep Creep to clean out mine).

2) Do a full Seafoam cleaning treatment: it doesn't do magic but my idle was better afterwords

(I have no affiliation with Seafoam, just a satisfied customer)

3) Since you mentioned loss in MPG one thing could be the DISA. A way to test if it works is remove it, make a plate to cover the holes on the intake (I used a metal plate, drilled 2 holes and used piece of rubber from an old tire tube to make a seal). Start the car and take it up above 4500RPM. You should see the flap closing around 4200RPM and reopen around 3800RPM

4) I was having a leak in the air hoses going to injectors: they are used to improve the fuel atomization but with heat and time they crack.

5) I would also check the vacuum line going the the secondary air pump valve and the fuel pressure regulator

Unfortunately some of these things require removing the intake, so I would start with the simple stuff (point 1 & 2) move on to #3 and lastly 4 & 5.

Again these are just some random thoughts but I hope they can help