Erratic Idling

[blackhawk]

I would need some feedback from the gurus out there. The idling on my E34 is erratic. It is sometimes fast and sometimes slow but while this is going on, the engine is still smooth. I find it hard to explain but it is like some of those modified Wiras whereby you can hear their RPM yo-yoing up and down, only that mine is not so bad.I have done the usual checks like checking the vacuum hoses and they are all right. My MAF and throttle body is new when I got my car. The only things I have not yet check are the ICV, ECU and the inlet manifold gasket.Perhaps I should try cleaning my ICV first. Any other items I may have missed?

 

[bimmerman]

I'm no Guru, just a poor guy who loves his BMW and your problem could be different from mine but I just want to share with you my own experience which I solved myself.

My car idles fine at 600RPM but occassionally the throttle will bounce up and down between 600 to 1500rpm and sometimes stall when I least expect it. Damn dangerous.

I first suspected the idling valve as this is an idling valve symptom. Then upon DIY inspection I noticed that my brake pump air hose had hardened and no longer felt like pliable rubber. It was hard like plastic and air was escaping through it's edges even when clamped hard.

I went and bought a new hose and installed it myself.

Cost: RM15
Problem: Vacuum leak through the brake hose
Status: Solved

So, go for the cheaper fixes first. Vacuum leaks can come from anywhere in your vehicle where you least expect it.

Oh, and the brakes also feels more responsive now too.

 

[bazet]

I tried these steps..
1. DIY ,clean up the ISV using WD40 / rendam with petrol overnight
2. service the throttle body fro Rm60 ans set back the TPS position
3. DIY, open up my AFM and clean it using thinner/alcohol using soft cloth

I will do item 1 once a month. But teh tremendous result comes from item 3.

Actually mine is M20 engine

 

[blackhawk]

Thank you bazet and bimmerman.

Most of the hoses were already changed before I got my car. Looks like I have to run through all the hoses and look for loosely fitted hoses too. Come to think of it, my brakes are not that responsive too. A bit hard.

However, to make it more difficult to diagnose, when I turn on my aircondition, the erratic idling is not that apparent. :dunno:

 

[bimmerman]

Originally posted by blackhawk@Jun 29 2005, 09:16 AM
Thank you bazet and bimmerman.

Most of the hoses were already changed before I got my car. Looks like I have to run through all the hoses and look for loosely fitted hoses too. Come to think of it, my brakes are not that responsive too. A bit hard.

However, to make it more difficult to diagnose, when I turn on my aircondition, the erratic idling is not that apparent. :dunno:

Well the problem on my car happens especially when the aircon compressor cuts out! Then the revs would start bouncing. Blip the throttle and it would idle back to normal. So my problem sounds very similar to your problem! Good luck brother. I think the answer could be in the hoses.

 

[bazet]

My bimmer start to have erratic idle when my aircon ECU gone dead ( RM500 replacement )....

Normally, when I turn on the aircon, the RPM will raise a little bit, but since the ECU was gone, when I turn on the aircon...it will drop..and that cause the erratic idle. The solution, I have to live with high FC, adjust the idle at 1000rpm..and when the aircon turned on..it will drop to 800rpm...

 

[c-square]

Originally posted by bimmerman@Jun 28 2005, 07:57 PM
I'm no Guru, just a poor guy who loves his BMW and your problem could be different from mine but I just want to share with you my own experience which I solved myself.

My car idles fine at 600RPM but occassionally the throttle will bounce up and down between 600 to 1500rpm and sometimes stall when I least expect it. Damn dangerous.

I first suspected the idling valve as this is an idling valve symptom. Then upon DIY inspection I noticed that my brake pump air hose had hardened and no longer felt like pliable rubber. It was hard like plastic and air was escaping through it's edges even when clamped hard.

I went and bought a new hose and installed it myself.

Cost: RM15
Problem: Vacuum leak through the brake hose
Status: Solved

So, go for the cheaper fixes first. Vacuum leaks can come from anywhere in your vehicle where you least expect it.

Oh, and the brakes also feels more responsive now too.

bimmerman.... where is the brake pump air hose? Mine is a e36 318i and am having pretty much the same symptoms you describe.

 

[flash]

Sigh, mine too. :beaten:

 

[525iBoy]

you guys forgot to check your
1) dist cap & rotor
2) spark plugs
3) valves adjustment.

Provided a basic tuneup is done (oil, filters, plugs etc.), sensors all ok & IF engine internals are in good condition the car will run rough due to typically one or more of the below
1) ignition problem (quite common)
2) fuel problem (not normally andissue)
3) air leaks (very common on older cars) -
Itms 1 + 3 the most common,
4) sensor problems - oxygen, AFM, idle valve (usually only idle V is the problem)

for I), check the plus and wires and dist cap& rotor
for 2) buy a GOOD fuel injector cleaner, change your fuel filter, chk you fuel pump relay
for 3) get a POWER Flashlight and look for hardened hoses. esp chk all hoses, hose clampes esp at joints and those near hot exhaust/engine parts
for 4) clean or buynew idle valve (300 or so)

If not the above then generally you are in DEEP S__ __ __ and will probly need to spend major $$ (ie. above 1K) on an AFM, or engine rebuild, head overhaul as you may have low compression, worn valves, worn cams, bearing etc etc.

 

[bimmerman]

Originally posted by c-square+Jun 29 2005, 10:09 AM-->QUOTE (c-square @ Jun 29 2005, 10:09 AM)