Lopey idle

Alecw81 · Post by **Alecw81** » 12 Apr 2011, 11:50

After installing the silicone intercooler hoses, my idle sounds like I have a big lopey cam. Not necessarily a rough idle, just an unusual sound.

When coming to a stop, my revs drop to about 500-600 rpm, but settle at 900-1100, and there's a distinct "womp" noise that is rpm dependent til it dissipates/disappears around 2500 rpm.

Any ideas?
All hoses are on tight and clamped well, withe the exception of the AIC outlet. I have a new hose on order as the old one is hard as hell and leaks even with a tight clamp.

Post by **jblackburn** » 12 Apr 2011, 12:53

Might try to reset the computer adaptives via yanking the negative battery cable.

My car does that idle dip thing whenever there's a vacuum hose loose but it hasn't yet realized it to glare that ugly orange light at me.

Does the engine feel about the same?

Alecw81 · Post by **Alecw81** » 12 Apr 2011, 13:07

The battery was out while I did the work.

The engine pulls harder.

Post by **jblackburn** » 12 Apr 2011, 13:37

If the battery was just disconnected, that idle will happen for a little bit as the car figures it out again.

No idea about the noise, maybe you're just hearing the turbo fins a little more now. Volvo 5-cyls and Saab Turbos have a distinctive 'wubba wubba' noise at idle (it's actually more evident on the NA motors).

linuxsuperuser · Post by **linuxsuperuser** » 13 Apr 2011, 16:21

I had a problem like this that appeared after performing a tune-up. But it did not go away and I would get sporadic Check Engine with a P0505.

After looking for vacuum leaks and buying a new expensive IAC, Front and Back O2 Sensors, New Ignition Wiring, New Evap Hosing and solenoid, PCV system change, Fancy OBD2 tool, countless junkyard sensors for swap testing.

The Problem was actually corrected by installing a new B+ fuse box wire that connects to the battery, the old one was not rusted but still resistive and showed a significant voltage drop.
Read about this here: https://www.matthewsvolvosite.com/2011/0 ... e-box-diy/

It's easy to check the cable with a Volt Meter, It could catch a serious headache. The Voltage Drops and Surges can alter the sensitive correctional information needed to ensure a proper idle.

Good Luck, I hope that new IAC Hose smooths out your idle, Mystery Problems are the worst.

S70 1998 NA with ~183,000 Miles