Okay...I replaced my breather system, plugs, wires, dist cap, rotor, air filter, cleaned the throttle flapper, made sure everything is plugged in and checked all the hoses I could find for leaks using carb cleaner. Also checked the intake manifold using card cleaner. Can't find what the heck is causing DTC P0505 (Idle Air Control System fault).

After reseting the code, the light stays off until I put the car in park and let it idle for a bit. The idle lopes approx. 50-75 rpm.

I've got a 98 V70 non-turbo with 108K. This code did not flash until after I replaced the stuff mentioned above. Any ideas on what else to check? I find it interesting that VADIS doesn't even list P0505 as a code, at least I can't find it in there. thanks

 

The Volvo code will be a different code.
Did you by chance switch the throttle switch and idle motor plug?
Are but hoses sealing good?

 

Just got back in after removing the IAC and cleaning it with a solvent and rechecking the hose fittings. Plugs are not switched around. After unplugging the battery for a bit and then restarting, the code doesn't come back on for a few miles and only after I shut the car down and restart. The light flashes about 15 seconds after restarting. Not sure, but it seems that the light comes on after the restart when the idle settles and the tach drops below 1000 rpm.

Any way to tell what Volvo code the P0505 from the Actron scanner equates to?

 

I will have to try to look tomorrow on Alldata for the crossrefrence.
Maybe someone here has alldata and can look it up.

 

P0505 = Adaptive Air Idle Trim (Upper/Lower)

Volvo DTC Code EFI-233
Possible source(s)
Upper limit:[*]Clogged air cleaner or air intake.[*]Contact resistance in terminals.[*]Incorrectly adjusted throttle body.[*]Defective idle air control (IAC) valve.
[ul][/ul]
Lower limit:[*]Air leakage.[*]Contact resistance in terminals.[*]Incorrectly adjusted throttle body.[*]Defective idle air control valve.
[ul][/ul]
Fault symptom(s)[*]Idling speed too high or lo

If you need additional troubleshooting assistance, send mea PM and I'll email you the detailed procedures.

 

PM'd you for the details....thanks!

 

Check your email.

 

Oh yeah, I'm feeling the frustration! I have performed extensive leak testing...positive air pressure with soap solution, propane and a tachometer, and a vacuum gauge hooked plugged directly into the intake manifold. No sign of a leak, nada, nothing... Yet, the idle still lopes and the code P0505 keeps popping up. I don't think the valve has gone bad since it worked before I starting screwing with the car, and testing shows it to be working fine. I'm at wits end... Tomorrow I'll be pulling the intake manifold off, again, and restepping through the process of replacing the breather system....hopefully something will turn up...

 

Maybe mass flow sensor is going bad.

 

I'll test it, but I can't believe that it would go bad right after I messed with things....I'm way leaning towards me being the causal factor, and probably some stupid rubber plug that has a hairline crack

 

Keep us updated.
Thanks for all the updates already.

 

tech,
need some more options... I put a new intake manifold gasket on, swapped out one of the hoses on the oil separator, replaced hoses and nipples on places that seem unrelated to my problem with the idle air control system fault, rechecked my spark plugs, and cleaned the MAF sensor.

what's next...what else could cause the fault? could a messed up TPS cause it? is it time to fork out the $150 for a new IAC?

 

I would try to find a set of both used at a Junk Yard from a 850 or S70 and try them.

 

what year range for those vehicles apply to my 98?

 

I would say 1995 to 1998.

 

[hr]thanks! Looks as though Ebay has some pretty good used parts prices as well

 

Still hunting down the source of my P0505 code. Looked at the new spark plugs I put in and remembered the difficulty I had removing one of them and the feeling that the new one did not go in all the way. Didn't see any leakage with testing, but if the plug isn't fully seated, could that possibly cause the code, in some strange backdoor way? Seems as though I'll need to re-thread it. Do you know the spark plug thread size...looks like the standard options for a thread chaser ar 14 and 18mm. Any suggestions of thread replacement if the thread chaser doesn't work...helicoil, timesert, etc?

 

Not sure if the plug not being seated all the way will do it or not.

Not sure of the size off hand. I made my own thread chaser last time from an old spark plug.
I cut a few groves in the end of an old plug and used that.

 

Let me re-phrase my question from yesterday... Do you think that an air leak at the spark plug could affect idle speed? I don't know if the car is sensing that the amount of air being exhausted is less than the amount at the intake because of the leak and if that difference is causing the idle fluctuation.

Oh...and the plug size is 14mm. The KD thread chaser requires a a socket that is too big for the engine. I bought a cheapie spark plug and cut grooves into it and cleaned out the hole. Still didn't get it all the way since I'm still blowing soap bubbles with the car is running.

 

That may be affecting the idle.