1998 S70 GLT idles high after Timing Belt change & Tune Up

lamplighter55 · Post by **lamplighter55** » 23 Feb 2010, 17:49

So proud I was able to replace the TB and tune up my 1998 S70 GLT (w/ only 65K) with info/pics from this website. The engine started fine and ran well while in the garage. Took it to highway and "Check Engine" light came up within a few minutes of driving. Noticed idling really high at 1500-2000rpm. (The car was going at 40mph without any pressure on the gas pedal) OBD displayed error codes P0101 (Mass or Volume Air Flow Circuit Range) and P0505 (Idle Air Control System). I went ahead and cleaned the MAF sensor and Idle Air Control Valve (again with helpful hints from this website). It ran smoothly at 800rpm for a while. Shut the engine and re-started after 30 min. it goes back to 2000rpm. (Cleaned the IAC valve a 2nd time, didn't changed anything) I rev the engine a few times, it drops to 800rpm and immediately returns to 2000rpm. Did I mess up with the timing belt or spark wire?I'm about to pull my hair out, any helpful advice is appreciated. Thank you.

xb corp · Post by **xb corp** » 23 Feb 2010, 18:27

what solution u used to clean the MAF & TB? it should be contact cleaner, like those you use to clean up electrical connections, self-dry type. not WD40 or degreaser...

Post by **Ozark Lee** » 23 Feb 2010, 18:32

There is a certain amount of weirdness that should be expected after major changes while the ECU re-learns things but your situation sounds like a real problem - not serious but a problem none the less.

My gut says that you have a vacuum leak, grab a can of carb cleaner and spray the vacuum joints and the gasket around the throttle body and listen for an idle RPM change.

If you do get an RPM change then you are in the area of the problem.

...Lee

lamplighter55 · Post by **lamplighter55** » 23 Feb 2010, 19:55

I used MAF sensor cleaner for the MAF sensor and air in-take cleaner for the IAC valve. Did manage to clean the throttle air in-take area and the IAC valve.

While trouble-shooting (with the engine running), I pulled the electrical plug to the MAF sensor & the engine started to choke. I restored the electrical connection & the engine ran smoothly (though @ 2000 rpm.) Then I pulled the electrical plug to the IAC valve and the engine also began to choke. I guess my MAF sensor and IAC valve are working fine, right??

Lee, I have also tried the "carb cleaner" technique as suggested to locate a possible vacuum leak. However, didn't notice any RPM change. Perhaps I didn't do a thorough job; will try again tomorrow. Thanks

Post by **jblackburn** » 23 Feb 2010, 22:33

If you can't find any obvious cause, maybe you cured a vacuum leak that the ECU was used to running with, and is still running with those settings. Pull the plug off the battery & reset the engine adaptives, and see if it can figure out how to idle normally.

gdog · Post by **gdog** » 23 Feb 2010, 23:01

Maybe a silly question but did you double ck the cam timing?

If one of the cams slipped a tooth, it could affect the idle speed...

lamplighter55 · Post by **lamplighter55** » 24 Feb 2010, 13:42

I pulled the battery and forced the ECU to reset the engine adaptives. Used the "cab cleaner" technique a 2nd time & couldn't locate a leak. It is still idling at 1500 - 1700rpm. The error code I continue to get is P0505 (Idle Air Control System). I believe I have installed the timing belt properly (too tired to double-check that night after TB change and tune up job). If the TB/cam timing is off by one tooth as suggested by gdog, should I be getting other error codes to show that the "timing" is off? Just wanted to make sure before I take everything apart again to verify my TB/cam setting. Thank you all for your input.

Post by **Ozark Lee** » 24 Feb 2010, 17:01

This definitely sounds like an IAC valve problem. Does it buzz with the key in position II? Is the hose from the IAC valve good - You should have picked up on that with the carb cleaner test but just asking.

...Lee

lamplighter55 · Post by **lamplighter55** » 26 Feb 2010, 14:25

Yes, the IAC valve buzzes when the key is in position II. I notice if I manually turn the throttle cable wheel pass its normal stop position (approx. 1/4"), the engine will idle smoothly @ 800rpm. Should I be messing with this cable wheel at all?

9394volvo850s · Post by **9394volvo850s** » 26 Feb 2010, 19:57

lamplighter55 wrote:Yes, the IAC valve buzzes when the key is in position II. I notice if I manually turn the throttle cable wheel pass its normal stop position (approx. 1/4"), the engine will idle smoothly @ 800rpm. Should I be messing with this cable wheel at all?

so with that you have found one of your problems. the rod that goes from the throttle to the wheel is adjustable so that needs to be fixed.