'92 240 surge at idle

happenstance · Post by **happenstance** » 04 Nov 2011, 17:51

hello- was hoping that this pattern of symptoms would ring some bells as to what my problem could be- have a '92 240 sedan, 114k. it was surging at idle, and intermittently stalling when coming to a stop as i would release the gas pedal. i took it to volvo, they said the diagnostics noted a problem with iac, and they noticed the throttle body was very dirty. they wanted too much for the iac work, so i went with just a TB cleaning, which seemed to work for a few weeks, no issues. then, same symptoms reappeared, so i decided to try and clean the iac. i did so last week ( it wasn't that dirty), and the car was running and idling really smoothly for 6 days, but the symptoms reappeared again today,- just surging at stops and a bit of hesitation upon acceleration, no stalling yet. did i not clean the IAC well enough, or does it sound faulty and in need of replacement perhaps? any other ideas? thanks

happenstance · Post by **happenstance** » 04 Nov 2011, 19:57

update: i took the car out after the first posting, and when i put it in park at my destination the rpms went way way up. then on the way home, had to make a stop, so i let run in park for about 10 mins- it sputtered and almost stalled once, then at the 8 minute mark the check engine light went on and stayed on. what gives????

Post by **billofdurham** » 05 Nov 2011, 12:14

Have you checked to see which fault code(s) have been set? You don't need to go to the Volvo dealer to do this. There is an On-Board Diagnostic (OBD) unit in the engine compartment and instructions for its use are pinned at the top of the forum.

With the Check Engine Light (CEL) on you must have at least one code stored. Do the check and let us know the result.

Bill.

happenstance · Post by **happenstance** » 06 Nov 2011, 11:02

Thanks for the reply, Bill- i was able to get 3 codes,- but just a side note, before i got the codes, while the car was running, i pulled out the wiring from the MAF to see if the was a difference in idle quality- there seemed to be a slight improvement, but by no means was it smooth. anyhow, i don't know if by unplugging it would then bring up codes for the MAF- ....what i got was- 1-1-3, 1-2-1, 2-3-2. any ideas/ suggestions? thanks

Post by **billofdurham** » 06 Nov 2011, 11:50

Pulling the MAF wiring with the engine running would give codes indicating a MAF fault which all three codes do, along with other things. The OBD can only store three codes and it may be that these weren't the original codes.

I would erase the codes and run the car to see if the CEL comes on again and do another check if it does. In the meantime the attached shows how to check the MAF for earth (ground) and voltage.

240 LH2.4 MAF sensor tests.pdf: (322.42 KiB) Downloaded 481 times

If the same codes re-appear you can buy a can of MAF cleaner at any car parts shop and spray the MAF to see if it improves. However, bear in mind that these codes also indicate possible problems in other areas and cleaning the MAF may not be the answer.

Keep us updated so we can help.

Bill.

happenstance · Post by **happenstance** » 06 Nov 2011, 12:05

thanks Bill,- how do i erase the codes, and get the CEL to go off?

Post by **billofdurham** » 06 Nov 2011, 12:20

Look at page 9 of the instructions - "Erasing Diagnostic System Memory."

Bill.

happenstance · Post by **happenstance** » 18 Nov 2011, 09:14

Hey Bill- i erased the diagnostic memory as per the instructions almost 2 weeks ago, also disconnected the negative terminal on the battery for a few minutes, and have had no symptoms and no CEL, the car has been running well, at least for now. Seems that with the throttle body cleaning, and my IAC cleaning, the system had to be reset due to disabling the battery, and perhaps thats why it ran well for a period then after a few weeks resumed the same symptoms (?) What would cause a reset to clear up my idle problems as described above? Thanks for all the help!!

Post by **billofdurham** » 18 Nov 2011, 12:32

The OBD is not intelligent enough to know when a repair has been done. Having said that it is a great piece of kit for initial diagnosis.

If the codes aren't erased the control unit thinks there is still a problem and runs the system to minimize any possible damage. Erase the codes and the control unit resumes normal service.

Bill.