89 240 no idle or constant RPM

theghoul · Post by **theghoul** » 26 Jul 2011, 22:41

Hi! Nice Site! Have an 89 240 with 2.4 system, I believe - ran fine for months after I bought it - all of a sudden no idle, and no ability to maintain any constant RPM - only way to keep it running is to keep pushing gas pedal every second or two. Checked the air valve with power supply on bench and cylinder inside turned with application of 12 volts from a power supply- connections on all look good. Tried to test terminals on throttle pos. switch - Haynes manual says to disconnect harness and measure certain terminals to ground- got no reading on any of the 3 to ground (at battery) but wondered- is this switch connected to ground on the inside or is this incorrect instructions to test this switch? Any ideas on this problem are welcome - its a great car but not right now! bob (theghoul)

Post by **billofdurham** » 28 Jul 2011, 11:56

Welcome to Matthew's Volvo Site.

Nice Site!

We think so, thank you.

Have you checked for fault codes using the On-Board Diagnostic (OBD) unit in the engine compartment?

Switch ignition off. Disconnect the connector to the throttle switch. The centre terminal on the throttle switch is the earth (ground). Test with an ohmmeter between the centre terminal and the terminal that takes the yellow/white wire (from ECU terminal #2). With the switch closed the reading should be 0 ohms. Gently open the throttle. Reading should be 2,000 - 3,000 ohms. Now check between the centre terminal and the third terminal 9from ECU terminal #3). Reading should be infinite. Open the throttle wide. Reading should be 0 ohms.

Bill.

theghoul · Post by **theghoul** » 28 Jul 2011, 15:34

Yes, did that - got no reading to ground - is the center terminal of the throttle switch internally grounded or does it need the wire harness connected to get the ground? When i checked, no terminal read continuity to ground -with the harness disconnected - I am reading the terminals of the thr. switch, not the harness itself - thanks for your help!! bob

Post by **billofdurham** » 29 Jul 2011, 11:47

is the center terminal of the throttle switch internally grounded or does it need the wire harness connected to get the ground?

This test is to see if the throttle switch itself is working. It does not require the centre, nor any other, terminal connected to earth. If the switch is good you will get the specified readings.

You can also listen to the switch to determine if it is working and correctly adjusted. Open the throttle and you should hear a click immediately it is opened. If the switch seems to be out of adjustment loosen the mount screws and turn the switch slightly clockwise. Turn the switch counter- clockwise until you hear a click. Tighten the screws and check the setting.

Bill.

theghoul · Post by **theghoul** » 29 Jul 2011, 13:34

Yes, but the Haynes manual does not say to connect the other lead to the center terminal - says to check to ground. I do hear the click when throttle is just opened - connections point down so very hard to get two meter leads in to check the 3 terminals - might have to remove the switch - thanks, bob

theghoul · Post by **theghoul** » 02 Aug 2011, 12:58

As an update, when RPM is 1000 or less its really hard to keep it running - when up around 2000 RPM its a bit easier- thanks, bob

theghoul · Post by **theghoul** » 10 Aug 2011, 09:04

Another update- switch does not have internal ground - took it apart and found this - was full of oil from a time when engine got doused with oil due to dipstick not in for a day or so before I bought it - cleaned the oil out and hope this was the problem! bob

Post by **billofdurham** » 11 Aug 2011, 11:41

Keep us updated, please.

Bill.

theghoul · Post by **theghoul** » 28 Aug 2011, 19:37

update- found that when I took out fuse for main fuel pump it had no effect - had the shop next door install one (Airtex, unfortunately!) and they mentioned when I picked it up that I could use an air mass sensor also- ran OK but hesitated at start of acceleration- also idel was high - after resetting idle and TPS- sounded OK - but I found that the air mass sensor was disconnected! When I plugged it in it would not run - pins 2 to 3 read about 4 ohms- any ideas? Wont be going back to this shop - thanks, theghoul

Post by **phils94850** » 29 Aug 2011, 03:30

Sounds like you have a faulty air mass.