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Car Forum / Volvo Cars / December 2005re: 1993 240 DL Wagon rough idle on start
Hello All: Weather has turned a bit chilly here (about minus 10 degrees farenheit last night.) The car is in an isulated but unheated garage. Started it up this morning and as usual it idled very roughly as if running on only a cylinder or two. Was in a hurry so pulled it out of the garage and was going to let it warm up, but then realised I'd forgotten to close the bathroom door (essential with several terriers in the house) so shut it off and went back in the house. Came back out a minute later and it tried to start and nearly fired but didn't. After waiting a minute or two it started and then idled roughly for a minute and I was on my way. By the way, once the temps fell below 20 degrees farenheit the rough idle was an everyday situation--but generally only for a minute or less. Vehicle in question is a US model and the alternator and battery are new and starter performs flawlessly. Recently tested the AMM and it seems good. Goes without saying before winter I replaced plugs, filters, oil change etc. I'll think about possible causes tonight but will appreciate any constructive comments. One thought I had is that the airbox thermostat may be bad and thus stuck in an open position. Seems pretty clear it is an issue related to the FI system rather than ignition--but who knows. I'll be taking it in to a friend's shop tomorrow to do some other work on it while when he has a free lift and do plan on cleaning the throttle body but would like any other advice. Cheerio, Doc > Hello All: > [quoted text clipped - 21 lines] > > Recently tested the AMM and it seems good. How did you test the AMM? Usually the only real test is to swap it or unplug it and see if conditions improve. >> Hello All: >> [quoted text clipped - 24 lines] >How did you test the AMM? Usually the only real test is to swap it or >unplug it and see if conditions improve. Agreed. Unless it has totally failed the tests outlined in the shop manuals and reading the OBD codes is fairly worthless. Swapping is the only way to be sure. BTDT!!! __ __ Randy & \ \/ /alerie's \__/olvos '90 245 Estate - '93 965 Estate "Shelby" & "Kate" >>> Hello All: > >>> Recently tested the AMM and it seems good. Should have mentioned I bench tested the AMM and it passed and is to spec. >>How did you test the AMM? Usually the only real test is to swap it or >>unplug it and see if conditions improve. Well..not sure if I totally agree with that but do have a new AMM and swapped it in--yet it did not solve the issue. >Agreed. Unless it has totally failed the tests outlined in the shop >manuals and reading the OBD codes is fairly worthless. Swapping is the >only way to be sure. BTDT!!! Replaced the airbox thermostat today and will wait for weather to get colder again and keep you posted. Cheerio, Doc > __ __ > Randy & \ \/ /alerie's > \__/olvos >'90 245 Estate - '93 965 Estate > "Shelby" & "Kate" >>>How did you test the AMM? Usually the only real test is to swap it or >>>unplug it and see if conditions improve. > > Well..not sure if I totally agree with that but do have a new AMM and > swapped it in--yet it did not solve the issue. If there's a way to test the AMM without specialized test equipment please enlighten us. I've replaced a few of them, I've not yet seen one that had any visible defect >>>>How did you test the AMM? Usually the only real test is to swap it or >>>>unplug it and see if conditions improve. [quoted text clipped - 5 lines] > enlighten us. I've replaced a few of them, I've not yet seen one that had > any visible defect I've often wondered if we could test the basic operation by putting a voltmeter on the output and seeing what it was giving at idle, at a specific low cruise, etc. and comparing that with the readings of one that works. I'd think the voltages would either be way off or would be jumping around. Unfortunately, I haven't found a good way of connecting to it. Mike > I've often wondered if we could test the basic operation by putting a > voltmeter on the output and seeing what it was giving at idle, at a specific [quoted text clipped - 3 lines] > > Mike That's a problem I've encountered as well. It'd be nice too if there was a good description of what each pin on it does too, it's a lot easier to diagnose something if you know what to look for. >> I've often wondered if we could test the basic operation by putting a >> voltmeter on the output and seeing what it was giving at idle, at a specific [quoted text clipped - 7 lines] >a good description of what each pin on it does too, it's a lot easier to >diagnose something if you know what to look for. I think that with the necessary accuracy of the signal from the AMM at various airflows and at a wide range of temperatures, the testing rig could get quite expensive. I think that it just might be more economical to just keep some good spares on hand. Even if you had some good way to test one at idle, it would be difficult to accurately test its linearity through the RPM range. __ __ Randy & \ \/ /alerie's \__/olvos '90 245 Estate - '93 965 Estate "Shelby" & "Kate" |
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