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Hi Guys,
I noticed that my car’s RPM goes down to around 700 when the compressor kicks in but goes back up to 900 when it disengages.
I’ve already cleaned the Throttle body and changed the Idle Control Valve with a brand new one, changed my spark plugs, and brand new battery but still this happens.
Based on my observations this only happens when the engine heat reaches it’s optimal level already.
Could anyone advise me on what possible issues might be causing this that I may have overlooked. please I’m quite desperate now since I have spent a big sum already to get this car running properly…There are quite a few things I’ve replaced on the car with brand new parts also:
1. timing belt
2. compressor
3. radiator
4. ignition solenoidYear: 1998
Make: Mitsubishi
Model: Galant
Transmission: Manual
Engine: 4G63a – SOHC 16 Valve
Mileage: 149,000km
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Replies
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While 900 is a tad high I´ld guess, what´s wrong with 700 with AC on ?
Isn´t there some sort of base adjustment on a car that old you can perform ? I remember some Mazdas, where you had to short a wire to ground and do a base adjustment of idle speed.
I think Eric showed more or less the same thing on a Honda of sorts in one of his videos.
I’m not 100% positive, but I think the idle is supposed to decrease when the compressor kicks in because the load on the engine has now increased and the idle control is still providing the same amount of fuel/air mix to the engine.
I tried resetting the PCM by taking the connection to the batteries and left it for an hour or more. Drove it for about 2 weeks already since i did that and still did not fix the issue… 🙁
[quote=”madrockwyo” post=174304]I’m not 100% positive, but I think the idle is supposed to decrease when the compressor kicks in because the load on the engine has now increased and the idle control is still providing the same amount of fuel/air mix to the engine.[/quote]
I assumed as much but a 200rpm difference makes me feels something’s really wrong… additionally, when the 700rpm drop happens the car shakes a lot further pushing my desperation to fix this…
This is the first car that I actually bought with my own money that’s why I really want to get it running well. 🙁
[quote=”Iznogood” post=174284]While 900 is a tad high I´ld guess, what´s wrong with 700 with AC on ?
Isn´t there some sort of base adjustment on a car that old you can perform ? I remember some Mazdas, where you had to short a wire to ground and do a base adjustment of idle speed.
I think Eric showed more or less the same thing on a Honda of sorts in one of his videos.[/quote]
it’s the first I’ve heard of such a procedure but it might be worth a try. Could you point me out on the exact link? I’m trying to search it on Eric’s channel but i can’t find it. 🙁 Thank you in advance!
[quote=”mkymnzns” post=174323][quote=”Iznogood” post=174284]While 900 is a tad high I´ld guess, what´s wrong with 700 with AC on ?
Isn´t there some sort of base adjustment on a car that old you can perform ? I remember some Mazdas, where you had to short a wire to ground and do a base adjustment of idle speed.
I think Eric showed more or less the same thing on a Honda of sorts in one of his videos.[/quote]
it’s the first I’ve heard of such a procedure but it might be worth a try. Could you point me out on the exact link? I’m trying to search it on Eric’s channel but i can’t find it. 🙁 Thank you in advance![/quote]
I´ll do my best, but I can´t remember off the top of my head, so I have to do a search too…..
On the computer reset, on one car, you were required to unhook the battery, then jumper or touch the two battery cables together for a minute or more. This drained all capacitors and other keep alive memory. Another thing that could cause a high idle is a bad MAP/Intake air sensor or O2 sensor that would be giving false readings to computer. But a code reader should identify those.
[quote=”mkymnzns” post=174318]
I assumed as much but a 200rpm difference makes me feels something’s really wrong… additionally, when the 700rpm drop happens the car shakes a lot further pushing my desperation to fix this…
This is the first car that I actually bought with my own money that’s why I really want to get it running well. :([/quote]
The 700rpm sounds about right, the 900 seems a bit high. I cannot think of why the would shake at all when just the AC compressor kicked in. Does the cooling fan also kick in at the same time as AC? could something be loose, or a loose/broken motor mount that causes shake? Try a search on here and possibly using general search engine for Mitsubishi Idle adjustment, and Mitsubishi high idle and see if any useful information shows up.
[quote=”madrockwyo” post=174484]On the computer reset, on one car, you were required to unhook the battery, then jumper or touch the two battery cables together for a minute or more. This drained all capacitors and other keep alive memory. Another thing that could cause a high idle is a bad MAP/Intake air sensor or O2 sensor that would be giving false readings to computer. But a code reader should identify those.[/quote]
I’ll try this out right now and report if there’s any change! thank you!
[quote=”madrockwyo” post=174485][quote=”mkymnzns” post=174318]
I assumed as much but a 200rpm difference makes me feels something’s really wrong… additionally, when the 700rpm drop happens the car shakes a lot further pushing my desperation to fix this…
This is the first car that I actually bought with my own money that’s why I really want to get it running well. :([/quote]
The 700rpm sounds about right, the 900 seems a bit high. I cannot think of why the would shake at all when just the AC compressor kicked in. Does the cooling fan also kick in at the same time as AC? could something be loose, or a loose/broken motor mount that causes shake? Try a search on here and possibly using general search engine for Mitsubishi Idle adjustment, and Mitsubishi high idle and see if any useful information shows up.[/quote]
Actually yes, when the compressor engages both fans start. The shake is feels more like it’s losing power with the load since it’s also pulling down the RPM.
Try to imagine that the engine is fighting to stay alive when the compressor load kicks in.It would surprise me if the idle speed did NOT drop down when the A/C kicks in, since an A/C system can pull up to 15 BHP from an engine. The fans starting when the A/C is turned on is also perfectly fine, as long as they aren´t running full speed.
If it ain´t broke, don´t fix it.
[quote=”mkymnzns” post=174637]
Actually yes, when the compressor engages both fans start. The shake is feels more like it’s losing power with the load since it’s also pulling down the RPM. Try to imagine that the engine is fighting to stay alive when the compressor load kicks in.[/quote]I’d say a 200 rpm drop is within the normal range for most cars. It feels like it’s losing power because it really IS losing power! My Kia Rio is nearly undrivable with the a/c turned on. I have to turn the A/C off just to merge onto the highway, pass someone, etc. Just a fact of life with most 4-banger cars.
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