Unpredictable occurance of high idle. ECU problem?
galant20
02-14-2004, 06:27 AM
It came out of the blue. As I exit the highway, I could feel that the engine wasn't returning to its proper idle speed. It was staying at 1200 rpms. When I shifted to neutral, the speed rose to 2600 rpms.
After checking with the computers, the dealers recommended replacing the throttle body at some US$800, which made me hesistant. The mechanics at two other garages were baffled but one suggested replacing with a second-hand throttle body. It worked for a while and then the same problem returned.
My current mechanic did the same, installing a second-hand throttle body. It worked most of the time. Correct idling depends on my luck when the engine is started. The idle speed will remain around there for most of the duration of the trip.
If I am not lucky, the speed could start to pick up from 1000 and reach to 1800 tops at idle and 1200 in drive mode. However,this speed could drop back to a nice idle with time, but not always. Switching on the air-conditioner when the engine felt like it was going to race, also seemed to help stifle this problem.
To "solve" this problem, I would switch off the engine and then crank it once without allowing it to start. Then I wpould start the engine again. Most of the time, it would idle properly afterwards, but not always.
What the heck is going on? My mechanic had also done electrical checks on the electrical connections and he could not find anything wrong. He suggested that the ECU may be the culprit.
Was he right? This website, http://www.carelect.demon.co.uk/mitind.html, also suggested the same. Please have a look.
Could it be true? What should I do? Is there another way?
After checking with the computers, the dealers recommended replacing the throttle body at some US$800, which made me hesistant. The mechanics at two other garages were baffled but one suggested replacing with a second-hand throttle body. It worked for a while and then the same problem returned.
My current mechanic did the same, installing a second-hand throttle body. It worked most of the time. Correct idling depends on my luck when the engine is started. The idle speed will remain around there for most of the duration of the trip.
If I am not lucky, the speed could start to pick up from 1000 and reach to 1800 tops at idle and 1200 in drive mode. However,this speed could drop back to a nice idle with time, but not always. Switching on the air-conditioner when the engine felt like it was going to race, also seemed to help stifle this problem.
To "solve" this problem, I would switch off the engine and then crank it once without allowing it to start. Then I wpould start the engine again. Most of the time, it would idle properly afterwards, but not always.
What the heck is going on? My mechanic had also done electrical checks on the electrical connections and he could not find anything wrong. He suggested that the ECU may be the culprit.
Was he right? This website, http://www.carelect.demon.co.uk/mitind.html, also suggested the same. Please have a look.
Could it be true? What should I do? Is there another way?
galant20
02-17-2004, 05:49 AM
By the way, my car is the 1999 Galant.
I have other noise problems which came on quite recently, some of which could be quite elementary so help is very much appreciated.
I can hear a slight "gear-moving" sound when I shift from R to N to D. The sound disappears very quickly. I have never heard this sound before. Could this be due to my compressor engaging and disengaging as I shift gears, sounds which are not supposed to be there unless the gears of my compressor are slightly damaged or misaligned due to the repeated violent drop of rpm as mentioned in the previous post?
I had read a technical service bulletin online that recommended upgrading the Diamond SP-II ATF recommended in the manual to SP-III. I had recently changed my ATF but the people at Mitsubishi gave me Dexron II fluid. The manual recommended Dexron II for RWD mitsubishi vehicles only and the Galant is FWD. Could this be the reason of my above mentioned problem? Should I have asked for Dexron III which is compatible to SP-III or some other fluid? Should I change it now? Is this necessary?
Another source of noise seem to be from the suspension. I have been travelling over short stretches of gravel roads over the past 6 months. I can now hear creaking sounds from some areas around the tires, probably the suspension. What is the usual source of this problem. Can I solve it by tightening some bolts and such?
Your help is very much appreciated.
I have other noise problems which came on quite recently, some of which could be quite elementary so help is very much appreciated.
I can hear a slight "gear-moving" sound when I shift from R to N to D. The sound disappears very quickly. I have never heard this sound before. Could this be due to my compressor engaging and disengaging as I shift gears, sounds which are not supposed to be there unless the gears of my compressor are slightly damaged or misaligned due to the repeated violent drop of rpm as mentioned in the previous post?
I had read a technical service bulletin online that recommended upgrading the Diamond SP-II ATF recommended in the manual to SP-III. I had recently changed my ATF but the people at Mitsubishi gave me Dexron II fluid. The manual recommended Dexron II for RWD mitsubishi vehicles only and the Galant is FWD. Could this be the reason of my above mentioned problem? Should I have asked for Dexron III which is compatible to SP-III or some other fluid? Should I change it now? Is this necessary?
Another source of noise seem to be from the suspension. I have been travelling over short stretches of gravel roads over the past 6 months. I can now hear creaking sounds from some areas around the tires, probably the suspension. What is the usual source of this problem. Can I solve it by tightening some bolts and such?
Your help is very much appreciated.
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