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Topic
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Hello,
The car in question: Mitsubishi Mirage/Colt 1.3 GLXi 1997 M/T 140.000 miles/230.000km. And its green.
The situation. The car always starts within a second, which is nice. Then the rpm’s are around 1500, and slowly decline to 1100 orso. Drive off, so far all is well. At the first trafficlights (3 mins away), the idle drops to about 500 rpm, the lights dim a bit, vibration etc etc. Really lumpy repsons to get the engine back up to speed. If you wait long enough it will restore itself to 800 rpm (as it should be). It has never stalled, but i need to pay attention to it when driving off. After say 10 minutes all is fine, coolant has warmed up, rpm fairly stable at 800. (750 +/-50rpm is prescribed idle)
What i have done:
-clean valve in throttle body (this was quite dirty, mainly on the bottom edge and back face.)
-cleaned and checked air temp sensor in the intake manifold
-cleaned and checked PCV valve
-cleaned EGR valve (this was fairly dirty but not clogged and ever so slightly leaking cleaning fluid in to the other hole, after cleaning the fluid would be held back)
-removed idle speed controller. (to gain acces to EGR) this didn’t seem to dirty,Can / should this be cleaned further? How does this work?
-checked for vacuumleaks with various aerosol’s (not found)
-checked coolant temperature sensor operation (works)Recent work on the car:
-Front brake rotos
-Radiator (but i am quite sure i’ve filled it properly, used all the bleed screws etc)Fuel filter never been replaced by the looks of things
Air filter, old but not at all dirty.I’m considering to just order those filters new, and trow in some injector cleaner too. But that just feels like guess work :sick:
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🙂 I am sorry to read that you are having problems with your car. You may want to look at the coolant temperature sensor. You may have two of them, one of them will be for the temperature gauge or idiot light on the dash and the other one will be for the computer to tell the engine what your temperature is for adjustments. These are usually mounted on the engine near the upper radiator hose. It will have electrical connections going to it and the two coolant sensors look alike, so it is easy to replace the wrong one. I wish I could help more with specific information about where the sensors are, but I do not have that information. Maybe someone else can help and provide the information. Good Luck.
It sounds like the IAC is not working correctly. Also
with the ports not being dirty.sounds like its staying
closed or is slow responding.I’ll keep my eye out for a possible 2nd sensor, cant find mention of such in my documents though. 1 fluid temp sensor + the procedure to check it (so and so many ohms) is in there.
@college man
Thats the electrical device Mitsubishi calls the ISC i assume? I think i didn’t gave that enough attention after all. The business end of it just looked like a piece of plastic, it covered with some sod, but nothing ‘terrible’. I actually thought it was a rotary actuator 😳 but it appears to be a plunger that opens/shuts? The manual atleast offers some coil resistance for me to measure (with a testing harness i don’t have)I’m going to rip it out and whats what.. and bring a mirror to look inside better. Better bring a torch if i don’t hurry up!
the device + the tiny bit of dirt that came out of the uncleaned hole. I did wipe the ISC clean last time i had it out.
The connector. Appearently i should meassure resistance between several of them (going to assume the test harnas is just to have better acces and not cross-wired..Resistance, meassured as indicated in the manual (should be 28-33 ohm @ 20C)
29.0-29.1 for the top row (center pin common)
29.1-29.2 for the bottom rowanything else i can do to test this without test harness? I have some batteries, wires and clips to hook up things myself, just not sure what should be connected to what (6volt is what this works on appearently) just haven’t got the time to do that now.
[quote=”college man” post=80857]It sounds like the IAC is not working correctly. Also
with the ports not being dirty.sounds like its staying
closed or is slow responding.[/quote]Whatever the issue might be, the result is indeed that the system that regulates my idle speed sometimes seems to take 10-15 seconds to wake up and realize we’re running a bit slow, before correcting it (with some overshoot). But only when its cold.
The temperature sensor i’ve measured is on the thermostat valve itself, you can barely reach it behind the valve cover and cables.
Another interesting bit of text in my manual:
Fail-safe function reference
Malfunctioning item: Vacuum sensor
Control contents during malfunction:
1 Uses the throttle position sensor signal + engine speed from crank angle sensor to take reading of the basic injector drive time and basic ignition timing from the preset mapping.
2 Fixes the ISC serve in the appointed positiont so idle control is not preformedWhat it isn’t really clear on is weither or not this should trip my engine warning light. This comes on during starting, and then goes off again within seconds as i believe its suppost to do..?
Just take it out but leave the connector on? Do i need someone to turn the key for me while i take a look, or can i just turn the key and then look if it has chanced position?
Sadly i have no time for this during day time hours till next weekend.
I’ll probably get to check this tomorrow evening.
I’m not sure what to conclude from this, today it was rather cold (+ fog). Did had to apply some throttle to keep it going now.
And what should i actually see when someone puts the key in the on position? A tiny bit of movement, or just a ‘click’ or should it move significantly/all the way?
*edit*
Another question, whilst i’m at it, in the schematic drawing in the manual, in the top left corner of the by-pass ‘chamber’ are two mostly black rectangles, what do they represent? Is there something on the inside of this valve that could be stuck/malfunctioning?
I hope this thing turns out to be broken, as it would be a nice and easy fix. There is about 6 of these car’s on a scrapyard i drive by every day on my way to work. What confuses me is that it only acts up when the engine is cold, if this is broken shouldn’t it have issues when warmed up too?
I had a Mitsubishi and it had the same IAC. When my idle started acting up I’d pull the device and lube it up the best I could with silicon spray and it would perform properly for several months and then I’d have to repeat the process. Finally, that got to be old and I bought a new one.
BTW, my car also had the idle position switch I see on your diagram. When that also failed I got a 2000 rpm idle. I’m just throwing this in for extra credit.
Seems i was too slow! I was just busy editing my old post with some more questions.
Did your typical idle problems also disappear after the engine had warmed up?
Also, can you just push down on this plunger to test if it will move? With next to no presure it would go down less then 1 mm orso, didn’t felt like something that should be pressed harder. Sorry for all the questions, don’t know much about electronis and less about servo/stepper motors. So i tend to be rather careful with them :blush:
The vehicle I owned was sold as a Plymouth Laser. I had so many problems with that car I don’t remember exactly what symptoms I was having with the IAC.
If you open up the back of the device you will encounter the armature of an electric motor. Inside the pintil (the part that moves) there’s a worm gear. So, the worm turns and the pintil goes in and out.
I think what happens is over time the worm gear gets coated with deposits.
Thats one to look at in the weekend then, thanks for the info!
I guess this answers my questions about pushing it down, lets not do that 😆
I think i’ll make a quick stop at the car junkyard place and see if i can pick up another of these units, hardly have to go out of my way for it and they take returns so might aswell have another part to test with me.
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