Low idling RPMs

SeminaristaKuno

We have a 1995 Lancer GLXI automatic that we bought secondhand. Pansin ko lang na nasa 600 - 700 RPM lang ang makina kung naka-stop, on ang aircon at naka-"D" ang transmission.

Kung bagong start lang sa morning ok sya. 1500 RPM tapos it drops to 1000 after a few seconds of warmup. After 15 minutes of driving ok pa. After mga 30 minutes gumagalaw na ang manibela at fluctuating na ang RPMs between 600 and 700. When I leave the office sa hapon ganun na sya all the way until makarating kami ng bahay. Once or twice nung sira ang aircon, namamatay ang makina sa stoplight kung naka-Neutral.

Ano kaya problema? Puno ang radiator, kaka-tuneup lang last month, at pina-adjust ko na rin ang setting ng gas cable. Wala namang noticeable power drop while driving between 1000 and 2000 RPMs. Sa idling lang talaga.

slamm

Try to check the following:
- sensors (i'm not familiar with what sensors controls the Mitsu engines though. YOu could have malfunctioning or dirty sensor.
- PCV (dirty?)
- Throttle body (needs cleaning)
- fuel lines/filter/air filter (dirty?)
- vacuum hoses (vacuum leak somewhere)

Mokkori

You say that the aircon is on when this happens right? Have the compressor of your aircon checked. It may be dirty... as slamm mentioned, it may also be the idle sensors... there's usually a sensor that controls the idle of the engine at neutral. On the extreme side, it may be your ECU... but unless something untoward caused it to short... I doubt that this is the case...

SeminaristaKuno

I'm pretty sure it's not the aircon since we got it serviced just last week. Compressor sounded fine naman daw. The engine also increases it's revs when the aircon is on so the compensation system is working. Sira nga lang thermostat so it's always on :(

Wag sana ECU :( Pero first suspects ko rin ay ang fuel and air filter. Paano ba masabing papalitan na dapat ang air filter? Yung filter ko medyo gray pa lang and wala pa namang particles na nahuhulog. Di ko pa nasisilip ang fuel filter and malamang papalitan ko na 'to this weekend.

May sinasabi din ang Popular Mechanics about O2 sensors that measure how much oxygen is coming in and adjusts the throttle settings accordingly. Kung luma na daw di na gumagana.

Di rin kaya ang octane ng gasoline ang may problema? Gamit ko Shell Premium with 93 octane. Di ba ang injected engines ay nagre-retard ng timing kung may knock na? Not really sure pero brainstorming lang.

Thanks for the help guys. Hirap kasi pumunta sa mekaniko at walang idea kung anong problema. Baka sabihin pa nun na kelangan palitan ang makina

ichi

theres this knob at the back of your air filter, try to twist is while the engine is on... you can adjust your engine's idling by doing this...

hope that helps!

SeminaristaKuno

Uy cool! What does that knob do? Will try it when I get home. Coding kasi. The user's manual wasn't in the car when we bought it so medyo kinakapa ko pa sya. Teynks!

yorimoto

how about "idle up"? di kaya yun?

16-Driver

Originally posted by SeminaristaKuno
I'm pretty sure it's not the aircon since we got it serviced just last week. Compressor sounded fine naman daw. The engine also increases it's revs when the aircon is on so the compensation system is working. Sira nga lang thermostat so it's always on :(

Wag sana ECU :( Pero first suspects ko rin ay ang fuel and air filter. Paano ba masabing papalitan na dapat ang air filter? Yung filter ko medyo gray pa lang and wala pa namang particles na nahuhulog. Di ko pa nasisilip ang fuel filter and malamang papalitan ko na 'to this weekend.

May sinasabi din ang Popular Mechanics about O2 sensors that measure how much oxygen is coming in and adjusts the throttle settings accordingly. Kung luma na daw di na gumagana.

Di rin kaya ang octane ng gasoline ang may problema? Gamit ko Shell Premium with 93 octane. Di ba ang injected engines ay nagre-retard ng timing kung may knock na? Not really sure pero brainstorming lang.

Thanks for the help guys. Hirap kasi pumunta sa mekaniko at walang idea kung anong problema. Baka sabihin pa nun na kelangan palitan ang makina

I know you just serviced your AC but check again on how much "freon" is in the system... LOW "freon" (coolant) level will set your compressor on and off frequently!

You said it just had a tune up.. yet your suspecting about the air and fuel filter? Hmmm... not much of a tune up to me then... Umm... Yeah check your fuel filter and while youre at it, check the fuel pressure too!

Yup, the oxygen sensor could be part of your problem too! Oxygen sensor senses how much oxygen is coming out of your exhaust. Too much oxygen -- needs more fuel. Less oxygen -- needs less fuel in the combustion chamber! A faulty oxygen sensor result a little rough Idling and bad fuel consumption! But a faulty oxygen sensor should give you a "Check Engine" warning on the dash!

MAFS (Mass Air Flow Sensor) could be part of the problem too! But as I said.. this is a computer operated sensor... It also should give you the "Check Engine" warning!

My question now is.... what did they do with the tune up?
What parts did they replace... if any?

Hmmm... check your spark plugs and plug wires! Check the resistance of every single one of them! If one of them is bad, it is misfiring... rough Idle! It acts like it wants to die! And also... get someone check your "ignition coils" it could be sending less (or none) electricity in one of the banks!

If this doesnt work... post us what you did and more questions...

slamm

Sigh, idling problems are really one of the achilles heels on EFI/ECU engines when they get old... and the source can range from vacuum leaks, dirty parts (PCV, intake plenum, etc), bad spark plugs, electrical system grounds/bad spark cable wires, faulty sensors, dirty sensors, fuel system, etc... it really has to be checked one by one. If you can get a computer readout/diagnostic from the CASA, it can help if its a busted sensor.

My folk's car also has idling problems but i'm still in the process of ironing it out (too bad i dont have the time to really get dirty at it).

SeminaristaKuno

No check engine light yet so I think that rules out the O2 and the MAFS sensor. Is the PCV a computer-controlled sensor too? Would have really helped a lot if the manual came with the car. Darn.

When I had it tuned up they replaced the plugs and oil filter, flushed the oil, and checked the timing. They found oil around the plugs due to worn out seals daw. I have a little leak din daw sa may oil pan seal pero it's not that critical or so they say. Haven't replaced those yet. I'm having the fuel filter replaced this weekend since I'm replacing the torn steering boots anyway. Hoses look good and the belt is new. No squeaking or unusual engine sounds. They recommended replacing the water pump though.

What's the best way to look for worn out plug wires? Spray them with water with the engine running in the dark and look for widdle sparks?

I'll run through your checklists one by one. At least I have an idea what to look for. Will keep you guys posted.

BTW, I haven't tried the air filter knob yet. Will check later.

ichi

Seminarista....as far as i know...all mitsubishi's has the knob colored white...and dont worry... the knob doesnt get hot even if the engine is running... hope it helps

SeminaristaKuno

Thanks for the tip ichi! Will try looking for it.

16-Driver

Originally posted by SeminaristaKuno
No check engine light yet so I think that rules out the O2 and the MAFS sensor. Is the PCV a computer-controlled sensor too? Would have really helped a lot if the manual came with the car. Darn.

When I had it tuned up they replaced the plugs and oil filter, flushed the oil, and checked the timing. They found oil around the plugs due to worn out seals daw. I have a little leak din daw sa may oil pan seal pero it's not that critical or so they say. Haven't replaced those yet. I'm having the fuel filter replaced this weekend since I'm replacing the torn steering boots anyway. Hoses look good and the belt is new. No squeaking or unusual engine sounds. They recommended replacing the water pump though.

What's the best way to look for worn out plug wires? Spray them with water with the engine running in the dark and look for widdle sparks?

I'll run through your checklists one by one. At least I have an idea what to look for. Will keep you guys posted.

BTW, I haven't tried the air filter knob yet. Will check later.

Check for corrosion in the end of each plug wires... sometimes they get corroded.
The best way to check plug wires is to use an ohms meter. Check for resistance for each and every single one of them!
Nope PVC (Positive Crank Ventilation) is not computerized.

SeminaristaKuno

Thankfully I only have 4 plug wires to check Looked through the engine compartment last night trying to trace everything. That engine has a lot of wires. And nope I didn't find the knob that ichi was referring to.

ichi

huwat?! theres this knob that chokes the air that enters the engine...try to look for it... hehehe its just there

SeminaristaKuno

Muntik na nga masunog ilong ko sa kakasilip eh

Nag-trace ako from the filter box to the throttle assembly. Hinugot ko pa yung sensor harness sa filter box baka maluwang na. No knobs on the filter box unless nasa ilalim sya :(

SeminaristaKuno

Update: my mekaniko won't touch the engine. Sabi nya it would be better if I get my next oil change and tuneup in the casa na lang. My fuel filter is not the usual white plastic filter. It's a big black unit that looks just like the aircon filter.

Looks like this will take some time to solve. Any updates on your parents' car slamm?

slamm

On my folk's Cefiro... I consulted a friend of mine a while ago who had a similar problem and he said to clean the servo (after the throttle body on the intake plenum). I could DIY it but its PITA to do and i dont have the time so i'll be bringing it to my mechanic at Nissan probably this week.

In the CASA, try to ask if they can do an engine diagnostic check on the car.

SeminaristaKuno

Problema kasi sa CASA bihira lang ang libre. Sana may libreng diagnostics ngayon na simula na ang rainy season. Sige will ask some of the Mitsubishi CASAs. Thanks!

sp!t_k!cker

bad trip! yun akin din nagkaproblema... guys gawa naman kayo ng checklist para dito... ganito na naging problem ko dati tapos pinapalitan na lang namin ng spark plugs evry 2 months... ngyn ata dapat every month na... namatayan ako kahapon twice, kanina papuntang katipinan once, pauwi thrice. twice sa visayas ave. 300m -500m lang ang difference... tapos once nun nakapark

SeminaristaKuno

Libre naman pala diagnosis sa Diamond Motors. Might be going to their C5 branch this weekend. Sana PCV or throttle cleaning lang kelangan.

Here's a simple throttle cleaning guide. Medyo mabusisi pero mukhang doable.

http://www.popularmechanics.com/automotive/sub_care_sat/2001/5/cleaning_throttle_bodies/

May mga problems din pala ang engines na di nagti-trigger ng "Check Engine" light at makikita lang 'to sa scan tool.