Mechanics

MODELS STUMBLE WHEN COLD

2000 Mitsubishi Other

Engine Performance problem
2000 Other Mitsubishi Models 4 cyl Front Wheel Drive Manual 155000 miles

this had to be resubmitted, I guess because it has been a while since I responded to your last post, but I did make a donation. Mitsubishi mirage 1.5l california emission 5 speed, minimal problem noticed/started at 60000miles and got progressively worse. At startup from fully cooled (8hrs+ off), car starts fine with key and idles, BARELY touch the gas in 1st to get on the road and it stumbles, it will have just enough power to roll the car but it won't stall. Release the gas and it will idle again, chugging along the road at idle speed. As soon as there's a load on the engine, it will stumble without power to accelerate the car. Give it a minute and it will work ok, but have some stumbling on acceleration. After it fully warms up it is fine. This car does not have an intake air regulator/mass airflow sensor (the 1.8l does, not the 1.5l like mine). Never had any active or pending codes. I have a big clue I think with the following: I live on a hill and can coast a half mile in neutral without turning on the car in the morning. I put the key to " on" and then coast 1/2 mile before putting it in gear and pop starting it while rolling about 30-40mph in 4th or 5th gear. The engine will not fire, specifically, when I touch the gas pedal I feel major stumbling (no acceleration at all) no change even if I floor it, and if I step on the clutch, releasing the engine, it will stall. In other words, the car will not pop start when cold, as if I have no gas or spark. But if I use the key at this point, it will start and idle perfectly, but still get the " regular" stumbling on acceleration as usual. Here's what I did so far in the past 2 years: NEW: oem spark plugs, 2 o2 sensors (california car), new pre-cat, 2nd cat is clean (light shines right through), fuel filter, fuel regulator, air filter, clutch, pcv valve, oil changes (of course), timing belt, battery, alternator, exchanged pcm from an identical car with 50k miles (same exact problem, no change after swapping pcms), removed and cleaned intake manifold, removed and cleaned throttle body and idle air control valve, removed and cleaned EGR valve and fully cleaned the exhaust and intake channels that run to it. (EGR channel runs through the head to the 3rd cylinder exhaust port, this was 95% plugged 1 year ago, it was scrubbed clean through and through), coolant temp sensor, air temp sensor, distibutor/coil, throttle position sensor, compression tested all within 5psi of each other @ 170, fuel pressure tested 48psi, new crank position sensor, fixed the common problem of worn crankshaft sprocket for timing belt by wedging feeler gauge pieces in the keyways to reorient proper TDC (got much more power and 4mpg after doing this, but still had same stumbling problem when cold). I am at my wit's end. Please help. The car gets 35 mpg around town but is dangerous when getting out of work's parking into oncoming traffic. I occasionally get oil fouled spark plugs (not always, not sure why), bg44k doesn't help, I just tried it. I tested for vacuum leaks using a propane torch all over the entire intake area, there are no air leaks. I sent all 4 fuel injectors to witchhunter. Com for cleaning and testing, seemed to help for a week, then happened again. I often shut off the car and coast down long hills in neutral when travelling and it never has a problem pop-starting when warm, it's only when cold when there's a problem as detailed above. I purchased an oil catch for the pcv valve but this didn't help either.I teed into the map sensor hose with a vacuum pump when cold and also was running bowserelectronics on my laptop to compare. With the vehicle cold and " on" position (not running), the absolute pressure reading on the computer is 29.8mmHg, it was raining and about 55 degrees F outside. When I started the car with the key, the vacuum gauge read 19mmHg and the manifold absolute pressure reading on my computer was 10.66 mmHg. I thought I nailed the problem but am thinking maybe this computer subtracts the actual vacuum from the normal outside pressure of 30 to get the 10.66? Tried it again several hours later and got 20mmHg on cold idle on the vacuum pump gauge and 9.9 on the computer reading of absolute manifold pressure, again it seems to work out to be a subtraction from ambient pressure. I also tested the map sensor with the vacuum gauge at 5mmHg increments with a multimeter and get consistent voltage readings, although I'm not sure which site told me at each 5 or 10mmHg of vacuum, the voltage should increase or decrease.7 to 1 volt.
Avatar
Frankmirageman
September 26, 2008.



Test the resistance of the IAC, like this. Also, symtoms like this also indicate a fuel problem, whats the flow? Can you get a pint in 30 seconds?


http://www.2carpros.com/forum/automotive_pictures/62217_mits_1.jpg


SYSTEM & COMPONENT TESTING -2000 Mitsubishi Mirage DE
Page 1 of 1
IDLE AIR CONTROL (IAC) MOTOR
1.Disconnect IAC motor connector. Check resistance between IAC motor connector terminal No. 2 and either terminal No. 1 or 3. Also check resistance between IAC motor connector terminal No. 5 and either terminal No. 4 or 6. Each resistance should be 28-33 ohms at 68 °F (20 °C). If resistances are not as specified, replace IAC body assembly. If resistances are as specified, go to next step. 2.If using lab scope, go to step 4 . Engine coolant temperature must be 68 °F (20 °C) or less. If not, an Engine Coolant Temperature (ECT) sensor that is appropriate temperature can plugged into ECT sensor connector. Turn ignition on (engine off) and listen for IAC motor operation sound. Operational sound should be heard when ignition is turned on and off. 3.For testing IAC control circuit, see DTC P0505: IDLE CONTROL SYSTEM MALFUNCTION in appropriate SELF-DIAGNOSTICS article. 4.Using test harness, or backprobing, connect lab scope pick-up, in turn, to IAC motor connector terminals No. 1, 3, 4, and 6. With engine running, compare IAC motor waveform to normal waveform. See Fig. 14 .
Fig. 14: Identifying Normal IAC Motor Waveform
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

9/26/2008

Merlin2021
Sep 26, 2008.
Resistance measured 39.3 at 71.5 degrees F. My multimeter is not perfectly at 0 when I touch the leads of it together, I read 0.6 ohms, so I'm assuming the resistance is really 38.7 at 71.5 degrees F (39.3 - 0.6). Fuel flow is unknown, but I get 38psi at idle and it takes 3-5 seconds to reach that level from 0psi in the morning, whether I crank it by key or pop start it. The fuel pump and filter are both new less than 2 months old.

Tiny
Frankmirageman
Sep 29, 2008.
Have you tried checking the fuel pump control module? It also regulates the fuel flow. You can do this by unpluging the pump from the module and powering the pump direct. Note: (UnPlug the pump from the module before trying this.) Also check the IAT(intake air temp) sensor, values are: IAT resistance=32-5300-6700 ohms
68-2300-3000
104-1000-1500
176-300-420

Merlin2021
Oct 13, 2008.
IAT resistance within range. For the life of me I can't figure out why it wont run after pop starting it when cold. I think that's the base of my issues with this car. I live on a hill. If I roll the car downhill and pop start it in 5th and then step on the clutch, the engine will bog for a few seconds bouncing at 200-500 rpm and then die out. I am still rolling downhill, so I try again and it will do the same. I have to pop start it 3-4 times before it will come to life and stay at idle. If the car is warm it will pop start no problem. Is there a circuit that is only used when CRANKING cold as opposed to only in the ON position when starting?

Tiny
Frankmirageman
Nov 2, 2008.
Does this car start normally with the key? Run cold when started with key?

Merlin2021
Nov 2, 2008.
Yes, the car starts perfectly with the key when cold. If I pop start it, it won't stay running as described, it'll bog around 200-400 rpm for a couple of seconds and die. I can start it with the key and it'll fire right up. As a matter of fact, I can start it with the key, immediately shut it off and try to pop start it and it will again bog for a few seconds and then shut off. I have to pop start it at least three times before it will idle on it's own. Or stay engaged in gear rolling for a thousand feet or so (the entire length of my downhill driveway) before it will idle. I'm thinking there must be some circuit that is active only when cranking (as opposed to the " on" poisition), but I used to be able to do it with this same car. It also doesn't explain why I can pop start it when warm without problem. I cannot hear the clicking of the IAC motor, but the resistance checks out perfectly.

Tiny
Frankmirageman
Nov 3, 2008.
Then the real question is, is if there is no problem starting it normally, why are we talking about issues when POP starting it? I thought you were doing that because of a dead battery? Who knows what trouble the PCM is having during a pop start, With the key on and rolling the computer is getting input from VSS, and wheel speed sensors.

Merlin2021
Nov 3, 2008.
The reason I'm asking about pop starting it when cold is because I think it must be related to my issue of it stumbling on hesitation when cold. Although I don't seem to be having much stumbling and hesitation now, it is still there when the vehicle is cold. I still should be able to pop start it when cold regardless of whether or not I have a problem starting it when using the key. As mentioned in previous posts, when I start this vehicle up using a key when cold, if I pull out of a parking lot onto a busy road as I do every afternoon, I would get a momentary pause as if the engine is starved. I don't want to get into all the specifics as I have done in previous posts. I just want to know, if you guys know, if there is any reason as to why this vehicle will not pop start when cold. I used to be able to do it. I believe the reason why I cannot pop started when cold is related to the same reason why I get that extreme hesitation when I pull out of a parking lot when the vehicle is fully cool.

Tiny
Frankmirageman
Nov 4, 2008.