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.
Friday, September 26th, 2008 AT 12:38 PM