2002 Mitsubishi Lancer Bucking

Maintenance/Repairs
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1

Good evening all,

Car is a 2002 Mitsubishi Lancer OZ Rally with a manual transmission, 132,000 miles. It’s the wife’s car, she loves it to death, and its been a very good car to us. Timing belt was changed at 70,000 miles, so its time to do it again and I’ve got all the parts ready.

Had been running fine, then the wife takes it to McD’s and it started bucking / stalling as she pulled out of the drive-thru. Check Engine Light (CEL) was on, one stored code P0441 - Evaporative Emission Control System Incorrect Purge Flow and had a pending code of P0304 - cylinder #4 misfire.

Took me about half an hour to get from work to the McD’s. When I drove it home, it acted fine for the first mile or so. As it got warm, it feels like the ignition is cut off completely for a split second then everything is normal again. I’d call it bucking, but it only happens once. It will do it once, then doesn’t do it for maybe 5 or 10 seconds, and then does it again.

It is very intermittent - it will do it two or three times in 30 seconds, then not do it for 60 seconds, then do it again.

Car idles fine even when warm. But it did stall once pulling it into the driveway. I can warm the car up in the driveway, it will start doing it, then it will stop and I can sit in neutral for 10 to 15 minutes with no issues. Idling, foot on the gas holding constant RPM, it doesn’t matter.

This evening, I changed the plug and wires and cleared the codes. The plugs were worn, but looked fine. The car certainly idles better…but still does it. I ran it around the block a couple of times, and once it got warm, it started doing it again. CEL remains off. But, looking thru the service manual, I did not hit the magic speed/time requirements for the computer to complete the diagnostic cycle, so that might not mean anything.

I can floor it and row thru the gears and acceleration feels normal, so I don’t believe it is a weak fuel pump. I do have a new one on the shelf, bought months ago when I thought the pump was making a weird noise, so I may just change it anyways. Mitsu gets a gold star for making the fuel pump replaceable without dropping the tank after you remove the rear seat cushion - thank you Mitsu!

Past that…the only things I think would seemingly cut the ignition would be a sensor - crank position sensor or camshaft sensor. The throttle position sensor might could do this, but I doubt it, as I couldn’t find any sort of dead spot when I was playing with the RPM in neutral in the driveway.

Thoughts?

thanks much,
ben

2

Mistake

3

The purge valve is part of the gas tank’s evaporative emissions system. If that system fails it can form a vacuum in the tank which prevents fuel from moving to the engine. And that could cause this symptom. Suggest as first focus to figure out why you are getting the purge valve diagnostic code.

4

Yeah I would address the Evap Emissions code as you could be sucking air and leaning out your fuel mix… I will add however that these can be tricky…and often times require a smoke machine to find the source…so good luck with that one. Can be as simple as a non venting gas cap creating suction for the pump and starving the system for fuel…or it could be a simple vacume leak from a rotten hose somewhere. Either way…try to remedy the Evap code before worrying about other causes. Most guys would pray for any CEL code to act upon in this situation…be glad you have one.

I was also going to recommend cleaning your MAF as well… Simple enough to do.

Blackbird

5

Good morning all - thanks for the suggestions. I’m going to take the car out today and see if I can get it to reset the evaporative emissions code. Since I cleared the codes, it hasn’t come back. But, I haven’t driven it long enough / fast enough to satisfy the drive cycle in the service manual.

thanks much!
-ben

6

Good morning all,

Took the car out today (it was pouring rain yesterday) and was able to get it to set the P0441 code again and it was bucking again.

Right after it did the bucking trick, I pulled over, shut the car off, and loosened the gas cap. I was greeted by a loud hiss. Hard to tell if it was pressure or vacuum, but I assumed that much delta pressure was not good regardless of what it was.

I drove around some more with the cap loose and it bucked once over about five miles of driving.

So I rolled into my local auto parts place, bought a new gap cap, and put it on. Cleared the codes, drove around some more, and it bucked exactly once very slightly (might have even been the A/C kicking on) and no more code. :slight_smile:

I told the wife that I’m 90% sure I’ve fixed it. She said “its that other 10% that worries me.” :wink: I’ll take it to work Monday, and if it doesn’t do it in my 50 mile round-trip commute, I’ll call it good.

thanks much,
ben

7

So glad that it was just your gas cap and you let us know. Had the same kind of problem with my John Deere riding mower. It had no power and would die after a few minutes running. It turned out the little hole in the gas cap was plugged up with dirt and the engine was starved of gas. Cleaned the hole in the cap and she runs like a champ!