Misfire P0301

Hi All,

I noticed yesterday that my 2001 was stumbling when turning left. Later in the day the CEL came on, and I retrieved a P0301 code. In both cases I was driving around town, not cold but not fully warmed up, engine temp around 40-70 C.

I haven't done any further investigation, other than trying some different driving experiments. I've been able to recreate the problem several times starting out with a left turn, when the car briefly runs on three cylinders. Going straight or turning right is fine.

Question: which cylinder is #1? My intent is to check the plugs and leads first, but since it's cold outside I'd like to focus my attention as much as possible on the problem area. I thought at first it might be fuel related because of the turning behaviour, but on reflection it feels more like an ignition issue.

Thanks in advance for any ideas/advice.
Jeff

 

Thanks Patrick and Bob. Further problems and experiences, since my OP, all related I think...

Tuesday I hopped in the car after leaving it sitting for close to 24 hours. I barely got it running. Full range of warnings on the dashboard, repeated unsuccessful ICE start attempts, SoC down to ~ 10%. I would have stopped trying, but I was half way down the block and wanted to get the car back in the driveway Anyway it eventually started running OK, I retrieved and cleared DTC P3191, and drove around town for 30 minutes or so with no issues.

Wednesday I tried starting, and immediately got P3190. I checked the plugs and leads, checked to see if any water around the engine ECU, and swapped the fuel pump and horn relay. No obvious issues, and no start after several attempts. I gave up fairly soon, as I was concerned about discharging the HV battery.

Today I disconnected the 12v battery, cleaned the throttle body and MAF sensor, then tried starting again, and the engine started immediately (whew! I was getting worried about ending up with a dead battery!). When I tried driving the car was behaving as it did on Tuesday for a few minutes, and I got P3191 and P304, but after a few minutes started working normally. I drove around for half an hour and the car was working perfectly. I was thinking that the fuel pump might be bad, and still think that. My next step was going to be checking the fuel pressure. But there's no indication of fuel starvation under full throttle, or any other signs of problems after I got going today. I watch the key metrics - temperatures, voltages, HV current, SoC, etc and all looked fine today after the initial issues.

I'm hoping that the cleaning of the MAF sensor and throttle body has solved the issue, but that may be optimistic. Anyone want to take a stab at this? I replaced my 12v battery a month or two ago. Will try again later today from a cold start. Is there an easy way to test the fuel pump? I also read about replacing the engine ecu. I also checked the readings for engine and air intake temps through the OBDC, and they looked to be fine, and all the other measures from then engine ecu look fine through OBDC. Not sure what other sensors might cause this set of problems...

I should also say that we got a ton of rain on the weekend and then it got cold on Monday/Tuesday. It's possible something got wet.

 

So I got through the issues I was having with the (very) cold weather a month ago, and had pretty much convinced myself that the main problem then was with a sticky throttle body. I replaced the plugs - nothing noteworthy about the old set - and carefully looked at the ignitors and harnesses. Car was running well, except for the original issue, which seemed to be getting worse - when turning left at any speed if I tried accelerating at all the engine seems to miss. Shortly after straightening out all would go back to normal. I had been experimenting, and it seemed to depend on the lateral force, and only when going around a left turn. I was thinking of maybe some issue with the fuel tank or pump.

Last week the starting issue returned, and I ran the HV battery dead. Didn't take long, as it was very cold (< -20C). I know that my (original) HV battery is not in perfect shape - no particularly bad cells, but not a lot of capacity.

I now have the HV battery out and am cycling through the cells testing capacity. I'd been thinking of doing this anyway, and it's been very enlightening. Results are encouraging so far - there is some variation, but no obviously bad modules. I've almost finished the first charge cycle on each cell, and the couple of slightly weaker cells have responded well to an additional discharge/charge cycle with increased capacity. It takes a lot of time but I'm feeling confident so far that I can restore the HV battery to a good state. I'm not in a panic to get it back in as it continues to be very cold here and I don't need my car. Have also ordered a second smart charger which will speed things up.

So back to the problem with the car - any more guesses? I continue to think that the driving and cold starting problems are related, but it's possible they are not. I'd like to test the fuel pressure, and may try to tap into the fuel line to do that.

Thanks in advance for any ideas.
Jeff

 

Followup: Car is running fine now and I'm convinced that the issue was water in the fuel.

I had positive results charging my (original) HV battery, and by doing a couple of discharge/charge cycles on the lower capacity modules I was able to bring their capacity up to arrive at a reasonably balanced pack. I had considered a replacement but am now confident that it's in reasonably good shape.

When I put the battery back in and attempted to start the car it cranked with no start. It was warmer but still well below freezing. My uncle, a fix-anything farmer was visiting, and he dribbled fuel into the throttle body during the crank cycle. I've done that many times with a carburated motor, but was a bit skeptical of doing it with this car. In any case the motor started immediately with this treatment (with the expected misfire codes!), confirming that it was a fuel issue. We then added fuel de-icer to the tank. I'm now on my third tank of fuel with de-icer added to each tank and haven't had any cold start issue. The hesitation on turns decreased with each refuel and is now gone.

I'm picturing the case where water settled in the bottom of the tank and the water level increased in the right-hand subtank around the fuel pump when turning left. This is based on some diagrams I have seen describing the fuel system, so maybe I'm way off base, but it seems like a reasonable theory given the behaviour I've described.