Mitsubishi Eclipse 3G Club banner
1 - 13 of 13 Posts

·
Registered
Joined
·
28 Posts
Discussion Starter · #1 ·
So I've been trying to find the cause of my misfire and have absolutely no clue where to start. I've check everything and I'm to a point where it isn't showing any codes so I'm at a loss, but I pulled the freezeframe data and wanted to see if anyone could help me interpret it and find a solution. So far everyone has been helpful but I'm at a loss.

DTCFRZF: P0300
FUELSYS1: CL
FUELSYS2: CL
LOADPCT: 29.4%
SHRTFT1: -4.7%
LONGFT1: 0%
SHRTFT2: -6.3%
LONGFT2: 0%
SPARKADV: 36°
MAF: 1.464 lb/m
TP: 4.3%

Like I said I don't know what to do with the information. Some of it makes sense but google isn't really helping me piece anything together and I know some of you guys know a lot more about it than I do. Some more information that might help is that it only does it when it's up to temp and the throttle basically dies when I press the gas. It runs fine above 30 but God forbid I have to drive through town. As of right now I have it parked for safety's sake but I need to get it back on the road ASAP.
 

·
Registered
Joined
·
28 Posts
Discussion Starter · #3 ·
You used to have misfires on all cylinders on bank 1. Did you figure out what that problem was?

Since your problem only happens when the engine is warm, I'd pay special attention to things like the EGR system. Both the EGR valve, and the EGR connector pipe should have gaskets and they're easy to lose when r/r ing the intake plenum. Make sure those are in place. Another thing to check is the engine coolant temp signal to the ECM. Look it up on your scan tool and make sure the ECM gets a correct reading when the engine is warmed up. I think it's fine because your scan tool says you're in closed loop mode, but it's easy to check.

I know you replaced all the vacuum lines, but you can have a vacuum leak from other things too, like the mating surfaces where parts meet. Like the throttle body to intake plenum, and the plenum to intake manifold. It's possible to install the throttle body gasket backwards; the tab should be on top and closest to the front of the car. It's also possible to create a gap at the bottom of the plenum if you attach the plenum to the rear brackets first...you should attach the plenum to the intake manifold first.

I'd get a can of starting fluid and try squirting it at these areas while the engine is running. If idle changes, you've found a leak.
So the EGR tube gasket CAN cause a misfire??? I did end up replacing the throttle body gasket and plenum gasket to see if it would help but I completely forgot about the EGR tube because it's been missing for a while. I've been so wrapped up in trying to see if there's a timing issue or leak that I completely lost track of it. The only other serious issue I've had is a small exhaust leak that I plan on fixing soon.
 

·
Registered
Joined
·
28 Posts
Discussion Starter · #6 ·
YES! The EGR pipe on the back will leak if you dont put the gasket back on. I did every bit of maintenance on my 2001 GT a few weeks ago and when I pulled the plenum off, there was no gasket for the EGR tube. I just bought this car back in January I think but, I have not driven it much until the last month. After I put everything back together, and then this week I get an EGR code. I know its that pipe leaking after the engine warms up.
DUDE if that fixes it after everything I replaced I'm gonna have mixed feelings. I'm going to give it a shot definitely. I know the gasket isn't easy to find cheap but if there's any chance of it helping I'm going to take it. Thank you for all of your help so far guys
 

·
Registered
Joined
·
28 Posts
Discussion Starter · #8 ·
Yes, I found one at an Advance Auto near me, but I tried to get another one and no one seems to have it. Its gonna be a Mitsu part but thats ok. The GTS is a major pain in the ass to get on. My GT is not much of a problem. It helps if you take the strut tower bar off and get someone with REALLY small hands. I know my is leaking when the engine gets warm as I smell exhaust gases when I pop the hood. The ECU on these cars can send you mixed signals. For example, I just fought the catalytic converter code issue and thought my pre cats were failing. After talking to my buddies dad that is a mechanic, he said O2 sensors can cause this code. The O2 sensor is like a battery that holds a small charge. Over time, that battery like all batteries becomes weak. I changed out my front 2 O2 sensors and have not had the code pop up for the last 2 weeks.
I changed the only 02 sensor throwing a code but I'm really running out of parts to change on the upper half. It may have been a dumb move but the cats have been gutted since well before the issue came up. It came up when I changed my timing belt but from what I can tell the timing was perfect on all four points. Even if it was a tooth off I don't think it would cause the engine to only misfire in closed loop though.
 

·
Registered
Joined
·
28 Posts
Discussion Starter · #10 ·
New (and final) update. I decided to go ahead and change all of my intake gaskets, empty the fuel rail, and disconnect all of the O2 sensors. I don't know which one of them did it but she's running like she's brand new now. Thank everyone for pointing me in the right direction and sticking with me from the beginning!
 

·
Registered
Joined
·
28 Posts
Discussion Starter · #12 ·
Disconnected all O2 sensors? Do you mean replaced?
Sounds to me like it was probably a leak in one of the gaskets.
No I unhooked all of them and the idle leveled out. It wasn't really what I expected but it runs perfect now so I'm going to get the three I didn't replace soon.
 

·
Registered
Joined
·
28 Posts
Discussion Starter · #15 ·
btw, by spacers I mean an adapter that goes between the O2 sensor and the pipe which makes the O2 sensor sit further out, thereby fooling the ECU into not throwing a code. Guys who do cat deletes use spacers to avoid throwing codes...
I haven't gotten the spacers yet but it's the next step. Weirdly enough the whole time I've only had a code for bank one sensor one. I'm gonna try spacers before i make any big moves though. For the time being I think I can deal with it drinking gas to make it to work and back since I work two minutes from home
 

·
Registered
Joined
·
28 Posts
Discussion Starter · #17 ·
My experience with O2 sensors with Mitsubishi's [I have owned 3. 1987,1997,2001]. Be careful using cheap, knock-off O2 sensors with these cars. I have had bad experiences TWICE that way. Make SURE what you buy is SPECIFICALLY for this car. You obviously cleared some issue by disconnecting everything. Did you disconnect the battery in the process ? Let's see if the issue comes back. ...J.D.
I replaced the one with a denso so I think I'm on the right track with that. I did disconnect the battery with it and I took it for a test drive after I got everything disconnected so from what I can tell the worst thing that's going to happen is it's going to drink gas
 

·
Registered
Joined
·
28 Posts
Discussion Starter · #19 ·
I use either Denso or Bosch and haven't had a problem. Both come with exact length harnesses, so no splicing needed. The difference in part numbers appears to correspond with the custom length of the harnesses.
That's what I noticed too so far. If I get this worked out completely soon I'm probably gonna move on to cosmetics tbh. She's seen better days and for some reason the silver Eclipses have really bad clear coat fading
 

·
Registered
Joined
·
28 Posts
Discussion Starter · #21 ·
Plug your O2s back in.... Your issue has nothing to do with the EGR.

Have you inspected your distributor cap and rotor?
Have you swapped plug wires/injectors around to isolate the issue?
What's the weather like when the misfire occurs?
New cap, rotor, plugs, and wires. The injectors were fine. The only serious issue i found before the issue came up was that the cats were melted inside which is probably what messed the O2 sensors up. The misfire happens in any weather but only in closed loop but I'm going to get those sensors replaced and use some spacers to kind see if it completely gets rid of the issue but the only time it's ran right in months is when I disconnected the O2 sensors. I plugged them back in to make sure that was the issue and the misfire immediately came back
 

·
Registered
Joined
·
28 Posts
Discussion Starter · #25 ·
Are you using low octane gas by chance?
Premium is recommended...

I don't think he was intending to run without sensors, but rather was just trouble-shooting to see if it made a difference. Also don't know if he unplugged all four sensors, just the downstream, or just the upstream. The results under all three scenarios might be useful in pinpointing the problem, right?
I was suggesting that the downstream sensors probably were not contributing to his misfire problem because it is my understanding that they DO NO affect fuel trim like the upstream ones do.
I've been using 93 octane since I got the car. But yea the O2 sensors were disconnected just to try to see if it would help anything. Sorry for not clarifying
 

·
Registered
Joined
·
28 Posts
Discussion Starter · #27 ·
I have been known to unplug O2 sensors, one at a time to track down the offending part, but deleting any O2 sensor on an ECU controlled engine is complete ignorance, unless you are throwing the whole system in the trash and going to something else. ...J.D.
That's how I did it. I got it down to the upstream on bank two. I'm gonna order the part from Napa sometime next week
 
1 - 13 of 13 Posts
Top