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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.
 

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2001 Spyder GT
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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.
 

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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.
 

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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.
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.
 

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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.
I cant say for sure it will cause a misfire, but it will throw the P0401 insufficient flow code. I am battling this now only because when I just did my spark plugs, I had no gasket.
 

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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
 

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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
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.
 

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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.
 

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2001 Spyder GT. Koni adjustable shocks. cold air intake, ST sway bar.17X8.5 rims. LED headlights.
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Bare with me because I only know what I know on this subject. Looking at the data, I would think that if you had a vacuum leak, your short term fuel trims would not be running in the negative range but somewhat positive to make up for the unauthorized air being introduced through the leak. Your long term trims are running about neutral. Again, bare with me here. Not sure I am reasoning on this correctly yet. Just opening up a new line of reasoning on this:cool:. ...J.D.
 

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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!
 

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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!
Disconnected all O2 sensors? Do you mean replaced?
Sounds to me like it was probably a leak in one of the gaskets.
 

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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.
On the 3.0l, I believe only the two upstream O2 sensors affect fuel trim by sending info back to the ECU, which then adjusts it. The downstream O2 sensors report emissions only. Not sure how the gutted cats would affect the downstream O2 sensors if you aren't using O2 "spacers"?
Theoretically, the downstream O2 sensors should throw a code with gutted cats and NO spacers...
 

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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...
 

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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
 

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2001 Spyder GT. Koni adjustable shocks. cold air intake, ST sway bar.17X8.5 rims. LED headlights.
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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.
 

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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
 

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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 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.
 

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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
 

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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?
 
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