The Top DSM Community on the Web

For 1990-1999 Mitsubishi Eclipse, Eagle Talon, Plymouth Laser, and Galant VR-4 Owners. Log in to remove most ads.

Please Support ExtremePSI
Please Support STM Tuned

2G Misfire only at certain times

This site may earn a commission from merchant
affiliate links, including eBay, Amazon, and others.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Psybion

Probationary Member
21
6
Mar 5, 2016
Tampa, Florida
I'm hoping that someone could help me with an issue.

I'm getting a misfire, it only seems to happen under mid-heavy load, and only for the first about 10 mins of driving. No codes come up unless I let it continue to misfire, which I dont. The one time that I did it was a random misfire code. P0300 or something.

Things I've done - Spark plugs, new MAF, new spark plug wires, new ignition coil packs. Possibly unrelated things - new alternator, new starter, swapped the box filter for a cone. Past the air filter the car is totally stock.

One other problem too, my idle is low, like 500-600 kind of low, a shop said it was the IAC and replaced it, it got better (it was dying on me if I didn't give it gas before that) but the RPMs still seem mad low.

Last. Problems that I KNOW the car has ( not sure if they're related but more info is usually better)
-Lights dim when I let off gas, which I think is associated with the low idle.
- What I THINK is lifter tick that goes on for like 30 seconds or so on cold start
- Bad valve seals (bluish smoke from exhaust if I idle too long.)

If you can point me in the right direction I'd appreciate greatly. I can do work just fine, but I'm no good with troubleshooting. In the end I'm an electrician, not a mechanic

Thanks in advance
 
I'm hoping that someone could help me with an issue.

I'm getting a misfire, it only seems to happen under mid-heavy load, and only for the first about 10 mins of driving. No codes come up unless I let it continue to misfire, which I dont. The one time that I did it was a random misfire code. P0300 or something.

Things I've done - Spark plugs, new MAF, new spark plug wires, new ignition coil packs. Possibly unrelated things - new alternator, new starter, swapped the box filter for a cone. Past the air filter the car is totally stock.

One other problem too, my idle is low, like 500-600 kind of low, a shop said it was the IAC and replaced it, it got better (it was dying on me if I didn't give it gas before that) but the RPMs still seem mad low.

Last. Problems that I KNOW the car has ( not sure if they're related but more info is usually better)
-Lights dim when I let off gas, which I think is associated with the low idle.
- What I THINK is lifter tick that goes on for like 30 seconds or so on cold start
- Bad valve seals (bluish smoke from exhaust if I idle too long.)

If you can point me in the right direction I'd appreciate greatly. I can do work just fine, but I'm no good with troubleshooting. In the end I'm an electrician, not a mechanic

Thanks in advance
I belive it could be your cam angle sensor or crankshaft sensor my 99 gs auto had same exact thing. Its lije $40 dollars and easy to install.
 
Could be a sensor, seems like you covered all the maintenance aspects of it, could be some residual oil build up on the plugs when it cold, pull them and check them before starting car worth a shot due to the bad valve seals
 
It's a 98 gst, which I believe is a 7 bolt.

Im kind of leaning away from oil on the plugs because when. I put brand new ones in and then did my typical 5 mile test drive, it still happened. When I take my plugs out they are relatively clean
 
I had a similar issue in another car which was associated with ground wires not making proper connection might want to take a look at those connections
 
Alright, quick update.

So I dropped by the parts store and picked up a new CAS and swapped it out. It looks like it wasn't the problem, though it does seem like it was A problem. The car now pulls way harder, I seem to have all the power back that I was missing, which I assumed was just part of the misfire problem. My idle is now stable at around 900rpm, drops to 700 when the fans kick on.

That being said the car is still misfiring. =(

Electrical connections should be solid, as an electrician I'm anal about that and it was one of the first things I did when I got the car.
 
And new wires you say? Mine actually shorted out to the stupid hood and I threw a shop towel on them before I shut the hood and the sputter went away. Just one of my experiences.
 
Alright, quick update.

So I dropped by the parts store and picked up a new CAS and swapped it out. It looks like it wasn't the problem, though it does seem like it was A problem. The car now pulls way harder, I seem to have all the power back that I was missing, which I assumed was just part of the misfire problem. My idle is now stable at around 900rpm, drops to 700 when the fans kick on.

That being said the car is still misfiring. =(

Electrical connections should be solid, as an electrician I'm anal about that and it was one of the first things I did when I got the car.
Try looking at your gap it should be on your manual I know mine is around 48 to 52 but I have a 99 gs 420a non turbo so yours couod be different. When I bought mine it starded having random missfire code p0300 and tge gap was to small so I bought the dollar gap gauge. It did the trick so hopefully you overlooked that n its a quick fix.
 
perhaps try checking out the other sensor. the crank and cam work together to let the computer know when to fire the plugs and if they firing too late or early cuz of a bad signal from either sensor then ull get a misfire and sometimes a no start
 
What plugs do you run? I almost completely cured my random misfires under wot by going with a smaller plug gap to .023, but still had it occasionally hear and there, so I swapped from ngk bpr7es to non-projected br7es and it never misfired again
 
Alright, parts store wanted way too much for the crank sensor so I ordered it, should be here in a couple days.

I'm running iridium plugs gapped at .044, is this too much? I asked about it specifically at the parts store and was told that it was the recommended, you know how parts store employees are though. I'll go ahead and grab a gap tool
 
Sorry, I meant to update this earlier in case people were wondering, and also to have a definitive answer in the thread for future searches.

Turns out the problem was 100% spark plugs. I was previously using a set of nkg iridium gapped around .04. I switched to a set of BPR6ES (as recommended, see thread link above) and made sure they were gapped at .028. The misfire is now completely gone.

I appreciate everyone's help.
 
I have random cylinder misfire P0300 it appeared again after crank sensor replaced really random idle and loss of power. Car is almost stalling but hasn't completely turned off yet. Any recommended spark plugs for 420a non turbo? I have the car manual and it gives Champion RC9YC5 (426) copper plugs. Need some help again! Thanks
 
I'm hoping that someone could help me with an issue.

I'm getting a misfire, it only seems to happen under mid-heavy load, and only for the first about 10 mins of driving. No codes come up unless I let it continue to misfire, which I dont. The one time that I did it was a random misfire code. P0300 or something.

Things I've done - Spark plugs, new MAF, new spark plug wires, new ignition coil packs. Possibly unrelated things - new alternator, new starter, swapped the box filter for a cone. Past the air filter the car is totally stock.

One other problem too, my idle is low, like 500-600 kind of low, a shop said it was the IAC and replaced it, it got better (it was dying on me if I didn't give it gas before that) but the RPMs still seem mad low.

Last. Problems that I KNOW the car has ( not sure if they're related but more info is usually better)
-Lights dim when I let off gas, which I think is associated with the low idle.
- What I THINK is lifter tick that goes on for like 30 seconds or so on cold start
- Bad valve seals (bluish smoke from exhaust if I idle too long.)

If you can point me in the right direction I'd appreciate greatly. I can do work just fine, but I'm no good with troubleshooting. In the end I'm an electrician, not a mechanic

Thanks in advance
Misfire and that cel light I'm leaning toward o2 sensor. Mine did the same thing once it went to close loop operation. The idle thing is always a bi*** with DSMs
 
Idle problems is almost always boost leaks, or throttlebody issues, or both.

Delete the FIAV, test and replace the ISC, new shaft seals. Adjust the TPS, and make sure you set the ISC correctly. If you don't have a scan tool that can do it, take it to a shop... Its that easy.

Also, as its been said, Iridium plugs WILL NOT RUN CORRECT with stock ignition. Its been beat to death. Don't ever listen to parts stores Bullshit when it comes to buying "premium" parts. Just get the right part with the best warranty.

Premium brake pads, premium plugs and wires, premium batteries, premium oil filters, air filters, cabin air filters, premium headlights, etc all of them, and 98% of the snake oil they sell are just ways to get you to part with more of your money. I worked there for 3 years and ended up getting written up for being honest about the fact it was a scam 3 times before the Management moved me to commercial delivery.
 
Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Innovation Products Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications MyMitsubishiStore.com RixRacing RockAuto RTM Racing STM Tuned

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds

Back
Top