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420A Misfire 99 Eclipse GS Non-Turbo

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Dalxyon

Probationary Member
7
0
May 3, 2015
Rockford, Illinois
Hey I have a 99 Eclipse GS Non-Turbo (Y-420A) and I replaced the spark plugs (Autolite plats) with NGK BKR6E-11 V-Power Coppers gapped @ .044 and I'm still misfiring. The code says cylinder 1 is misfiring. I checked my wires, all are good. 1 and 4 wires @ ~270 ohms, 2 and 3 wires @ ~ 245 ohms. I checked my Ignition Coil Pack and banks 1 and 2 are both @ 1.6 (checked at 200 ohms) and the terminals are 1/4 @ 12.7 @ 200k ohms and 2/3 @ 12.4 @ 200k ohms. I ran seafoam through the exhaust for the carbon build up on the cylinder heads, through the oil, and through the gas tank. Replaced my EGR valve hard rubber line. Replaced valve cover gasket and spark plug gaskets. Replaced PCV hose since the old one broke. Cleaned my throttle body, idle air control valve, and idle air control valve sensor. Replaced gas cap.

I do need a new exhaust header and downpipe due to crack between cylinders 2 and 3 on the header and the test pipe is rotted. Car smokes up from the test pipe because it's rotted and I need to clean the oil that dripped from the valve cover.

Questions: What would cause my misfire at this point? Why does my engine rev up when warming up (just hitting the C on the thermostat the engine revs up from 600rpm to 1.2k and back down to 600 and keeps doing that for about 20 seconds)? Why does the car jump forward when almost stopped (rpm jumps up about 300rpm and car kicks forward)? Does this model have a MAF sensor and where would it be?

Also going to throw in that I'm new to the DSM game and this is the second car I've worked on. First car was a Lumina with a 3100 V6. The Eclipse is also my daily driver and I only own this one car.
 
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Fixed the engine revving up when warming up and when braking. It was an elbow line adapter by the MAP sensor (middle line in the first pic). I found out where the MAP sensor was and I need to know how to diagnose and clean/repair one. If I can't clean/repair it then replacing it may be inevitable.

Any ideas on the misfire issue that I'm still having?

UPDATE: Still have a vacuum leak somewhere. Car doesn't rev up on it's own when warming up but does still randomly push forward when almost stopped.

Can anyone help here?
 

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Fixed the engine revving up when warming up and when braking. It was an elbow line adapter by the MAP sensor (middle line in the first pic). I found out where the MAP sensor was and I need to know how to diagnose and clean/repair one. If I can't clean/repair it then replacing it may be inevitable.

Any ideas on the misfire issue that I'm still having?

UPDATE: Still have a vacuum leak somewhere. Car doesn't rev up on it's own when warming up but does still randomly push forward when almost stopped.

Can anyone help here?

A lot of things can cause a misfire.

It may be due to a vacuum leak or it can also be caused by dirty fuel injectors.

A weak fuel pump (low fuel pressure) or a faulty fuel pressure regulator could also be causing the car to misfire.

Have you changed the spark plugs and the wires recently?

If not I'd recommend going ahead and changing those.

Don't skip anything when it comes to maintenance, your car will thank you!
 
Welcome to the site. Looks like you just joined. As for your car issues, misfire could be a lot of things. If it misfire at idle, try popping of your injectors one at a time and see if you hear an idle change. That should help identify the cylinder that is misfiring. If you can find it, a noid light is a pretty cheap tool to make sure you are getting spark.

I am not sure what your gap is supposed to be but the 4G63 takes a 0.29, 0.44 seems high to me. You could have gotten a bad plug too. try swapping it and see if the misfire moves. You can do the same thing with the spark plug wires.

I am going to warn you, bumping your own thread is frowned upon. Also, with a little work I am sure you could find some answers with the search bar. I took a very quick look for you and already saw some things you could try.

Good luck!
 
It does misfire at idle. I didn't think to check the fuel injectors for two reasons. One I ran Seafoam through the gas to clean that up, and two I've never checked fuel injectors and don't know how to.

My car is a 420A so the gapping from the 4G63 does not apply here.

I changed my plugs twice. Once because of the misfire code and CEL. Second was because my buddy bought Wal-Mart Autolite plats and didn't check the gap. Needless to say the misfiring with the Autolite plugs was not because the plugs were bad but because we were ignorant. I then changed the plugs to NGK coppers @ .044.

I have not changed my wires. I checked them with a multimeter and they appear to be fine.
 
It does misfire at idle. I didn't think to check the fuel injectors for two reasons. One I ran Seafoam through the gas to clean that up, and two I've never checked fuel injectors and don't know how to.

My car is a 420A so the gapping from the 4G63 does not apply here.

I changed my plugs twice. Once because of the misfire code and CEL. Second was because my buddy bought Wal-Mart Autolite plats and didn't check the gap. Needless to say the misfiring with the Autolite plugs was not because the plugs were bad but because we were ignorant. I then changed the plugs to NGK coppers @ .044.

I have not changed my wires. I checked them with a multimeter and they appear to be fine.

Go ahead and change the wires since you already changed the plugs twice.

Maintenance is very important don't skimp or try to cut corners.

You can normally tell if a fuel injector is bad just by looking at it.
 
How do I get to them to look at them? My intake manifold is in the way I believe.
 
Hey, I'm having the same issue with my 97 gs. Yesterday it was doing the high rev then back to normal and today the car turns over but wont start. Its throwing a p0300 code random misfire when it was running. Was wondering if you've looked into the coil pack? Or, maybe know how to diagnose one?

plugs replaced
wires replace
o2 sensor replaced
new fuel pump
new fuel filter
new fuel pressure regulator
 
check which cylinder is misfiring then swap the injectors around and reset the ecu and see if it changes. If it changes then you have a bad injector. You may also have a bad valve as well which can cause misfire.
 
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