420A Misfire

[tunerfish]

Hey everyone,
Long time lurker, first time poster here

My car (99 GS) is throwing CEL P0300, P0301,P0302,P0303,P0304,and P0300"pending". I recently did a tune up which included
-Spark plugs(NGK)
-Wires
-Coil pack
-Fuel filter
-Air filter
-PCV
This didn't solve the problem so I then replaced the battery, cam sensor, crank sensor, timing belt and everything that goes with it(tensioner, water pump, pulleys), and the alternator. The car then ran the best it had in along time, but today the same 6 CEL's popped on. Also the lights are flickering so I put a volt meter on the battery. The results were...car off 12.8v, car on 12.7v and then all accessories on 12.9v clearly this is to low(same results with old alt). I will be replacing the negative wire on the battery tomorrow and see if that helps. Then from there I guess go with the ECU being thats where the voltage regulator resides.

I really hate just throwing money at it, and would like to know for sure before buying a new ECU. Is there any other 420A 2G related issuse that anyone can think of that may cause this?

The car has 129,xxxmi all stock, I also did a compression test, the results-
cyl - 1 2 3 4
dry- 215-210-215-220
wet- 235-220-220-230

-Tunerfish

 

[eclipsek17]

Did you gap plugs? What are your current fuel trims? Have you checked to see if you are running too lean or rich? Did you check alternator output voltage?

 

[Silver99OZ]

What NGK plugs did you put in? I found that the standard/copper work best, gaped to factory spec. When checking your battery voltage with the car running, check not only from the posts of the battery, but also check at the clamps themselves. Judging by your readings so far it seems as though you have a loose or corroded connection.

Also, on the factory positive terminal clamp there is an insert that can be popped out. After removing the negative battery terminal clamp, remove the positive and you can then use a screwdriver to pop the insert out. What happens is you can get corrosion between the insert and the terminal clamp itself. Clean all surfaces of the insert and the terminal clamp thoroughly and re install.

 

[tunerfish]

Thanks for the replies guys,

eclipsek17-
I haven't done any fuel system diagnostics because the dimming lights,and volt reading at the battery lead me to believe the problem lies somewhere in the charging system. I didnt think the alternators bad because it was the same results with the old one too. If nothing else the fuel system will be my next move.

silver99oz
Yes, I used standard NGK plugs gapped at factory spec. Thanks for the tip about the insert it was so corroded I couldnt even see there was one in there.

I went out this moring and replaced the NEG wire and cleaned up all other terminals. I then did another voltage test after, but this time everything was right where it should be...Car off 12.8v, car running 13.5v, then with all acces. on 14.2v. The fuel pump also sounded alot stonger upon cycling the key. Now I have to wait for night to see if the lights still flicker. Then see if the CEL's come back

-Tunerfish

 

[eclipsek17]

I didn't think of that, but that makes sense. If it does come back up, check fuel trims with a data logger to check if air fuel mixture is where it should be.

 

[tunerfish]

Well I thought I was golden, the car ran great when for a few days. Then today the CEL's came back. P0300, P0301pd, P0302pd, P0303pd, P0304pd, P0300pd, and now it says EVAP is incomplete. Its seem to be triggered with fast acceleration, or highway speeds (60mph+). I am at a complete loss here, I replaced most everything I thought it could be. I'm gonna triple check my vacuum lines, and maybe the EGR valve. I heard that when you replace the cam sensor, and crank sensor(I did) you should have the car flashed at the dealer..is there any truth to that? Anything else anyone can think of would be great.

-Tunerfish

 

[eclipsek17]

Does the car drive normally? Do you have hesitation when attempting to get on the gas a little more than normal?

I have heard of getting the car flashed at the dealer when certain things are done. I am not sure what cars this applies to though or what it is exactly. Maybe that is what it is though.

 

[tunerfish]

The car drives great. I dont feel any hesitation that im aware of. I mean its only the a stock engine how fast is it gonna be haha. The only sign of a misfire is at idle, if you look at the side mirrors you can see theres a shake slightly. If I accelerate fast(or highway speed) the CEL starts to flash, and shows those misfire codes. It doesnt happen every time though, its intermittent.

I have a exhaust leak just before the catalytic converter, maybe this is causing the O2 sensor to give a false reading, thus giving a false air/fuel ratio?

 

[eclipsek17]

That's a possibility.

I am not sure I am helping too much, it would be easier if I could check it out myself. I was just wondering about a hesitation because that could be caused by lack of fuel or clogged cat which may also cause misfire.

Check the basics over though, could just be something being overlooked. Check fuel pressure, exhaust backpressure, o2 readings, etc. Do you have a vacuum gauge? Do a vacuum test, hook a vacuum gauge to intake manifold and check the results at idle, while driving, and while deceleration.

 

[tunerfish]

All your help is appreciated,

I need to run new exhaust as I just found the pipe going into the muffler has rotted away as well. I just don't want to replace the converter only to find it wasn't the problem, then have the new one get ruined as a result. Sometimes I seem to think the car is a little sluggish at acceleration,maybe do to a clogged cat, maybe it could just be in my head hahaha.

I will be buying a fuel pressure kit tomorrow, as well as do a smoke test on the vacuum system. From there I will test the O2 sensors. If nothing by then I will look into the EGR valve and exhaust. I don't have a vacuum gauge so the smoke test will have to do.

-Tunerfish

 

[Aproductions]

I just had the same issue. The iat sensor was loose and cause a big vacuum leak. It's a brass fitting in aluminum so when I took it off of course it broke in the manifold.

 

[tunerfish]

I just checked the IAT sensor, and it wasn't loose, but the wires are taped up for some reason. Yet another thing that may be a problem hahaha.

 

[mustracetsi]

I just checked the IAT sensor, and it wasn't loose, but the wires are taped up for some reason. Yet another thing that may be a problem hahaha.

They are taped. Untape them check wires are not shorted cut or burnt, make sure each wire is seal and tight individually before you retape it together. Check you tps sensor. Fix exhaust leak your loosing power and probably running rich. Egr can cause multiple engine codes. Check egr. Egr pipe can melt tps and ait harness wires. It happen to my 420a talon. Resulted in killing my ecu cause egr pipe melted tps sensor wire and shorted out the ecu. Rewired new lines and redirected away from pipe or anything real hot. I bought an eclipse rs months later to ad to my dsm love and same thing but was able save everything because first thing I checked and noticed.

 

[tunerfish]

Thanks man I will check all that first thing in the morning.

I just did a smoke test using a cigar and I had smoke come out of a few places, the vacuum elbow on the throttle body badly(fixed), then there was smoke coming out of the EGR and out the side of the vacuum valve controller thing before it. There where however two strange places it came from, lightly from within the throttle return spring, and also lightly out of one of the valve cover bolts(right of cyl4). Im gonna pick those parts up, then do the exhaust and see where Im at from there.

 

[EclipseWarrior]

I know this is an old Post, but my 99 GS is giving me those same codes, and the Service Engine light flashes 6 times and then it stays on. This happens to me only in the highway at speeds 60+, even if I reset the codes they come back again once I hit the highway. New ECM was installed after my old one turned off my car while driving. Gonna do some of the stuff you all mention here and see how it goes.