P0300 Random Misfire

[99eclipsegst99]

Hello I checked through I didn't see anything similar to the issue I have been having.

From the begining I am driving my 99 Eclipse GST Spyder (4g63) and all of sudden I hear a pop. When I get home I notice that two of the bolts snapped off the exhaust mainfold on the left passenger side. So i ordered new bolts and replaced them.

After that my car throws a P0300 Random Cynlinder Misfire. It sounds like VW bus, sluggish and now power what so ever on take off.

Changed the plugs, the wires and nothing. I take it to PEP Boys to diagnos and they tell me its my ignition coil and that i need to replace 2 of them for $200 a pop and $80 x 2 in labor for each. Which I found out later by doing research its only one coil pack and I got from the dealer for $100.

I put in the new coil pack in yesterday and still nothing, still throwing that p0300 code. I heard someone say that it might be my catalytic that is clogged and might have popped the bolts of the exhaust from the pressure.

Before I go through of ordering a new one, thought I get a thought or two. Any help greatly appriciated.

-Noob-

 

[RadDsm]

Here is a good place to start, there are a few things to check for.
http://www.obd-codes.com/p0300

 

[99eclipsegst99]

Thanks for the speedy reply RadDsm. According to the list here is where I have gotten.

•Faulty spark plugs or wires - -replaced
•Faulty coil (pack) - -replaced
•Faulty oxygen sensor(s)
•Faulty fuel injector(s)
•Burned exhaust valve
•Faulty catalytic converter(s)
•Stuck/blocked EGR valve / passages
•Faulty camshaft position sensor
•Defective computer -checked no problems.

My suspicion is the catalytic convertor since I had to replace the two bolts that snapped off the exhaust manifold.

 

[Tfitch90]

Did your check engie light ever start flashing or des it stay solid ?

 

[99eclipsegst99]

Tfitch90 - It stays solid, i reset after i put in the new ignition coil and it showed up again with P0300.

 

[fourgsixthree33]

Could very well be a clogged cat. Swapping out a coil pack isn't very hard to do. Find a used one either at a junkyard, here in the classifieds, or somewhere like DSM Graveyard - Your #1 Source for DSM Parts! . It isn't hard to change at all. Just got to get familiar with the bolts and where they are located.

EDIT: Just seen you already swapped it out. I would pull the cat off and check it out. Maybe even see what it runs like with it off. Also, check your o2 sensors.

 

[banishedmunk]

I would replace the camshaft position sensor next as it is very easy to replace a single bolt and an o-ring.

 

[99eclipsegst99]

fourgsixthree33- Glad I wasn't crazy for thinking it was the CAT. What started the whole problem might have been too much pressure in the exhaust, which snapped off (2) of my bolts on my exhaust manifold.

Funny thing is, the CAT is only 2 years old and it was one that California made me put on because of the emissions, but I live in New Jersey now, so I can pretty much get a universal CAT.

I will hit the CAT next and let you all know what happened. Thanks for your help!

Rogert that,

Next Steps-

CAT
Cam position sensor
O2 Sensor.

 

[805DSM]

Im in the same boat, im running straight pipe and my rear o2 is bad, i've changed the coil & transistor
And plugs, the wires arent that old "ngk's" and still no change, sucks.

 

[jdub1992]

These cars are tricky

 

[chino9656]

I was hoping you would have an update for us by now...
I remember reading something about the backpressure from a clogged cat causing manifold bolts to pop off or strip. Sounds like a good source of the issue - hope you got it fixed!

 

[Swish]

Funny thing is had this same problem at one time and used to curse the hell out of the car because it would always send me into limp mode.

well oddly enough all this went away when i fixed my 40,000 boost leaks and replaced the plugs :\

 

[banishedmunk]

I highly dout that a clogged cat will cause any manifold bolts to pop out. the amount of force required is well beyond the point that the motor would choke out.

 

[cowboy]

I'm having the same issue what to do

 

[99eclipsegst99]

Mystery Solved!

Timing belt was off, the two little white dots were about 2/8 of an inch off, hence the random misfire. Wish I would have known that before getting, new plugs, new wires, pulling the ECU out and replacing the coil. It's all good though, I will have it back together by Tuesday and will let you know how its running. By the way my car has 160K on it, the timing belt should have been the first thing that came to my mind...duh!

 

[99eclipsegst99]

I dropped the car off at the Mitsubishi Dealership a week ago and the "experts" diagnosised as a timing was off.

I picked up the car today and it still shows up with P0300. I paid $500 for a new timing belt and new water pump and the car still runs the same, minus all the puttering it was doing earlier. Then the service manager tells me I need a new turbo. $1800.00. I laugh and tell him if it needs one I will put in myself.

CRAP!

So I am back at to the check list.

Step 1. Check the oxygen sensor(s).
Step 2. Check the catalytic converter(s).
Step 3. Check the EGR valve / passages.
Step 3. Check the Fuel injector(s).
Step 4. Check the camshaft position sensor.
Step 5. Check the camshaft position sensor.
Step 6. Check the exhaust valve.

I will keep you updated and any input would be greatly appricieated!

 

[snowborder714]

You are running on the stock 7 bolt engine that originally came with the car, correct?

 

[99eclipsegst99]

Yes, sir that is correct.

 

[PieEyedPiper]

I've had my fair share of P0300. Can you explain, in detail, the events that lead up to this? Any recent modifications? Go back a few months if you have to. I'd also like to hear exactly how the car behaves when this happens. Does it happen all the time? Is it only low rpms? Does it drive fine ever?

Do you know why the bolts on your manifold broke themselves?

 

[99eclipsegst99]

The events that lead up to this was when I had the car shipped from California to Jersey. In Cali my car was lovely, only problem I ever had was the alternator and the tranny, both of which we replaced and rebuilt.

When it got here it was fine for 2 days and 1 day I am driving I hear this pop. When the pop happened I had no power what so ever and it sounded like I had an exhaust leak (cause it sounded like VW bus) I have to put the pedal to the floor to get it moving, rough idle at stops, to where the car was shaking when I was stopped at a traffic light.

I saw the check engine light come on and plugged the logger into the car. It came up with P1500 and P0300. I changed the plugs and the wires, no change.

I take it to my dad's friend shop and they say the P1500 was due to the alternator wires touching the O2 wires, which created a short. I think GREAT problem solved!

When I picked up the car it still sounded like $hit. The mechanic comes out with a cigar in his mouth and says, you got 2 snapped bolts on your manifold and your CAT sounds like it's blocked. I take it home; order the two manifold studs from the dealer.

When I put them on, guess what?

It was a little quieter but it still had a very hard idle (to where it's below the 1 on the RPM Gauge on the left side) still shakes the car at the stop lights and no pick up what so ever. Grandmas are blowing past me giving me the finger.

I get frustrated so I take it Manny, Moe and Jack (Pep Boys) and they tell me it's the ignition coil. I have to tell you Manny, Moe and Jack almost got me, they said I need 2 coils at $200 a piece and x 2 @ 80.00 for labor. I take the car home and I ordered my own coil from the dealer for $120.00 and replaced the coil myself.

I close my eyes, praying while turning the ignition and FML, the car is still running like $hit.
My last course of action is taking it to the Mitsubishi Dealership, they are the experts right, they work on Mitsubishi's all day long. I take it in, they tinker with it for about 3 hrs and the service tech comes out and says my timing belt is off and shows me the two little white dots are about a 1/8 off.
I think at last these guys know what they're doing; they keep the car, promise me it back in 3 days, and guess what they kept it for like 7 days and at the last day the service manager is telling me, they fixed the timing, put in a new water pump and I need a new turbo for $1800.00. I'm like no that's ok, if it needs a new turbo, I will put it in myself.

I pick up the car from the Mitsubishi Dealership and it's running a little better no hard idling, still faced with no power when you step on the gas and guess what??
The check engine still reading a P0300. FML.

That's the whole story start to finish, soup to nuts. At this point, I am going to do like RadDsm suggested and go through the points of the P0300. Which is:

Step 1. Check the oxygen sensor(s).
Step 2. Check the catalytic converter(s).
Step 3. Check the EGR valve / passages.
Step 4. Check the Fuel injector(s).
Step 5. Check the camshaft position sensor.
Step 6. Check the exhaust valve.

Oh i forgot to ask one more question? Before I go through and order a new turbo, does anyone think it's the turbo??

LMK.

Thank you for all your help everyone!

 

[snowborder714]

I would add power transistor to that list of things to check/change as well.

 

[genegoesfast]

Are you by any chance running a 1g cas on your 2g motor?

 

[99eclipsegst99]

snowborder714- I will put that at the top of the list.

genegoesfast - Is that a "CAT"? If it is, the CAT was a California issued CAT, to pass California emissions.

 

[Frskrgps]

check the crank position senor. i had the same problem then my motor walked.

 

[snowborder714]

Do you see a piece like this on your engine? It will be on the passenger's side of the head, near the thermostat housing.

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Or does yours look like this?

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