Left work Friday afternoon everything was okay. No signs of previous issues, no codes. Sitting at a stop light the car started shaking real bad, hit the gas to go and she kept running but very rough. Check engine came on. Went to blinking mode as a kept driving. Pulled into Autozone read P0300. Nothing obviously disconnected. Smell of raw fuel out the tail pipe with blue/white smoke but not too heavy.

Made it home, problem continued. Would rev fine and run better at 30/40 MPH but was rough. Left it alone until yesterday. Seemed to run better when cold, but not right.

I have ohmed out the injectors, the coils, all read okay. Pulled all plugs, all are dry except #1, which was a little wet, but none are fouled. Did a compression test (not fully warmed up I am sure) All cylinders came out to 210 PSI, except #4 which was 150. repeated and got same results.

I can smell raw fuel so I know it is not running right. No leaks. When I crack the throttle and release, I can hear a gurgling sound in the vacinity of the throttle body, maybe at the EGR area/cylinder 5. I have heard that for a while. Maybe related, maybe not. I dont hear any sign of a vacuum leak.

What to check next???

edit: forgot to add, when it was still warm, to get it to refire after shutting it down, I had to pump the gas pedal.

 

You have a bad coil or 2 or more. P0300 is a coil problem, i t just doesn't say which one. You will have to remove the coil wire harness connections one at a time while the engine is running. If the engine does not idle worse, that coil is working. When you unplug a coil and the engine runs the same, that is a bad coil.

 

could also be your MAF acting up aswell. see if you can borrow someone elses and see if it works. or clean out your MAF and see if its still going on. I had this problem and it was my MAF. just to give u another idea besides the coils. sometimes the MAF wont pop a code till its completly shot.

 

Not necessarily.
Copy and paste from here. http://www.obd-codes.com/p0300

What does that mean?

Basically this means that the the car's computer has detected that not all of the engine's cylinders are firing properly.
A P0300 diagnostic code indicates a random or multiple misfire. If the last digit is a number other than zero, it corresponds to the cylinder number that is misfiring. A P0302 code, for example, would tell you cylinder number two is misfiring. Unfortunately, a P0300 doesn't tell you specifically which cylinder(s) is/are mis-firing, nor why.
Symptoms


Symptoms may include:

• the engine may be harder to start
• the engine may stumble / stumble, and/or hesitate
• other symptoms may also be present

Causes


A code P0300 may mean that one or more of the following has happened:

• Faulty spark plugs or wires
• Faulty coil (pack)
• 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

 

Considering you dont have a coil or injector code, I would guess it is a mechanical failure of the injector (o-ring). For something to happen suddenly and to the severity of yours, I dont think it would be rings/valves, or egr or such. At any rate, diagnosis is in order.

 

Well, it was fuel related. Specifically, a nearly clogged filter. I would have thought it would have just shut down, but it acted just like a dropped valve. Bought gas at a station I dont normally buy from. Not sure it was a tank of bad gas or just timing, but the filter was the issue. I thought it might be the fuel pump, but it seems to be running perfect now.

#4 compression is still low. With 232K on the clock, doesnt surprise me.

 

It's back. It was running fine all weekend and drove it 80 miles Tuesday with no problems. Went to leave work last night, same thing, not quite as bad and the check engine light never came on. Running very rough, raw fuel out the exhaust and lots of smoke until it warms up.

Disconnected plugs one at a time, each had an effect on the idle. I can here clicking sound near the EGR area that comes and goes with the issue. I guess I will check that next.

 

faulty injector prolly. Could be a bad coil too.

 

No, I checked each one and it is a random misfire. And it is way to bad to be only one.

 

Does anyone know if the EGR sticking open would cause multiple misfire and raw fuel smell? I definitely hear a clicking noise near the EGR area when it is misfiring.

 

Well the EGR seems to be working fine. Couldnt get it to misfire today!

I got my new intake boot on, so maybe the leak after the MAF was it.

A Gen 7 is looking better all the time....

 

Yes a leak after the MAF will cause a lean condition and a lean miss. Did not realize you had a leak there.

 

I guess I forgot to post that.

I had sealed it up pretty good after the first round of symptoms, so i didnt think it was they first problem. Found it when I took the intake assymbly off to get to the fuel filter, it actually ripped as I was taking it off, not sure how bad it was before.

Its fixed for good. Just have to see if that solves it for good.

 

Sparky, I have the exact same problem. Started today when I started the car after work. Very rough idle, heavy fuel spray/smell out of the exhaust pipe, and code P0300 (random cylinder misfire). I did some thinking and this is what I have come up with.

Since I have a rear main leak, I suspect my Crankshaft Position Sensor has become so fouled up that it now sends conflicting signals to the ECM, resulting in random cylinder misfire. I have not yet had the chance to verify this, but I would like to hear from you or anyone that can comfirm or deny that the CPS can result in a rough idle/fuel out of exhaust pipe.

 

In the FMS, a magnetized plate (at the CPS), is one of the items to check. I think anything that confuses the the ECM could cause this.

I am fairly confident that the air leaking past the MAF caused my issue.