I have a 05 with a 3.4. the engine has a erratic idle, misfire, randomly shuts off and smell like gas when it dies, sometimes has hesitation at acceleration, sometimes has back fire. I have done a tune up with iridium plugs and AC Delco wires. I have replaced throttle body gasket because it was leaking. I have changed the idle air speed sensor, throttle positioning sensor, mass air flow sensor, crank shaft positioning sensor, cam shaft positioning sensor. I have put all new coils and coil module plate. I have also changed the fuel filter. None of the parts/sensors have fixed the problem.


What else could be causing this?!

 

What trouble codes are you getting? That would narrow it down a lot.

If I were to guess, it sounds like it's either a bad cat or one of your O2 sensors.

 

evap lick large and a p0300 misfire

 

With the random mis-fire issue, you may want to find the firing order for the car and verify that the plug wires are correct. That could also account for an erratic idle you mentioned. And if the firing order isn't right, you're sending fuel into a cylinder that is not igniting at the right time (could explain the gas odor).

I mixed up too plug wires on a 3100 once and the idle sounded like crap. That was quickly found and resolved that night.

 

I would definitely check the plug wires, but if you're seeing a large leak from the evap it would give those same symptoms (assuming it was causing a vacuum leak...which is likely since the evap runs through the vacuum system).

The erratic idle, misfire, and stalling are common issues with a big vacuum leak, and the gas smell would be from your evap leaking into your engine bay (evap reroutes the vapor from the gas tank back into the intake).

Best of luck,
-Riggs.

 

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

Possible Solutions



If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs).



Check spark plug caps, spark plug wires, connections and correct order.
Easy to make a mistake.
Otherwise, check the coils (a.k.a. coil packs).

In some cases, the catalytic converter has gone bad.

If you smell rotten eggs in the exhaust, your cat converter needs to be replaced.

In some cases cases the missing was faulty fuel injectors. (But they Code)

Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. (Wires grounding-out. You got New wireis.) ???

The underlying cause could be a lean fuel condition, which may be due to a vacuum leak in the intake manifold or:

Unmetered air getting past the airflow sensor.

EGR valve that is stuck open.


I think the first thing you do, ... since this comes after a "Tune-up" with New Wires and Plugs is:


Verify that each New Wire is:
On the right Coil Post
Run to the Plug without crossing another wire or grounding out.
SEATED firmly on the Coil Post
Seated firmly on the Plug
IS the RIGHT Firing Order.

 

ok it has new Wire and plugs and yes it is in the right firing order as fare as the cat no smell rotten eggs how can i fine the evap leak i dont rilly have the money to put it in the shop

 

Tons of good info in that post Rick, but the P0300 is the code for multiple misfires. Usually means **** went terribly wrong, and you should look up the other codes you're getting with it :P Considering that he got the EVAP leak code along with it, I'd start there and get that issue knocked out first. Good chance they are related, as a decent size vacuum leak will set the P0300 code.
You can try tracing the evap back from its vacuum source. I'm not sure where it connects on the L36, but probably somewhere around the front of the throttlebody then back to the firewall.
Getting it smoke tested would be the easiest route, but assuming that this leak is big enough to cause the car to run like crap you should find it pretty easily. If you can't find it just by visual inspection and listening for a whistling noise, you can run the car and spray carb cleaner along the evap line. Listen for a change in rpm's, as the idle will change when you spray the carb cleaner into the vacuum leak.

I'm betting you either knocked something loose or cracked some tubing when you did the other maintenance, so it is going to be easy to find.

If worse comes to worse and you can't find the leak, you can disconnect the evap and cap off the vacuum port temporarily until you can get it smoke tested. I would not do this as a long term solution, as the evap would still be sucking vapors off of the gas tank and releasing them into the engine bay while the evap is disconnected.

Let us know what you find out.

-Riggs.

 

I've also heard of using a spray can of "starter fluid" to accomplish the same task. Helps you pin point the location of a vacuum leak.

Rick suggested making sure the wires are tight and not crossing. You may also consider faulty wires that may be arcing (I had that happen once with a brand new set of el cheap-o wires). Arcing typically generates a snapping sound and is best looked for in the dark (as you can see the glow of the arcing more clearly). Using a bottle of water and misting it around the plug wires can sometimes help. The description your giving doesn't lead me to believe they are arcing, but it's a simple enough check to mark off the list.

 

Yep, you can also use an unlit propane torch. Pretty much any flammable vapor that you can kinda concentrate into one spot will work. Just stick to something that's safe to run though the engine.