If you have been following my ongoing struggles with my 8, you most likely already know that I have been plagued with a boggy feeling spool, a cold idle surging/misfire feeling that is very pronounced every morning but fades as the car warms up, a loss of gas mileage and overall the car does not have any snap. Things have gone from annoying, to seemingly worse every day.

No burning oil
No odd engine noises
Idles fairly stable and smooth
No codes.

I suspected a failing upstream 02 as the oem sensor is seized in the stock housing, however I was stopped dead in my tracks during the swap as the sensor is basically welded into the car and I didn't want to push my luck.


However...........I put a temp gun on the exhaust runners today just out of curiosity. I saw numbers that were a touch under 500 degrees for cylinders 2-4, but cylinder 1 is a solid 100 degrees colder than the other three. This strikes me as a big problem. Common sense led me to try wires and swap the coil in question, and though the car is smoother now it is still a dog, and still -100 degrees in cylinder 1.

Talked to STM and they advised me to listen to the injector to see if it may be stuck open. It sounds just like the other 3, clicking away fine. I am left to consider a blown headgasket, valve issue, or a bad ring? I would have thought I would use oil, see temp issues, or black smoke? Very confused and at wits end here, if anyone has any insight fire away. In the meantime I am trying to get it out to STM Friday.

 

Have you done a compression/leakdown test on all cylinders?

Might want to check that before you move the car anywhere. You can get a compression checker from most auto parts stores.

 

As for the O2 sensor, the last time I changed one I did it with the exhaust hot. BTW, the only time the car uses the O2 sensor is when the engine is warm and running at constant load and speed.

 

Just thinking out loud, but the cylinder one injector may still be leaking even if it is clicking away. The solenoid may be running properly, but is not getting closed completely. If this were the case, you could check it fairly easily by running the car for just a couple of minutes, then kill it and wait a couple more. If cylinder one is misfiring badly on the second start-up, it may be the injector. Next step would be to check fuel pressure after shutting the car down. Don't let the car get hot beforehand...you don't want temperature loss to impact the residual pressure. If it drops more than a couple of psi in 20 minutes or so, it may be worth it to pull the rail.
BTW, contamination on the injector tip (think of an old shower head with calcium deposits on it) can cause droplets of fuel to enter the cumbustion chamber instead of a mist, which can cause misfiring when cold. Once the engine warms up, it can atomize the fuel well enough in time for ignition to make the issue deminish.
Good luck, man.

 

I would lean towards a leaking injector. Last summer cylinder 2 was 100* cooler than the rest, I was having idle issues and others similar to you. Replaced the injector, done deal. I would pull the injector and at least inspect it.

 

Thanks for the input guys. Unfortunately my work schedule and the fact that its a DD have really handcuffed me here. The guys out at STM should be able to take care of me.........I really hope it is as simple as a shot injector or something of that nature.

As for the 02 sensor, I am pretty familiar with open/closed loop, and I have watched it like a hawk on a scan tool. Amazing how fast this car switches to closed loop when it starts cold, I would say even on a 40 degree morning it is looking at the 02 sensor before I get rolling.

Interestingly enough, I yanked the #1 coil to see how rough the motor got and it actually broke up pretty bad. So there is some sign of compression and spark. A compression and leakdown test will likely be the first steps tomorrow. Cross your fingers for me.

 

Updates. Took the car to STM tonight. Emery drove the car, once again he told me he thinks it feels fine to him. For peace of mind I had them run a compression test, and the cylinders ranged from 140 to 150 but never varied more than 10psi. Oddly cylinder 1 was strongest. A read of the plugs indicated that they all appeared similar in burn, so the plot thickens.

As for the cylinder being 100 degrees colder, they did not think it was that big of an issue. He suggested swapping the injectors around to see if there is any correlation. Also Emery walked me through the engine bay and showed me three critical grounding points that are trashed with rust. Surely this isn't helping me any, as they are grounds for nearly every 5 volt referenced sensor.

The 02 sensor is still in the list of possibilities for the surging, since I was unable to have it replaced. They were quite busy, and after talking with the guys I decided to wait for the 02 install until we put an upgraded o2 housing in the car. I am going to try ruling the 02 sensor out by starting the car with the front sensor unplugged, and driving it around the parking lot. I will immediately know if it is my cold start surge culprit.

So my plans for this weekend now that the engine essentially has a mechanical clean bill of health, is to clean up every ground I can find, and to bolt in my cat delete pipe to rule out a clogged stock cat.

 

Can anyone tell me what the box directly to the right of the injector resistor pack is? It resembles a heat sink and appears to have more resistors inside of it. I am very curious.

 

Fuel pump resistor for operating during idle and cruise.

 

Idle and cruise..............the two places my car feels like ****!
Interesting. I wonder how that could be tested.

That looks rather rusty in my car and considering it seems like the gremlins I am dealing with are fueling related, this could be something to explore. Wonder where I can snag one of these!

 

So I was able to go outside tonight and check all four injector plugs for obvious signs of a bad connection, and while I was at it I measured the resistance of each injector. They were 2.3 ohms across the board, so nothing is fried. My next experiment will likely be to swap the injectors around and see if the cold cylinder follows.

 

Trailing 02 sensor is reporting .8 volts constantly idling. Engine hot, after 40 miles, this strikes me as rich???? Same sensor read right around .76-.80 at 50mph under very low load/no boost watched these numbers all the way to work.

 

Its only the front O2 sensor that matters for closed loop trims and not the rear O2 sensor.

 

Doesn't the trailing sensor report the overall state of the cars tune after it has been trimmed and sent through the converter? I was under the impression that the trailing sensor should hover around stoich under low load ( .5/.6ish, then richen up as you start giving the car more throttle?
Just thinking out loud, I could be dead wrong here.

 

I might be off here, but as I understand it the rear sensor reports back to the ecu what it picks up-- at that point that reading is compared to the frt sensor to measure the difference with in a range, that range determines if the cat is working as required.---thats all it does--