Have a 03 audi allroad. 2.7t Just got done doing a passenger side head gasket and now have a misfire on cylinder one thats constant and a occasional missfire on cylinder 4. Now the strange thing about it is Ive had the misfire go away on ocassion just to come back on me. This is what ive done so far to try and diagnoss the problem. Ive changed and tried new coilpacks Ive installed a new conector. Ive checked to make shure the injectors were pulsing, new plugs. Have stripped some of the sheathing back to check wiring harness, Ive sprayed starter fluid arund to try and locate a vacum leak and have done a compression test. Everything has checked out so far. When I drive the misfire code will go away mainly at idle and always on cylinder 1. Im going to pull the manifold off and install new gaskets and check to see if something is not right under it. I did break the valve cover evap hose and have slid another hose over it and didnt know if the motor in some way regulates that and causes a lean or rich condition. Please anyone my wife likes my hair and i dont want to loose anymore on this freakish nightmare.

 

Have you tried switching the coil to see if it moves? You may have a bad one. Checked your plugs/gap? Plugs seated properly/tight? MAF? Wires?

Could be your ICM. Two little electrical blocks that sit on top of your air box. Not sure if they throw individual codes when they start to go bad.

good luck. keep us updated.

 

Lets back up a little.

Explain the misfire. When it happens. Driving along, on start up, warm,cold
Pull the codes and post them.

What was up with the head gasket. It blew out, car overheated, bent valves?

It can only be something wrong with one of three things compression spark or fuel It's most likely one a few things. bad spark, no fuel or too much fuel or something (oil, water, or gas) is creeping into the cylinders. Figure this out and we can chase it down the next avenue.

To give you something to go on till your next post,

You can check spark signal with noids (google them up) I use a small led inline from radio shack. swap the coils and spark plugs and see if the misfire moves.obviously if it does you have a bad coil or spark plug

What psi were your comp tests on all cylinders??? (avg of 3 tests per cylinder with engine cold and another test with engine hot) Do it again and post that info.

Check for fluid, with the engine cold stick a long tube down the two problem cylinders and see if you can suck anything out. There should be no fluid in there. Fluid in the cylinder will raise your compression reading by sealing the rings, this will cause a misfire or detonation. If you have fluid determine what it is coolant or oil or gasoline.

You can check the injector signal with a test light, then pull it out and actuate it with a small 9 volt battery while spraying sea foam trough it. Then let the tip soak in sea foam and do it again. You should have a clicking when you actuate it with the battery and a nice even spray pattern.

Stop stripping wires you need to replace that sucker now. Use solder to connect them. Braid the wires solder them and use shrink wrap. It's a pita but I go from terminal pin to the next terminal pin. If the wire is bad I run a new wire right over the top and cut that one out. Make sure that you go from pin to pin and don't have relays and modules in between though.
The only thing that should be stripping in a shop is a few chosen babe customers for example; https://www.audiforums.com/forum/alb...pictureid=1770 I'd like to test her intake

 

Ok will try and answer all the questions posted. the cose is 301 on a generic reader. misfire doesnt move within coil packs. Have repalced spark plugs on that cylinder multiple times. misfire comes when cold or warm at idle. if you drive the car it goes away till you idle it again. I had to replace 2 valves on the head why the headgasket. Ive done compression tests multiple times at cold I usually see 150 on all cylinders. Ive peeked down with a bore scope and have seen no puddles of fluid in the cylinder. Ive checked spark on the coil pack and looks good and have scoped the injector to see if it was pulsing. I checked the injector wiring pulse with a light and it was good. Yesterday I screwed around with it and installed a different coil pack and plug did nothing sprayed some starter fluid around the intake and no rpm increase but the misfire went away shortly right after that and went to the gas station and drove a mile and then missfire came back. Im going to pull intake off tomorrow and check injector spray. Im really leaning on taking away the mechanical aspect away of it. Dont thinka mecahnical aspect would come and go. As for stripping wires your right. I just soldered conections but really feel I need to take the harness back and just replace the whole wire and see if there is another problem. Does a crack in the pcv tube cause a missfire problem. By the way there is no ignition control module on this car they are built into the coils.

 

Most likely carbon on the valves. If you have compression and replaced all spark components. its either a leaking injector or carbon on the valve.

1. Swap the number 1 injector with another to see if the misfire moves. If it does replace the injector, if it doesn't. Pull the intake manifold off and look at the intake valves. Clean the carbon off and inspect them to make sure they're are burnt or cracked.

You should find your answer there.

 

Im going to try that tomorrow.I had forgot to get new inatke gaskets when I did the job and want to eleminate one possibiltiy there as well. I might have gotten a piece of dirt in the fuel line. Didnt think so but u never know. will peak at the valves again when its off.

 

You can do a leak down test for that too. You need to seal the rings with a little oil. Pressurize the cylinder and see how fast it leaks out.

How has your coolant res. been. Has it been getting low?
You most likely would have seen coolant in that cyl. though.

You need to also inspect your cam lobes for damage.
If they are worn it's very evident.

Is it possible these valves got hit as well and aren't seating?
leak down or inspection will determine that.

 

I need to comfirm this still but it appears to have a window of goodness to it. When I first start the car it misfires. Let it idle for about 5 minutes missfire goes away drove it for a little bit and the misfire comes back. This has done to me the last 2 days. Im not shure if a coolant sensor can cause this problem. Acts like there is a temp range it works fine at. I dont have a leak down tester but going to take it to a shop soon if I cant get it. Wife wants her car back. No coolant problems everything appears rock solid there.

 

Thsi could be a bad injector which does not pulse at short (3 ms) pulse widths. I had this happen awhile ago on a Jag, it was the devil to find, but it does happen. As soon as a load gets on the engine and it increases the pulse widths, the injector functions fine.

 

Well I have comfirmed the car will quit misfiring once temp hits the first bar on the gauge. I drove around for 15 minutes or less with smoothness and then bam back to idle misfire and roughness. I can try swapping injectors. My buddies dad owns a german shop so I told them they could have a hour to try and diagnos it. Will see what they come up. Like chasing a ghost.