Emissions Warning Light On, Fault code reads misfire...but she runs just fine!

[michaelwoodward]

Hello can sombody help?

I've just bought a S4 quattro cab and have a new love in my life. Problem is she's sick; after driving my first 100 miles the emissions control unit warning light came on. Diagnistics reads engine misfire in all the cylinders. Turns out the fella I bought it off spent £400 on new coil packs trying to rectify this problem; this worked but it did come back on now and again.///hadn't been on for a while apparently. Mmm.

There is absolutely no noticable affect on performance, not does the engine misfire. When I took her into an Audi garage recently tp check out the fault codes, they couldn't find any misfire and cleared the fault. After a road test the light stayed off.

Now it back on and i've been reading a few posts about cleaning MAF filters and also adjusting the spark plug gaps; wider/normal spark plug gaps of .035-.045 inches might cause a misfire? A guy in a post gaped them to .022-.025 and this seemed to clear the misfire (he had also replaced the coil packs).

Has anyone experienced anything similar or can any tell me if this gaping stuff hold the answer?? Thanks very much!

[michaelwoodward]

Just spoke to Stafford Audi. Apparently all coil packs/spark plugs and gaps were checked. Doesn't sound like there's a straightforward explanation here, they thought it might have been a improperly cleared fault code. As the light's come back on, it ain't at all.

Sounds like no one, including audi, has the foggiest clue! A glitch possibly....

[JIGGY C]

Just spoke to Stafford Audi. Apparently all coil packs/spark plugs and gaps were checked. Doesn't sound like there's a straightforward explanation here, they thought it might have been a improperly cleared fault code. As the light's come back on, it ain't at all.

Sounds like no one, including audi, has the foggiest clue! A glitch possibly....

Have you tired the maf route? I have the same issue although its only just happened a day or so a go so I will keep you up to speed with what happens to mine

[michaelwoodward]

MAF filters....nice one Jiggy will find out if the guys at Stafford Audi had a look at that and let you know. No noticable effect on performance, just the annoying orange glow of the ECU light right?! If that doesn't sort it i wonder if i should accept it's a glitch....audi want it "for a couple of days" to "test some parts from another car". Sounds like they don't exactly know what's wrong and very expensive at the same time.

[michaelwoodward]

Jiggy guys at Stafford Audi tell me MAF problems would show up on diagnostics....didn't think that would be the problem. Your light still on?

[michaelwoodward]

Have just read the following - can anyone verify if this could be a root cause? Had a brake warning light on when i last visited Stafford Audi, they replaced a bulb.

"Brake light switches can be a problem, it has two switches in one, half puts the stop lights on, the other tells the computer that you are applying the brakes, so it can turn off the fuel injectors, if the engine is coasting, saving fuel and cutting emissions. The engine management light or EPC (Electronic Protection Control) will be on sometimes and the engine will run normal."