i have a 1999 a6 quattro with 2.8l v6. it hesitates on acceleration and occasionally backfires. it idles fine and once i get up to speed it goes fine, but the condition keeps getting worse every day (it started around 2 weeks ago after i did an oil change at meineke). so far i changed the air and fuel filters which didnt help. there were no engine codes present at the moment. after that i disconnected the battery, disconnected the MAF sensor and cleaned it. hooked everything back up and when i started the car, CEL came on. so i hooked up the code reader and got two codes: p0102 which was about the MAF sensor and p0301 cylinder 1 misfire. i cleared them both up and went for a drive. when i really stepped on the gas the car would hesitate and unless i took my foot of the pedal it would back fire (only backfired around 5 times total since this all started). the CEL started flashing and stayed on. i hooked up the code reader again when i got home and only code p0302 cylinder 1 misfire came on. so im assuming the MAF sensor is fine at this point

what can i do to fix this problem? could this be something simple that the guys at meineke could have messed with in order for me to come back to them and give them more business? where should i even start at this point? i was gonna clean the throttle body but wont be able to do that for a couple of days because no one has the new gasket in stock and id have to order it. what should i look into thats the cheapest to start with?

thanks!!

 

UPDATE:
just had all the codes cleared and took it for another drive. when it was a little colder it ran almost good, but once it warmed up and i stepped on it, the CEL came back on. i hooked up vag-com this time. here are the codes that came back:

16684 p0300 35-10
16685 p0301 35-10
18014 p1606 35-00
16684 p0300 35-00
16685 p0301 35-00

EDIT:
im suspecting the injectors mght be clogged or something could be going bad with the fuel delivery. i might run some seafoam through the car later this week. ill post updates later on. any "push" in the right direction from any of you guys would be much appreciated... i just want the car to run the right way... it feels like it lost a lotta power over time...

 

How many miles are on your 2.8?

I would have reason to believe that the coil pack and / or spark plug may be to blame for this random misfire / hard acceleration you're talking about. I would start by checking the wiring to your coil packs and making sure everything is secure. Who knows what they could have done at Meineke, but from a routine oil change it would be pretty hard to disrupt the coil packs.

 

165k miles with some change on it. ill look into the coil packs and spark plugs asap. where would i find the injectors?

 

From what I understand, they have orange plastic connectors on them, so it makes them somewhat easy to find. When you take off the beauty covers, towards the very top of the engine you will see the orange injectors - They are a little higher than your coil packs / spark plugs.

See this page for more details / pictures.

 

UPDATE:
just changed the spark plugs, cleared all the existing codes, and cleaned the MAF sensor again (had to take it off anyways to get to the spark plugs, might as well). when i first started the car it sounded kinda weird and idle was inconsistent, maybe between 500-800 rpm. took it for a 10 mile drive with a combination of hard/light acceleration, hard stops, easy stop etc. and the hesitation is GONE (sweeet!!!!!); however, i noticed that when i come to a complete HARD stop the idle rpms drop to about 400 and it sounds like the car almost dies but it comes back to 600+ rpms within a second. when i come to an easy stop it idles normal, maybe a little off when its still cold but i guess its not much of a big deal.

when i was changing the plugs, on the driver side of the engine bay i noticed some oil on the plugs and near the area where the oil filler cap is. the most of it was on cylinder #4. my hypothesis is that when i went for an oil change to meineke they could have spilled some oil into my spark plug wells and that could have caused the whole hesitation problem (besides my plugs being old as s**t lol). i guess ill be doing my own oil changes from now on... ive been getting too lazy.

bottom line: the major problem was fixed and no engine codes have come back yet, but then again i only did a 10 mile drive. i will drive it to work tomorrow which is 35 miles each way and if anything happens ill come back here and post another update.

the minor idle problem i have sounds like something could be going out but i guess it wont be too soon. anyone have an idea what could be causing this?

thanks for all the input!!!

 

The oil you found is most likely not from someone spilling oil, but from faulty inner and outer valve cover seals. I'm guessing yours have never been changed. This is normal for a car of your age / miles.

This is a relatively cheap and easy fix to do, but it does take some fancy maneuvering about in order to get it done without taking the entire car apart. Here's a link on the how to.

As far as your idle, this maybe from a lack of vacuum. Does this happen all the time now, or just sometimes?

 

the idle happened to me this morning when i first sarted it up and it was fine the rest of the day. i drove the car around 70 miles today and so far no CEL. im pretty sure the valve cover gaskets have been changed around 20k miles ago, at least thats what the previous owner said. the thing is that the oil i found in there wasnt just residue, it was still liquid.

 

When you have that weird idle problem, does the car seem to want to lunge forward? For instance, if you have it in drive and your foot is on the brake and the idle speed drops, does it make you have to hit the brake more for the car to not move?

 

no it just seems like its about to stall. just did around 180 miles since i fixed the hesitation problem and the idle thing happened only a few times. hasnt happened to me today tho. one thing i noticed is that when i first start the car, as long as i dont just stick the key in and start the engine, it doesnt happen. tried doing a few sudden stops today and it hasnt happened either.

i dont know what it could be. maybe the computer was adapting to new plugs in the car? it sounds stupid but is that even possible?