audijim113

2000 A8 170K miles - 3-1/2 hrs from home (west michigan). Engine lost power, missed. At first there was no check engine light. After I shut it off, terribly hard to restart. After terribly hard start and stumbling, CEL came on. During stumbling, it started blinking for a bit but stopped blinking as engine revved

It was already after 6:PM so I attended a meeting because that was the purpose of being there. At 10:PM, decided not to drive home late a night and stayed in motel.

In morning, after difficult start I started calling shops. Called my mechanic at home and he suspected a coil pack. Difference of opinion between him and owner whether I should drive or try to find repair place. No Audi Dealers or ever VW in outskirts north of Detroit (sort of a less-than-friendly environment for any foreign car) Did find one mechanic who put a OBDII tester on but he said it wouldn't work on my car.

Started heading back on highway. I could maintain highway speed but could feel lack of power on slight hills. After hr drive east of Lansing, I called an Audi dealer who said as long as lite not blinking it should be able to drive. Called a couple other shops and got conflicting opinions on drive / no drive. Moot point anyway as this was Wednesday and everyone I spoke with couldn't squeeze me in to even look at it until Monday. AAA towing only up to 20 miles otherwise cost an arm and leg to get home. Didn't know anyone in those areas so I decided to drive all the way.

Made it to my shop and left it. Wife came picked me up. Like everyone else who had a short week due to Memorial day, he may not be able to look at it until next Monday.

Question: Are these symptoms what you'd expect with a bad coil pack? Could driving for 3-4 hrs with the miss cause any other damage? If the plug wasn't firing, would raw gas washing down that cylinder damage the rings, etc? It did not get any worse on the drive home. I only turned it off once to go to bathroom and was able to get it started. It would even idle halfway decent and I didn't smell any bad rotten eggs out the exhaust which might have indicated it was pouring gas in the cat.

Someone suggested coil packs are wired in pairs and if one goes, it might take out another. Any truth to this? What should it cost for a coil pack replacement at an independent shop?

sonata54

Coil packs are very easy to replace, if you take off the three engine covers(you can use your key to turn the cross locks), you will see 4 on each side held in by 2 small screws each, each coil pack can be unplugged from the wires as well so that you can replace a single plug if need be. on autopartswarehouse you can get a non-oem single plug for around $45 or a set of 8 for $225. If you can access vag-com or a code reader you can probably see which cylinders you are getting misfires in.
If you do end up replacing the coil packs you might as well change your spark plugs while your in there!

A8CT

Sounds like fuel pump to me. Any obd scanner will tell you if you have a specific cylinder misfiring.

The hard start comment leads me to believe its not a coil.

silverd2

If it's a coil pack gone, the ECM "should" have shut off that injector as soon as it was detected. I've driven long distances with a single failed coil and had no gas smell or fuel fowled plug, as a result.

Also as Bob correctly stated, ANY cheap OBD code reader (Autozone, etc..) will tell you exactly which cylinder is misfiring...it just won't tell if it's the injector or coil...usually the coil...much more likely to fail.
Easy to check >>> switch misfiring cylinder coil with the one next to it (or any other), clear code and see if the misfire moves to the other cylinder...if so, it's the coil...if not, then the same needs to be done with the injector on the misfiring cylinder.

BUT, If you get a random multiple misfire code (more than one cylinder) it is NOT a coil pack problem and not likely an injector problem either.

Nope, coils do NOT fire or operate in pairs...each coil pack in your model car (40V) has it's own built-in power output stage and gets signals individually from the ECM.

Adjuster

Is there an ohm test that can check and see if the coils are good or bad?

I've got a random misfire that is driving me nuts. It runs fine around town, but now if I push it past 60mph for more than a few seconds, the engine light flashes, and the ECU drops off a few injectors/coils, and it runs rough.

Stop, or put it in neutal, shut off the engine, start it again, and it's fine....

I'm getting very good at doing this as I come off the freeway, to re-set the ECU so it will run smooth around town..

Also my fuel ecnonomy sucks big time when the CEL flashes.. Drops to 14 or lower at 65mph, while around town, it's in the 20's much of the time. (or at 60mph on side roads, no cruise control used.)

Seems like it goes into the drop spark/fuel mode when the cruise control is activated, and the car is going a steady speed over 60mph for a half mile or so.)

Help? Ideas?
This all started when I changed my plugs, and ran 5 gallons of toulene in the fuel tank to clean up everything. I've since put the OEM plugs back in, and have run 5 tanks of fuel, and it's better than it was, but still misses/random misses.

I've also replaced all the vac lines with the braided cover, and can't find any vac leaks. Put a new air filter in. I have yet to change the fuel filter.

silverd2

No specific test for the coil pack itself, except to switch a known misfiring cylinder's pack with another. Bentley has a procedure for checking signals getting to the coil packs (and built in power output stage)...but in all I've experienced and read, the coil packs just go and don't fire again. I've replaced 2 that went suddenly and completely, without warning...about a year apart...never more than 1 at a time.

Random or intermittent misfires are virtually never the coils.

With starting a list of other causes, I'll just guess (what I would suspect if it was mine) from your history, that maybe the toluene worked a little too well, broke loose trash and went to the injectors. I'd be thinking about taking them off, inspecting and attempting a good cleaning of all of em.

I've never taken mine out, but not too difficult. I'd think there's a way (with the right size hose) to maybe back-flush each with carb cleaner (or similar)...might need to jump power to each to open for this. Just a guess, but what I'd be considering, since the problem started with a fuel system cleaning and the injectors are at the end of the line AND trigger the same blinking CEL and misfire codes as a coil...and coils don't behave that way.

audijim113

First, let me put some things in perspective. I don't have a OBDII meter. I had very few tools with me. Although I have worked extensively on most of the Audis over the last 25 yrs, I am getting past that point. (I'm 67 yrs old). I'm not totally dumb about the workings of the car but have not done must on this A8 other than to change the purge valve a month or so ago.

Regarding the fuel pump, it was replaced by an INDI shop (not cheap) about 2 months ago. Following that, I did get a CEL and i believe it was the "small emissions" leak. CEL has been on and off over the last couple months with no discernable impact on the way the car is running. As mentioned, I did change the purge valve. (Never put any toulyne in the system)

I also swapped the gas cap with my wife's 98 A8 to see if it would make the CEL go away or go to her car. It didn't

Following the fuel pump replacement, I smelled gas in the trunk. Shop said it was a loose clamp on a hose but the smell re-ocured awhile later. Now it's only faintly noticeable. Shop said they would replace the "o" ring seal on the pump but I have been very busy and not able to get it in.

Previous to drive to Detroit area this last Tuesday, I thought I noticed a "stumble" but not something that rose to the level of concern. After driving towards Detroit for a couple hours Tuesday PM with the AC on, I noticed a slight decrease in power going up inclines. Following a pit stop, it was extremely hard to start and missing big time, shuddering and wanted to stall. It felt like it was running on 7 or less cylinders and loping. Eventually the engine revved up. Prior to revving it up, putting in in gear almost stalled it. Getting out on the highway, it would run but the power was decreased.

I'll skip over the recommendations, suggestions as to whether it was a coild pack, etc and just talk about what I noticed. Getting to my first destination I shut it off and it was really hard to start but I did get it going. On the way to my second destination I stopped at a McDonalds. Coming out, I could not get it going and didn't want to run the battery down.

Across the street was a repair shop. They didn't do foreign, (just American stuff). They were also closed but sitting around smoking cigars. The reason I went in was to ask if he knew of a shop that knew Audis. He made a few calls but it was almost 6:PM and couldn't reach anyone. At that point, I thought I might have to find a shop in the morning and asked if he thought my car would be all right in Micky Dees lot. He said to try and get it to his lot. It wouldn't start but he helped push it across the street.

He then said maybe he could connect his OBDII to it. Afer connecting it, he said it didn't work on my car. Maybe he didn't know what he was doing but he was doing it as a courtesy so I wasn't going to slam him. He then tried to start it and finally it caught. He revved it way up for a while. After a a bit of revving, it almost seemed to idle. Knowing I had another 45 minute drive to get to a meeting I planned on attending, he said why not try and drive it so I did. On the highway, it could go 60-70 but I could tell it wasn't right and power fell off on slight hills.

Getting it to my meeting, I parked it and went in. After the meeting, it was 8:30 and I had planned on meeting someone for dinner so I knew I had a ride if I needed it. It was up in the air as to whether I was going to stay overnight anyhow and I had brought a bag with a change of clothes, etc.

At dinner I debated whether I wanted to be stranded along the highway in the dark if it died completely. I decided to check into a Red Roof.

In the morning, after some lengthy cranking, it did start and I drove all the way, making some phone calls along the way to ponder options and possible problems. I made it home and to the lot of the guy who normally works on my car by 3:PM. That was Wednesday. Being a short (Memorial Day week, he was backed up and wasn't sure whether he'd have time to look at it. It's now Saturday and he hasn't gotten to it yet.

I realize without codes, etc, it's hard to diagnose, but having driven cars for over 50 yrs it (missing) did not feel like fuel. It was distinct like the stumble and miss from a cracked distributor cap or wet wires back when they cars still had distributors with points, plug wires and one coil.

Of note, when the fuel pump did go out on me two months ago, I was driving on the highway, coming to an exit and it suddenly lost power at highway speed. Giving it gas did nothing and I coasted up he off ramp where I was dead and no amount of cranking would work to start it. With my situation this week, once the engine was started, I could keep it running. Even when I got to the shop, I let it idle when I went in to see if it would dies. I went in to see the owner to see it perhaps he wanted to bring it inside. It continued to idle for 5-10 minutes until I took my junk out when my wife picked me up.

silverd2

Jim, if I was close by, I would gladly come over and help.

I like you and feel like I kinda know you, esp after speaking with you on the phone a while back.

I have no idea why their code reader wouldn't read your car, unless you have a problem with a module...all North American cars from 1995 on have the same port and same standard computer language...I guess you'll find out when your mechanic reads it...if his works, ANY working code reader would work.

I bought an OBD2 reader years back and keep it in my car. I did this after my wife was having a problem miles from home and stopped by the VW dealer to have her car checked. Turned out that it was not a disabling problem, which I took care of later. They charged her $80 dollar to take the reading and since it was a problem that tripped the CEL, it was easily readable with a regular home OBD2 reader, which I learned I could buy for $40-80.
It has saved me a fortune and countless hours of trial & error searching for problems. Even if you don't do the work yourself, it can forearm you for visits to the mechanic (I've met too many "honest" ones that still ripoff their "best friends"). Also, the reader can sometimes tells you it's an incredibly easy fix that needs little effort to correct.

Please let us know what you find out. I'm always curious to hear the outcome...I never stop learning from others' experiences.

Cheers,
Sam

audijim113

Your reply was much better than the others. Hopefully those who said, "just do this, etc, will realize I wasn't asking for a "how to", but rather a "what to you think it is?"

Those who jumped in without reading offered all kinds of "this is easy", "swap this" etc. No one seemed to understand that I was on the road in an unknown area with no tools, no scanner. After I got back, I was looking for feedback on what happened.

Thanks

silverd2

I understand. But in defense, I often offer a lot of "what to do" to friends (in person), whom I know do nothing at all to their own cars. But I find that they are at the mercy of mechanics of "questionable" talent and/or honesty...and I hope my input will forearm them with knowledge to compare to what their mechanic says...and also hope "maybe" to urge the mechanic to be a little more honest, if he thinks the customer knows a little more and are not just readily willing to accept any line he hands them.

I know there are a handful of honest mechanics...but they ARE human and there's just a handful of honest humans.

Cheers