MikeTTR225

I just pulled what was left of my hair out on my 2001 a8l.

Was getting random misfires and lean codes. Did the MAF clean thing, as well as changed out all of the vacuum lines. changed the plugs as well to the bosch platnum +4 (so that is not the issue as it purrs now with them)

It had a leaky breather valve (top back of intake manfold) you should check that. Still had a problem so did the spray the engine with something flamable (wd-40, starter fluid, etc.) trick. [RPM's will go up if there is a air intake leak]

Turned out the main problem was the throttle body gasket (its some sort of paper/mica like construction)

The new one is metal (the passat uses the same part number, so its cheaper from VW), changed the intake manafold gasket while i had it apart.

After the leaks went, so did the misfires and lean codes, purrs like a kitten now. How this helps, took a few weeks to figure it out....

Adjuster

If the intake gasket was bad, or the throttle body gasket was bad, I'd think at idle it would run poorly, and the engine is smooth as can be at idle, and around town under 4000RPM.

I know this car has sat around for many years with LA California spec fuel in the tank over those years, and I have no idea what deposits that might have left. Or if there was corrosion from the ethanol they cram into the fuel blends to reduce "smog."

I know when I bought it in LA, and drove up from there to Boise, it was running great, and ONLY the CEL flashed for the first time when I was pushing over 120mph.

Prior to that, it was running fine. Power was amazing at high speed, and the S version's intake manifold and other engine changes really come to life as the engine RPM increases over other A8's I've driven, and they are no slouches at speed either.

I'm very happy with the S8, but then I put 5 gallons of Toulene in with a tank of gas, and it's not been happy since.

I figure the Toulene must have disolved some crud in the tank/lines/injectors/filter? And that crud is causing problems still.

However, with a new fuel filter, and I've put 20 gallons of Toulene into the car over 6 tanks of fuel, so I'm pushing it to clean itself pretty hard.

Yesterday, added the 5 gallons to this current tank of fuel, and at first, it was not happy. (Added the Toulene, and then drove to fill up the tank, and put in 11.7 gallons of pump 91 octane from CostCo, locally filled/supplied by Chevron, with Techron additive in it as well, with 10% ethanol in it like all fuels around here for the most part.)

The prior tank was on top of a tank of the same 91 with 5 gallons of Toulene in there, and I put 12 gallons of 87 octane Conoco gas, with ZERO ethanol in it. (Around here, Kicks66 stations are the only ones with ethanol free gas.)

The funny part was the car ran excellent, with that tank of fuel, now I can go 60mph, no flash, flat ground pushing 70mph no flash, but slight hills, and it will flash... ON that tank.

I put the Toulene in and drove to CostCo, and DANG it was way worse. Dropped about 3 injectors I'd guess, and I was not pushing it too hard, but I did boot it 100% WOT getting onto the freeway, and a few other times as my dad was following me, and I wanted to see if WOT runs would help to clean out the injectors or fuel system with this short drive of 10 miles to fill up the tank, and reduce the blend of toulene to petrol. (I dont' like to run more than 30% toulene much, as it can cause wear since the toulene has no lubricating effect, and dilutes what effect petrol has on the pump and injectors, and any other moving parts.)

So, now the good news.. Filled up with the 11.7 gallons, went shopping and had a hot dog with my dad, and driving home? No flashing CEL up to 70mph, even up the slight rises.. and it flash a few times while acclerating, but did not drop any injectors out this time...

Perhaps the crud is finally disolved, and cleaning up?

If not, I found a local shop that has the right equipment to test, clean and re-test the injectors to confirm they have rated flow, and no issues. (New o-rings, filters etc.)

If the injectors don't do it, any easy way to test pump pressure/flow? I used to have a gauge with adapters for the schrader valve type ports on some fuel rails, but wonder if I'd need an adapter for this vehicle? I need to look closer at the fuel rail I guess.

Oh, I put a K&N panel filter in too. (I know they can trip CEL lights, but not make them flash.) Also put new activated charcoal cabin airfilters in, and they work well, but are not as thick as the OEM ones. But are working fine, so I'm not going to complain about 28.00 filters, when the OEM ones are 80.00 or more at the dealer.)

Need to do the fan clutch, and put my new Goodyear "gatorback" serpentine belt on there at the same time. Thanks for the tips on how to do it.

Adjuster

UPDATE: Well, the fuel injectors were in excellent shape, that's the good news.

The flow test before cleaing was 1cc better on one plug than the others, but the other 7 tested out exactly the same BEFORE they were cleaned, as AFTER they were sonically cleaned. There goes 128.00 out the door, but I now know for sure the injectos are fine. (OHM readings/test were fine too.) New filters, O-rings, and what I think they call Pintle Caps on them.

Put them back in, and of course, there was no change in how the engine runs. Still get the random misfires if WOT, or speeds above 65 to 70 mph...

Engine starts and idles fine. Smooth, and runs great, there is an exhaust leak on the right side, but I can't imagine that's the problem, and I have not found it yet. (It's either a loose manifold, or fitting somewhere on the down pipe/cat.)

The fuel injection guy was stumped too. Says he agreed the Toulene might have loosened up some gunk, but that the injectors are clean, and with a new fuel filter, it's not either one of these..

Now the pump I guess? I'm going to do some checking on this aspect, as I don't hear the pump making noise, and there is plenty of fuel pressure, the engine pulls strong to red-line in all gears, the CEL just flashes, and the ECU cuts out injectors after it's run at a steady speed on cruise control.

Again, just to recap... Bought the car, drove it from LosAngles to Boise and it only flashed the CEL when pushed above 120mph. If I wen 115mph, no flash.

Got home, put 5 gallons of Toulene into a tank of gas, and WHAMMO. The engine started to run very rough, CEL flashing at even 45mph.. Idle improved quickly, but the CEL flashed and injectors were dropped and only ran smooth after I shut off, and re-started the engine.

I pulled the plugs, and put Autolite Irridium/platnium plugs in, stock gap from the box.. (My screw up, should have checked it, later found out the "gap" was .40 to over .45... RE-gapped them all now at .30 and they work great, nice and smooth, pull smooth to redline.)

Okay, so a few tanks of fuel later, it's doing no CEL flash at speeds up to about 60mph.. Ran another tank with 5 gallons of Toulene, and it's cleaned it up to where I can run 65 or even 70mph at times with no CEL/Random misfires...

Changed out the fuel filter, new WIX brand one, no improvement. Pulled the injectors, and had them cleaned now, no improvement.

I take it the options are:
1) Intake manifold leak, or vac leak somewhere
2) Failed or failing fuel pump?

Any other ideas?

This car is fun, but driving me nuts.

aduggs

I had similar symptoms before my fuel pump finally failed. It would give misfire codes at WOT above 6000 RPM. After changing the fuel pump, it went away. A failing pump can cause the engine to run a little lean, which is not noticeable at lower RPMs.

Adjuster

It's got to be the pump, have rulled out all other possibles. (No vac leaks, no leaks from spraying carb cleaner around, the injectors were fine, and now are really super clean, not that they were dirty... And the fuel filter is new.

What's the link to the pump source? I'll do a search, and I've watched a few vids, but will have to go over it all again to make sure I get it right, and only pull the pump once.

silverd2

Pump source:
http://www.worldcarparts.co.uk/Defau...&ProductID=342

I've not been forced to do this job yet (wait for it) but, other than the fuel pump vids, the best advice I've heard is to precisely mark the exact orientation of the fuel pump housing with a sharpie BEFORE pulling it. The pick-ups seem to be much easier to line up correctly (with or without a borescope) upon reinstallation...the one step that universally is said to be the toughest and done incorrectly, leads to future gas starvation problems...and further reinstallation attempts.


Videos:
http://www.google.com/#hl=en&sclient...w=1318&bih=847

Adjuster

I pulled up an ebay seller of the same part number here in the USA, so It's on the way now.

Hope it's the same part, or same quality, it did not say it's the Siemens brand, but I'm fine with Walbro or others like Denso etc. (Just as long as it fits the housing correctly, and that part appears correct even down to the two different size studs for the power connections.)

Now I just need to clean out my own fuel system, as last night I found out I have a 1.9cm kidney stone surrounded by other smaller stones in my right kidney... that explains the pain, I'm just glad it's not tried to move down the tube to the bladder, I've had them get stuck there before, and it's amazing how much pain it causes.

silverd2

I have never seen the same pump available in the US.

If the price was better than the UK price and REALLY the same pump, with the same 2 fuel pick-up fittings on the bottom, I (and others) would love to know the source for future reference.

Sorry to hear about the stones...past and present. I don't want to know what that feels like...ouch...just euthanize me.

Adjuster

Yes, my level of trust that what is being shipped to me is the correct part is decreasing as I've read the stories about the wrong pumps, or pumps that have been defective right out of the box brand new.

If the pump is not correct, I'll just return it, and pay more to get one from the UK or other EU supplier.

Adjuster

Pump arrived, it is the wrong part. Looks fine, but has no second hole/port on the lower part of the pump....

Bought it from AIP out of CA. We shall see how returns go...

Now on to the next source.. The EU or England most likely.