Completely Random Starting Problem

[cvbadazz]

Ok, I have a 2001 Audi A4 1.8 t Automatic with 121,000 miles.
Every so often could be minutes, hours, or days; cool, or hot engine; the car will just crank and crank, but not start. If I walk away for and hour or so, come back it will start like there was no issue. I bought this car 2-1/2 monthes ago for my wife, and have been working on it since, she hasn't even been able to drive it yet because I don't trust it.
What I've Done:
Fuel pump
fuel pump relay
fuel filter
crank position sensor
coils
plugs
collant temp sensor
K&N air filter
seafoam in gas
I can't figure it out, I have an appointment at the dealer on monday, but would like to see if anyone else has any ideas.
Also, only pending code is po171.(I assume from all of the cranking)
I know there are some smart guys on here who could help, please for all of my sanity HELP ME!

[cory.smith]

You underestimate the ability of a failed ICM to completely ruin your life. Pull the wires for your injectors, and pull the Coil and plug for cylinder #1. With plug in coil, have your wife ( or whomever) turn the car over. Check for spark. If none, then ICM (ignition control module).

Also, check this link. See if it helps.

http://db.tt/5yibMrj

-Cory

[cvbadazz]

supposedly I do not have a ICM. Apparently each coil has its own control module, I guess this started in 2000 on up models. correct me if I'm wrong.

[cvbadazz]

Any Ideas? please help before I have to go to the stealer ship!

[Lunchsacks]

did you seafoam the vacc lines? or oil? just gas?

also. from my experince as a 1999 passat owner MAF. if that thing has 1 spec of dust on it the car runs like poop. trying cleaning and or replacing your MAF

also check for vacc leaks.

try these if they dont work shoot me a pm and ill give you my number to try some other stuff.

[D's Avant]

Sounds like ECU problems to me... Are you chipped??? If so, the chip could be bad our loose, check the connections from the chip to the ECU board IMO.

I did everything you listed above with a starting problem and it ended up being the chip connection.

[Lunchsacks]

Sounds like ECU problems to me... Are you chipped??? If so, the chip could be bad our loose, check the connections from the chip to the ECU board IMO.

I did everything you listed above with a starting problem and it ended up being the chip connection.

po171 code

is a BAnk 1 lean error code.

nothing to do with electronics. all mechanical. his car is running lean from a vacc leak or MAF covered in dust.

[cvbadazz]

I will try cleaning the MAF again, I sprayed carb cleaner around the motor, and did not find any vaccuum leaks. I do not have a chip that I know of.

[Lunchsacks]

take the MAF out and spray it lightly with brakeclean and let it sit out for a little bit. then replace and try to start it up.

[cvbadazz]

I did seafoam in the gas twice, and in the vaccuum lines once. cleaned MAF this morning, and waiting to see how long it goes without not starting.

did you seafoam the vacc lines? or oil? just gas?

also. from my experince as a 1999 passat owner MAF. if that thing has 1 spec of dust on it the car runs like poop. trying cleaning and or replacing your MAF

also check for vacc leaks.

try these if they dont work shoot me a pm and ill give you my number to try some other stuff.

[cvbadazz]

Well, so far so good it has started about 6 times in a row, I will update if doesn't start tomorrow.

[mylittlemonster]

If it keeps on happening, it wouldn't hurt to replace your coolant temp sensor. They fail a lot and cause problems similar to yours. Did mine recently because of those problems.

[cvbadazz]

Well I took it to Audi, they scanned it and it showed some kind of ecu relay, which Audi says is $19 plus they said the ignition can cause the relay to act funny and throw a code. So I put in a new ignition switch and ordered the relay just in case.

[cvbadazz]

I t wasn't the ignition switch, relay coming tomorrow, Audi dealer says that has to be it if it wasn't the ignition switch.

[somebody5788]

Can't believe nobody has said this. It's probably your crank position sensor. But you need to plug in with vagcom and crank to see if it reads the RPM when it wont start.

[-:vw:-]

Before you spend any more money I would verify that it is getting fuel and spark not one or the other or neither. Once you've determined this then you can start looking at the various sensors. Do you know the exact relay the dealer ordered?

[cvbadazz]

ECU power relay, that is what the code pulled up. Also, I have already changed the crank position sensor. The dealer said the relay is located under the ECU. How hard would it be for me to do on my own?

[-:vw:-]

Hmmm under the ECU in the box or under the ECU and under the ECU box?? It's probably not too bad, it's fairly easy to work in that area access is simple.

[Lunchsacks]

Only other solution is to replace the whole car! lol..

Its getting there! we will get this figured out! :)

[-:vw:-]

Ya... I'm having a similar issue with mine, however it's only done it once, but it would start for like a week. Is the car chipped? I'm wondering if it's not chip creep in the ECU...

[walky_talky20]

Yes, the ECU power relay is a somewhat common failure. If you go through some diagnostics, you would have noticed that you have no spark, and in fact no power to the coil packs during the failure mode. Relay is indeed inside the ECU plenum chamber, actually "beside" the ecu. The rear screws that hold that box together are hard to get at unless you remove the wiper arm and wiper tray. But if you have some finesse (and a 1/4" drive ratchet and various extensions) you can get it with the wipers and tray in place.

That failure is a tricky one that is often elusive and intermittent. Vag-com is usually required to pull that code, I believe a generic scan tool will not catch it.

[-:vw:-]

So a bad or dead relay would leave you with no spark and no fuel... Nice, there goes theory #29 for my car lmao! I had spark and fuel and for some reason it still wouldn't start... To the P.O., did you verify a lack of spark and fuel before you started replacing parts?

[walky_talky20]

^ Certainly no spark as the ECM power relay provides power directly to all 4 coil packs. Not sure if lack of that power input on the ECU would cause no fuel. I've never tried it.

[-:vw:-]

Yup, definitely not that for me then...

[cvbadazz]

I received the relay, will put it in this morning. If this doen't work, anyone interested in a nice 2001 A4 1.8t? lol

[cvbadazz]

By the way, it is relay #30. I don't think I have a chip.And I just bought the car 2 months ago, so haven't got a vagcom yet, and the Autozone scanner does not show anything.

[-:vw:-]

Was the same with mine. No codes... Check ECU ground directly behind the coolant bottle as well. Pull off the wires hit the connection with a wire brush and reground.

[-:vw:-]

Update:

Mine died on my at work today, wasn't even cranking. Pulled the ECU, opened it up, pushed the chip (GIAC) down, it was definitely lose. Put everything back together plugged it all back in. Fired first crank.

[Lunchsacks]

By the way, it is relay #30. I don't think I have a chip.And I just bought the car 2 months ago, so haven't got a vagcom yet, and the Autozone scanner does not show anything.

anyupdates?

Update:

Mine died on my at work today, wasn't even cranking. Pulled the ECU, opened it up, pushed the chip (GIAC) down, it was definitely lose. Put everything back together plugged it all back in. Fired first crank.

This is why i use apr

[cvbadazz]

I replaced the relay, and so far so good. I will drive it more tomorrow, but so far it starts everytime.