Why won't the audi a4 start?

**Steve-O Z33** · 11-19-2009 11:46 PM

So my fiance has a 96 audi a4. Recently, 1 of her cats started rattling and went to shit. So I took it today and got the bad cat replaced. It also stopped up 1 of the mufflers from blowing out the cat, so the muffler was removed. (sounds much better with only 1 muffler) The car runs good and has lots of power compared to before BUT it has been having starting issues since the cat started rattling. Now it's still doing it.

You have to crank it for a long time to get it and it nearly dies due to flooding. You have to rev the engine to keep it running for a few, then it's ok.

I'm thinking the O2 sensors are contaminated from the stopped up exhaust. Does this sound right?

And we just had the car serviced for the ignition switch recall but I've heard a coil recall is coming. We checked the coil and it seems to be firing just fine.

Any other ideas or does it sound 99.9% likely that the O2s are done for?

**Quick Shot xMLx** · 11-19-2009 11:53 PM

They circled the problem...4 times

**Zealous** · 11-19-2009 11:57 PM

lol

**Steve-O Z33** · 11-20-2009 12:04 AM

Originally Posted by Quick Shot xMLx

They circled the problem...4 times

They didn't even do that right.

The circles overlap.

**blink** · 11-20-2009 12:06 AM

There could be many reasons for a no-start. First thing to check is that you are getting a spark, so take a spare plug with you and check for a spark when you get to the car. You will typically need another person to look or crank the engine, make sure the plug is plugged in well and makes a good connection on the metal (ground) of the engine, secondly you need pulses from the crankshaft sensor to switch on the fuel pump. If the fuel pump is not being activated, I would suspect the crank sensor first. You can check the fuel pump relay too, as it can sometimes fail. Usually these problems are a loose connection or a simple part like a relay, and I agree with you that throwing expensive parts at a problem like this is not wise. Get the codes read out from the computer; your answer may be there already for you...

Not mine, just a google search.

**Gspec** · 11-20-2009 12:13 AM

O2 sensors dont come into play during start up...the pcm doesnt even look at what they are doing until the motors running....You problem lies elsewhere.

**Steve-O Z33** · 11-20-2009 12:15 AM

I don't suspect the fuel pump itself b/c it comes and goes. But a sensor, maybe. I'll check the crank sensor. That makes sense.

Voltage is dropping pretty low at idle as well. Near 12 volts. The battery isn't that old. Normally, it's close to 14. Audi said they had to jump the car off twice. If I sit at a light for a while and then go, the car hesitates occasionally.

**Gspec** · 11-20-2009 12:20 AM

A Good many cars these days are VERY picky about battery voltage....(some Chyslers wont fire with anything under 11.75 volts) Battery age doesnt always metter as dead cells/internal shorts can show up only weeks after being put to use....Have it load checked, and def get your charging system inspected.

**Steve-O Z33** · 11-20-2009 12:30 AM

It's doing all sorts of stuff. Gremlins maybe?

The voltage, at times registers below 12V on the gauge while trying to start. Then it'll spike to 13 and fire up. Pretty weird. It's inconsistent though.

It's worse to start after sitting a while as well. If you park it, shut it off, then restart, it usually has no issues. If you take it to buy groceries, it's not gonna start by the time you get back to the car.

**blink** · 11-20-2009 12:43 AM

This guy...

I am the original owner of a 98 A4 2.8 Quattro and I just started to have the same problem. Engine cranks but won't start. It starts in the a.m. fine but then if I drive for a short distance turn off the engine and then try to restart it, it MAY NOT. I have no idea when and why it decides not to start. If it won't start, it takes several attempts for it to get going. I am afraid to burn the starter or kill the battery. Haven't done that yet. When I drive to work and park in the garage, the car will always start 8 hrs later on my way back home. My mechanic who serviced it in August just can't figure it out. He ran the diagnostics test on it twice. The car drives beautifully ones it gets going, no problem whatsoever. 98K miles and the engine is superb. I believe it is an electronic problem that has to do with the onboard computer or some sort of relay module. I want to trade the car but I am afraid to go to the dealer and have it stall on me on the lot. I have done some research on the Audi Forums, identified several others with the same problem but not the solution. It stalled on me today, and I called the tow truck. By the time the guy arrived,the car decided to start.
It is definitely, not the ignition, nor the fuel pump, or coolant sensor, or the fuel injector, or the V belt or alternator. I recently replaced all those for 5k. I took a stupid gamble because I love this car so much, nothing else in that category drives likes it.

an answer...

You can use a test light to determine if you are getting voltage to the starter. disconnect the forth wire from the left on the firewall looking from the front of the engine back. This is the starter wire. Unplug the wire and use a test light to see if you are getting voltage that far consistently. If you are then your starter or solenoid is probably bad. If you have no voltage take a jumper wire from the positive battery terminal and touch the starter side of the connection the car should start or at least turn over. If you have no voltage at the connection toward the ignition I would suspect your starting problem may be due to a Multifunction transmission selector switch. If it fails it will prevent any current from going to the starter from the ignition. The other annoying thing is it is intermittent and will only through a code after a long failure. It will get worse because of corrosion the longer it is not replaced. (The dealership should have checked the systems manually but instead will usually let the computer tell them what to do.)

**Steve-O Z33** · 11-20-2009 01:10 AM

^good info.

My coolant gauge is also staying on C most of the time. I assumed that has nothing to do with starting though.

I'll check the battery, starter, and alternator tomorrow. Thanks for the help!

**bene** · 11-20-2009 12:45 PM

i know its been ruled out and i dont know anything about the a4 PCM...

but this sounds EXACTLY like a 02 problem...

your long term fuel trims are screwed up by a faulty second 02 sensor.

**Gspec** · 11-20-2009 07:21 PM

^As I stated before, ECM's, PCMs and ECU's don't read O2 data during start-up...

**Steve-O Z33** · 11-21-2009 12:43 PM

Actually, it's the coolant temp. sensor. I removed it and have 1 ordered. I talked to a mechanic that just fixed a car with a bad CTsensor. It makes the AFR too rich at all times, thinking that the car is cold. (like it just started up) He said the car he worked on was flooding, cutting off, etc. Just like the audi. So I'm 99.99999% sure this is the problem now. I had a code come up for a bad coolant sensor as well.

**Gspec** · 11-21-2009 12:59 PM

^I've run into that before...mostly on Nissan's and Mazda's....Does your motor have 2 coolent temp senders? (one for the gauge, and one for the computer) If so you should make sure they're sending you the right one.

**hughretro** · 11-21-2009 01:17 PM

Glad it see ya got it taken care of.

**Steve-O Z33** · 11-21-2009 05:41 PM

The program that the mechanic had said that there was 1 sensor at the back of the head on the pipe. That's where it was. I did have to remove something from the TB that said VDO on it in order to get to the coolant temp. sensor. (VDO makes gauges and makes the OEMs for Audis and VWs)

The TB was all gunked up too, so I cleaned it.

**bene** · 11-22-2009 03:21 AM

Originally Posted by Gspec

^As I stated before, ECM's, PCMs and ECU's don't read O2 data during start-up...

no but it does read fuel trims which are fucked up by the sensor when the car is starting at operating temp...

**Gspec** · 11-22-2009 03:37 AM

^I'm not going keep beating a dead horse....believe what you wish...

**BonesZ33** · 11-22-2009 11:36 AM

Originally Posted by Steve-O Z33

The program that the mechanic had said that there was 1 sensor at the back of the head on the pipe. That's where it was. I did have to remove something from the TB that said VDO on it in order to get to the coolant temp. sensor. (VDO makes gauges and makes the OEMs for Audis and VWs)

The TB was all gunked up too, so I cleaned it.

glad to hear you found the problem.. Imagine all that trouble for a coolant sensor. I always thought that cleaning the TB would mess up idle and other things on some cars?. i always leave it alone