1.8t crank no start/miss strong gas smell

[Philoby]

04 b6a4 quattro ultra sport 1.8t sits for the day or over night. Try to start only cranks, keep trying for min or so finally starts. Runs rough and smells very rich. No codes... Replaced crank sensor, coolant sensor, new plugs and did 2nd air delete. When warms its fine runs good even if you shut if off and re start... Only does it when it sits for a while or car still kinda warm and re start it few hrs later, when cars hot you smell coolant. Any ideas?

[johnwiz]

If you hadn't said that you replaced the CTS, I would say that was it. Had the same problem on my A4 and our Passat and it was the CTS.

[travrach]

Ever change the coils?

[OttawaWill]

Which coolant sensor? The one in the coolant flange on the back of the head? The one in the lower rad? Or both?

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[ecjr173]

Funny I'm going through the exact same thing. Same symptoms but mine doesn't run rough. I've changed spark plugs, coils, rear CTS, thermostat and battery. I have a post about this and the Air Temperature Sensor was also mentioned. So I bought one from ECS but hasn't arrived yet. I also took it to my mechanic and he said it was probably a blown head gasket cause I had white smoke from the tail pipe the day I took it to him.


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[Philoby]

I replaced both coolant sensors, crank position and new plugs... Its not throwing a code either. After work ill try start, it cranks fine but doesnt fire.. Itll try too but then die, after a min of two itll start. Smell very rich with gas. Runs good once it starts. Its been burning a little coolant enogh to smell and top off every 3-4 weeks, i was told on b6 a4 1.8t awm heads are common to cracking, they said that was my hard starting. Any one else have this issue and fix it?

[ecjr173]

I did try some head gasket sealer. It's meant for cracked heads and head gaskets. Says it's a permanent fix but I'm not to sure about that. To my surprise it did something good cause I can start my car on the first try now. Before I had to crank 4-5 times. So I will see how long it holds. Hopefully long enough to safe some money to properly fix the head/head gasket.


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[chad99]

It seems strange that you have no stored codes even with misfires on cold start. When my headgasket was starting to go I sometimes would not get a CEL but if I vagcomed the car I could see that the multiple misfire code was stored even with no CEL since last cleared.

The coolant smell, is that just in the engine bay or is that out the exhaust?

[Philoby]

Both engine bay and rear exhaust in the mornings you smell coolant burning pretty strong.

[old guy]

Both engine bay and rear exhaust in the mornings you smell coolant burning pretty strong.

All of your symptoms point toward a blown head gasket.

[Philoby]

I pulled head, head gasket doesnt look bad cant see any blown outs on it. Cyl 2,3 pistons are cleaner than 1,4. Exhaust ports on 2,3 are very wet. Its a awm head. Could head be bad and leaking coolant in cylinders and cause it to hard start and miss until it warms up?

[chad99]

I pulled head, head gasket doesnt look bad cant see any blown outs on it. Cyl 2,3 pistons are cleaner than 1,4. Exhaust ports on 2,3 are very wet. Its a awm head. Could head be bad and leaking coolant in cylinders and cause it to hard start and miss until it warms up?

That's normally what happens, mine would do the same thing, then once warmed up the head expands and leak goes away till it cools down again, sounds like you solved it.

[Philoby]

I hope the head is the issue since its off but #2,3 pistons were cleaner than other two, but no coolant puddle was laying on top pistons... Also the exhaust ports on 2,3 were very wet aswell so im assuming the head is the problem but my question is before i pulled it off and was driving it, when car was hot and went to work it cooled down until i went to leave work. It would crank but no start... Id have to crank for min before it would run and smelled very rich, and miss until it ran for 30 sec or so.... If head is cracked and leaking coolant would that cause it to crank and no start but then run rough? It has new coolant sensors and crank sensor

[chad99]

My headgasket wasn't leaking badly, I never had hard starts or rich smell but I had misfiring when started cold for as long as the SAI pump was running. I also had combustion smells in my coolant tank. But no coolant smell in exhaust.

I would imagine if the engine has a hard time starting it would be full of fuel and a rich smell would be expected.

Clean position tops means the gasket was at least part of your problem so it sounds like you are at least in the right track

[Philoby]

Im gonna send head out get checked, so hopfully machine shop can prove its bad i looked everywere i couldnt find any cracks in the head so hopfully they can. I appreciate ur help man

[diagnosticator]

Im gonna send head out get checked, so hopfully machine shop can prove its bad i looked everywere i couldnt find any cracks in the head so hopfully they can. I appreciate ur help man

Leak test the head is not wrong, but the setup must be leak free or it will show a leak where none exists. I don't know of any 1.8T cylinder heads that have been proven to have a crack that leaks coolant into one or more cylinders. What is actually happening is the head gasket between cylinders 2 and 3 has failed, allowing coolant to leak into those two cylinders. It's not just a coincidence that two adjacent cylinders are showing evidence of coolant leaking into those cylinders. Because the head gasket is a multi layer steel gasket, it will not be necessarily evident that the gasket is leaking between cylinders, but that is the only conclusion possible. When a cracked head is blamed for the leak, and no crack/s are proven to exist, the belief that the head is cracked is typically incorrectly confirmed since the new head and new head gasket fixes the coolant leak, but it the result of installing a new head gasket, not the replacement of the cylinder head.

[Philoby]

I agree man i did some research the heads on these b6s are a castes from another company cosmo or how ever its spelled, i was told from lots audi guys the casting on these heads were weak and cracked thats why i pulled it off