Need Some Help... Again...

[canonball]

Gonna try to keep this brief. Car is running like poop right now and there are a few things going on and I don't know if they're related or separate issues or what and could really use some advice. For reference I've got an '05 A4 quattro 1.8t 6 speed manual.

Before all this it was running great for some time. So then one morning a week or two ago I noticed the temp gauge hanging around right in between normal and cold. On my commute into to work that morning it varied but stayed in that range. It did this for two or three days, think I asked around on here and got some tips that it could be a temp sensor on it's way out. Despite the cooler temp readouts the car ran totally normal. I ordered a new temp sensor and while I was waiting for it to arrive I noticed the temps seemed to be reading pretty normal but the fans were now kicking on at full when I'd first start the car up and seemed to run until the engine warmed up. Odd, but whatever, still everything else was operating normal. Then last Friday when I was leaving work I started the car up, started up normal, but was misfiring under load. I got down the road a bit and then pulled off to pop the hood and have a look-see. Then got back in and started driving (engine was getting warmed up at this point) and it wasn't misfiring anymore, drove perfectly fine al the way home. The next day I ran to the store and it did the same thing, seemed to misfire a bit until it got warmed up and then ran perfectly fine. Monday I went out to head off to work, expecting some cold start misfires, and instead it was just plain running like crap, like a coil pack went out or something. So I left it and stole my wife's car. When I got back I was trying to get my car into the garage and it didn't even want to go on it's own legs at first. Turned it off and back on again and immediately gave it some revs and go pedal to try and encourage it to move and it drove in just fine. I've started it up a couple times since and it's not misfiring (at least at idle) but I can tell it's not running right and it's definitely running rich. Nothing coming from the exhaust except some very fuel-y smellys. Just got the new temp sensor in the mail today and I'll have fresh coil packs next week (no idea how old the current ones are so thought I may as well get a whole new set in). I'm gonna work on getting those in, but wondering if these will actually help my issues? Also I noticed that I've got a slow coolant leak that the best I can tell looks like it's coming from the auxiliary water pump. I replaced my valve cover gasket and timing chain tensioner gasket a few weeks ago. I had been checking it every couple days for leaks and haven't noticed oil or anything leaking from the valve cover. Just noting that in case there's something specific to check out.

blah, so much for keeping it brief. Anyway, I'd really appreciate some insight. Want to avoid just throwing parts at it and crossing my fingers

Ah, one more thing. Anyone here use the elm327 obdII scan tool? I picked one up a while back, haven't used it yet, wondering if that may help to at least read codes. I don't have vcds at the moment.

[Cybersombosis]

Where abouts is the coolant leak? The 1.8T doesn’t have an auxiliary water pump, just the main one in the block. Are you just noticing the coolant level going down but no leaks on the ground? If so, I hate to say it but you may have a cracked head. I’d use your OBD scanner to see which cylinder is misfiring then do a compression test and see if that one is low. You can also check the color of the top of the piston down the spark plug hole. If coolant is getting into the combustion chamber, it will be cleaner than the others. Usually it’s cylinder 2 or 3.

[TobiqueSlang]

if You've got a misfire an OBDII reader will at least tell you which cylinder is misfiring, swap that coil with another one and see if the misfire moves with it. misfires are tricky sometimes, they can be caused by a whole bunch of different things.

[Mike Tries]

If you have a cracked head, taking a peek down the spark plug hole may indeed reveal a cleaner-than-it-ought-to-be piston as Cybersombosis said, but you may also have a little puddle on top of one of them making it very obvious. Or... a puddle on top of all four of them like I had (AMB heads suck).

You said your exhaust smelled fuelley, but not like coolant? Maybe the coolant leak is a water pump leak. IRregardless, check to see just how low the coolant is. The car could be overheating, but without enough coolant to register on the temperature sensor, it may appear cold. I am not sure if that's possible on these cars, but it happened to my Mustang back in the day (I caught it before it overheated and it was fine).

I have the elm327 scan tool and it is quite good. I have the paid-for version of torque, which I use often for various things. It will not show you as much as VCDS does. I also have VCDS with that cable, but also I have a generic ebay cable and some other software, like nefmoto, and some logger program which could help you if you really get down in the weeds on this thing but you don't want to go the VCDS route. That's a super long way to say try your scan tool, maybe try out the Torque app, but if that doesn't work, try a better tool (VCDS is quite good).

Also, I have noticed that Torque doesn't display some things accurately. I was seeing "boost pressure" readings that made me think my car was broken, but when looking at the actual values in some of the laptop generated logs revealed that things were fine. Trust, but verify, in other words.

[Nirvana09]

I had similar issues years ago and it ended up being an upper coolant sensor. Took a few bad new before I put a junkyard german sensor and it works great. I had my thermostat replaced months before that and it acted like your first problem - temp sitting between low and high. What coolant are you using? It might be something not compatible causing your sensors to slowly die?

[canonball]

Yeah, exhaust smells fuel-rich, doesn't seem like coolant. No smoke or anything either from exhaust. Very small puddle of coolant under the car, from what I can tell it looks like it's coming from (what I'm assuming is) the auxiliary water pump. Attached a few snaps, you can see where it's pooling up on the block and the pump... or whatever that is. I had my thermostat replaced recently, as well as the upper coolant hose so theoretically those should be ruled out. I'll run the scan tool tonight and see what it comes up with. A cracked head would be super lame, really hoping that's not the case. Fingers crossed, thanks for the help guys!!

[Mike Tries]

Isn't there only one water pump? On my 03, it's in the block, and is driven by the timing belt.

[kwilson]

That's the thermostat. Not a pump you are looking at. It looks like either it and/or the J plug may be leaking.

[walky_talky20]

The absolute most important sensor for determining Rich Mixture upon a cold start is the Coolant Temp Sensor. It has very high authority to control the fuel quantity. It has enough control to make it too lean to start or even too rich to start.

The dashboard gauge is actually a separate reading from what the ECU sees. The Coolant Temp Sensor is actually 2 sensor in 1. Side A is for the ECU, Side B is for the dashboard gauge and such. They can fail separately or together. It can fail however it wants, really.

By your description: your gauge was likely reading "colder than actual". If the ECU side of the sensor was doing the same, this would absolutely cause a "too rich" condition upon cold start. This would persist until the engine and oxygen sensors warmed up enough to go into "closed loop" operation and adjust fueling based on the indicated AFR (wideband oxygen sensor reading).

As for the misfires: Quite likely the misfires are just a "rich miss" or even the plugs fouling because they are getting drowned in fuel. Your existing ignition coils *could* be a little weak, but I would fix the CTS first and then reevaluate. No need to throw away good coils.

TLDR: The CTS will almost certainly fix your rich condition and that is probably all you need to do. And fix that coolant leak. Yipes. New T-stat and J-plug looks to be in order there.

[Larhal]

That's the thermostat. Not a pump you are looking at. It looks like either it and/or the J plug may be leaking.

+1 J Plug / Thermostat

[Puddin Tane]

If you do replace the J-plug, consider a machined aluminum one instead of the usual plastic. Much more of a "do it once" product, by all reports.

[kwilson]

If you do replace the J-plug, consider a machined aluminum one instead of the usual plastic. Much more of a "do it once" product, by all reports.

This. Also, don't go cheap on the thermostat. Stay with a reputable brand. I prefer using a genuine part as I have seen many of the cheap ones fail quickly.

[walky_talky20]

Genuine T-stat is pretty ridiculous on price ($250). I'd probably try to get the OE brand, which I believe is MAHLE / BEHR for this application. More like $60-80.

[canonball]

Ah, thanks once again for all the info friends! It's been hectic around here and I had to put the car stuff on hold for a min until I got through the holidays, this adulting stuff is hard! Ha anyway, I got out in the garage this evening, plugged in the scan tool and of course it pulled some misfire codes (P0300, P0303, P0304) and a P2181 "Cooling System Performance". Since I recently replaced the valve cover gasket and went back and double checked each of the nuts to make sure they were all still torqued down. I also pulled the coil packs to see if maybe the center gasket might be leaking into the spark plug wells. This was kind of a SMH moment because I was a dingus and didn't clean them up very well before when I replaced the gasket so of course there was some oil in there and I had no way of knowing if there was more in there than before. So I cleaned them all out and went ahead and replaced the spark plugs while I was at it. I snapped a photo of the old plugs, I never can remember what means what when it comes to "reading" the spark plugs. I checked around the head as best I could without removing intake manifolds, exhaust manifolds, etc. Looks ok as far as I can tell. The car has been sitting in the garage for a week without even starting it up and there was a substantial puddle of the pink stuff in the drip pan. A couple drops on the bottom of the oil pan near the drain plug. The only area I can see that it might be leaking from is the thermostat where it's dripping onto the block and running down the engine. After I got the new plugs in I started the car up and it was a little rough on initial startup but quickly returned to normal, I let it run for a bit with the scan tool running which showed the engine temp going up but the needle on the dash was all the way to the left still. Took the car for a quick spin and besides the coolant temp discrepancy everything seemed normal, car ran and idled well and I didn't notice any active misfires. At one point I took screenshots of the live data, I also took another screenshot showing the coolant temp readout on the scan tool and a photo of the gauge readout on the dash which still looks a lot colder than what the scan tool shows. There's also a snap of each spark plug well and spark plug in case any enlightened individuals see anything funky going on there.

Oh and I just had the thermostat replaced at a local shop a couple months ago, so I may run it back up there and have them take a look at it. I imagine they shouldn't crap out that quick?

[seanf86]

Genuine T-stat is pretty ridiculous on price ($250). I'd probably try to get the OE brand, which I believe is MAHLE / BEHR for this application. More like $60-80.

It used to be, I bought a new Behr branded stat 10 years ago and it had the Audi logo ground off, I purchased another one last year for my other B6 and it came with a sticker saying it was made in China and definitely not OE equivalent.

That being said these cars are getting older and its probably still your best bet to get the Mahle one.

OP change the O ring on the hard pipe that goes into the thermostat when you do change the thermostat, I had a very similar leak and it was the o ring on the hard pipe that bolts into the thermostat. I changed everything to be safe.

[canonball]

Sit-rep:

So I started to replace the coolant temp sensor when I noticed that it looked like the lower rad hose might be leaking, figured I should hold off so I don't have to drain/fill the coolant multiple times. So then I went ahead and replaced my coil packs with new ones and threw in a fresh set of spark plugs.

Fans are still coming on at startup and staying on as far as I can tell which from what I've read sounds like the thermostat may be stuck open? Besides that and the coolant leak it's running good. I took it for a spin last night and then drove it into work this morning and it seems happy.

I also realized something after my last post, I was concerned because of the scan tool's reading of the coolant temp and what the car was saying on the gauge but I realized the scan tool displays differently. I believe our cars normal operating temp is somewhere around 200°F, I've seen people mention different ranges that average about that much. So when I was looking at the scan tool I was mistakenly thinking that the needle should be in the middle like on the car's gauge but realized it's they don't read the same (yeah, I'm a dingus). So realizing that it looks like the car's gauge is reading accurately and inline with the scan tool. Once it's properly warmed up it seems to run at about 185°F which is probably just on the cooler side but I imagine that may be contributed from the fans constantly running and keeping the engine cooler than it needs to?

These are the codes I'm dealing with right now, first four are from the initial troubles with the car a couple weeks ago. It hasn't misfired at all since replacing the plugs and coil packs (*knock on wood*). The last one is new and looks like an engine temp too low, probably also whats causing the 2181?

============1==============
P0300
Raw code: 0300
ECU: OBD-II
Status: Confirmed
OBDII: Random/multiple cylinder(s) - misfire detected
Audi: Engine Misfire Detected

============2==============
P0303
Raw code: 0303
ECU: OBD-II
Status: Confirmed
OBDII: Cylinder 3 - misfire detected
Audi: Cylinder 3 Misfire Detected

============3==============
P0304
Raw code: 0304
ECU: OBD-II
Status: Confirmed
OBDII: Cylinder 4 - misfire detected
Audi: Cylinder 4 Misfire Detected

============4==============
P2181
Raw code: 2181
ECU: OBD-II
Status: Pending
OBDII: Cooling system performance

============5==============
P3081
Raw code: 3081
ECU: OBD-II
Status: Pending

[walky_talky20]

Fans coming on immediately on startup are due to the cooling system performance code. It knows there are cooling system problems, so it races the fans for insurance against overheat.

You have temperature accuracy problems. Either due to a lazy thermostat or innacurate coolant temp sensor. Based on you also having cold start enrichment problems, I'm heavily leaning toward your temp sensor being faulty. But lucky for you, your thermostat is also leaking. So you get to change them both and can skip the guesswork. Both items are high failure rate, so even if one or the other isn't technically faulty *right now*, changing them together is not a bad idea at such mileage.

That's my take.