Sputtering during AWS warmup...other issues as well.
 

S5 vert, 156k miles.

For the last 2 months, my car will sputter like it is running rich or misfiring during the aws warmup cycle. It runs and idles fine otherwise.The TPS is set with the test light method and I don't have the bouncy idle issue commonly associated with a misadjusted TPS. No mil light to speak of, or anything out of the ordinary.

It will also sometimes buck during deceleration. For example, I am coasting down a hill with the car in gear and it will sometimes go "puff" like a backfire and it jerks the car slightly.

So for the other problem...

It also doesn't start up first try when the engine is hot if I let it sit for more than 10 minutes. If I kill the engine ay operating temp and then start it right back up it fires right up. If I kill it and wait 10 minutes, it'll just keep turning and won't start. Here is the peculiar thing, if I just hit the start for a split second, and allow the fuel pump to prime the system, and try to start as soon as the fuel pump shuts off, it fires right up. This issue has been around since I bought the car a year ago.

Suggestions on the issues above? I don't really have any driveability issues, just those annoying little bugs in the system.

The fuel injectors could be associated with all the symptoms you describe so I'd start by having them cleaned/tested.
While they're out, go through the whole fuel system- replace filter (and soft lines if necessary) and check the pump sock in the tank.

my s5 sputtered while the aws did its thing. then i replaced the fuel filter and it was gone!

I replaced my fuel filter 5k miles ago. I mean unless it just happened to pick up a bunch of trash from the fuel, I doubt it is clogged.

Also, fuel injectors? wouldn't I have other driveability issues on top of that? I am not discounting what you have said, just asking.

I am also wondering if my fuel pressure isn't just too low. Pump getting weak maybe? I don't have a pressure gauge unfortunately, but I might just go snag on up and see.

Not necessarily,at least for a while.
Injector performance degrades and you could be seeing the beginning of the downward spiral.

Obviously, diagnosing over the interwebs is a dicey proposition.
The injectors were just the first thing I thought of that could explain all of your symptoms but there could be many other culprits.

Hmmm, This morning, I started her up and she sputtered and missed a bit, then warmed up and ran great. I went to work and didnt fire it back up for another 8 hours. 8 hours later, fired it up, and perfect.

In texas this time of year, it is much cooler at night than during the day. 30* difference most of the time. The issue with cold startup "seems" to be temperature related. I have never had the issue during the day when it is warm.

I deas with that info? I can't imagine what winter is going to be like considering the way it is now.

OK then...

Operating under this theory, if you were to stop the car say, Friday evening and then not restart it till Saturday afternoon, it should work perfectly.
If so, we need to start looking at things that are directly related to air temp.
If not, your "ambient temp" theory is flawed.

and we can do this, This friday actually, as I am off and have no need to go anywhere.

Thursday, when I get off of work, I will not start the car until 2pm friday afternoon.

Good.

You might spend the downtime researching what components are directly affected by air temp.
Offhand, I can only think of two...the intake air temp sensor and less directly, the pressure sensor.
I have a feeble grasp of the intricacies of the intake/ignition systems and how they interrelate...HAILERS would be your guy for that, but I'm baffled why your minor ambient temp variations would cause the trouble you're experiencing and suspect there is something else going on and the air temp is a red herring.

When I worked for Alyeska on the pipeline, I became quite familiar with the effects of extreme cold on anything mechanical...shit basically just fritzes out- or even breaks- randomly.
However, your climate in Dallas, and even mine in Denver, is tropical in comparison, and I've never experienced anything like you describe even in sub-zero temps.
Hence my skepticism...

I was looking at the FSM last night and started wondering about the water thermo sensor and the thermowax unit. I also started thinking about the AFM. I park on a hill facing down when I come home whereas I am level any other time I park. This issue ONLY occurs when I am parked at home. Maybe the vane getting stuck?

Of course We'll still do our test on Friday.

Unlikely.
My understanding is that the S5 AFM is much less sensitive to attitude than the S4 unit...then again, anything is possible and there's no reason not to explore the possibility.

We'll see today what happens...

If this test doesn't work I'll start parking on an even surface in my driveway.

Although I hate my car is having issues, I love the process of elmination :)

So, I did the ambient temperature test, and sure enough it did what I thought it would. Started up just fine without a hiccup. The ambient temp is 75* outside right now.

Usually when I start the car it is 60* or a little higher. I havent recorded the temp when it acts up so I'll have to do that tommorow morning.

So, some more info on the situation, and it is definately temperature related. Thoughts?

I am almost 100% positive, from my internet research and extensive study of the FSM that my problem is related to the water thermo sensor. I havent tested it yet, but I will and hopefully my suspicion is correct.

If anyone wants to chime in on the thread with thier thoughts, go for it, I need it.

Also, I have a broken stud that THANK GOD doesn't leak on the water pump housing, so I'd rather avoid removing it like the plague. Is it possible to remove the water thermo sensor off the back side of it by taking the alternator and its associated stuff off to gain access or am I screwed?

..

You have to remove the waterpump housing.:(

God tells me he can get me out of this mess, but he's pretty sure you're fucked.

Well, I was jacking with the car on Monday....

I just went around and tested the TPS, made shure the air injection solenoids where working, the BAC is working, etc.

I tried to reset the idle by grounding the check connector. Engine doesn't start. It tries to then dies. The only way I can get it to start with the check connector in place is to depress the throttle slightly. It wasn't like this before, so this is new.

I am at my wits end. This is such a strange problem. NO CEL or anything.

What would not allow the car to run with the test connector jumpered? I know the BAC doesn't run with it grounded, but it should at least start and idle. I cranked the idle screw all of the way out and still no go unless I depressed the throttle some.

Hailers? Anyone? Ideas?

Out of curiosity, what happens if you try to start the car w/o the check connector and then add the check connector "after" the car starts up?

Not sure, haven't tried that. I can get it to start with the connector grounded by depressing the peddle slightly, and once it is started, I can let off and it will continue to idle. I would imagine it would idle fine, but I'll try it anyway on Friday.

Anyone else?

The alternator needs to be removed. If your hands are small enough, you can do this with the alternator still on.

Just disconnect the wires to the sensor, use a open end wrench of 17 mm and turn that dog out..nothing hard about it...