Shop Audi Intake Manifolds

This AC can be shutting down for any assortment of reasons.

The first thing that needs to be done is a complete evacuate and recharge to get the proper amount of refrigerant into the system as certain pressures can be shutting the system down from either high or low extremes at higher RPM.

From there you can find out if there are any other issues while monitoring the pressures. You would also need a scan tool to examine the return signals from pressure sensors for accuracy.

Kilometers

Aggggggggggggg...the dreaded ford with the 171/174 codes....does it sound as if theres a vacuum leak when its idling ?If so pay close attn to the intake manifold tuning valve There is an 0ring for a seal and it becomes hard and sucks air and will give you these dreaded codes..but also a faulty pcv valve can cause it,don't rule out manifold gaskets,this is a big problem on a lot of fords but honestly havn't seen it much og the 3.0 engine...Good luck

Aggggggggggggg...the dreaded ford with the 171/174 codes....does it sound as if theres a vacuum leak when its idling ?If so pay close attn to the intake manifold tuning valve There is an 0ring for a seal and it becomes hard and sucks air and will give you these dreaded codes..but also a faulty pcv valve can cause it,don't rule out manifold gaskets,this is a big problem on a lot of fords but honestly havn't seen it much og the 3.0 engine...Good luck

...as I found out, it was the IMT O-ring. See my follow-up post #15 in this thread. Thanks!

the auto manufacturers want all vehicles to go into closed loop as fast as possable,thats the reason for heated 02 sensors..honestly no such thing as to fast.

A fuel injected engine with no problems should actually go into closed loop rather quickly. The time you posted is normal. There is no way it's going to wait until the engine is at operating tempature, that would take too long. In open loop the PCM is ignoring the O2 signal and using a base calculation so the emissions would be way too dirty for too long waiting for a 195° coolant temp. You should be getting some good crosscounts so I'm not sure I trust your data (plus the scaling looks wrong for the O2s). If I was getting counts like that with no O2 performance codes, I would probably hook a scope up to the signal wire and get a reading right off the O2.

You can google "criteria for closed loop" and "fuel trims" and should get some good info to read on those subjects.

As for your lean banks 1 & 2, HT posted the common problems for those and that really needs to be looked at 1st. The easiest thing to do is pop the hood and listen for a hissing noise. Find a big vacuum leak and there is your problem. No vacuum leaks and then it gets a little harder.
With these codes pretty much ANYTHING can cause them. The 1st thing you need to narrow down is the cause. Is it too much air, false air or too little fuel?
This is where freeze frame data and your fuel trims come in handy. Freeze frame date is just some basic info the computer saves at the time of the failure. It's there so the tech can see what was going on at the time the code was set and try to duplicate the conditions to get the same failure.

On this one the main PIDs you are going to be looking at is vehicle speed and engine load. A vacuum leak will have it's biggest effect on the trims at idle and almost no effect at high rpm and engine load. Lack of fuel will have its biggest effect on the trims at high rpm and engine load and almost no effect at idle. So in at nutshell, how fast was the car going when the codes set?

If you can't access freeze frame then get a driver, get in the passenger seat, hook up your scanner and go for a spin. You are going to be looking at the LTFT PID and while I haven't found an exact number, with Fords, once the the LTFT gets up over +25%, you are going to set a lean code. On the reverse, when the LTFT goes -25% you are going to get rich codes...

One other common problem on Fords is under reporting MAF sensors. One clue is the baro reading being skewed (there is no baro sensor on this car it's a calculation from the MAF). I'm at sea level so am use to seeing readings of 29.9 or 30.0 ". 26 & under is a red flag and at 1st thought yours was skewed but I see you are close to 4000' where you are at so this is probably a normal reading.

Look for the obvious stuff 1st, if nothing jumps out then you are going to want to narrow it down to air or fuel.

Thanks, Sidom. Good info there. I will go after the vacuum leak(s). I've got some high freq loss in my hearing, so may have to get someone with better ears to help.

The LTFT is around 3% - 8.6% at about 55 mph. Symptoms I mention are at the low end of the speedometer - less than 30mph or so. No freeze frame data shows up, but it does have the capability to show FF. No crosscounts available. (That info is in the "enhanced" parameters. I just have the basic stuff for Ford.) The data I furnished was during warmup while sitting still. Yes, I am at about 3600'.

At 56 mph and 70% TPS, Absolute Load is 71% and Calculated Load is 97%.

Here's a section of a chart from a recent session to illustrate.



Thanks again for your help.
-Dale

The LTFT is around 3% - 8.6% at about 55 mph.

I have to wonder about some of this data. The codes you are getting are by definition telling you that the trims have reached their limits during at least some point in history. I would really wonder why I am getting normal trim readings while also getting PO171 and PO174 codes being set.

PS: see if you can reduce the size of your images a little bit so they won't make the page so wide. It's really hard to scroll left to right to read and it's because of the oversized image.

My readings seem to coincide with what Sidom was saying above with respect to a vacuum leak. You guys are on the same page. All I need to do now is get out there and try to hunt it down. :)

I'll remember to resize my charts in the future. Thanks, HT.

Out of all the data you've posted, I really haven't seen any of the PIDs I would really be looking at for lean or rich codes. If you are limited to 4 PIDs, the ones I would be looking at would be STFT, LTFT, ENGINE LOAD, RPM/vehicle speed.

Until you can see your LTFTs go in to the 20% range you aren't in the problem area. I haven't see a Ford yet that will code in the teens. This is where freeze frame data can be so helpful. Right now you having to try this condition and that one to find the area. With FF you can see temp, speed, load, etc. 1/2 the battle is finding out when it's failing after that, then its "what hell is causing this"..

I haven't had a problem with the Taurus but the 4.0 Explorers had a plenum issue with gaskets and bolt and would only code after a cold soak (sat all night). After they warmed up, everything expanded, sealed and the trims would come in line for the rest of the day. So you'd think, I'll just look at the trims after a cold soak and that will tell me.....

That would be too easy.....

On Fords, part of their cold start strategy the is trims go high, real high for a little bit, which makes sense, this means the PCM is adding fuel which you want when it's cold so if you go that route you have to be real familiar with what normal high trims look like and what trims that are too high for too long and will set a code look like. Honestly in these cases where FF is pointing to a cold soak problem, I just smoke the manifold after it's sat all night. Its much quicker and more accurate (unless an installer does me a favor and warms the car up for me before I get there....that's always a fun phone call for the SA ).

So 1st I'm assuming you already followed HTs original advise and looked for the obvious leaks, looking at the PCV hose very carefully and making sure then snorkel was hooked up to the throttle body with no cracks or splits, no obvious exhaust leaks....the basics... If all the is done then you have to find the spot where the LTFTs go over 20% until you do that, you're in the wrong area and chasing ghosts......

I did see a TSB for the 4V 3.0 for an O ring problem on the intake but that is for the S engine not the U engine and IIRC you said you had the U.

We see that combination of codes a lot of Fords and it's nearly always caused by a bad vacuum leak. That's not the only possible cause but the most common. Check all the main vacuum feed lines. Listen for a hissing noise. They commonly suck holes right through the rubber connectors at the source or in other parts of the PCV system.

Thanks. I will look for one.

Will a vaccuum leak also cause it to go into Closed Loop so soon?

Thanks again,
-Dale

Too soon? Never heard of that happening for any reason.

Cat Temp: 106 deg both banks.
Engine Temp: 120 deg

I had the understanding that Closed Loop happens after the cat temp, O2 temp, and engine temp come up to operating temp. At the time it went CL-1, the O2 sensors were still bottomed out. At the very least, it's not supposed to go CL until after the O2's start swinging, is it? Here, the marker is positioned at the first scan in Closed Loop. All of the data in my first post apply to this marker position.

My understanding for closed loop was

1. Engine temperature
2. 0/2 response
3. Internal timer expire
   

Engine temp at the marker was only 120 deg and the O2 response was nil at the time of going Closed Loop. Don't know what the timer is set at, but I would think it's more than 13 seconds of runtime. Haven't found the criteria yet. Struck me as being a little strange.

I don't know. I would suspect either your scan tool is giving you bad info about the loop status or there is a problem with the PCM. Have you got a different scanner to try?

No, I don't have another one. This one was just upgraded at the factory very recently.