Can you log iat temp water temp and oil temp? I am thinking you may have a bad temp sensor that is putting the ecu back into cold start mode?

 

Thanks Tim,

I did clean the MAF, but did not perform any diagnostics on it. I found a thread that explains how to check the voltage output. I'll do that as a start. I don't have a logger... I'm thinking a Durametric is in my future

That is an interesting theory and I'm up for anything at this point... It does come off the cold start cycle and the idle will go down from stone cold. In fact, that is the envelope that the idle behaves normally. Then as it gets hot enough to check the idle, it sits high, then falls and may creep up just a tad. I actually noticed that it was maybe 50rpm high and when I let out of the clutch in neutral, it slowed down ever so much. I guess that load was enough.

Thanks '02996ttx50 for the suggestions. I have re-set the TB as you described after pulling the battery neg connector. Nice to know there is no step down. So, when you found a leak, was it obvious enough? Like a tube that had pulled loose? Do you think you would have held pressure for a while? I'm just trying to actually eliminate any areas I can.

Thanks guys... This is super frustrating! The first note of it in the service records is about two years ago and it managed to allude the dealer then and also the PPI. They didn't get the car warm enough. I have fixed a few small issues so that is a plus!

Franny

 

Franny,

The part numbered 9 in the vacuum line diagram may have something to do with it. Try pinching hose numbered 12 and see if that helps. Part # 9 is a venturi and a check valve. It may be damaged??

 

Thanks Tim,

Isn't that the break-boost line? If so, I disconnected it at the end (4) and sealed it off (first photo). No change The other end of it goes right back to the intake plenum...

I would love to get in and crimp tube 18 and eliminate that whole mess.

Hey, how about that bit that goes off to the right (2nd photo). Looks like it goes to the oil tank? I can't seem to get a diagram for that run. Oil gets hot... Is there any check valves there that could fail?

I'm making the wild assumption that since I can hold pressure that it must be a check or solenoid valve. Does that sound reasonable?

These things could be a little easier to get to... Maybe I'll get some vice-grips from HF and grind the teeth smooth so it won't harm the tubes and crimp a few sections off.

Keep the suggestions coming. It is going to be epic when I finally find it!

Thanks again,

Franny

 

Have you thought about just taking the car to a competent shop in the Denver area? Might be easier.

 

I have, but the car has already been to both dealerships here and one couldn't fix it under warranty and the other missed it completely at the PPI. We do have some good shops here, but outside of performance shops they mainly focus on older cars. I think the shops are great for large R&R jobs and I wouldn't hesitate to take it in for something like that, but a tricky issue like this I can see a shop chewing through $1500 in shop charges and not getting it. For that money I can replace most of the vacuum system and TB and be pretty assured to actually get it.

My experience with shops has been so-so and always expensive. I'm betting this is a $30-$100 part - I just need to find it. A new TB is only $450...

Also, this is how I bond with a car... My 3.2 Carrera was a bit of a mess when I got it a year ago and it is a dream to drive now. I also learned quite a bit! That is an enjoyable car to work on. The 356A was a basket case and it is now like butter to drive and both did spend a little time in the shop, but anly about 25% of the work was done there and all of it was big stuff I can't do (like and alignment, AC recharge, etc.).

I appreciate your suggestion and it may come down to that in the end, but I'm not ready to throw in the towel just yet

Thanks,

Franny

 

Ok, so I have a bit more info...

I got a hold of a Actron 9580A diagnostic scanner and the car has no codes active or pending (that it could tell). I plugged it in and had someone drive for over 30min in traffic/highway/city and looked at the active data. The scanner will monitor temp (water) and that stayed right on target the whole time and lined up with the gauge on the dash. It also monitors the O2 senesors and the difference between them. They were pretty much identical. The MAF seemed to be going up and down as you would expect with throttle and seemed to settle in at idle about the same every time. It also monitors the throttle position and the RPMs. That is what I really watched... I was looking for some deviation with the throttle % down and the idle up or some inconsistency. What I saw on the throttle position was exactly what was happening to the idle... Now, the car was actually pretty well behaved today and would settle down to the high 700's pretty quickly (within a couple seconds), but it followed the throttle position - it was the throttle that was not settling right down; not a high idle and the throttle closed.

Now I'm starting to think the dealership set up some sort of delay to try and "fix" the issue before. The documentation does say a reprogramming, not just a reset. I don't know... What would cause the TB position to hold for a few seconds at a percent or two high and then settle to the nominal idle percentage (~3%)? I did notice this when I had the intake plenum off and had someone actuate the throttle... But that was with a warm at best engine and certainly not the same as actually driving.

More information, but more questions...

Thanks,

Franny

 

I set the scanner to record and graph over about a minute or so (78sec). The little blip up to 1270rpm was me to get it to do its little trick before the fans turned back on

Graphs are:

MAF (lb/M)
Calculated Load (%)
RPM
Absolute Throttle Position (TPS%)
Coolant Temp (F)
Air Intake Temp (F)
Ignition Advance (deg)
Short Term Fuel Trim Bank1 (ST FTRM1%)
Short Term Fuel Trim Bank2 (ST FTRM2%)

Let me know your thoughts... It seemed to oscillate in a minute or so cycle. Pretty consistent. When the cooling fans turn on, it settles down to 760 or so and stays there. These graphs were taken with all accessories off (no AC) and the cooling fans off.

I'll post the next graphs in the next post...

Thanks!

Franny

 

...and the rest

 

So, here's a question... What is the correct throttle position percentage for a normal idle with the car well warmed up? Maybe the computer is driving the TB below that to try and get the idle down and then eases up, but the idle then creeps up?

Am I still chasing a leak or am I looking at a bad component (sensor, or MAF or TB)?

Thanks,

Franny

 

I ran another data log... This one is over about 70 seconds... It was after the ride home so good and hot. I didn't touch the throttle at all, the clutch was in, temp was at 198deg, no AC or fans on.

The idle never settled down to 780, but the TB never went below 3.2% either. when it is idling at 780, the TB is at 2.4%... I just don't understand why it won't close the TB to 2.4%. It does when it is cooler. It seems to idle high because the TB is being commanded to be open. Is 2.4% correct for idle or is that too low?

Arrrg This is so frustrating...

Thanks,

Franny

 

I did not read everything real closely but I would replace the MAF if you have not already. You can get a Bosche for decent price from amazon.

 

I do have a graph of that too; same run...

You think the MAF would cause the computer to command the throttle open a bit? The car did throw another P0507 last night

...or if the computer is commanding a lower throttle and the TB just isn't responding, and the %throttle is just being read off the potentiometer in the TB... That would kind of make sense... Because a P0507 says that the computer is past its ability to lower the idle. Weird if it reads so high... It would seem like it has plenty of room to lower it at 3.4%.

Thanks,

Franny

 

I am far from a pro but have found when I have a miss/rough idle etc its the MAF. It can cause some real weird problems and in the scheme of things cheap. Have you cleaned the throttle body? I also like to clean electrical connections with some form of electro clean spray.

 

it's true. hunting idle is *always*? either a faulty maf, and/or a very minor leak. or lastly the tb sticky/dirty. if the maf is fried? the ecu tries to compensate, and idle is where we see/feel it. also, a tb reset whenever the maf is fooled with, is often overlooked. at the risk of repeating myself lol