Chas

I really need a backup car!!!

My 951 had a horrible idle problem all of the sudden, so I checked it out tonight. Found that the screw that is directly behind the throttle body on the top of the intake manifold was missing. Temporary fix: duct tape. Worked great!

While I was at it I took off the cold side IC pipe (between the IC and throttle body) to check the throttle body for damage, check the condition of the BOV diaphram, etc. I also adjusted the length of the throttle cable to help the throttle return all the way (get the TPS to make it's click). Put everything back together, and the car ran absolutely BEAUTIFULLY for about 20 minutes.

I was driving at this point and noticed a tiny hesitation, then a couple seconds, then more hesitation....then I looked at my wide band o2 readings, and noticed the following:

say I'm driving at 2,800rpm or so...
obviously with no throttle I get infinity:1 a/f ratio (as the injectors are off)
as I give it just a taste of throttle to turn on the injectors, I jump to 15:1, where I want it
now....as I slowly give it throttle, I watched the a/f ratio slowly get leaner and leaner

So as I figure...the intake is getting air that the car doesn't know about.

I looked for 2 hours for vacuum leaks in the IC pipe and all banded connections...everything looks fine.

I know there are two "inputs" on the J-pipe, can they be a source of unmetered air? (I don't really know where they come from)

On the IC pipe, the BOV is fine (but this doesn't even matter as both sides are metered air, and the car at least WAS building boost normally. Now the "input" on the other side of the IC pipe (across from the BOV), it appears that this goes directly to the intake manifold...should I look for problems with this hose?

PLEASE HELP!
This car has to get me back to school for one last semester!!! I want to graduate :-)

Thanks in advance for any help, and please let me know if I need to provide any more information.

Chas

...sorry, just thought of one more idea...

Could my AFM be bad? I imagine if the "barn door" position sensor isn't sending any readings...the ecu thinks the minimum amount of air is flowing at all times?

turbite

I think the AFM and a leak are too very likely possibilities.

I'd start with measuring the AFM's voltage.
If that checks out, take it to a mechanic for a $20 5-minute smoke leak test.

It would have to be a pretty good size leak I would think, and would show up right away.

Chas

yeah...such a big leak that hopefully I can find it tomorrow with some daylight...

Is it weird for the AFM to just go bad like that...I didn't really mess with it all that much....also I was at about 15psi when the engine started its new "fuel enrichment trend" (as I am now calling it :-)). So I'm thinking a blown hose could be a very real possibility.

Turbite, can I check the voltage without testing pins on the DME? Maybe tap the wires right there in the engine bay?

Chas

Okay I'm back at it trying to find the problem....does anyone have any ideas?

Keep in mind that the car is not drivable...

It starts and idles...but as soon as you give it some throttle it dies out lean...

It's so consistent (and at this point predictable), that I would guess the fuel system (pump, filter, fpr, dampner) is just fine...at least I hope so :-)

I have some classes to take next week, and I'm starting to wonder if I'm going to make it back down there

Chas

UPDATE!

Help me on this one...I just disconnected the small hose form the hotside IC pipe...the banjo bolt thing...and I can blow air freely through it. That's bad, right???

From what i understand...this goes to the cycling valve...so the line should build pressure to like 4psi (i.e. no free air flow at all), and then start bleeding a tiny bit of air at 12psi or so?

Could the free air flow cause my problem? I know that the air leaving the IC pipe would cause a rich situation, but does this mean that a related problem could be letting even more unmetered air INTO the intake system?

Zu_langsam

From my personal experiences if there is a leak in the line to the cycling valve/ waste gate you will see boost go WAY up, like 20+ psi. I see no way for this to be letting more air in though, you will have a boost leak from that line and also no form of boost control.

Ahmet

Check the intercooler pipe to throttle body and turbo to intercooler pipe hoses, OFF THE CAR. I say that because they have a tendency to rip around the harder to see sections, and usually only seperate under boost so it's very hard to catch them w/out taking them off the car.

Good luck.
Ahmet

Chas

but my point is when I blow through the end of the banjo bolt that connects right at the IC pipe, it feels (and sounds) like I'm just blowing free air out the other end somewhere under the intake...I am curious how much resistance (pressure) there should be when I blow through this line (assuming there is no "reliaboost" type device attached)

Ahmet

You do mean blowing not into the intercooler pipe, but into the hose (that goes to the cycling valve). I don't know if the stock cycling valve is supposed to be vacuum tight in this way or not, but either way this is not likely to be your problem.
Ahmet

Chas

Ahmet, I am talking about blowing in the rubber banjo bolt hose that goes to the cycling valve...and I mean it's like blowing through a straw...no resistance whatsoever

I would take the time to check for those rip type problems....but my car is having issues more than just under boost. The car can barely hold idle...in fact at the end of the evening when I stopped for the night, I couldn't even get it to hold idle. And AS SOON as I push the throttle at all, the a/f takes a dive bomb to the lean side.

turbo944

Yes, that definitely sounds like you have a hole somewhere after the AFM that is letting in unmetered air. When you open the throttle the barn door isn't opening on the AFM as the vacuum increases to pull more air into the engine and thus it's reporting less air than is actually going in, so with the fuel going in as reported by the lower volume airflow by the AFM, you go lean.

I would think that the cycling valve may possibly be open, however try sucking on it instead of blowing, that would let you know if extra air could be coming back into your system that way. Then again without the car being on, knowing that the cycling valve isn't supposed to be open with power off to it, it might be hard to say whether the air is coming back in from there. Have you checked the hoses attached to it to make sure that one of them isn't disconnected?

Ben Z.

Man, I'm not sure where the leak would be, but I agree with you and seriously doubt that it's an intercooler connection.

Flight_951

My AFM went bad recently, and ran very lean at partial throttle. Amazingly the car did not have idle problems, but did run too hot and failed the emissions test (which was my big clue). It did this seemingly overnight and I've never tampered with it. I'd also lean more towards an air leak in your case. It doesn't have to be very big either. With dual port wastegates and boost control most people have their CVs disconnected. It's fairly common for them to be leaky but I thought this affected boost, but not the car's idle.

kasturbo

This might be a dumb question, but how do you check the afm voltage? What should the readings be?