no aux air regulator-asking for trouble?

09-27-2002, 11:25 AM

I have '74 2.0 orig F.I,
I have strugled setting the idle all summer and cannot seem to get it right. I know that the AAR is working properly by inspecting the vacuum pull when it is cold and when it is hot.

The valve closes when hot but never completely so that there is no suction. I have also moved the dial back an forth on the ecu,
seems to run better on the lean side a couple of ticks.

To make a long story short, I bought a nylon\plastic spacer with
o.d.= 0.5" and i.d. = .19" about 1" long and plugged the AAR vacuum hose with it to control the air flow. This eliminates the AAR
completely and is now idleing consistently at @1100. I don't mind the idle being a little high since the a.c., headlights, etc. brings
it down a little when on.

It seems to me that a constant air flow in the vacuum is better than one that fluctuates caused by the AAR, but I am probably wrong.

I am finally satisfied with the idle but am I asking for trouble?
Could someone please correct me if I am wrong, or did I just discover something cool here.

Thanks everyone.

Jim Smolka · 09-27-2002, 11:43 AM

With the AAR disconnected and a small inlet into the vacuum chamber a couple of things are happening.

1. Unfiltered air is entering into the combustion process (Vacuum leak).
2. A possible lean condition

Worth having the CO amount checked to determine rich/lean.

Personally, I would either find a good AAR or plug it completely, then adj CO.

Of course there is my favorite option, replace 1.7 to 2.0 D-Jet system with 3.2 DME system

09-27-2002, 12:16 PM

Thanks Jim for the quick reply.
The incoming air is actually filtered, I plugged the hose w/ the spacer 1/2" in, and another hose to the air cleaner box as
it was connected with the AAR.

The 2.0 AAR are NLA and almost imp. to find
My main concern is that it is idleing consistantly now, but I am not
100% that this solution is harmless.

I agree with the 3.2, only if I had your $$$

Thanks

rockaria · rockaria's Garage

The AAR on a L-Jet like I have is taking air from an already metered source. I do not know about the D-Jet. But on the L-Jet I don't think it will be lean at all. I have the same problems with the AAR and have done a similar solution. I put in a CO meter to check the Air/Fuel mixture and it seems just fine.

I hope this helps,

mostrow · 09-27-2002, 12:44 PM

I have heard that certain Audi models had a similar aux. air regulators that were interchangeable with the 2.0's. Anyone seen this or know which Audi model had the similar part?

Matt

efrenv · 09-27-2002, 01:39 PM

I did exactly the same thing you did. Plugged the auxiliary air regulator inlet. The car actually runs smoother (when engine is hot). The auxiliary air regulator makes a difference when the engine is cold (to lean the mixture and higher idle) but after the engine heats up it only leaks air and it looks like it does not help on anything. Not sure too. Maybe it's an inherent mechanical limitation of the device, unable to seal 100%. Just a thought...

pbanders · pbanders's Garage

The AAR provides additonal air during warm-up to increase the engine speed and overcome additional friction present in a cold engine. Air coming through the AAR is filtered through the air filter, so there is no unfiltered air - I think what was meant was "unmetered" air - but even that's not accurate because it's only true in systems with AFC, not MPC.

Having a constant bleed will not cause a lean mixture, as the MPS and ECU set the mixture by manifold pressure, which will vary appropriately. Your problem will be that you will have difficulty in getting your idle speed down to the spec level if there is a large leak.

Removing the unit will affect your cold drivability, which will suffer. I'd suggest squirting solvent into the intake port to free up the rotating vane. Seems to work in most cases. If it doesn't help, you can pry the unit open and clean it up. If the resistive heating element is dead, you can use a string of resistors to substitute (there's a posting of Dave Darling's somewhere on this site that describes how to do this).

dave blackburn · 09-27-2002, 05:55 PM

I found a replacement AAV on a BMW 320i at the junk yard. This was for my 1.8L. The part numbers were not the same but it works great. I think it was $1.50.

JamieC · 09-27-2002, 08:40 PM

A little off topic, but somebody was asking about parts interchangability. I uncovered the following list of Bosch fuel-injection parts compatability--I can't vouch for its accuracy, but it might help:

http://www.type2.com/library/fuel/fuelibo.htm

Brad Roberts · 09-27-2002, 11:30 PM

I second BA's suggestion.

I pull these apart all the time and clean the piece that rotates inside. It is connected to the heating element. To test them I hook them up to a battery charger. If it gets hot but still leaks air.. I pop the top off of them and clean it until I can twist the "piston" inside the bore. Repeat cleaning until you can rotate it with your finger.

I can shoot some pics of this if you need them. The top just pops off by sticking a punch or screwdriver in it and prying up. Make sure you mark it somehow so when you reassemble it the clocking position is correct.

B

gint · 09-28-2002, 08:22 PM

I'd like to see some pics Brad. I need to go completely through the brown car's FI stuff. All of the cold start stuff quit working a couple of months back and even before that I had some bucking below 3k especially when cold. New throttle switch already. I'm going to go through everything using BA's docs and Kjell Nelin's page.

pbanders · pbanders's Garage

Quote:

Originally posted by JamieC
A little off topic, but somebody was asking about parts interchangability. I uncovered the following list of Bosch fuel-injection parts compatability--I can't vouch for its accuracy, but it might help:

http://www.type2.com/library/fuel/fuelibo.htm

This list is accurate, but there is no substitute for the 2.0L AAR, and it is a NLA part. I thought I had a source on a lost cache of old AAR's - turned out to be a goose chase. The only solution is to restore your existing AAR.

NEVER throw away a 2.0L AAR, no matter how crappy it looks, they can always be restored, and they are irreplaceable. If you have one that you don't want, I'll be glad to take them!

pbanders · pbanders's Garage

Quote:

Originally posted by ginter
I'd like to see some pics Brad. I need to go completely through the brown car's FI stuff. All of the cold start stuff quit working a couple of months back and even before that I had some bucking below 3k especially when cold. New throttle switch already. I'm going to go through everything using BA's docs and Kjell Nelin's page.

Bucking when cold is usually a lean mixture. Likely suspects are the CHT and dirty injectors.

Brad Anders

gint · 09-28-2002, 08:33 PM

Thanks Brad. But it did the bucking thing both before and after new 3 new and one barely used injectors were installed. I'm suspecting the head temp sensor as well. I don't think that is the issue with the cold start though. Even when cold start circuit worked OK the engine bucked. I think I might have two seperate issues.

dave blackburn · 09-29-2002, 01:40 PM

Pardon my ignorance, what is the difference between the 2.0L AAV and all the other ones? Different warm up times till close? Thanks,

pbanders · pbanders's Garage

Quote:

Originally posted by dave blackburn
Pardon my ignorance, what is the difference between the 2.0L AAV and all the other ones? Different warm up times till close? Thanks,

Different orifice shape (flow vs. time), different inlet/outlet diameters (I have a nice T3 unit that looks identical, except it's got the wrong size port on the outlet), different inlet/outlet angle (it's about 135 degrees on the 2.0L unit).