AAR and High Idle Options

[lsintampa]

75 2.0 FI w/backdated exhaust

Motor recently rebuilt.

Injectors cleaned / all are very good. New points, condenser, blah blah. Most everything is new .... except:

FI parts were all just laying about for IDK, maybe 10 - 15 years or so.

Car DID have A/C - but not any more.

The shop that did the motor rebuild did a great job, but they didn't sign up to muck with the FI system. They did a great job on the rebuild and did as much as needed to get the car running, but left the FI tweaking for me.

Which is fine - assuming I can tackle it myself, or (if not) farm it back out. I asked for the option.

That said, I notice that the hose that goes to the IN port of the AAR (the larger of the two hoses), gets sucked closed when the car is running. By that I mean the suction is so great it basically collapses the hose (pinching it).

I haven't had the time (wife just got out of some surgery yesterday) to play with it, but I'll pull that hose and replace it with something a bit more sturdy.

I don't know what effect that would have on the idle - if any.

Idle is a bit high, in the neighborhood of 1100 (more or less at times). Depends if I just am sitting or came to a rolling stop, etc. But mostly let's call it 1100. The car is very responsive and runs strongly. No issues there.

I don't have access to any high end diag equipment, so most of what I can do would be try this - see if it helps. I do have vacuum gauge, timing light, basic stuff.

I'm wondering if (since the car did have A/C), somewhere in the past if some adjustments were made to the FI system to account for the extra strain the compressor and pulley added to the motor? (resulting now in a high idle) I think they (the shop) did all they could without mucking with components. Adjusting throttle cable, air valve, etc.

So, what effect on the idle would the AAR intake hose collapsing on itself have?

Should the suction be that strong to cause the hose to collapse? (I think the hose is one that came from the AA FI hose kit).

I think it makes sense to first address the AAR hose situation before moving onto the idle issue, just don't know if they are related or not??

Thanks,

Len

[JawjaPorsche]

Your idle should be around 700 to 800.

Finding a vacuum leak can be a pain in the ass. I think your "high" idle is a vacuum leak somewhere! It took about a month of replacing that then than to solve my high idle.

I would get a better hose for your AAR then move from there. I even used clamps on mine. See picture. I have a 1.7.

Hope your wife is recovering well from her surgery.

[SLITS]

I doubt you would need the AAR where you live. In California, I just plug them off.

[76-914]

That's a Hell of a vacuum! Disconnect the AAR and plug the hose. If that does it then you'll need to clean up the AAR.

[rgalla9146]

That's a Hell of a vacuum! Disconnect the AAR and plug the hose. If that does it then you'll need to clean up the AAR.

If the hose is collapsed the the AAR is closed. Plenty of vacuum is appropriate. Same as fully warmed up. Same as a plug.
Timing ?

[TheCabinetmaker]

Factory calls for 900 rpm at idle. I keep mine at 1050. Sounds like you have a piece of soft heater hose instead of the hard rubber, cloth covered stock hose. It would take more vacuum than our engines produce to suck that hose shut. Like slits said, you don't need the aar where you live. It probably never opens anyway.

[lsintampa]

I replaced the hose from the AAR intake to the CSV with a more sturdy hose.

The hose doesn't collapse. But now the idle surges between where it should be (about 900) up to almost 2,000, then down almost to stall and back to normal, back up and so on.

I adjusted the needle valve on the TB just a bit. It was turned all the way shut. Now it is maybe about 1/8th of a turn (or less) open.

I'll search the board for surge / idle and see if anything pops up.

[TheCabinetmaker]

The surging is probably lean idle hunt. Turn the knob on the ecu clockwise and see if idle stops hunting

[lsintampa]

OK, my bad.

I didn't have the d-cell valve connected.

SO... I replaced the hose to the AAR - and it does NOT collapse as the old one did.

I adjusted the timing very slightly, hardly at all.

I backed off the TB needle valve around 1/8th of a turn or less - it was all the way in.

Car idles at about 1100 - 1200 RPM more or less all the time.

IDK, I'd like it to be lower, but I don't know if it will.

Pulled the hose of the MPS and car runs like (IMG:style_emoticons/default/barf.gif)

Anyway, all back together, the AAR hose doesn't collapse in on itself, and idle is a bit high.

Not hunting now.

[Dave_Darling]

If you remove the hose to the MPS, the FI thinks the car is at full throttle so it dumps lots of fuel in. No real surprise the car idled poorly at that point.

Make sure the distributor is advancing and retarding correctly, and triple-quadruple check for vacuum leaks. Including the PCV setup.

--DD

[lsintampa]

75 2.0 FI, cat delete, exhaust backdated

I stand corrected. I thought the idle leveled off, but the car was HOT when the hunting range was tiny. But ....

Idle does hunt, most of the time.

At cold start the hunting is between 900 and maybe 1200, then at midrange hunting is near stall to maybe 1000, then when hot the idle is high and the hunt range is small - like from 1200 - 1300.

Once the motor is a full temp, the idle remains high with very slight hunting - as mentioned above.

All the V-lines are NEW. The FI components are original - as far as I can tell.

I think the AAR is working because once the motor warms up, the idle does drop.

I've not bypassed the AAR as yet. Still trying to figure out the idle issue.

A question about the air box... I don't know what the small tubes are for that seem to run through it. They are about 1/4 inch in diam and I thought they were for some sort of support or something. Anyway, should they be tight? By tight I mean that I can sort of wiggle them about / turn them.

I copied a photo from another post for reference. The tube I'm talking about is the small one in the photo with the water streaming down from it (under the big TB opening).

I seem to recall mine were loose, but I'd think if they are supposed to be "sealed" that my issue would be bigger than what it is.

[Dave_Darling]

Those are supports for the plenum; they run from the roof to the floor of it so it does not squish when weight is put on it. They can be open at the ends, but they should not let air into the plenum. The welds (??) around them that attach them to the roof and floor of the plenum seem to crack with some frequency after four or five decades, so it is worth checking those for leaks.

--DD

[r_towle]

You only need one vacuum hose to run the car, the one to the mps.

Remove all others from the plenum and plug the plenum.

Does it hunt then?

If no, plug ONE hose at a time back in and test....

If it still hunts, it could Fuel injector seals, intake boots, intake head gasket....all potential vacuum leaks.

If you have several small leaks, they add up to one big leak....

[lsintampa]

The surging is probably lean idle hunt. Turn the knob on the ecu clockwise and see if idle stops hunting

Must have been - I turned it clockwise quite a bit and the surging / hunting has all but stopped.

Idle now is about 1100 - near steady.

I'm still tinkering and (IMG:style_emoticons/default/driving.gif)

[Bartlett 914]

Those are supports for the plenum; they run from the roof to the floor of it so it does not squish when weight is put on it. They can be open at the ends, but they should not let air into the plenum. The welds (??) around them that attach them to the roof and floor of the plenum seem to crack with some frequency after four or five decades, so it is worth checking those for leaks.

--DD

(IMG:style_emoticons/default/agree.gif)

These can be a source of a vacuum leak. There is a lot of weight and vibration that can cause the welds to crack