Need help with idle / air / vacuum

[[email protected]]

Ok, so if anyone has been keeping up here is the latest. Brief update:
1975 3.0 csi
car has been sitting most of 30 yrs.

Engine replaced last week with 1977 3.0 from a sedan.

All fuel delivery and upper intake remain original. (Intake welded since yesterday)

Engine block and cylinder head only changes.

Engine runs.

My problem/question is: idle is very high, the brass angular cut pipe protruding from the air box side of the throttle flap is sucking vacuum, if I block that, the idle drops and engine runs ok. So I feel there may be issue with something that controls vacuum. Potentially from that valve between the starter and alternator mounted to the block.
Any insight may be helpful. I am not familiar yet. Please help. Fred

 

[MMercury]

Not quite familiar with a "brass" angular pipe. Nevertheless, I presume you have a stuck or maladjusted auxiliary air valve - used as part of the cold start system. There are two basic styles, early and late. You probably have the early style, but one never knows?




http://www.e9coupe.com/forum/showthread.php?t=6525

http://www.e9coupe.com/forum/showthread.php?t=12086

http://www.firstfives.org/faq/aux_air_valve/aux_air_valve.html

 

[[email protected]]

Thanks mercury that helps.

 

[sfdon]

That brass pipe is a feature of the late cars- EGR. Big and nasty running across the valve cover and down to the forward exhaust manifold. You need to delete it and the rest of the smog junk.

 

[[email protected]]

I deleted EGR I am talking about the pipe protruding from inside the throttle body. That one is sucking vacuum because maybe the AAV is stuck. I'll let you know. Fred

 

[Tierfreund]

most likely the AAV. Common culprit on many D-Jet, D-Jet-like and some L-Jet cars.
My 88 Jag V12 still has the same bloody thing. Sometimes it can be fixed (try to free it up with brake cleaner). If not, there is a reconditioning/rebuilding service by Bosch classic.

Same thing (only also has an idle air circuit incorporated but the heat dependend part is the same). Good description of it and how it might be fixed:
http://www.jag-lovers.org/xj-s/book/AAV.html

 

[[email protected]]

Yep , it looks like the culprit. I have removed the AAV oiled it, and it was working with a heat torch warming it up, I reinstalled it, still won't work. Looks like I'll have to disassemble it in order to make it work, with the hot coolant from the car (which isn't as hot as my torch.) I hate to disassemble it in fear of breaking it, but not much to lose now. Fred

 

[Stefan]

As in earlier threads mentioned, you should put the aav in a saucepan and heat the water and you'll see (hopefully) the piston moves from open to closed position.
If not the piston moves all the way, it's jammed or more likely in this case (since you said it had moved) is that the heat expanding wax inside the aav have lost the ability to fully expand due to ageing.

 

[bill]

Check to make sure coolant is circulating through the chamber behind the air-slide. The coolant passages are somewhat narrow and can clog with sediment. If coolant isn't circulating the air-slide won't get hot and won't close, thus high idle.

 

[Tierfreund]

Check to make sure coolant is circulating through the chamber behind the air-slide. The coolant passages are somewhat narrow and can clog with sediment. If coolant isn't circulating the air-slide won't get hot and won't close, thus high idle.

+100000

been there, had that. Any neglect in the cooling system at any time in the life of the car will start the coolant pipe rusting from the inside and the rust flakes will start blocking the very small tubes and hoses and the housing of the AAV. In which case the AAV may even work properly in traffic from engine heat but will not see colant flow and temp when driving with airflow in the engine compartment. Had a 3.0Si that idled at 1800 when hot coming directly from the autobahn but would idle at appropriate 800 when tooting along in city traffix.

 

[Stefan]

Check to make sure coolant is circulating through the chamber behind the air-slide. The coolant passages are somewhat narrow and can clog with sediment. If coolant isn't circulating the air-slide won't get hot and won't close, thus high idle.

+1 for that tip from bill. Also noticed that it's narrow in that chamber. With a badly maintained engine this could be an issue.

 

[[email protected]]

The coolant is flowing hot through the AAV . The AAV slides back and forth fully closes and opens back from a torch and then cold water, so I will attempt to disassemble and polish/clean cylinder. But it will require strong hits from a hammer . I'm hoping not to damage.. The slide is definitely not free. It's challenged from corrosion . Also I have two injectors That aren't firing, so I will replace them as well. I have good coolant flow. New hoses, t-stat
And the steel return pipe is rust free. My 40 yr old radiator is leaking , which I'll have re- cored. On a good note this car is running and driving in and out of garage, has 150psi compression across the board and I'm close. Hasn't been driven in about 30 yrs. thanks for the advice and encouragement. Soon lets hope she is mobile again. Fred