idling problem

[briam213]

hey im new here anyhow iv got a 74 2.0L with the original fuel injection, and im having a problem wiht the idle. i was told that it was the aar, which was not working, and i bought one and installed it, and i had a plug in the hose from the aar to the air cleaner, the previous owner had done this, and it idled nice for a couple minutes, but would end up idling at like 1800. when I installed the new aar, and unplugged the line. i started it up and it revved to about 2000 and slowly rose, and i took it for adrive and it ended up idling at about 2800 fully warm, i have played with the idle screw on the throttle body, which seems to have no effect, i have played with the idle air adjustment screw on the top of the ecu which doesn't seem to affect teh idle, it just makes it run really badly and i can't get it back to normal, i emailed dave@pelican parts about it and he suggested air leaks and advannced timing, i checked for air leaks, and i replaced a couplehoses, but the thing is is that when i plug up the line from the aar to the air cleaner, it idles right, at least for a few minutes, adn both teh hoses on the aar are fresh, and i am pretty sure that the timing isnt off, because itdid run nicely before i messed around with all the idle mixture stuff, and im really at a loss, and i keep coming to a brick wall with the fact that it idles right wiht the plug in the aar, im guessin gthe previous owner did something to make this happen, but i can't figure out whats going on and its not very driveable like that, and it doenst have as much power with the plug. any help would be greatly appreciated, thanks, brian

[AaronM]

The adjustment on the ECU is for emissions really, and it's not meant to be used to adjust for idle or anything. IIRC the way to adjust the knob on the ECU requres a CO measurement at the tailpipe.

One thing that seems to work for a lot of people is to replace _all_ the vacuum lines. The FI system is very sensitive to vacuum leaks anywhere and a lot of people have reported that their cars were completely different (better) after replacing all the vacuum lines.

Aaron

[WOODPIE]

hello briam213. well i'm not the best person her to give advise on getting your engine to idling right but i can echo what i have been told by others and have also read too. it would be nice to just open the hood and replace the aar and a couple o hoses and it would idle good but that usually ain't it. you got to make sur all hoses and everything ain't leaking and your timing is right and your valves are adjusted good. then you make sure you have proper fuel pressure and your injectors are all working. the adjustment screw on the ecu won't make the engine run too much faster or slower it is only for fuel-to-air ratio at idle (lean or rich). do you have power to the aar? see, we can speculate all day about what might be wrong so you first have to positively eliminate all other potential problems. are your spark plugs good? how about the points, or do you have electronic ignition? Solid or hydralic lifters? the brick wall you keep coming to isn't a brick wall at all. it's just a very steep learning curve. use the search function on this board to find all that has been said in other posts about idling and other related engine running problems. if you can pinpoint a particular problem, and you can't figure it out then, maybe i or someone else will be able to hep.

Ed


I just had to.

[Bleyseng]

Well, I read your story and I think that the AAR valve is not getting power so it is not closing. The AAR valve has a little heater in the bottom of it, when its cold it is open letting air in raising the idle. When it heats up it closes returning the idle to normal.
I also think the timing is off too that's why it idles at 2800 when warm.
The combo of the large vacuum leak from the AAR valve and the timing being off results in the 2800rpm idle.
Geoff

[John Rogers]

We have had this happen a couple of times with our stock 1974 2.0l and every time it was vacuum leaks from hose connections. One time it was also a bad gasket at the head to intake joint that would cause an idle change as temp went up/down? Use the spray carb cleaner or start fluid slowly and easily at each hose conn and on everything that could have a vacuum on it including the intake plenum and you'll find it. If you have the fabric hoses cracks in the neopreme are very hard to find as the fabric hides them. Good luck.

[Dave at Pelican Parts]

It sounds to me like your new AAR may be faulty, or might not be getting power. The wire that "feeds" the AAR should get +12V any time the fuel pump is running. (Easiest way to check it is with the engine idling.)

Remember, the AAR should close and not let any air through it after ~5-10 minutes of the engine running. If you plug the hose going from the air cleaner to the AAR with your thumb, does the idle come down to ~800?

I'm thinking you may still have vacuum leaks in addition to this.

--DD

[briam213]

thanks for all the help guys i hadn't thought of the aar not getting power, but that isn't the whole problem, because it still idles really high when its warm, but i do know it normally works. i think vacuum leaks are part of the problem, im suspecting the really large ones on the manifold tube thingsgoing into the throttle body, as those are about the only ones i haven't replaced in the last year. im going to check out the timing this weekend, everything else should be in good condition i adjusted the valve last winter, which was within 1000~ miles, i check the plugs regularly, i have not checked the points recently, or the fuel pressure/injectors, not in a huge hurry since were supposed to be getting up to a foot of snow in the next 24 hours thanks for all the help
brian