Sticky CIS Idle (not linkage)

Pat S · 05:30 PM

Okay, I have a freshly rebuilt 2.7 (1974) with CIS. I have no cold or warm start problems, in fact it starts first try everytime and runs great.

That said, the idle sticks. When I stop at a light for example, it wants to idle at 2k or about 1.3k, always one of the two, never in between. A sharp quick tap on the accelerator raises the revs to 3-4k then drops it nicely down to 800-900 range.

I initially though, bad/dirty linkage or pedal sticking. But I've rebuilt the pedal cluster and tested pulling back on the accelorator: with the rpms stuck near 2k, the pedal is in the full up position, it doesn't physically move or drop the idle.

So any ideas? It seems almost like there is something internal to the CIS sticking. The system did sit for 3-4 months while I was rebuilding the engine if that helps. The only other oddity is that on the WUR, there is a red/yel (I think) wire connection from the harness. I believe there should also be a ground wire connected to the clip but I dont have that connected since the wire broke off in the clip. Don't think it matters but I wanted to post it.

Pat

mr914 · 10-18-2003, 05:43 PM

Air leak IMO

Check the tubing/fittings.

I had a cracked/split rubber tube between my intake runner and manifold.

Pat S · 10-18-2003, 08:24 PM

SoCal, Thanks. A quick search on Decel Valve located many with the same issue. I'll troubleshoot that puppy more in the morning.

stlrj · 10-19-2003, 02:04 PM

What happens if you disconnect the throttle linkage while the idle is hanging up, instead of blipping the throttle. That should tell you if it has anything to do with your linkage.

Joe

gustaf · 10-20-2003, 06:20 AM

I had the same issue with the same setup (74 CIS) as you are running but my car would also occassionally die when coming to a stop sign. I determined that it was running a bit rich and leaned it out and it has performed flawlessly since.

Pat S · 10-20-2003, 06:28 AM

Well I just notices that the upper spring on the linkage may not be working . I't stretched out and loose even though the linkage is not fully closed. I think I'll replace it first. I have a Gunson on order, so I'll do mixture second, and if those don't work, I'll look closer at the decel valve.

I did test the valve by pinching off the top hose when the idle was stuck high. It dropped the idle very slightly but not enough. It may just be out of adjustment as well.

Thanks,
Pat

10-20-2003, 08:07 AM

A similiar problem on my '77 was solved when I found that the distributor advance weights were hanging-up because the grease had turned tacky over the years. It didn't affect acceleration because there's a lot of force available to "open" the weights, but the little springs couldn't always pull them all the way back in at idle.

Ed Cavalier

Pat S · 10-20-2003, 08:38 AM

Okay well I have resolution at a super cheap cost of $3

It turns out the PO (man I don't like those POs) must have figured any old spring would work for the top linkage spring. I noticed it was bent and just didn't seem to fully close the linkage while checking out the decel valve. So I went to the local garage and picked up a new one. Once I saw it, it was obvious that the one I had was way too long.
I put the nice new correct one on and I'm returning to my set idle everytime. I can't wait for my Gunson to get here now!

Thanks for all the help and for pointing me to the problem,
Pat

UTKarmann_Ghia · 10-20-2003, 10:48 AM

Congrats, I should've been a bit more specific/assertive when I asked you about that spring on Saturday

Pat S · 10-20-2003, 03:24 PM

Yeah the lower spring was okay though. After you left I found the upper spring in the box that I stored my CIS in so I put it on. It seemed a bit loose at the time (it was loose enough to fall off and end up in the box), but now that I know how tight the correct one is, I realize it was way too loose.