Help - It's not the decel valve

Jcon · 06-25-2002, 04:13 PM

If my car gets slightly hot it likes to stall when the RPMs drop. It happens in stop and go traffic if temps get above 200 or if I run it and park it, then restart it before it cools.

It will start fine, it's just that everytime I push in the clutch to come to a stop the RPMs fall past idle and it stalls. A couple weeks ago I got stuck in traffic and thought I might burn out my starter.

Other than that it runs great. It sounded like my decel valve, but when I went out to block off the vacuum hose I found that the PO had blocked with a bearing and reattached the hose to the valve.

Any other ideas?

dean · 06-25-2002, 04:55 PM

Put a vacume gauge on it. Maybe a vacume leak

Superman · 06-25-2002, 05:05 PM

Since I put the cams in, my car wants to die when the throttle is closed quickly, but it never does die. My decel valve has had the same vasectomy as yours. With the decel valve hooked up, idle hangs too high too long. A post was made weeks back suggesting smashing the valve slightly. It may be getting too much gas when the throttle closes but the air flow sensor plate is still high.

Jcon · 06-25-2002, 05:33 PM

If it were a vacuum leak i would expect the problem would be constant, not just when the car gets a little hot.

I read the thread on "smashing it" , my thought was that if the vacuum line has been disconnected for the two years I 've owned and the problem is new then it's likely something besides the valve. I wonder if the sensor plate gets hung up once it;s hot b/c of a combination of grim and expansion?

Any guesses are welcome

Jcon · 06-26-2002, 09:03 AM

Bump

Hladun · 06-26-2002, 11:02 AM

Jcon, the stalling problem you describe is exactly what the decel valve is meant to stop. You say yours is plugged and your engine stalls; that's exactly what you should expect. The decel valve is a necessary part of the CIS system.

I don't understand the "smashing" comments since the decel valve is adjustable. When it works properly your idle speed should "hang" momentarily on throttle closing. If you don't like the "hanging" then you'll have to live with stalling.

1980SC · 12:20 PM

I wouldn't say it's necessary. Mine was removed years ago, and my throttle drop to idle is perfect!

There are two types of deceleration valves. The one on US '78-'79 and euro SC's are adjustable by the screw on top. The US '80-'83 have a disc shaped deceleration valve which looks like the AAV. This one can be crushed slightly.

-Rob
1980SC

Jcon · 06-26-2002, 01:37 PM

Again ... The decel valve has been "disconnected" for 2 years, and the problem is a new one.

Any ideas on where to look next?

Superman · 06-26-2002, 01:44 PM

With my decel valve vacuum line plugged, my idle used to return perfectly. It hung high with the vacuum line unplugged. The dying thing only started after I rebuilt the engine and put different cams in.

My decel valve is one of the non-adjustable flying saucer things. Unplugging it might solve this problem, and might also get rid of any popping on deceleration.

Hladun · 06-26-2002, 02:11 PM

Jcon,

The CIS system is mechanically complex and funny things happen due to component interactions. Often my car worked too, but fixing the deceleration valve fixed the stalling problem. Good luck in your hunt elsewhere.

RoninLB · 06-26-2002, 03:05 PM

Jcon..I assume the idle is 950-1050.......Ron

Jcon · 06-26-2002, 04:31 PM

Yeah, in fact the first drive of the day it runs perfect starts right up, settles to about 850-900 RPM fairly quickly. Example.. this morning I start it up, drive about 8 miles in 75 degree weather to the gym. I stop at two or three lights, a couple of stop signs no problem.

I park at the gym and come back one hour later. Starts right up idles nice I stop at the first stop sign exiting the parking lot and it stalls. As soon as I push in the clutch the RPM neeedle drops like rock and it stalls. It stalls everytime I stop on my way home to swap it out with my very relaible Honda accorda. Say what you will, but it always runs and I treat it like Shhiitt.
Any thoughts?

Jcon · 07-12-2002, 02:19 PM

OK - It's been a couple of weeks and I know you've been thinking about this problem for entire two weeks.

Could it be anything ignition related? When it dies there is no stumbling ...it dies like you turned off the key. It always starts right up and idles fine until the next stop.

I gotta get it fixed this weekend - any thoughts

IXXI · 07-12-2002, 03:46 PM

I had a similar stalling problem with my ’78, although the problem was intermittent.

I looked at the decel valve (still connected on my car), etc. and couldn’t find anything obvious. Out of frustration I started tapping on all things CIS related while the car was running. When I tapped on the aux air regulator, the car stumbled. I’ve replaced the AAR and the problem is gone.

I’ll agree with the comments that the decel valve is there to prevent the rpms from dropping too fast, and maybe the AAR shouldn’t affect the drop off speed, but the CIS components seem so dependent on each other that somehow it did.

Btw, since you have an ’8,1 the CIS components (and their names) from our cars don’t match up. They only way I finally figured out the routing for my year was looking at the Haynes manual.