In the last week or two, I've noticed that my `83 Ninety Eight has not been idling very well when cold. I'll start it, the choke closes and it fast idles like it should. Normally, about 30 seconds is enough. A tap on the gas and the car should return to a nice idle. Instead, the engine struggles to stay alive until it's been driven a few miles. It stalled on me in drive coming out of my neighborhood.

The idle seems to change from about 550 to 800 RPM in park until it's at operating temps.

If I shut the car down for a few minutes, it will idle poorly until it's driven for a few miles.

There are no other performance issues.

The only recent issue was a defective fuel filter a few weeks ago which left me stranded. The anti-drainback valve popped out, cutting off the fuel supply.

Any ideas? Another bad filter? Bad gas? EGR acting up?

Thanks in advance!

 

Check idle pull off, it should open about an eighth inch once the car turns over to give it more air. If it doesn't then it stays totally shut until the car warms up and a choke coil slowly opens the choke valve. It is operated by vacuum. The diaphragms eventually fail or you lost vacuum to the diaphragm.

 

The choke was open when warmed up , but I'll check that and report back when I have a chance. Thanks!.

 

Immediately after start up you should be able to see the choke open slightly. You can also observe the choke pull off to see if the diaphragm is moving after start up. It is an easy thing to check and fairly easy and cheap to fix so that is a good place to start. The choke coil takes over as the car begins to warm up.

 

Also check your hot air warm up system, the heat riser that feeds hot air through your intake manifold during warm up.

 

I'll check that, too. Wife just had a baby, so garage time is limited. Hope to get out there this week.

 

If the butterfly opens up as it should and it continues to idle poorly, I would tap the EGR with a hammer and see it it settles in properly. My guess would be the EGR valve sticking and may need replacing. I would also check all the vacuum lines for cracks and splits near the connections.
Hope this helps,
Cheers
Eric

 

I'm suspicious of the EGR. The idle is erratic, especially when cold.

I'll add that to the list.

 

If you suspect a stuck open egr valve, Check the temp of the egr valve while it is idling. If it is stuck open it will be almost as hot as an exhaust manifold.

 

Congrats on your new arrival. I hope your car is running OK to bring the little one home.
Cheers
Eric

 

Thanks so much!