dpatterson

1989 22re

Just last week the idle began surging up to 1600-2000 rpm before the engine warms up. Once up to temp it is normal. Also the pulsing idle cuts in half when the brake is applied.

The fuel seems to be cutting off after the spike and drops down again and really affects the driving at lower speeds.

Now all of a sudden this morning the heater is not blowing warm air.

Any suggestions?

Odin

Hmm, my guess.
Surging idle and loosing the heater are common signs of air trapped in the cooling system.

How's your coolant level? Is your overflow bottle cracked/broken, any leaks or cracks in the overflow/return line? If the underside of the radiator cap is rusty replace it. I've seen new caps that were bad too so being new isn't a guarantee that it's operating normally.

You might want to take your vehicle to a radiator shop and have the whole system pressure checked if you can't find it easily.

dpatterson

Sure enough.... I did notice a coolant smell a couple days ago but no sign of a leak. The fluid level is definitely low enough to cause air in the system. There is some coolant in the overflow tank also but not much. I'm going to top her off and then see about removing the air.

Thank you for the help!

jennygirl

Does applying the brake also mess with idle once it's warmed up? You may have a hole in the brake booster diaphragm, causing a vacuum leak to be sent through the brake booster vac line when you apply the brakes.

You can test by pulling the brake booster vac line from the plenum and plugging the hole (on the plenum). Don't drive it like this: it is dangerous because it disables the brake booster. Also make sure you plug that hole on the plenum well during the test.

Odin

If you're using a thermostat without a hole drilled in it or a jiggle valve it might prove a bit difficult to remove all the trapped air. I've never had a problem with it in any vehicle until about a week ago when I replaced most of the hoses.

I jacked the front end up and filled the system then started it and waited for the thermostat to open. Then I finished filling the radiator up, installed the cap and topped off the overflow bottle. Normally this works well and the system bleeds out the insignificant amount of trapped air on it's own under normal driving conditions. Unfortunately after a couple of days of driving my idle was acting just like yours.

Once again I jacked the front end up but this time I used the Lisle Spill Free Funnel (24680) to get the fill point WAY UP THERE. I've had that funnel for about a year but never needed to use it till now.

When the thermostat finally opened up it expelled a couple decent sized burps and several smaller bubbles kept coming up as the thermostat would open and close. After seeing those small bubbles I had someone hold the throttle steady at about 3000-4000 rpm and I started squeezing the hoses to help work out any remaining air, which there in fact was.

I kept at it for about a half an hour until I didn't notice anymore bubbles. After all that my idle is back to being smooth and consistent. It was easy yes, but it was also a bit of a pain.

jennygirl

Good info Odin, I tried to burp mine the other day but I don't think I did that good of a job.

Either way it did help and my idle is good to go. I bet there is still more air in there and I wanna get it out!

Thanks again

dpatterson

@jennygirl

The idle was only acting up when the engine was cold and it was perfectly normal once at operating temp. But applying the brakes cut the surging in half (600-1200rpm). Release the brakes and it spikes much higher (600-1800rpm).

I topped off the coolant and ran it until the thermostat opened then topped it off again. I am going to try jacking it up and bleeding it now but the idle is normal again.

Thanks!