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Weird idle issues b21ft

ogamer777

ogamer777

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Joined
May 22, 2016
Location
New North Winchestersonville (PNW 425 gang)
1982 B21FT 15G KJet

I replaced all the old and cracked vacuum lines under the hood with new silicone lines. I did everything under the intake manifold, one line at a time so i wouldnt get things mixed up. Everything else was self explanatory. Went to test drive and see if it drove any better. Something isnt right. Now when i get into max boost (3.5-4psi) the car stumbles almost like its fuel cutting. Before i changed all the hoses the car would steadily stay at 3.5-4psi, with cracked lines. What could cause this stumbling and high idle after driving at max boost? It will idle at 1500 for around 2 minutes then go back to 1000. The idle is very sluggish meaning it takes a while for the rpms to drop after i press the gas pedal while idling, if that makes sense.

I did remove the distributor cap to get access to the vacuum lines under the intake manifold, but i made sure everything was how it was before i took stuff apart.

My boost gauge shows ~18 inHg for vacuum at idle. Boost tops out at 3.5-4psi.

Any thoughts on what i should check? Thanks for your help
 
There are some sneaky spots on a B21FT for air leaks. The intake manifold gasket, injector seals are a couple. If the air handling hoses are oily and permeated they can also act like an air leak.

Maybe the idle system needs some cleanup like removing varnish from the idle motor?
 
dl242gt said:
There are some sneaky spots on a B21FT for air leaks. The intake manifold gasket, injector seals are a couple. If the air handling hoses are oily and permeated they can also act like an air leak.

Maybe the idle system needs some cleanup like removing varnish from the idle motor?
Click to expand...

Thanks for your input. I'm hoping it's not the intake manifold gasket but if it is then it is what it is I'll replace it. In the meantime, I think a lower mile idle air valve will replace the current one. May as well throw in new injector seals as well. Will do all that today and report back. I think I covered all the other hoses I could find, aside from brake booster line and charcoal canister line. I did replace the 5/8"(?) ID hose from charcoal canister to throttle body.

Could it be my timing is off? I did remove the distributor cap and touched the rotor a little bit when I was prying old hoses off.
 
You are not going to change the timing by moving the rotor by hand. An 82 uses the check valve in the vacuum hoses going to the control pressure regulator. I would make sure you put the check valve back in place facing in the right direction. I don't remember off hand which way it goes but there pictures and diagrams in the manuals. Maybe even a engine compartment sticker still shows it?
 
I had a leak that bugged me for quite a while and it turned out to be the throttle body to intake manifold gasket.
Dave B.
 
It's actually a delay valve, not a check valve. This pic shows the correct orientation however the system shouldn't be working with the engine warm. Make sure the TVS (thermostat valve) is closing.

ThermalControlValveHoseRouting.jpg
 
Yes, but you can check it by removing the hose that goes to the CPR and blowing through the hose that comes from the intake manifold (you could also use a vacuum pump) if you don't have access to a fuel pressure gauge. It should pass air when cold and shouldn't when warm.
 
We got it solved... The vacuum line that goes from the throttle body to the charcoal cannister and the advance/retard diaphragm got hooked up directly to the CPR, with the remaining parts connected to the delay valve and the manifold after the throttle body. I think the advance/retard, along with the charcoal can were hooked up to the t-fitting on the CPR. Anyway, it's fixed now. Car no longer feels like a 1981 244DL M46 car with a slightly high idle. It's still a little slower feeling than my 245Ti, but, that's mainly due to my having a 3.91 instead of a 3.73., since I swapped my car from an Aw71 to a M46.
 
ogamer777 said:
Yep. Thanks. Car is running decent now. Vacuum at idle is around 18inHG. Still, on the mission to replace all vacuum lines with silicone lines. The goal is no vacuum leaks at all. I want to have a strong 22inHG at warm idle.
Click to expand...

A B21FT has only 7.5:1 compression and I think you should be happy to get 18in HG. I doubt you can get it higher.
Dave B
 
ogamer777 said:
I've read on here that the B cam is the bee's knees for b21ft
Click to expand...

Only for people that want to use a Volvo cam. I suggest you buy a real street performance cam. It is better.

A B21FT 240 with a manual or automatic stays in the low rpms so little that you don't miss any loss of bottom end torque. Personally, my car has plenty of low rpm torque when off boost. Manual has 3.73 automatic has a 3.91 axle. You just zip through first in both transmissions.
 
dl242gt said:
Only for people that want to use a Volvo cam. I suggest you buy a real street performance cam. It is better.

A B21FT 240 with a manual or automatic stays in the low rpms so little that you don't miss any loss of bottom end torque. Personally, my car has plenty of low rpm torque when off boost. Manual has 3.73 automatic has a 3.91 axle. You just zip through first in both transmissions.
Click to expand...

What street cam do you suggest?
 
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