Kjet 242 stalling during idle

I did some playing around with the auxiliary air valve this weekend. I watched a video of a guy with a sticky valve diagnosing it by putting it in a freezer and a toaster oven to simulate the low + high temps that would make the valve inside open/close. I followed his steps and my valve does not move at all regardless of temp, it’s just stuck partially open no matter what.
The part # on the aux air valve I pulled from my car is 0 280 140 114.
The part # I am finding for what should be in a 1976-1978 240 is # 0 280 140 100.
I have gone ahead and ordered a remanufactured part with the part # ending in 100.
What really is the difference between these if anything? I see Bosch aux air valves for Porsches, Audis, alfas and volvos that all look exactly the same with only slightly different part numbers…

Yeah, you could probably interchange a lot of different applications of those. The bigger engines probably have a larger air channel. They all pretty much work the same. In my experience they don't fully close till the electrical element is heated with power. There is also the little nut that lets you adjust the position of the valve so it works better.

After a long week of 8-10 hour work days followed by working on this car until I run out of sunlight I think I need to just call it quits until next spring. I spent so long cleaning up the intake, putting 2 nice clean coats of vht high temp silver paint, installing a brand new engine harness from Dave Barton, new intake + throttle body gaskets, new silicone vacuum lines, a remanufactured Bosch auxiliary air valve + new air valve hoses, a nicer fresher rubber k jet boot…. I went to crank it up after I had everything put back together carefully…. Forgot about the cold start valve - fuel squirting everywhere as I cranked it - immediately ruins/totally destroys the fresh paint on the intake + the paint on my snow scoop will need to be sanded down and fixed too. I cleaned it all up and waited a while for the gas to dry out before I tried to start it again, and it will start and then just immediately die. I do not have the mental strength to continue thinking about this car at the moment, it is killing me. I love it so much, but I need to stop. Thanks for all of the help everyone.

Don’t worry, I’m in the same boat chasing vacuum leaks/idle problems in my kjet as well. Sometimes it idles at 700, sometimes 1200, sometimes 2000, sometimes outright die, just depends how it feels after I let off. 99% sure there’s a leak in my brake booster but haven’t made my way there yet, have you checked yours?

When you have a little distance from it (time wise) - I would suggest doing a methodical fault trace / system check of the overall K-Jet. There are specific test procedures outlined in the K-Jet greenbook that should be followed, to remove any guess work. You need a fuel pressure gauge hook up that will connect to the the CPR, you need to know that both line & regulated pressures are in the ballpark, for starters.

lookforjoe said:

When you have a little distance from it (time wise) - I would suggest doing a methodical fault trace / system check of the overall K-Jet. There are specific test procedures outlined in the K-Jet greenbook that should be followed, to remove any guess work. You need a fuel pressure gauge hook up that will connect to the the CPR, you need to know that both line & regulated pressures are in the ballpark, for starters.

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I agree. Thats what I would like to do. I work with a tech here at the volvo dealership who worked on these back in the day, and COULD help me but he pretty much refuses to. He says he hated k jet back then and never thought he would have to see it let alone work on it ever again. I might be able to find the correct equipment here to do the tests, but i just have very little idea what I'm doing and that is becoming more obvious as I get deeper into this project. I also have only a few more weeks or a month or so before the inevitable white stuff comes to Rochester and I have to put the car away for storage. Luckily it's already sitting where it will get covered up.

lookforjoe said:

When you have a little distance from it (time wise) - I would suggest doing a methodical fault trace / system check of the overall K-Jet. There are specific test procedures outlined in the K-Jet greenbook that should be followed, to remove any guess work. You need a fuel pressure gauge hook up that will connect to the the CPR, you need to know that both line & regulated pressures are in the ballpark, for starters.

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This is excellent advice.

Give yourself a little time to recoup and then read all the associated green books. Kjet isn't that hard to understand and troubleshoot. But it does require some of the needed tools like the fuel pressure tester. You'll also need a good dwell meter with volts and ohms to test various parts of the system. A professional tech who hates kjet is someone to be avoided. Don't let him touch your car with his hateful ways. Kjet is easy and all you need is to take the time to learn how it all works. Take away the guessing and get it diagnosed.

Be aware that it can have up to three things going on with the engine management. There is kjet basic, kjet with lambda control, and kjet with lambda control and Constant Idle System. Get all the green books from OZvolvo.org and learn how it all works.

I got it running! It’s idling beautifully. I might have had some bad grounds, or maybe some dirty connections. All I really did was spray some contact cleaner into the air/fuel plug, and the warm up regulator plug, and I had to change the ground ring terminals to larger o rings so I could get them connected to a thicker bolt on that black post holding the intake up. So I’ve got a brand new main engine harness all wired up and the intake gasket done among some other little things while I was in there. Now I just need to figure out this throttle spring so I can get the car to move…

Spring on the throttle spool, or on the thottle body itself? If the former, I'd just hunt down a 1980-82 throttle cable and spool from a K-Jet non-turbo car and swap those parts on. That way, if you decide to, you can use the 1980-85 style cruise control system on the car.

John242Ti said:

Spring on the throttle spool, or on the thottle body itself?

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I was having an issue figuring out the spring on the throttle spool. It looks like I might be missing the larger one with the little hook on the end. Either way, with what I do have I got the throttle linkage all connected and took the car on a little drive around town. It’s doing the same thing it was doing before once it warms up. I need to keep on the throttle to keep it running. However this time, if I put the car back into park after it’s warmed up it will idle fine again. Before I did all this work it would just die no matter what gear it was in after the car got warm. This makes me think again that I’ve got some sort of vacuum issue going on. Either way, I’m very happy I got the car all put back together and I can move it around again, and I can now rule out a few things that might have been causing this problem.





Yeah….the blue silicone hoses have to go….

I drove the car to and from work today. It was low 50s temp here in Rochester. I made it one stop light further before the car started to want to stall in drive, I figure that’s because of the cooler air than before. Another thing I have noticed is that it hates reverse especially. When I try to back into my parking spot it needs immediate throttle or it will die - no sputtering just boom dead. When it tries to stall in drive it at least gives me a second to give it some gas before it shuts down. When I’m in drive and I’m moving it still shifts through the gears and gets along just fine.

rearwheelpeel said:

I drove the car to and from work today. It was low 50s temp here in Rochester. I made it one stop light further before the car started to want to stall in drive, I figure that?s because of the cooler air than before. Another thing I have noticed is that it hates reverse especially. When I try to back into my parking spot it needs immediate throttle or it will die - no sputtering just boom dead. When it tries to stall in drive it at least gives me a second to give it some gas before it shuts down. When I?m in drive and I?m moving it still shifts through the gears and gets along just fine.

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Could it actually be the transmission / torque converter causing the engine to bog so low it wants to stall/die?

So my car now starts right up, idles beautifully, and no longer stalls at red lights or in reverse. However it will stall at low speeds while turning sharply, like backing in or pulling out of a parking spot. I’m able to keep it from stalling by giving it some gas. If I just back up or pull out straight it’s no issue, and slight turns are fine, it’s only when I really need to crank the wheel. What might cause this?

I'd check the throttle plate adjustment. The small amount of open from closed may be causing it to lean out and stall when the throttle is closed. These B cam cars like a 900 rpm idle, too.

If you achieve the otherwise same idle speed while going straight I assume it manages just fine.

Power steering is belt driven off the crank, so possibly when at far lock it's putting more load on the engine. I assume this load applies faster than compensation can fight it.

At the same time, at least with my B21FT with CIS, when I mess up and almost stall the engine I'll see tach speed drop down to close to 0 before bouncing back up when I push the clutch back in. So I think you have have some gremlin that determines it will shut the fuel/spark/something off when this happens rather than adjust itself get the engine back up again.

Given you're starting the engine with a flywheel starter at maybe 200-300rpm, the engine should be able to self recover from about that speed, no problem.

Like Car Talk, describe your senses as the engine dies. Does it sound like it's still trying to run but can't, does it sound like you keyed off? How low does tach go (if you have one) before combustion stops?

Also back to dl242gt's question from 2021, do you have kjet basic, kjet with lambda control, or kjet with lambda control and Constant Idle System?

The car has basic k-jet, no lambda control or constant idle system, just a valve cover mounted idle air control valve that is new/refurbished. When it starts to stall at full turn the tach wobbles down towards 0, but the car wants to stay running. I’m learning to deal with it and just give it a little gas as I turn, so it’s more of an annoyance at the is point but I would like to figure it out. I also just recently replaced gaskets and cleaned the whole intake and throttle body, so it’s definitely possible I need to keep playing with the throttle adjustment.

Ok, so it looks like fuel/air is not getting completely cut, but maybe can't fight that extra load properly.

Do you have AC on the vehicle? You could toggle that on so the compressor loads the engine and see if that similarly causes problems.

Also try jacking up the front so the tires are free in the air and see if full lock left/right causes stall, or if it's fine up in the air, that'd point more to extra load from power steering rather than some deeper weirder interaction of full lock changing the power steering load on the belts.

But if it's still a bit more likely to stall overall than you believe is normal, likely an idle / airflow adjustment. Do you happen to know if it's generally running a bit lean? It may be the kjet balance plate isn't moving quite as much as it should for the given airflow.

The throttle plate adjustment is pretty basic. You need to loosen the locknut on the throttle plate adjustment screw and turn the screw till it's backed off and the throttle plate is closed. Then turn the screw till it contacts the bracket and then give it another 1/8 to 1/4 turn till it's just pushing on the throttle plate enough that it isn't hitting the inside of the throttle body. That usually sorted the letting off the gas stalling issue. The idle speed is adjusted with the plastic thumb screw under the intake manifold. There is an oring on the thumb screw that can make for a sneaky air leak.