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Kjet 242 stalling during idle

rearwheelpeel

Slow Learner
Joined
Jul 22, 2014
Location
Rochester NY
I fixed my timing issue today on my 1976 242. It has an auto trans and b21 engine with kjet. It starts right up, and idles while sitting in park very smoothly with no hiccups. When I shift into drive it will sputter out and die unless I keep on the gas. While at a red light I have to keep one foot on the brake and flutter the gas to keep it running. If I just keep my foot on the gas it shifts through the gears fine and moves like it should, and I can let off the gas and coast at a decent speed, but when it slows down to an almost stop it needs more fuel. It seems like quite the coincidence this happened after replacing the timing belt and water pump, as i was not having this issue before doing the job. I?m wondering if something got bumped while we were working. I?m hoping someone has some ideas on where I can start to look for the cause of this issue. Fuel or vacuum related? Thanks in advance....
 
Idle motor plugged in properly?

76 has an auxiliary air valve - bolted to the valve cover

CIS didn't come in until much later (in the scheme of things)

Worth checking the flame trap hose(s) and the hoses for the aux air valve, if it's not an obvious disconnected vacuum line, etc.
 
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76 has an auxiliary air valve -

CIS didn't come in until much later (in the scheme of things)

Worth checking the flame trap hose(s) and the hoses for the aux air valve, if it's not an obvious disconnected vacuum line, etc.

I’ll check the flame trap tomorrow. I did recently change valve covers from the original cover that had that cam driven air pump on it to a later vented cover. Am I supposed to add an idle air control valve or something now that that is gone?
 


If your cam cover has the valve shown here, sitting behind the plug wires, then you have an idle control valve. It's the aux. air valve. What you might need to do, if the flame trap and AAV hoses aren't the problem, is either adjust the idle screw for a higher idle, or adjust the throttle stop screw so the plate doesn't slam shut, then compensate for the higher idle by tightening the idle screw, allowing the engine to drop back down to 850 rpm or so when in P or N.
 
Is it running rich? My o2 sensor is bad so my kjet defaulted to running rich as all hell, it's a manual so I'm not stalling when driving but it does struggle to idle and wont start on colder mornings unless I either close the idle screw completely or crank while mashing the gas pedal, my aux air valve is bad aswell. I don't know if there's a way to check if the o2 is bad but they need to be replaced more often than the later 3 wire sensors, you can also check your aux air valve easily. With the engine off disconnect the hose from the top and shine a light into it, you should see a little flap resting in an open position, once the car is started and gets up to temp (~5 min) you should be able to remove that same hose and see that the flap is now closed.
 
Thanks for the suggestions. Besides the change of valve covers, this car is all original 1976. It has no o2 sensor and no iac. The one area I have tried to keep my hands out of is the k jet rats nest... I have replaced Injector holders and seals but nothing else. I definitely have a lot of brittle rubber hoses however. So I’m not counting out a vacuum leak in the fuel system somewhere. Unfortunately it is getting close to the time of year where I should be putting this car away for winter, so I might just stop stressing about this issue for a few months. Maybe by then I’ll be ready to make the right decision and just go to lh2.2 or 2.4.
 
I started the car up just now after having it sit for a few days. It started right up, was idling smooth. I shifted into drive it was running great, I decided to take it into work after my lunch break. I get to the first traffic light, its still running great. I go down a longer street, get to the next traffic light, and it starts to stall out again like before. I kept it running at every light by keeping one foot on the break and giving it gas. Now at the parking lot at work I can't even keep it running in park. So this makes me think now that the issue happens once the engine gets warm. I dont see any visible broken vacuum lines, everything seems to be plugged in, and my flame trap is nice and clean.....
 
A few things work off engine temp - on yours mainly the aux air valve and the control pressure (sometimes called Warmup) regulator. Also cracked (air) hoses can often be worse once engine is operating temp.
 
I would try and get some kind of a/f meter in there to figure out why exactly it’s stalling, too much air or too much fuel. Figuring that out would definitely narrow down your problem and you can take it from there. Easiest way to find a vacuum leak would be hooking up a fog/smoke machine to the intake and look for any smoke pouring out where it shouldnt be, no messing with hoses unless you find a leak
 
D9B08j3l.jpg



I decided to pull the intake. The gasket broke apart like porcelain and a few of the nuts were not even finger tight. The two rubber hoses from the air valve mounted to the side of the valve cover were cracked and need replacing. This will give me a chance to get all ocd and clean up this side of the motor. The car is parked in its winter resting spot, so if I don’t get it moving again soon enough I’ll wrap it up and she’ll just have to sit for a few months.
 
Willing to put money on your intake manifold gasket if nuts were barely finger tight. As engine heats up maybe it expands allowing air to pass through aswell as vibrations slowly backing those nuts off. Give that air meter a good clean while you’re in there
 
vACSbiBl.jpg


What is this sensor in the idle bypass unit attached to the throttle body? It had a ground wire that was grounded onto one of the Allen bolts holding the unit to the throttle body. No positive wire was attached.

There is also a sensor towards the back side of intake side of the engine right near the last intake runner. It looks like I have to remove it to replace the intake gasket. Is this the thermal time switch?
 
That's an A/C idle up solenoid. It raises the idle when the compressor comes on.

Yeah, that's the thermal time switch but you don't need to remove it. Just cut the gasket since the sensor doesn't need it to seal. The same gasket is used on Penta engines that have a heated intake manifold with water running through it.
 
D9B08j3l.jpg



I decided to pull the intake. The gasket broke apart like porcelain and a few of the nuts were not even finger tight. The two rubber hoses from the air valve mounted to the side of the valve cover were cracked and need replacing. This will give me a chance to get all ocd and clean up this side of the motor. The car is parked in its winter resting spot, so if I don?t get it moving again soon enough I?ll wrap it up and she?ll just have to sit for a few months.

Is the car 'Safety" (Pumpkin) Orange?

Bay looks clean overall. What's with the blue hose for the booster & heater hose though?
 
Is the car 'Safety" (Pumpkin) Orange?

Bay looks clean overall. What's with the blue hose for the booster & heater hose though?


Yes the car was orange originally, then blue, and now it?s blorange? Blurange? The blue hoses are silicone hoses I bought from Amazon. Super flexy and easy to work with. I might be going a little over board with the blue however?
 
Is this Mikes old car? i think i have seen it a few times. It's a great car.


It is mikes old car. I’ve done a bunch of stuff to it, but the paint will live on. It is a great car. I’ll start a project thread soon so I can show off my progress and maybe keep all the questions I have organized in one place….

EyPSFfvl.jpg
 
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