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1990 300e, 1989 300te
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17 Posts
Discussion Starter #1
I have an 1990 300e with a 3.0 I recently installed new iac hoses and now the car runs awful. i removed the fuel distributor and plunger housing and cleaned it up still no change. so i had it smoke tested and the only place that they found smoke was the plunger plate and from under it which looks like a vacuum line would run. but nothing is there. just a rubber nub. Does anyone know where this line would go? i have a 89 300te but the line runs to the head into a little valve that the 90 doesnt have. any ideas would be greatly appreciated.
 

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1987 300E, 1955 Plymouth Belvedere, 2005 Silverado 4x4
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963 Posts
Today I pulled a fuel distributor from an 89 300TE to isolate a running issue with my 87. I intended to grab a vacuum thermovalve as well but discovered that the 89 did not use the thermovalve, there was a plug in it's place.(pipe plug not electrical plug). On my 87, one of the vacuum lines from thermovalve runs to the throttle housing. apparently a running change occured in 89, eliminating the thermovalve, and I assume they capped off the vacuum nipple on the throttle housing with the rubber cap you described. I'm thinking in your case, nothing goes to that nipple.
 

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1990 300e, 1989 300te
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17 Posts
Discussion Starter #3
i think that could be it. they showed me the smoke coming from there i suppose i can just cap it off with a bolt and rtv and see if any changes happen.

any other ideas for the junk idle?
 

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1987 300E, 1955 Plymouth Belvedere, 2005 Silverado 4x4
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963 Posts
When changing the idle hoses, did you disturb or disconnect the plug to the Idle Potentiometer that sits right behind the ICV?
 

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1990 300e, 1989 300te
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17 Posts
Discussion Starter #6
I did disconnect the connecto when i was removing assembly? Could i have screwed the pooch in doing so? I also checked my duty cycle and its running 80% for pin 3 so im guessing that it has to be replaced as well.
 

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1987 300E, 1955 Plymouth Belvedere, 2005 Silverado 4x4
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963 Posts
Just make sure the connection is tight and no wires broke loose from the connector. the Idle Potentiometer is NLA from Bosch and it's tricky to get back to spec if you remove it from the Air Meter. Even if you removed it all you could do would be to observe the resistance surface for wear, but no repair is possible. That Lamda reading is pretty high, it should be fluctuating around 45% to 50% with engine at operating temp. If unfamiliar with how to adjust, check the stickies for Air Fuel Mixture Adjustment.
 

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1990 300e, 1989 300te
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17 Posts
Discussion Starter #8
I can get one used from my other car that was wrecked. The connector cracked and one pin is a little loose. When it does run it runs fine than drops to 300 rpm. Ive tried to adjust it with the screw but the cycle would only increase never decrease.
 

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1987 300E, 1955 Plymouth Belvedere, 2005 Silverado 4x4
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963 Posts
If you have a wrecked car with a compatable fuel distributor/air meter assembly, you might want to try to transfer the whole assembly to the driver and see how it shakes out. also that connector can be disassembled so if the one on the wrecked car is good, move it to the driver too.
 

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1990 300e, 1989 300te
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17 Posts
Discussion Starter #10
Thats the direction i was going. The wrecked os an 87 but i seen no major dofferences between the 2. So ill give it a run tonight and see what happens. Disassembled as in cut and spliced?
 

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1987 300E, 1955 Plymouth Belvedere, 2005 Silverado 4x4
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It would be good to clean the unit but you don't want to get any grit inside the fuel dist. if it's still on the wrecked car, spray it down with carb cleaner before you remove it. otherwise wait until you have it on the driver then spray it down. Tthe idle potentiometer connector is apparently a two piece affair that can be disassembled and the wire and terminals slid out My car is in the shop right now so I cant take a look, but check out the one on the wrecked car, it may be obvious how it goes together. I have seen new replacements for about $15.
 

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1987 300E, 1955 Plymouth Belvedere, 2005 Silverado 4x4
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963 Posts
BTW I'm working the same idle/ stalling problem as you, but in reverse. you're using an 87 FD on an 89, I'm using an 89 FD on an 87.
 

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1990 300e, 1989 300te
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17 Posts
Discussion Starter #14
its funny hoe that works out. well i took the fd off my 90 and was getting ready to swap. than i seen a large black vacuum line with a white stripe. i followed it back to what i think is a check valve that than splits to a sensor with a connector than to the intake manifold. I applied vacuum to the black line and it held vacuum. i think this was my mystery line right out side of the butterfly flap. was going to put it all back together but im going to replace my injector seals. there hard so hopefully that solves it.
 

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1990 300e, 1989 300te
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Discussion Starter #15
So i made the change over and nothing changed. line in different fd and is misfiring again. mis fire goes away after 2k rpm. i checked my duty cycle and its still at 80 to 90%. I recently did valve stem seals and read that the o2 may be fouled. is obviously running super rich put i have no idea why. i was thinking of going to the eha but im not sure if it fits the symptoms. any ideas? and i pulled the plugs and there all giving good spark. im at a loss. i love this car and dont want to give up just yet.
 
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