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1988 560SEC
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26 Posts
Discussion Starter · #1 ·
I have a 88 560sec. I've had problems with FRP's and high idle. Because of the problem it doesn't get drivin as much as I would like.

I barely made it home the other day. Loss of power then died in the driveway. I replaced the fuel pumps and filter and that fixed that.

But I had trouble getting it started ( a recent problem when cold, probably the cold start injector). I took the FRP out and jumpered 30 and 78 sockets to run the fuel pump constant. After it started with some priming through the throttle body or what ever it is named it ran at idle really well. As soon as I put the FRP back in it ran with a high idle and some hunting.

I've had the high idle for a long time and have been trying to figure out why. I don't have vaccum leaks and ICV is good.

Anyway does the fact that it idled normal with the jumper give any indication of why it idles high with the FRP?

Thanks :D
 

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1988 560SEC
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26 Posts
Discussion Starter · #3 ·
I've tried 3 different relays with no improvement.

OK I just went for a 10 mile drive. The car felt strange, it would keep a steady speed but I could feel a rhythm of uneveness.

I pulled in the driveway put it in park and it would drop the idle to 700rpm then jump to 1500 down to 1000 then work its way down to 700. At 700 it feels rough. Also as the rpm's are dropping down the oil pressure drops and the fuel economy goes into the red. It keeps doing it over and over again. It has new plugs , distibutor cap rotor and wires.

Any ideas.

Thanks again
 

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w126
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1,535 Posts
Rough idle @700rpm with some speed fluctuation. I'd start with checking for vacuum leaks. Spray carb cleaner around the intake, vacuum lines, injectors etc. Also, try to get under the upper manifold where the two pieces join.

After that I'd check the idle control valve. There are a lot of posts regarding idling issues("high idle hell").
 

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1990 560 SEC(gone but not forgoten) 1988 560SL 1998 E320 4matic wagon
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258 Posts
I'm having the same kind of rough idle issues except the idle is steady at 700 in gear acts like a miss but the ignition checks out. I just did the chain and guides. A lot of my rubber vacuum hoses and other parts are hard or brittle.I saw a thread where the guy pulled the intake and found all the rubber hoses under there cracked and split. I wonder this is what causes a lot of these idle issues. You cant even see this stuff.After doing the chain I dont even want to think about ripping the intake off.
 

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1988 560SEC
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26 Posts
Discussion Starter · #6 ·
All of the injector holders, seals, vacuum hoses,rubber connectors and injector hosing have been replaced recently. I'll spray it like you suggest. I probably didn't get something connected properly even though I double checked everything.

Thanks for the advice Aspect, I'll get started on that.
 

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1990 560 SEC(gone but not forgoten) 1988 560SL 1998 E320 4matic wagon
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258 Posts
I heard carb cleaner will eat the rubber bits. Is there something safer like wd40?
 

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Registered
1988 560SEC
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26 Posts
Discussion Starter · #8 ·
Melting rubber parts - that's something to find out about first. Thanks

OK after having trouble getting her started I took the aircleaner off, tapped on the injectors with a mallet and metal rod, then pushed on the air injection connections, shut it off. I noticed the EHA valve was leaking, put new o-rings in started the car and it is idleing fine and seems smoother when I push on the accelerator. So I guess I'll go for a drive and see what happens next.
 
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