HELP with diagnosing rough running engine at idle (2.4)

[Sunroof]

I have tihs very peculiart problem that has been tough to diagnose, because of my lack of experience.

I have the 2.4 with CIS (1973.5) with 45K since major rebuild.
The car starts in the morning with my throttle lever just fine, but the tach will go up and down at idle when warmed up and wants to die. On exceleration pulling to 5500 rpm, it runs great through the gears, but then lugs at idle.

I adjusted my mixture to richen it up, have been playing with my idle adjustment, changed out my spark plugs, fuel filter and gave the car an oil change.

This morning I decided to pull the line off the top of the bell shaped decel valve and it semed to be fine. Can that be my problem? Just how does the decel valve work? Can it cause an erratic idle?

Thanks
Bob
73.5T

[Paulporsche]

Bob,
Usually if your idle fluctuates that means your mixture is too rich, so if you have been richening it, most likely you will only be making the symptoms worse.

If you search you will find lots of info on the workings of the CIS.

I am assuming you are putting the hand throttle lever back down as the car warms up.

It's possible by pulling the line off the decel valve you have created a vacuum leak, which is leaning out your mixture back to what it should be, so your fluctuations stop.

[Sunroof]

Paul.
Actually, this whole mess started after I changed out the spark plugs and the fuel filter. I need to take a good look at the vacum lines and wires to make sure I did not loosen anything. What's unusal is tha tit has been intermittent. YEsterday afternoon and intot he evening it ran great, idled steady and I could'nt wait to start it up for a drive to work this morning. Maybe its a cold start issue only! New cold start valve and WUR are less then a year old. New injectors, air box, runners, pop-off valve, fuel lines, accumulator, fuel pump, etc. This kind of stuff can drive you nuts.

Thanks
Bob

[Nitrometano]

Try cleaning the throttle and the CIS sensor plate with carburetor cleaner and a clean towel. Remove the injection boot. Clean the throttle inside and the butterfly. Clean the sensor plate inside (up side)and downside (air box). There is oil residues and dirt that acumulate there and cause intermitent problems. My brother 911 have the same problem. We clean that parts and put a bottle of Sea Foam into the gas tank and the problems disappeared.

Good luck!!

[Sunroof]

Thanks Nitro.
When I adjusted my mixture this afternoon, I had to hold the sensor plate up with one hand while pushing on the allen wrench adjuster with the other. This was after removing the air filter housing. I did get a glob or two of oil on me that could be from the sensor plate and creating the problem you mentioned. I will clean it up this evening.

What is SEA FOAM?

Thanks
Bob

[Nitrometano]

Sea Foam is a product that remove moisturize, clean injectors, remove carbon, etc. I have proved it and it works. I put one can in my parents, sisters, brothers and clients cars. I only use it only in the fuel system and in the piston chambers to remove carbon.
This is the link:
http://www.seafoamsales.com/motorTuneUpTechGas.htm

I like this product.