CIS Runners - Please Help Diagnose This Problem

[Sunroof]

I ran a thread recently on a strange problem I encountered after changing my spark plugs and fuel filter. I have the 2.4 CIS with no thermotime switch. Here is whats happening:

I will start up in the morning or when COLD using my trusty hand throttle. I will experience a slight rough idle and hestitation until suddenly at warm up (over 190), I can lower the hand throttle and the idle will be smooth and exceleration/deceleration okay.
If I start to lower the hand throttle anytime before warm up, the idle will bounce up and down, which is a bit more than normal.

I cleaned my sensor plate, rechecked the plug wires and checked my mixture. I used the correct plugs and gap, did not disturb any vac. or fuel lines when replacing the plugs and fuel filter, but obviously something happened in the course of or after the filter and plug replacement.

My WUR, injectors, cold start valve, wires, coil, fuel pump, accumulator, air box, runners, fuel lines are all new and have breen installed within the last 2-8K.

Here is what I find interesting....The decel valve works perfectly after the warm up, but lets the idle drop to zero with this cold run issue. The rough idle and crappy performance during the cold phase came on rapidly and after the plug and fuel filter change.
The car starts and runs great after turning off after a run (warm up). My guess? Could it be the WUR heater wire? It was close to the fuel filter and that was a tough one to R&R (had to take the fuel accumulator out for that). I have yet to re-check that.

Any thoughts on this one?

Thanks
Bob
1973.5T

[Elombard]

Check the voltage at the WUR plug, I think you have to do it with the engine running (I think this is what you were talking about checking). Mine ran really rich when the WUR got no power until it was really warm.

Actually if cars clold unplug the WUR and see if it runs the same? I wonder if you shorted and blew a fuse or the relay failed? On my bastard there is a realy back left that is for the WUR (round black thing).

OF course check pressures before spending money!

[Paulporsche]

Sunroof,
The best way to tell would be to check your cold control pressure.

EW,
Where is that relay located--engine compartment?

[Elombard]

Yes mine is on the fuse panel thingy on the drivers side engine compartment.

[Elombard]

Not sure if it was part of the original 73.5t set up or if it was added when they put the 3.0 in.

[rcecale]

Ask Westy about your CIS issue. From what I've read, he's a guru on the topic!

Hiya, Brian!!!!

Randy

[Hladun]

My guess;

Changed fuel filter=higher fuel pressure=richer=too rich=surging

Set the CO and check WUR pressure with the proper gages.

[bigchillcar]

bob,
first of all, is your 'basic idle' set correctly for a cis model? i.e. set to ~ 1000 rpms when the engine has reached operating temp (180 degrees)? i'm assuming you know how to use the hand throttle appropriately..fully up for cold start, gradually lowering throttle until operating temp is reached (or nearly so to support the steady basic idle speed). i'm guessing from your post that you have done so..but an incorrectly set 'basic idle' will definitely cause idle hunting symptoms.

you write that you 'checked the mixture'..does this mean you had it checked with a gas analyzer? was this before fuel filter replacement? if basic idle is set properly, i'd be inclined to suspect mixture as well. people on this board seem to have a paranoia concerning the 'mystical wur'..maybe i've just been lucky, but i don't tend to first suspect this item. good luck.
ryan

[Sunroof]

Okay, I did set my idle and I did change out my relay on the engine electrical panel with a spare I carry. I know how to use that hand throttle, believe me. The WUR warm up wire looked okay. I thought I may have placed the fuel accumulator too tight over the wire bundle when I R&R'ed my fuel filter. The accumulator sits over the bundle. Okay on that one.

I think the suggestion that the new fuel filter may have had an impact on mixture is a strong consideration. I have the smaller filter and I try to change it every 3-4K because my tank is original and rusty. Thats my next big project, but for now I never let the fuel level get below 1/2. I did get some minor particulate come thru the filter when I drained it after removal. Kind of opens up a new set of criteria!

I do not have a CO analyer. Its strictly hit and miss. Opinions are thus far leaning toward mixture setting. I will keep trying. Appreciate the feedback as its always a learning curve with CIS.

Bob

[bigchillcar]

bob,
there is a way to approximate mixture at home if you know how to measure duty cycle..do a search on mixture and duty cycle for details..fairly accurate from what i hear..i have NOT tried it myself.
ryan

[Paulporsche]

Also try the push/pull method. Or you can try leaning in small increments until the fluctuations stop.

[Hladun]

In my opinion, unless your an F1 mechanic, setting the CIS richness without a gage is a recipe for disaster. The CIS is very sensitive to richness adjustment. You drive a Porsche; tune it right!

[Paulporsche]

I think that is good advice for anyone. If you don't feel comfortable/safe/confident doing any of the things mentioned on this BBS, go to a pro.