I need some CIS help.
 

Sorry this is long but I wanted to include as much detail as possible to my problem. I am not shotgunnig to replace parts.

I admit to being a CIS newbie. I have managed to stay away from it by having two cars of my own with webers. I did a search and could not find the information I was looking for.

The car is a 73T with a 76 2.7 running with a 75 CIS system. Most of the manuals cover the really early (73.5) or the late (78+) CIS systems. The early system is vastly different and the late systems have more stuff that the 75 CIS does not have. For example there is no AAR on this motor. I can only find a Cold start, Air device, WUR, Throttle body, air plate, fuel dist and some injectors.

Background:

The engine in question was swapped in last Jan and has been sitting not driving. The 2.7 long block was swapped in after the other 2.7 had problems at the track. Now, Its time to get this car on the road. The car is at my house for two weeks while the owner is away on business. I WILL have it running when he gets back even if it means I have to learn the CIS system. :D All joking aside, here is what we did during the engine swap.

The injection system was complete cleaned and revamped. Airbox cleaned and inspected to find no cracks. Pop-off installed and working correctly. New air boot, runner sleeves, injector sleeves and o-rings, and new injectors. The injectors were replaced after 4 were found to not emit fuel. The fuel dist and air plate were disassembled and cleaned. The fuel dist was not taken apart. It was cleaned by blowing solvent through until clean (eww that was nasty). The plunger is now very free. The air plate is properly centered and height adjusted per factory manual. Fuel pressures are right in the middle of the specified range for cold, warm and bleed down.

previous symptoms: Car stumbles and will not take throttle. Lots of popping through intake. Sounds very lean. Will not idle and barely drives.

Here is an update from my Saturday of turning wrenches. I still have some problems.

I need help!!!

I got the car to my house on Wed night. It did not run well at all. First order of business was repairing the non-functioning alternator. This was easy, two crossed wires would not create an excitation field. At least Df was grounded and it did not short the alt. Simple fix.

Today I pulled the air plate and fuel dist. I have set the metering plate to the factory specified dimension, ie. just below the right side of the taper. Next I pulled the throttle body and cleaned it out. Lots of black crud came from the air bypas passage. I readjusted the plate and it seals tightly. The only air getting through should be via the bypass and idle speed screw. All vacumm lines are new and sealed tightly.

I got the car to run stabe enough to check mixture. It was really lean. Gunsun read 0% CO! Many small adjustments in the CW direction brought this up to the JWW recommended 3.5%. Wow the car runs great there. Great bark with throttle opening and fairly responsive throttle for CIS.

There is one problem. The car idles at 2500 with the idle screw completely closed. HMM this is not good. Maybe its timing.

I pull the dist, clean the sticky plates put it back in and fire it up. While running I retard with the timing light and get to 5 ATDC. Idle slows for a second and then cuts off. I can not restart until I rotate more advance. Maybe timing is not the problem. Must be an air leak behind the throttle body.

A quick search mentiones the AAD having problems and leading to high idle. I figure the best thing is to disconnect it and see. I pull the vacuum line from the AAD and plug with a bolt. I still have high idle. No change. I do the same with the vacuum side and still no change although the engine tries to die like I would think false air would do.

I pull an injector and put the trigger gun from the compressor in the hole. It seals nicely with the o-ring. 80psi and it sounds like there could be an air leak. I can't really tell since the noise is just amplified inside the airbox. I can't feel any air coming through anywhere. Top, bottom, sides, intakes, throttle body. Nothing! I can open the idle screw and get air out. I don't know where the air driving the system is.

I finally pull the entire CIS system. What a PITA! I just hope I can get it back on. I don't notice any cracks, leaks or otherwise in the air box. I finally decide to split the airbox and reseal. I pulled all the screws, separated the halves and find nothing but old sealant. I clean it all up and reseal with black silicone. It should not leak at all now, if it even did before.

Meanwhile, I check the wiring. The clip harness to the cold start injector is completely fried as is the surrounding wires. It appears that a common connection point using a crimp connector is the origin. This is where the power splits for the WUR, cold start and whatever connection goes to the air metering plate. So, before I repair this wiring...

Where does the signal for the cold start come from? How does it act upon the injector? Is it a solenoid valve to start some fuel spray? Where does the on/off signal come from?

What does the connection to the air metering plate do? Maybe this is the switch to show when the car is starting to squirt fuel through the cold start injector. If so, does power come from the yellow wire going to the starter?

How important is the power connections to the WUR? What exactly does 12V do to the WUR?

I notice a switch on the throttle body that is actuated using the linkage. There are no wires going to this switch. Is it needed? What does it do?

Any ideas where to look for an air leak? I swear this system is tight! I checked it with a propane torch. No change. The oxygen line from my torch. No change. The only change I could get was using the acetylene side of my torch when placed under the air metering plate. I guess this means its just sucking it into the intake. I checked all the injector inlets, the intake gaskets, the 6 runner to airbox gaskets the throttle body, all vacuum lines, the underside of the intake above the fan. No leaks. I don't know where that air is coming from.

Thanks for educating me on the details of CIS. Now let the lecture begin.
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Hi, for high idle, make sure that the throttle linkage is not hanging up. Put your foot under the gas pedal and pull up. Make sure your hand throttle is working properly (if you have one) Not sure exactly what CIS version you have as I am surprised that you have an AAV, but the deceleration valve (bell shaped thing on the left side) allows air to bypass the throttle too. It's supposed to keep the car from stalling when you let off on the gas immediately).

Regarding the switch on the sensor plate, I believe this is intended to kill power to the fuel pump when the sensor plate is parked. Safety item.

Regarding power to the WUR, the WUR may not heat up enough to stop enriching the mixture after warmup. A bad connection here will likely cause your car to idle well after heat soaking, but poorly after driving a little.

The cold start valve is controlled by a thermal timeswitch mounted in the left cam cover.

Can't remember what the switch on the throttle body does.

Doug

first of all, does your cis setup use an aav or the hand throttle? the hand throttle was earlier and allows you to adjust warmup idle by literally connecting to the actual throttle cable in the floorboard via a plastic armature..pull up on the hand throttle and it effectively 'presses down' on the gas pedal. the aav controls initial idle via vacuum instead of this direct mechanical method (personally i prefer the hand throttle, as it allows you to set the idle speed you desire).

'basic idle' also has to be set at precisely 180 degrees (operating temp) on a cis car. this means if set properly, artempting to start a car with hand throttle installed, but all the way closed, will result in a car which barely idles. a properly set hand throttle will result in an idle speed of ~ 3000 rpms at operating temp. the hand throttle should be full up for cold start or even lukewarm starts per the manual, but is unnecessary for hot starts. i would suggest setting timing first of all and also points gap (are they new? dirty?). once this is done, let the car warm up and try setting basic idle again at operating temp. i'll let you reply to this info and see if i understand what you've reported before saying more. good luck!
ryan

Thanks for the help so far.

Doug, the car has an Aux Air device as described by the factory manual. This is the bell shaped thing on the back left of the throttle. It has 3 vacuum connections. It looks like something that would bleed air through at closed throttle. How can I test it? It is adjustable via a screw on the top but this does not seem to do anything.

This was a 2.7 transplant so the fuel pump is not wired in with the CIS.

Does the warmup regulator enrichen mixture by changing fuel pressure to the distributor? Is this why cold and warm pressures are measured?

Yes, this is an early CIS and has a hand throttle. It was previously disconnected but now functioning properly.

The high idle is with the linkage disconnected. The hand throttle will be adjusted after I get the car to idle.

The CO was set with the engine warm but at high idle since I can't get it to idle at a reasonable speed. It heated up very quickly as lean as it was running.

What is the timing spec? I do not have the timing sticker on the fan strap. Can I just set 32 BTDC at 6K like my other cars? This is how I currently have it set. This leaves timing idle about 10-12 BTDC on a 2.7 dist. It has an optical trigger so no points gap or dwell to worry about.

let's see..on my car a '74 i think i recall that i have static timing set at 5 btdc with idle ~1000 rpm. dynamic is set at 6,000 rpm with vacuum retard unplugged and i think i recall it to be 35 degrees..your '75 may vary. also, did you check your oil filler cap? if these seal is rotten your engine will run lean. i guess you've tried the 'carb cleaner' method for checking for vacuum leaks (idle should increase if found)..or is that what you used the torch for? not familiar with using that method. anyway, you should have EITHER an aar (sometimes called aav) or a hand throttle, but not BOTH at work..they are supposed to do the same thing, control warm-up idle.
ryan

Jpnovak,

I am no CIS expert, but this may help:

http://members.rennlist.com/jimwms/CIS/CIShome.html

The bell shaped thing in the back is a decel valve, and the car should run fine with the vacuum hose plugged. The 1975 did not have an aux air regulator or AAV. The warm up regulator uses a bi-metal strip to "warm up" rather than using engine heat, and yes it does regulate the pressure to the fuel distributor.

It sounds like you still have a vacuum leak. Plug the decel valve, check any vacuum that might be going to the warm up regulator, the decel valve, and the vacuum advance on the distributor. Once the engine is warmed up, it should run without any of these devices, so you can plug each line and maybe see which one is causing a problem.

Rex

The device on the left that you described is the deceleration valve. It opens when the vacuum is high enough (adjustable). When it is open, there is a path through it around the throttle plate, and will cause your idle to be high. Two of the lines to it provide this path. The third is the vacuum line that controls it (possibly tee-ed off of one of the others). I'm sure there is a way to test it. Once the car is running, the adjustment should affect how the car drops to idle when you rev the engine. Too much one way and the car stalls. Too much the other way and the idle is too high. If it's operating, and the idle is too high, then you can make the idle fall to normal by loading the engine slightly (brake on, feather the clutch). If it's totally shot, I'm not sure what it will do. Fixed high idle may result.

Yep the WUR reduces the control pressure by allowing fuel to escape back to the tank. When the car is cold, it's open. It closes as the car warms up. Lower control pressure allows the sensor plate to deflect more, which causes a richer mixture.

Doug

I think this system is the same as your 74. I guess the air device is the same as the decel valve. It has a hand throttle, no AAR as you describe.

I set my timing at 32. In the TX heat I like the safety margin for detonation.

I used my acetylene torch for the "carb cleaner" method of finding leaks.
When the engine is running, you can wave an open, unlit torch head in many areas. This will also fit inside many tight spots. If you have open gas line this will richen the mixture. If you have an open oxygen line this will lean the mixture. I detected no changes ANYWHERE except when positioned underneath the air plate.

Rex, Thanks for the link. I have read through that many times. I think I have a air leak too. I plugged the Decel valve and no change. I just can't find it anywhere. None of the methods I know of have made it appear. Maybe I need to lean out the engine again and try to get an increase in idle speed.

Thanks Doug. I guess I was typing.

Do you know which direction for adjustment of the decel valve does what? The valve was screwed all the way in. I opened it a few turns but this did nothing. Maybe I didn't go far enough. I tried to blow air through and also suck on it to see if there is a vacuum. I could not pull anything through. It seems to be sealed tight.

Nope, I can't remember. In any case, if plugging off all of the lines doesn't change anything, the problem is elsewhere. I suppose it doesn't hurt (and elimnates a variable) to leave it out while troubleshooting.

Does the idle screw affect things at all?

Doug

OK, so we're guessing you 're getting too much air at idle which is causing the high idle condition.

I'm not sure what you mean exactly by an AAD (pics would help). There is an AAR (Auxiliary Air Regulator) which provides extra air when cold. If this was stuck open, or wasn't getting current to its bimetal, it would still let air in even when the engine's warm, thus causing a high idle like you desribe.

Can you post pics?

ianc

Doug, The idle screw does increase idle slightly. However, when the idle screw is bottomed out, the idle is still about 2500. Yes there must be a large air leak that I can not find.

ianc, the AAD is the bell shaped device attached to the front left of the throttle body. This is the same as the decel valve as described above.

jamie,
when you start the car does it immediately jump up to 2500 rpm's? i'm wondering if your hand throttle is way out of adjustment. it could cause this, especially if your idle never drops below 2500..like your gas pedal is always pressed down a little, which as you know is all that's accomplished by the hand throttle..it manages to pull the throttle cable mechanically so you don't have to 'hold gas' with your foot to warmup. maybe a longshot, but this is adjustable..if you do see idle speeds ever that are normal that would seem to rule this theory out..just wondering if someone misadjusted it and your throttle is always a little open..
ryan

The hand throttle is adjusted properly. The car will immediately go to high idle even with the throttle linkage rod disconnected. I have checked the throttle valve in the body and it closes tightly.

Just wanted to post an update. I finally found the air leak. It took a complete removal of the CIS system. I now know that there are TWO o-rings on the cold start valve. one larger one that seals the mount to the airbox and one small one that seals the cold start to the mount. The smaller one was split and leaking air.

It took a while but I have it all back together. First turn of the key and it fired up with about a 1400 rpm idle. I suspect this will go down once the thermoswitch kicks in. It was too late by the time I finished to do much tuning. That comes tomorrow when I will warm it up good and set the CO again. The car sounds so much better now.

Thanks for all the help.

Have to weigh in here: Jamie's working on my car, which has been frustrating me for a half year. I officially nominate Jamie for sainthood, you guys wouldn't believe how much work he's done to get my car running. I was close to getting out of the game, now I'm going to be a Porsche owner again!! At least all the parts I've swapped / cleaned / replaced mean the system should be pretty healthy (please!)