Tripster

Got a head scratcher goin' on here. A 930 engine was recently transplanted into an '84 Carrera. swap is complete and running but has CIS issues.
When warm the engine runs as expected. Cold start is difficult. The engine will crank much longer than it should and will belch a rich puff of smoke when it finally fires. The idle starts off at about 500rpm and chugs to 800rpm. The WUR checks out in spec through all conditions. I replaced the WUR with another just to verify - no change.
What could cause a LOW idle? The AAV is functioning properly. If you block off the AAV during the first few minutes of cold start the engine will die.
Every CIS problem I have ever encountered caused a HIGH idle, never a low one. Also, very important - this engine has minimal CIS - consisting of only the fuel head, WUR, AAV, and cold start valve. CO is an eye watering 8%, when reduced to the spec 3% the engine runs poorly.

Any thoughts appreciated, this car needs to get on the road!

Chet 930

Even though you verified the WUR with another, did you check the fuel pressures for cold and warm pressures? The WUR is only one part of the what the fuel pressure determines to be in check. What about the fuel accumulator? Did you install one with the conversion? The CIS system needs that to maintain system pressure on start up. What did you do for fuel pumps? The turbo's have two pumps that feed the CIS system.

diabolos88

seems like alot of people are very similar CIS issues right now, alot of posts in last week seems like hitting on same problem.

RarlyL8

I have been helping Tripster with his conversion.
- 2 fuel pumps, stock Carrera front and 930 rear. Both functioning.
- Fuel accumulator holds in spec.
- Fuel pressure is in spec throughout the range from system/cold/warm.
- Engine runs well when warm.
- Engine does not want to idle when cold and starts rich.
- CO is pig rich 8% and runs badly when set to 3%.
- Engine pops through exhaust when turned off (warm only).
- Engine idle cannot be set above 800rpm when cold. Warms to 1100rpm.
- AAV is functioning properly, if you close it off the engine will die (when cold).

What is the flow rate for a Carrera pump? Could this be the problem even though the system registers in spec?

LeonardZ

My 79 acts the same way when I start it cold. Two years ago I disconnected the Cold start valve b/c it filled the cylinders with gas twice. Runs ok after warm up though. Might check it, It would also cause the same symptoms you describe IF the car would start at all due to the enormous amount of gas. It still chugs now, only without the smoke and gas fumes each time...or the removal of the plugs and cranking to dry them out!

SGOGT4

Check your spark plugs

Chet 930

If the motor has to run at 8% CO warm, I would track that down first because it sounds like that is whats causing the rich cold start. 3% is very rich already and if wont idle there something is wrong. Is the air sensor plate adjusted correctly? Is the fuel head ok?

Tripster

The car could not run any better when it's warmed up, idles perfect, very smooth with good power and no surges. When we adjusted the CO to 3% @ normal temp, the car sounded like crap, and was harder to crank @ normal temp that it was @ cold start @ 8%.

senna21

While I'm sure there's something else going on here what temp plugs are you running? If you're running too cold a plug you certainly will have cold start problems and then have it run "fine" when warm. Did these plugs come with the engine? Many turbo owners run colder (usually no more than one step colder) plugs to help ward off PreDetonation (knock) under boost. If the plugs are too cold they may not be producing enough spark to properly ignite all of the fuel within the cylinder when cold and causing the high CO reading and also having unburned fuel in the exhaust after you turn off the engine, I.E. popping in the exhaust. Even though it seems fine when warm I suspect you're still not burnig all the fuel in the cylinder. If this has been the case I'd suggest you change the oil after you get this sorted out as running very rich when cold and when warm will wash the cylinder walls with fuel and add gas to the oil diluting it's lubricating properties both of which will accelerate wear in the engine.

Explanation of Plug Heat Range click HERE

Remember heat ranges are not the same between brands!
www.ngk.com

Chet 930

Thats a good point Senna.

Tripster- I understand what your saying. Something is still wrong though on the warm motor conditions. I know it can be frustrating chasing it down believe me. Been there done it. I would still try to figure out the 8% CO. Its just so high. That rich of a mixture can cause wear issues too if all the fuel is not being burned in the cylinders.

WERK-I

What are your timing specs? (with distributor vacuum advance plugged)

SGOGT4

My suggestion of checking the plugs was not so much related to what temp plugs you are using as much as whether or not they are fouled up. Mine were and it made my car hard to start.

Tripster

First let me say I appreciate all this input.
Timing @ normal temp is around 5% ATDC @ 1000 rpm.
Tonight when I get in I am going to try and bypass the Thermal time valve, if no change I will pull the plugs to see whats in it, I will say the plug theory makes hugh sense.
The only thing I failed to add in the earlier post is when I drove the car to work a few days back, it DRANK the fuel. As before with the Carrera high strung 3.2, I would use about $10 dollars of fuel to get to work. When I drove it in this week I used around $25, and trust me when I say I know that sounds crazy. But the car ran great. We are talking 60 miles HWY and 5 CITY miles total.

Chet 930

Lol.....at 8% CO I guess it did!

Tripster

Engine has a new tune up. There is no dought with the responses Im getting here the problem will be found pretty quick.