Cis after rebuild or engine tear down

[SteveT]

I have been seeing posts over the last while of CIS problems, or rather out of adjustment after rebuild.
I tore down my engine for head bolts, and other assorted problems as it turns out. And I am wondering if I have to do major adjustment to CIS after I get it all back together- and which ones?. I haven't changed anything(cam, distributor,etc.)........in fact I left the distributor in the same place. I figured I would just bolt the CIS back on and go.
Also, I told my wife to ask our mechanic when she took her car in last week if he could adjust the CIS when I got done(because I don't have the exhaust gas sensor tool - who does?)............she said his eyes got all glassy and voice cracked.....told her it was the hardest injection system there was(of the hardest motor there is) ........and why did I tear the motor down in the first place?

Are Porsches really that hard? Steve

[DRV]

CIS is probably the easiest to work on, if your mechanic is scared of your car find another mechanic. There is an analyzer made for the home mechanic called the "gunsten gas tester", I had one and didn't like it I though it was to hard to work with, other people like it. I found an air fuel exhaust analyzer made by actron that works good, but they no longer sell it. So long as you don't move any adjustments on the injection system it should run the same as when it was removed. If you can get a analyzer and a CIS pressure tester with the good manuals CIS isn't hard to work on.
Dennis Varney

[Superman]

One of the posts discussing post-rebuild CIS problems you've seen recently was mine. After rebuild my engine was running VERY poorly. I had to turn the mixture adjusting screw about a full turn richer in order to get it to run. I know this was not normal and some very respected mechanics have agreed. Then after a day or so, and less than an hour of running, it changed, I leaned the mixture out again, and it ran much better. JW and Tyson think that my Frequency Valve was temporarily not functioning, perhaps because of a relay.

I have been driving CIS cars since 1975. Porsche continued to build their Turbo cars using CIS into the 1990s. CIS is neither unreliable nor mysterious and hard to tune. My problem was odd. I'd say there is a 98% chance your engine will fire up instantly and run perfectly. It would still be a good idea to take it to someone with a gas analyser for final adjustment. It takes a couple of minutes and I could train my 9 year old daugher to do it in that period of time.

Some folks, apparently including your mechanic, have fits trying to troubleshoot CIS systems. The pros can do it in minutes. The rest of us have to follow the troubleshooting steps in the CIS manual, such as Bosch publishes. Either way, there's no mystery, magic or voodoo.

[wckrause]

I agree with the man in the cape. If your CIS worked fine before the rebuild, then the most that you might have to do is a mixture adjustment and maybe an idle speed adjustment. If your mechanic is afraid of a little CIS, then dump him. He probably just likes to hook up his test equipement, and let the computer tell him what to replace. Get the Probst book on FI, it will save you lots of $$$.


If you consider what CIS replaced, then it is a very simple and easy system to trouble shoot and adjust.