Need help setting CIS - yes I have searched
 

Hi guys I sent this to souk (he is the guru) in a pm, but then I thought it would be best to have it on the forum so it is searchable for other users.

Yes I have searched my issue but still have questions.!

I live in a small city in Canada so competent mechanics are tough to locate, so I don't want to have my mixture set by the ones here.

I am having the comon problem of; after the engine gets warm it stumbles and stalls at stop signs. I have read lots and it brings me back to the mixture settings. My car also idles high 1200 is the lowest I can get it to. This is with the idle screw all the way in!

I have checked for leaks by spraying carb cleaner and do not get any surges.

Today I went out, (air cleaner off) I turned the idle screw out on full turn (that way I will have some adjustment area). I then turned the mixture screw "lean" 1 full rotation before it stumbled. I then turned it "rich" until it stalled. It turned 3.5 full rotations (2.5 rotations from where it used to be). This seemed excessive :eek: . It will not start right now (I assume because I flooded it) I also think I turned the mixture screw too quickly. It didn't CLICK and Ididn't stop, I just continued turning slowly

Anyways when I was turning it rich, the idle really picked up 3-4000 I am guessing.

My questions are;
1- since I am setting this "from scratch" and I am having high idle rpms, where do you suggest I start out with in relation to the idle screw? I would like to have room for adjustment so thats why I turned it out 1 turn.

2- I took the car for a short 2-3 minute drive before trying this today. This would not have brought it up to operating temps, should I really warm the engine up before I set the adjustments?

3- should the air cleaner assy be on, or does it make a difference?

4- how slowly do I turn the mixture screw? Since there are no CLICKS should I turn it 1/4 of a turn and let it sit for a minute/ 30 seconds then turn it agin etc etc?

Thanks I really would like to have this set up nice for the weekend.

Shawn

You probably don't want to hear this, but the only way to properly set the mixture is with an exhaust gas analyzer.

Shawn I sent you a reply to your PM, but lets keep it on this thread.


BUT! AGAIN, FOR YOUR BENEFIT AND OTHERS, THE IDLE MIXTURE SCREW DOES NOT CLINK!


Here's what I wrote in my PM back to you:


The idle mixture screw does not click! This was an error in printing somewhere and folks have been thinking this falsely.


From what I can tell, the car isn’t starting now after you tried to adjust it. From the reading I suspect it is too rich now. So you’ll have to back off the idle mixture screw. Try 1 ccw turn, and try to start. You’ll have to repeat if it doesn’t work. Crank on the engine and open the throttle with your foot if you suspect it’s got too much gas in the cylinder, it’ll clear it out. You just have to keep cranking…but not too long.


As for your original problem, you probably have an internal leak, via the deceleration valve or the AAV. Your AAR may not be closing when hot. Check that first. Make sure you have current to it. Check that it's got the right resistance. You can also remove it and clean it.

Your "common" problem (stumble/stall) is actually rare. Also, you can't adjust CIS fuel mixture without a CO% machine. That said, you can establish a baseline by activating the sensor plate with the engine off/ignition on, and all six injectors connected but in containers. They should squirt fuel just as you begin to lift the sensor plate. You have the possibility of so many problems that there is really no one place to start, you might have air leaks, your sensor plate might be out of adjustment, you might have points/timing incorrectly set, you might have bad plug wires, bad/fouled/incorrectly gapped plugs. I respectfully suggest that before fooling with the car that you buy a good service manual (some say that Bentley is OK, I use a factory book), and possibly even some Bosch repair guides for CIS.

What would the injector flow baseline do for him? The idle mixture and any changes in the idle mixture setting are fractionally small compared to the injector flow rate when spraying into a container.

I agree that the 2.7 issue (and even with the 3.0, but more likely with a 2.7) could be ignition, but from what he described .... he's now stuck in a fuel related problem. Until he can get things back to where he started, he shouldn't go looking for trouble with anything else other than what he did to get to this point.





I'm not coming down on you Shawn, but I get a lot of folks come to me after they've screwed up the system by making adjustments without actually giving thought or understanding the problem. By the time they have had it, the system is so out of whack it's almost impossible to provide remote assistance.

Best you can do now, is to get the car running again, then start troubleshooting. It's not going to be a simple turn of a screw, so you'll have to be patient.

Well, let's see, how about getting his injection back to the point where his car will actually start. This is a basic procedure, following all airbox or fuel distributor replacements or sensor plate height adjustments, done to avoid excessive cranking, or flooding. I'm suggesting that he does this so he knows that his injectors fire at the right time in relation to his sensor plate position, and I'm recommending that he has them in containers to avoid introducing even more fuel into his engine. Our poster has obviously lost his way, this is the most effective path back.

I for one don't know that his original problem was fuel related. The poster stated curious symptoms, with no verbiage regarding if he has assured himself that all ignition settings are correct. I'm not trying to complicate things, but the logical sequence of diagnosis is to do everything else before attempting to perform fuel injection adjustments.

You need to go back and read his post. His car was running UNTIL he started to fool with the idle mixture screw.

You better explain you're injector baseline a bit. I'm too stupid to understand how that will get him the fine adjustment he needs when he hasn't done anything to his airbox or fuel distributor. He's simply turned the idle mixture screw to far to the rich side.

Running, yes. But warm stumbling/stalling and a 1200 rpm idle with the screw all the way in can both indicate ignition problems.

Replacement of an airbox or fuel distributor can replicate an out of adjustment condition created by the poster. The baseline will establish what side of "correct" he's on; the injectors will either; (1) spray when the ignition is switched on (rich), or (2) not spray until the amount of manual sensor plate lift is excessive (lean). He stated that he moved his mixture adjustment both ways, it is not for me to guess if he accurately remembered what he had done, the point here is to get the setting to where he can start the car.

Not necessarily.


If he's really got it in an over rich state to where the injectors would firing into a jar with the ignition on, then he'd surely hear them without removing them. He would have to bypass the airplate switch to have a valid test with the injectors in or out of the runners.

Lifting the plate to spray with the engine off to determine if he's lean is about as good of a test as pouring gasoline into a carburetor to determine if the car needs different jetting!


Here is what he posted. Read it again.

Souk:

So I have this right, in an attempt to help a poster I've been told by you that I "need to go back," and that "I better explain," and that I probably can't read.

You've also in no uncertain terms told me that diagnostic procedures that I used for 30+ years in the trenches are invalid, and you're very quick to assume that the poster knows how to listen for injector hum with the ignition on and the fuel pump running, all the while that the CD is buzzing and the cylinders are filling up with raw fuel.

What I learned as a shop owner and hands-on technician was to always listen carefully to the car's owner, but never read what the car's previous shop/mechanic wrote on a work order, or told the car owner what might be wrong with his car. I did follow the first part, now it's time for me to apply the rest to this thread.

The procedure you describe may be valid for some cases (when the settings are very far from correct), but the poster's case is not that.

My telling you to go back and read, was simply so you'd arrive at a starting point that would be helpful to the poster. That point is that the car was not running right, then he made adjustments to the idle mixture screw afterwhich the car would not fire. So the obviously first step is to get the car to fire and running. And the easiest path to that end would be for him to undo what he did, which he decribed in his post. After the car is back running, then the real troubleshooting can continue.

You didn't "listen carefully to the car's owner" or you would not have listed nearly all the potential problems....as opposed to simply helping the guy get his car back running (rough or otherwise).

As for the injector sound. It is very distinct and loud enough that one would have to be near deaf to not notice the change in audible energy coming from the injectors with the engine off. My assumption that the poster would notice this is probably better than your assumption that buying several CIS books is going to get his car running be the weekend. I've got plenty of CIS book, and not one puts it all together well enough for someone to understand how to troubleshoot CIS without screwing things up first...followed by a long affair of frustration...then nirvana.

And lifting the air meter plate is too crude without the engine running in this case.

The idle mixture screw may be off by 1-3 millimeters given what the poster wrote. It would be nearly impossible for a guy of his CIS familiarity to know whether he moved the plate 1mm or 3mm from the procedure you broadly described. What's the pitch of the idle mixture screw? How's that applied to getting the his car running right? You were not being very specific.

So yes, I'm telling you your procedure is invalid in this case. :) At the very least it's unnecessary.


All right Peter. I've got nothing against you, but I see folks posting in an attempt to help. Sometimes it's too vague to help the guy that needs help, and he'll run off and do all sorts of things to his car before he comes back with bad news and need help in a worst way. I've been there.

What I saw in your posts was nothing specific enough to get this guy going in the right direction. So I was pushing you to get deeper into the poster's problem and get this guy's car running so the original problems can be investigated.

Ok its running.

It was just flooded due to richness. I let it sit while I slept (I work shiftwork) Anyways I turned it down a full turn CCW turned the key and it started.

Idle screw is out about 1/8 turn from full stop. Otherwise is stumbles. Mixture screw is 1.5 turn CW from where it used to sit. It is richer and the idle is still around 1100, if I turn the idle screw in more it starts to stumble.

Souk you are right, my decel valve for sure needs to be checked/cleaned/ replaced after it is idling I gave it the shot of gas as you describe and it shoots up then stays around 2100, until I restart it. That will be my next project. and then more troubleshooting to get to perfeection.

Pete and Souk THANK YOU GUYS VERY much, I wish I had one of you guys closer , I know you disagreed on some of the points but you both have a great deal of knowledge and it is great to see your desire.

Shawn

Shawn: Good deal - check those spark plugs, make sure they're all clean and gapped right (better yet, put a new set in), and then get the car to someone with a CO machine.