wierd CIS stuff, please help I' desperarte!

[Bart911Man]

Hey guy's ,

Here's the story.

I bought my '80SC Targa in March and it ran perfect.
I parked it for a few weeks to do some mayor interior works, took out all karpetting, sonor isolation, changed safety belts, didn't remove any wiring except for installing 3th brakelight. In the meantime I arch soldered a whole at the drivers side.

After reassembling engine would start first time but after e few seconds starts to run very badly, backfires, idle drops to 500rpm or lower until it dies. Starting back is OK but again after a few second same stuff. I changed idle setting for the engine to stay on. after a few minutes engine seems to run better but stil very slow in acceleration, backfiring less but stil there, feels like sonetimes a cilinder is not in the running.

What is already done:
-new ignition: coil, distrib cap, rotor, wires, plugs,... no change
-injection: checked injectors, all spray nice patterns
- checked vacuum tubes, look fine except this: between the decel valve ande the trottle hous there is a Y peace with a tube going nowhere, it just ends next to the fuel filter but isn't connected to anything.

I started looking at the oxy sensor, disconnected it, no change
disconnected the relay next to the controle unit unther the pasanger seet, no change
--- I tested the relay and it works OK, also it gets activated when running engine.

I feare that the controle unit died (during soldering... I disconnected + but left - connected) [ok that was stupid...]

Over here in Europe these controle units are very rara since they are not mounted on EU cars (this is a US import).
Is it possible to run the car without controle unit? is there retuning to do?
Is there something else I missed?

Please help, weather is nicening and I realy need a ride...

Bart:[img]

[sammyg2]

We will need to know some fuel pressures to offer much help. Do you have a system pressure gauge set up?

[Bart911Man]

Good remark indeed, i forgot to mention that the first thing i did was change the fuel pump.
I fugured pressure would be o.k. then, is the fuel pressure gauge still necessary? how does it apply?

I worked and tested some other stuff today;
- I blocked the open vacuum line and there is some very small improvement, i still think it needs to go somewhere.
- While idling took out the relay AND the controle unit from unther the passanger seat, nothing changed, (this realy bugs me)
- While running took out one by one the spark plug connectors, almost no difference (!!!!) to be noticed only ofter disconnecting two or more I got worse engine conditions.
Checked the sparks, had old WR5DC in, my mechanic gave me W3CC (about 1mm to 2mm shorter) that i put in a wheek ago (the plugs, not the mechqnic... )
- using the "water spray" technique at the exhaust (spraying water and looking how fast it evaporates) it seems like cylinders 1 and 4 heat slower than the rest... could be normal with the air flow starting there...
- Today my rpm meter gave up, on high rpm it works, unther 3000 its very slow and not representative.
(when engine is warm it runs but the sound of it is like it runs on 4 or 5 cylinders...)

I must be missing a very litle bug that's in my blind spot, please help me see the light, I'll send u some premium belgian beers, can be german to if u want to


Bart.

[Bart911Man]

Here's the vacuum line that i need to connect somewhere, someone has any clue what the undocumented item is it connects to?

[Bill Douglas]

Hi Bart. Try blocking the loose vacume hose to keep up the vacume level for the rest of the devices and see if this helps. Bill.

[Bart911Man]

Yeah, did that, a litle better but no porsche power yet.

[Bill Douglas]

Sorry, no more ideas.

There is a very good book on CIS which Pelican sells.

Some guys on this BBS really know their CIS and will be able to help but I guess they are at home right now instead of being at work and killing time by playing on this BBS.

I guess I'm one of the first people in the world to have to go to work on a Monday morning

[Bart911Man]

Damn, its monday morning for me to now.
While our US friends are kicking some serious butt in the world foot(soccer)ball games. Hopefully I'll get some nice input frome you guys.

[Bart911Man]

Coucou?

[Bill Douglas]

Bump

[Talonz82]

I have had a similiar problem and this is how I came through, I started at the fuel pump and checked my pressures, once verified I moved to check each and every injector for flow, then re-checked cap, rotor, each plug wire and regapped plugs, re-checked timing and each and every vacumne line, hose fiting etc., checked ECU and o2 sensor for proper function, pulled out the gunsen gas tester and set mixture.

I could hear my frequency valve and since I heard it make noise I assumned it was good, till i got a good shock from it.

replaced my frequency valve, found a air leak in the hose return to the oil tank and decided to recheck the setting on my valves, I did fine some of them out of adjustment, (which will make the car backfire, if valves to tight).

The car is cured, it runs excellent and all that indepth checking has left me with a greater knowledge of the systems/sub-systems and how they function and interact....

anything else I can do let me know...

Peter

[Superman]

The easiest system to verify is ignition. Make sure each spark plug is making a snappy, blue spark. Make sure those sparks are happening at the right time. While you have your timing light out, checking timing and also making sure the spark is advancing properly, hook it up to each spark plug wire, just to make sure they are all firing. Unless your distributor cap and rotor are new, replace them. Once you have verified that the ignition system is behaving properly, then you can be sure the problem is a fuel problem.

That's my guess anyway. If you have one of the systems that uses a computer under the passenger seat, I believe your car would run poorly with it disconnected. JW has gone over this several times recently. Try this: There is a relay, size and shape of an ice cube, under the seat next to the computer. Disconnecting this should make your car run VERY POORLY. If disconnecting it does not have this effect, then this is your problem. You might begin by just replacing that relay.

[fred cook]

How about distributor advance? Have you checked to see if you are getting a: correct, b: some, c: any distributor advance while the engine is running? Also, remove the dist. cap, rotor and shield and check the advance weights and springs. While sitting, the distributor could have decided to (finish) rusting up.

Good Luck!

Fred Cook
80 911SC Coupe

[Bart911Man]

Thanks guys,
Looks like i still need to check quit some stuff.
The bad thing is I inplugged the relay unther the passanger seet, nothing happend, disconnected the unit, no change...
and in fact the engine runs VERY poor.
I'll start with this path, 'll let you know the result.
How could I run the engine without the controle unit? Over here in Europe they're very hard to find (checked relay out of the car and contacts seem to be ok...) and i could get trough technical with the co not so good...

Thanks so far!

[Superman]

REPLACE THAT RELAY. It's cheap and it very well may be your problem.

[Mifintifin]

Bart911Man

1. Sounds like it could be one of two things. The welding screwed up your ignition module and that's causing the problem. If it is this, when you rev the engine up the problem won't go away, it will probably get worse. If it does go away or improves when you rev it up, go to 2, it’s probably not the ignition.

2. Your frequency valve has quit. Most likely not the valve that failed but something in the Lambda driver circuit got zapped due to the welding. The CIS mixture was tuned with the valve running. Now that it isn’t, the mixture has changed for the bad. This has much more impact at idle than at higher RPM's. A quick test to see if it is mixture is to first get it running by opening the idle speed screw some. Next, with the air cleaner off gently lift the CIS metering plate up and see if the idle improves. If it does, great, you know it is set to lean. If not, gently pull down on the lever to the plate and see if it improves. If it does, you know you are running to rich. I suspect you are to lean because the Freq. isn’t running.

If it is problem one, you will have to replace the ignition box. If it is problem 2, you will have to do some more diagnostic work to find what has failed. Check the wires, in particular, grounds first. As Superman suggested, replace the inexpensive relay. Then move on to the O2 auxiliary box and then the DME.

In the meantime, you can retune the mixture to run without the frequency valve. You do this with a 3mm Allen wrench in the little hole between the rubber air boot and the fuel distributor. I won't go into the procedure here. You can either use a CO meter, or since it will be badly off, just use your ear to tune it back into range first. You will have to turn the mixture screw a little (extremely sensitive so a little is like 1/8 turn) clockwise for richer, counter clockwise for leaner. What direction to start depends on what you found in 2. Once you get it idling smoother at the higher rpm, slow the idle down some and repeat the procedure until you get down to 800 or 900 RPM. Finally, tweak the idle screw to bring it back up to 950, or so. When you are finished, make sure you make the final adjustment clockwise and don't forget to take the Allen wrench out of the hole and put the plug back in it. There was a plug, right, because every Porsche mechanic always puts it back in (hah!).

Good Luck,

Mifintifin

82 SC Coupe
83 SC Cab

[Bart911Man]

Hi Mifintifin,

Seems you're right on in point 2.
Pushing the metering late indeed makes my engine run lika a baby, vrooooom, i cinda missed the sound... snifff.
I musta killed something during welding. Ill go to the shop this evening for some parts and fiddle around until its tuned up. I'll send some reply then.

Thanks a bundle!
Bart

[Mifintifin]

Your welcome,

Check your fuses and wiring. Maybe you shorted or melted a wire when you were welding.

Mifintifin

82 SC Coupe
83 SC Cab

[Bart911Man]

Thanks for the tip.

Does anyone know about wiring in the 'chassis' just below the drivers door. Welding was actually done unther the car above the airco tube.

Bart.

[Bart911Man]

Mifintifin,

Thanks for your most valid input! Retuning mixture and idle gave my engine back its old spirit. (I indeed blew my ctrl unit during welding) My mechanic will fine-tune her next week.
It's 25C, sunny, engine runs like a jet... mama-mia i'll make up for some lost time today!

Ciao!
Bart