Need help!

[kev091789]

Are there any pelican members in the pensacola area that are fairly familiar with the cis 911's. Any help would be greatly appreciated.

[tirwin]

I'll come to Pensacola! Sorry, I know it was not the answer you were looking for. What's your issue?

[kev091789]

Well I believe I've fixed all the Vaccum leaks, changed plugs, new fuel filter, replaced the voltage regulator because it was having a charging issue and also replaced the battery. If I'm driving and let of the gas and put it in neutral it will shut off. It is just about impossible for it to find its idle.

[boyt911sc]

Kev,

Do you have a CIS pressure gauge kit? If you don't have one, get one. Without a pressure gauge kit, diagnosing your problem/s would be very difficult. Start with the fuel pressures (control, system, and residual). Test the WUR and FD using the pressure gauge. Then check your vacuum system by locating any unmetered air. Do not tinker the mixture setting before you could confirm the absence of unmetered air. Do the test one step at a time.

If you have any question just ask. There are many capable members in this forum to give you a hand. Keep us posted.

Tony

[kev091789]

I'll be receiving my cis tester soon. Also forgot to mention that the lambda has been removed along with the oxygen sensor obviously. And the decel valve is capped off and the valve right above it is open.

[tirwin]

What year is your car? US or RoW model? When you say the lambda has been removed do you mean the ECU under the passenger seat has been removed?

[kev091789]

Sorry, it's a 1980 US spec and yes the ecu has been removed from u.der the passenger seat. The oxygen sensors wires were cut and there is no cat. (All done by the PO)

[tirwin]

No oxygen sensor connected the duty cycle of the frequency valve defaults to 50% if I remember correctly. But that is controlled by the ECU and you have no ECU. So I'm wondering what the frequency valve does in that case? Just stays completely open? That would be providing extra fuel all the time.

The 15ºC temperature switch connects to the ECU. No 15ºC switch input, no extra enrichment provided on cold start.

The throttle position switch connects to the ECU. You don't get idle and full throttle contact behavior. Idle contact position delays O2 sensor feedback to prevent erratic idle. Full throttle contact position means the ECU switches to open-loop, fixed duty cycle. This is what the Bentley says.

Without an ECU, my guess is you're going to struggle a little bit to find a happy place that you don't go lean under load and yet have decent cold starts. Likely only get one or the other. Not much different from carb conversion with no choke in a way I guess. I would be more worried that you're not too lean. If you want to leave as-is, a wideband O2 sensor with data logging would not be a bad investment -- good insurance policy. Or get an ECU and O2 sensor and connect back as the guys in Stuttgart intended. Did PO do this because someone thought it was a good performance idea or because he couldn't get the CIS working properly and this was masking other issues? Who knows?

Curious as to what others think about this.

[gazzerr]

I'm surprised it runs at all without the ECU connected. I wonder what else is missing. You'll have to R&R the whole thing to be sure I'd say. Is all the electrical still there?

[HarryD]

If I am not mistaken, in 1980, the car has Bosch K-Jetronic CIS with a Lambda controller to control emissions. The box under the seat is not an ECU but the Lambda Controller. I would think the CIS System should run without the Lambda module.

It was in 1984, when Porsche went to true Electronic fuel injection via the Bosch Motronic injection system.

[HarryD]

You may find these web pages informative:

911 CIS Primer - Introduction

[Bob Kontak]

Originally Posted by tirwin

Curious as to what others think about this.

Hey Tim,

I don't think the 80 has wide open throttle enrichment, but that is the least of the OP's issues.

What Tony says is the first step. Pressure gauges needed in this scenario.

However, I also don't think the car will run for shiet with the frequency valve not being energized, even at default 50% duty cycle. That rabbit needs to be run to confirm it's working.

What a shame.

[kev091789]

I know, tell me about it Bob.

Harry D, your correct it's the lambada controller, I've read about people doing this before but apparently it's tricky to find a happy medium for cold starts and lean wot. Anyone know how much it would be to and how difficult it is to replace the lambada controller and everything involved with it?

[Bob Kontak]

Good you have some comprehension of the issues.

Tony (boyt911sc) has a box, I bet, but is the plug in harness missing?

[tirwin]

Originally Posted by Bob Kontak

Hey Tim,

I don't think the 80 has wide open throttle enrichment, but that is the least of the OP's issues.

What Tony says is the first step. Pressure gauges needed in this scenario.

However, I also don't think the car will run for shiet with the frequency valve not being energized, even at default 50% duty cycle. That rabbit needs to be run to confirm it's working.

What a shame.

Bob,

I looked in the Bentley and there was a diagram for 80 and a separate one for 81-83. It says there is an idle and WOT contact. I am just repeating what I thought I read. But you're head is where mine is. Definitely need to check the fuel pressure gauges. I was wondering out loud if the car would even be able to kinda sorta run right with no ECU. The OP may need to really check out what may else have been done. Might take a little detective work. Not trying to be an alarmist or anything but when someone says a bunch of stuff has been ripped out it makes you wonder a little bit what else may have been done, right?

Maybe the OP should try to take some pics of the engine in a few places so we could see if there is anything else that is glaringly obvious that is different?

[kev091789]

I'll definitely get some pics up tomorrow. Thanks for all the response guys. Very appreciative. The weird thing is it used to idle just fine til I replaced the air flow sensor boot.so I makes me wonder if someone e messed with the mixture to cover up that vacuum leak
I'll double check tomorrow but I didn't see any plug in under the passenger sear

[tirwin]

This is what I was looking at. Apparently I'm looking at it in Australia. (it's upside down on my phone but not my computer)

[Bob Kontak]

Originally Posted by tirwin

I looked in the Bentley and there was a diagram for 80 and a separate one for 81-83. It says there is an idle and WOT contact.

My comments are all from memory.

However, if the frequency valve is energized, assuming it is present, OP will still have 50% duty cycle and can dial it in to run fairly well.

I remember that matrix in your wide band O2 sensor thread that showed what happens and when with CIS with Lambda. May be beneficial down the pike.

Not currently though.

[Bob Kontak]

I am at the shop. I think the 80 has "off idle" and a 30% throttle switch but not WOT. I have the factory manuals at home.

I will check when I get home. They may or may not be more informative.

No argument here at all, Tim. Let me do a little digging.

I clearly see three terminals, though.

[kev091789]

Thanks a lot Bob, I'm on duty tonight (military) so when I get home tomorrow I'll take some pictures of the engine and see if that helps at all, hopefully I'll have my cis pressure gauge kit too.