tomphot

This is driving me crazy, maybe someone has an idea for me.
'85 Euro 911 - M&K muffler SW chip
I tried to get a passing grade on the GA emission.
First attempt - as I bought the car with a Cat straight pipe bypass. I failed by a little -
CO% - .16 - allowed 1.12
NOx - 1380 - allowed 1258

Went home and bolted the Cat Conv that also came with the car - failed even worse.
CO% - .00
NOx - 2610

At the same time, I went to a really good local guy to tune up the car - new spark plugs, Valve Job, oil change.
NGK - BPR8's were taken out and replaced with Bosch WR7DC

Picked the car up and now it won't start when warm.
I changed the DME (dated stamped 8/84) and fuel filter (stamped 9/89) to see if that would do any good - it didn't.

We have since played with the fuel mix with no success.
Last night while playing around with it, we noticed there was no spark when warm.
We are running a fuel pressure test today as well.

Could it be the CHT? Is it coincidence that the CHT went out at the same time as the other work? I can see what appears to be the old style 1 wire CHT sensor under the car.
Could the addition of the Cat Conv be causing this?

Any thoughts would be appreciated before I start replacing things aren't bad.

Houpty GT

I am not familiar with the 3.2 motronic fuel injection but if you can richen the mixture you will increase CO% and HC emissions but reduce your NOx emissions.

tomphot

Doesn't Porsche recommend a CO% up around .16?
Why is that?
When I added the Cat, I ended up with 0

Houpty GT

Any CO% they are going to recommend is probably going to be pre-cat since the cat is going to further react the fuel components. Seems that you running lean enough that you removed any measurable amount of CO%. The problem is that running lean increases exhaust gas temperature and this causes an increase in NOx. How is your O2 sensor? You can get a universal for less than $20 if the 3.2 still uses a single wire like the 3.0 does.

rusnak

The Bentley Service manual for the Carrera has several resistance checks that you can use to troubleshoot the system. I'll check mine when I get home to give you the resistance value for the CHT. I'd chime in further, but I have to admit that CO number has me stumped. Seems it would be the other way around. Maybe that is a bad number. Can you double check your emissions results? Also, you said the Cat came with the car. Is it the Porsche factory one? Do you know how old it is, and can you see light when you look through it with a strong flashlight shining into the opposite end?

tomphot

Thanks for your help - my first test showed the .16 CO% reading without the Cat Conv - the next 2 tests both showed .00 with the Cat - so I guess those are correct as they were done at 2 shops. Could this be related to the warm start problem?

I do have the ohmmeter values for the CHT sensor test - we will be doing that tomorrow - resistance should be 1.4 - 3.6 at 60 - 85 deg F.
If we are in those values, that means that the sensor is OK and is working right?

The Cat was bought in CA in '04 after some failing tests by the PO.
When I put it on, I noticed a hole about 5mm around that went in about 4 inches through the center of the core.
I'm not so worried about passing emissions as I should be able to get a waiver - I'm more worried about getting the car to start when I need it too.
Should I put the bypass back on during this process?

rusnak

ok, then if it is running lean, that might bump up the nox number. I hesitate to give more advice right now until I get my own fuel air ratio problems under control.

rusnak

doing my own search, came across this fyi

http://forums.pelicanparts.com/showthread.php?t=378587

DRACO A5OG

What are you using to monitor/read the Air Fuel Ratio?

Sorry to say but I would have stuck to the NGK's they are better than the BOSCH. The iridiums are amazing. Autozone sells them for cheap.

Check the OHMs on the CHTS but I would update to the double wire CHTS.

tomphot

Tested for the values on the CHT sensor - they all came back within spec.
Also did a fuel pressure test - the values were good during idle and after 20 minutes.
Talked to an "expert" at the local P dealer - he thinks I should check my DME control unit to see if maybe that is heating up and won't re-fire the car. There seems to be a sparking issue that happens after the car gets warm and sits for 5 minutes. It will start right away, but after 5 minutes, I have to wait 30 minutes to let it cool down before it starts again.

rusnak

try this on google:

type[ siteelicanparts.com "warm start" or "hot start" ]
[site:tech.bentleypublishers.com porsche.911 "warm start" or "hot start"]

The search function on most forums is not so good, but you can find tons of stuff through Google.

btw: I didn't type the smiley. I typed ":P"


http://tech.bentleypublishers.com/fo...me=porsche.911

tomphot

Thanks - I love the tip on doing a better search - that's always been a frustration.
Still working on it

rusnak

You can also try Board Reader www.boardreader.com

But I usually find so much on Google, I haven't tried it yet.

A google search would look like this: (type this in the Google search window)

"site:Pelicanparts.com "no start""

or

"site:Pelicanparts.com +911 -SC +start +3.2"

DRACO A5OG

The DME relay will get hot after use. try swaping out the relay. Check to see if it is the older 16AMP the new one should be 30Amp.

I burned out my relay when I did not connect the CHTS all the way in. Don't know if that was the culprit, but after properly torqueing down the CHTS and new Relay. Bingo.

Also if you suspect the DME itself. Steve Wong posted a method of checking solder joints that will typically break and cause poor to no start issues. Very easy to re-flow the joints. http://forums.pelicanparts.com/showthread.php?t=391126