bavareze

Hi.

I had before a 88 carrera and I just bought a 77 that has a 80 SC motor in it.

the problem is that while it is cold (first 10 minutes after starting) it misfires a lot, especially at partial throttle. no misf at idle and also running ok while revving high with full throttle

this looks to me like some sort of cold start enrichment failure or mixture too lean overall.

I have proper manuals for the 3.2 L-Jetronic but nothing on this K-Jetronic. Does anybody have any idea where to start looking and what to try?

thanks!

Mark Salvetti

Welcome to the world of Bosch CIS fuel injection. If you really want to troubleshoot this yourself, you'll need to get a set of the gauges needed to measure the fuel pressures. Start with this thread:

http://forums.pelicanparts.com/porsc...g-dummies.html

You can download a copy of the Bosch manual here:

http://www.dmcnews.com/Techsection/B...chtech-12d.pdf

Mark

Reiver

Cold start valve is probably dead.....easily replaced.

Assuming this is the US model your AFR is controlled by your adjustment near the fuel head (3mm hex) that sets the CO level and then your enrichment is controlled by your o2 sensor.

Without an analyzer it is a guessing game to set the CO....any indy P shop can do this in a few minutes that it takes to warm up their analyzer.

The US system runs very lean purposely and if it leans out from there can cause issues (too lean exploding airbox)...when I had a 930-16 I fattened up the CO/AFR to keep that from happening...and it ran better too.

I've a 930-10 Euro now and that has a dif system altho the CO is adjusted in the same manner at the fuel head (actually the inner side of the fuel head) that is adjusting the intake plenum/plate.

theiceman

I don't think its the cold start valve. It only helps for a second or so to help it start, after that is out of the picture.
Id say its likely to be AAR or WUR. or base CO adjustment. Need gages before you even start

bavareze

I see people saying I need "gauges". I have fuel pressure gauge, the generic one from harbor freight. Apart from that, what else do I need so I can start? An oxigen level monitoring for exhaust?

Reiver

To set the CO baseline you need an emissions analyzer...or a good AFR gauge. A tailpipe device like the one at the emissions test or a commercial AFR set up that takes time to rig in your vehicle. CO can be converted to AFR numbers btw.

Find a local indy Porsche shop, call them and swing by...it only takes a few minutes to set the CO if their analyzer is warmed up.

Mark Salvetti

If it is the Master kit (big red box with a bunch of hoses and fittings), it can be made to work:

http://forums.pelicanparts.com/porsc...er-review.html

If it is just a pressure gauge, that's not what we're talking about. Read the CIS for Dummies thread. I know it's a long one, but there are few shortcuts with CIS.

Mark

bavareze

a quick visual check revealed that 3 injectors are pretty loose in the intake manifold. I guess I can start by replacing those orings and then worry about other possible problems. would I be able to remove the injector sleeves with the intake runners on the engine or no? just so I know if this is an afternoon or week-long job :-)

Reiver

Try just removing the injectors and replacing that o ring...the sleeves should be fine.

Mark Salvetti

The injector sleeves are staked in-place. If you look closely at the intake runner, you can see where a punch was used on the aluminum in three or four places around the sleeve to hold it in place. Sometimes they still come out when you pull the injectors, but if the injectors are already loose, you shouldn't have a problem.

Note the sleeves have an o-ring as well, and it can get hard and brittle over time.

Mark

bavareze

good news is that 4 injectors came out with the sleeves, so only 2 need a bit of work to be removed. and those are not the ones in the back so it's good!

now I see the car has spark plugs NGK BR9EIX. I've seen a thread on pelican saying it needs BR7EIX. Shall I go ahead and buy a set or BR9EIX are just as good?

cheers!

Reiver

Can't remember what lump you have.
If it is a Euro 930-10 9.8-1 compression you need the cooler 9's....factory rec.

If it a US 930-16 with the lower compression the 7's are called for.

bavareze

I cleaned and replaced the injectors. Results:

- backfiring marginally improved
- better idling rpm holding
- better throttle response

I guess I still need to troubleshoot fuel pressures to get the best out of it

Thanks for the help!