dr bob

Got a spare LH brain to try?

andy-gts

if cats are plugged wouldn't they run hotter and cause sluggish performance with a light load…..hmmm, pulling them sound pretty easy for the result may find one of the issues….I like bc's idea here….but I know dr bob is right with his diagnostic pathway...

Rob Edwards

Brendan, spanner's in the mail. I have a spare LH brain here for testing purposes if you need. Holla back.

BC

I don't.

BC

Thank you. You are a saint.

BC

I get that the ignition is a suspect. But I have tested this and can continue to.

What I can do relatively quickly is out a test pipe in.

Really frustrating because it's never the same stuff over again and in my experience. It's always something slightly different.

BC

I have verified tps and temp 2 (temp II) at the ecu plugs. Higher ohms than 250, but it's about three hours since the car ran.

I'll probably wake in the morning and put the h pipe on.

Then I can also run a wide band to see what's up there.

Ken - is there more detailed instructions for the three pin pot plug and the knock thing?

I'm an IT director - I just send checks to the guys that do the actual wiring. But I sure can read a manual and set direction and policy on a project from that.

BC

Ohmed the coil wires.

I would need a well running 928 to check against, but when its cold and for 5 minutes of running after that, its okay. Not wonderful though.

BC

Swapped to an h pipe.
Swapped drivers coil.

This was after a test drive where it can barely idle now. Sounds like a pro stock with a lumpy idle.

Not a 4cyl idle. A bad v8 idle.

No change with coil, a different igniter.

Hot idle bad. Starts cold okay but got worse quicker with no cat.

BC

Next?

BC

How do I check the maf ohms at the ecu pins? Looking for that link.

hacker-pschorr

Did you plug in the wideband? What does it say?

Compression check?

Did you try a different LH / EZK?

Do you have a spare MAF?

BC

I'm. Going to swap to an unrequited maf. It's an unknown quantity but I'll take any evidence right now.

Car has 78k on it and it ran basically fine before I fvcked with it and started replacing parts to "make it better".

I do to have a other lh. And if I did, the car had porkens chips and 24lb injectors.

Rob Edwards

I wonder whether it's chip-related. Do you have the MAF screens and Ken's other recommendations? Colder plugs? 89+ octane?

Recommendations (from liftbars.com):
- Rebuilt MAF
- New knock sensors
- New CPS (crank position sensor)
- New TPS (throttle position switch)
- New hall sensor (cam position)
- Cam timing: 0° (-2|0 cold, PK32V'r)
- New OEM O2 sensor (not universal)
- Bosch WR5DC (7992) spark plugs
Required:
- S4 camshafts
- MAF screens installed
- 24# injectors (special o-ring)

I can still pop an LH and a known good MAF in the mail later today, am gone for a week starting tomorrow. I know it would be rich with the 24's but a good O2 sensor might get it close enough to at least run semi-normally (?)

JET951

The glowing cats bit , reminds me of the 1989 > 928S4/GT/GTS that have old age trouble with their Exhaust Temp Monitoring system ( ETM ) ,that cuts out the ignition on one ignition bank ( kills one coil /module)

So if its a 1988 year type then there is no ETM , but it doesn't mean you do not have an issue with ignition on one coil bank , and yes they do still idle ( very low ) running on 4 cylinders( which makes the cats glow ,because of raw fuel still being injected) & yes they very much feel like they are being pulled back

Quick check for you to do with the engine idling }

Disconnect one of the two mutiplugs from the ignition modules ( next to the engine lid lower catch)for just a few seconds , reconnect then disconnect the other , again just for a few seconds ( this just stops their relevant coils) , if both ignition modules/coils are working then you will see little no difference in disconnection one as compared to disconnecting the other , meaning on a 928S4 that is idling at the correct RPM , all that happens is a drop in RPM , the idle control motor compensates immediately and raises the RPM , mild vibration from the imbalance , but the engine still idles , so in a case where both ignition banks are correct you get same result with disconnecting either module

Now if one module is not working , if you disconnect this one ( multi plug ) you will see do difference at all , because its not working , however if you then disconnect the other one then the engine cuts out , because its the only one working

And yes we see a few ignition modules play up every year( be it 944S2 , 928S4 , 964 etc etc ) as they reach old age & yes only replace with the correct Bosch type , because the non Bosch ones give us the most trouble

Ignition module 928 602 706 01 ) Bosch 0 227 100 124