dkcaims

Have a 90 c4 that is still being worked on at one of the premier "porsche only" shops in Denver after having a bunch of work done in the past few weeks.
Would like to keep the bill under 5 figures. Yeah pricey, but all the work needed to be done if I want to drive it another 125k miles and keeping this car in peak condition is not cheap.

With the hammer attached, it's indicating that the timing is jumping around from 15 degrees retarded to advanced (don't have an exact figure on how much advanced)
Under acceleration at around 4k rpm the timing starts to jump around.
You can keep it floored and it might take 30 seconds to go from 4 to 5k rpm.
The hammer also is indicating a hall sensor fault (they've replaced that 3 times)
Has new DME relay, fuel filter, distributor belt, hall sensor, plugs.
It is supercharged, if that matters.
They replaced the cat with a test cat they had lying around since the exhaust had a foul smell to it, but still has same problem as of 30 minutes ago.
They are now going to look into the ECU and related wiring since the supercharger black box is piggybacked into it.
Does anyone know if the black box is only there to control the 7th injector in the TPC SC?
The problem was intermittent over the past few months, but for the last week or so has consistently occurred. Should make it easier to track down.

Anyone have any suggestions I can pass along to them.
Mechanic has been working on Porsches since the late 50's, utmost confidence in him.

Thanks for any thoughts.

Makmov

EuroSport?
AutoWerks?
Dart?

It's gotta be Eurosport they are the only Porsche only shop I know of.

I guess the question is: is it a mechanical problem or electrical problem? Do they know?

I would start eliminating am stuff first.

Does it still have lamba? Is that working? whats the specs on fuel mapping? What is it using for an Air/Fuel meter?

If it is stinking exhaust it's either too rich and you are smelling unburnt fuel, if it's another strange smell like buring metal maybe going lean and burning off the tops of the pistons.

That would be one of the first places I would look: at the piggybacked ECU. The wiring probably works or it doesn't so that should be easy to trace down.

dkcaims

At this point they are thinking electrical.
Lambda? As far as I know... They are going to crack open the DME/ECU today.

dkcaims

Oh...and the timing jumping around only seems to occur once the car has warmed up. Hmmmm

Makmov

Yeah lamba = 02 sensor.

Hard to say, especailly with aftermarket stuff. Could have a board that heats up and starts getting a bad or broken connection. The factory stuff has it's problems but generally by and large it is pretty reliable and either works or doesn't.

the other questions is how is it piggy backed, what data lines are connected to both DME and ECU? How is it getting powered? It's own power supply or drawing power from the DME? eek Hope not.

The DME: Motronic 2.1 isn't terribly sophisticated.

Just remember when all else fails just mash it up with a big hammer and get a new one.

And yeah I know Greg and talked to him a few times. He has made it clear that he not that fond of 964s. Which was kind of a turn off for me, but his shop is all full up with cool Porsches.

boxsey911

If you search "4000 rpm" you'll get a lot of threads come up. Often the problem is a broken distributor belt but you say you've already put a new one in. The other thing that often comes up is a problem with the WOT microswitch. So it might be worth checking that out. Here's an example:

https://rennlist.com/forums/964-foru...esitation.html

dkcaims

Yes...I've read nearly every single 964 post on RL.... just thought someone might have something new for me to investigate.

Geoffrey

Don't you know that the engine will run without the hall sensor even plugged in? I think you need to find someone who understands how the ECU and piggyback are put together. If I read your post correct, and you are saying that it IS Supercharged, AND it takes 30 seconds to run from 4-5k, THEN SOMEONE is foolish for continuing to test the car in that manner. BAD, BAD things will happen to the engine when running with retarded ignitoin timing and / or lean fuel mixture which are the most likely items to cause slow acceleration.

The distributor sensor is telling the ECU only which cycle the engine is on, and has nothing to do with the ignition timing or crankshaft position. The 60-2 flywheel and crankshaft sensor are enough to run that engine alone, although without the distributor hall sensor, it might run on the wrong cycle which ONLY means that it will be injecting fuel 360 degrees from where it was designed to.

Other items are the knock sensors, are they Ok? Is the ECU retarding the timing because of knock or noise simulating knock? I'd suspect not since you are seeing values of -15 degrees which is a value the knock sensor cannot retard to.

The TPC black box controls the 7th injector which is for intake temperature cooling as much as it is for extra fueling. It also interfaces to the ECU. I would start with a call to Mike at TPC.

Don't continue to test the car in the same manner. Only the uninformed would hold his/her foot flat on the floor hoping the engine will accelerate past 4k. You WILL damage the engine that way, especially with a supercharged engine which has a very low tolerance for parameters that are out of spec.

How do I know? Because I know all of the tables in the ECU AS WELL as the code the performs functions not found in the tables (where other chip tuners often get into trouble). In addition, I can live remap the ECU, and have thousands of hours programming MoTeC engine management systems on air cooled engines of all types, blown included. The ONLY engine I have ever damaged on a Dyno was a Supercharged engine experiment. I learned the hard way that these engines are not tolerant to ignition timing or heat from the supercharger. Mike has done a GREAT job and putting together a package that works reliably.

dkcaims

They are not testing the car in that manner... I'm the foolish one for doing that once and only once. I'll have the shop call Mike and discuss things.

Thanks Geoffrey.

Makmov

I agee something is clearly not right and your left foot is not going to fix it.

Geoff is also correct about many chip programmers miss things. I don't trust a lot of that voodoo majick. I don't know even what kind of equipment you are dealing with. There are only a couple who can get a chip right, I cannot imagine there are anymore than that who can get a whole SC ECU right.

axl911

If the SC system is TPC then it does indeed control the injector AND the engine's timing.

I don't know about the earlier SplitSecond version, but the newer UniQ backbox reads boost signal and engine crank timing from the flywheel. It manipulates the timing signal before sending it back to the engine ECU.

Hope this helps.

dkcaims

The SC was installed in 02 by ON THE EDGE in Colorado Springs (Bill Rader's shop I think). Closed a few years ago.
Here is a pic of the install wiring schematics for the TPC black box...

axl911

Yep. That's the older style box. Not sure but I think it does modify the timing to the ECU.

TPC Racing

Please give us a call at the shop and ask for Tom. 410-799-7223

dkcaims

I'll pass the information along...Thank you