dkcaims

Funny you should mention that Marc...
That's the unit I'm ordering this week with a DashDaq display.
But without a baseline, how am I to know what boost levels it should be at, at 3k, 4.5k, and/or 6k rpm's?
For example...
If my system shows boost levels of 2.5psi at 4.5k rpm, but everyone else claims theirs is 4.5psi at 4.5k rpm's, then I guess my car has some issues.

Marc Shaw

Good point.

If you get the EGT probe, order up an extra long cable as the 8' one is too short. AMHIK.

Marc

evoderby

With all due respect, you are experiencing electronics problems and are planning to throw more random electronics at it to try and solve the problem. Whilst having onboard wide band lambda, egt and boost data logging is very nice, the chances of this helping you solve the problem is very slim to say the least. IMO a very methodical approach is required in trying to solve this, so let's start with what we (think we) know:

1) TDC sensor is giving a way too weak signal (1.2V vs. 3V minimum requirement)

2) Hall sensor faults recorded as shown on hammer


ad1) Speed sensor / crank position sensor is a primary input to the engine management system. Primary input basically meaning: if this fails, all else fails.

This makes this sensor a primary candidate to focus on and investigate why it is giving too weak a signal. There are several potential causes: A) metal swarf covering the sensor----> clean. B) inaccurate distance to trigger notches ----> readjust between 0.8 - 1.2 mm . C) signal interference ----> check sensor wire shielding and make sure to route wire away from potential sources of interference (ignition leads etc.). D) faulty sensor---->replace

E) in your specific case the option also exists that a faulty piggyback module is causing the substandard readings, since when looking at your diagram the Piggyback is directly connected between the crank position sensor and the Motronic ECU.

My guess is that the Piggyback starts modifying the Crank Signal (as a function of registered boost through the vacuum/boost hose) as a somewhat crude method to alter ACTUAL ignition timing. In other words it fools the Motronic in thinking that it is firing the plugs at say 15degrees BTDC as mapped in the 964 Chip. The reference crank signal gets delayed however by the piggyback, making the plugs to actually fire at say 6 deg BTDC.

Why is this important?? Well it shows that if options A and B proof not to be the cause of your problems, we need to look at either the sensor, the piggyback or the wiring to be faulty.

Your mechanic's report shows the crank sensor to have been replaced already, with the same outcome. As a check I'd suggest fitting the old sensor again and cut its wire harness to allow hooking up an oscilloscope to the sensor output directly. As per workshop manual the amplitude should be a minimum of 3V, and when properly adjusted it easily will be. As a next step hook everything back up to the piggyback harness and, again with the oscilloscope, look at the output signal AFTER the piggyback. You will probably find your reduction in voltage here, either being caused by a faulty wiring harness or a faulty piggyback.

And so on...and so on. Please notice the Motronic Ecu hasn't done a thing up to now, before you go replacing expensive Motronics first make sure it is receiving the correct signals to act upon!


add 2) Hall sensor. As Geoffrey has mentioned this is a secondary input to the engine management. In other words, a failing signal will not cause the engine to stop running properly.

The Hall sensor is either faulty or OK. Since your sensor has been replaced 3 times already the wiring ( +. - & earth) is the only source for faults to register.
---> recheck the wiring (vibration can cause broken cables to intermittently connect/disconnect).

Since this sensor is not of prime importance, I suggest simply disconnecting it for now and again focus on the crank sensor. (Although this fault does probably say something about the general state of your wiring)

Additional steps:

Once again notice the Motronic Ecu hasn't done a thing up to now, before you go replacing expensive Motronics first make sure it is receiving the correct signals to act upon! After succeeding in this and problems remain, by all means focus on how the Motronic is performing itself, as well as fuel pressure / flow, blocked injectors, boost/vacuum leaks etc.

Lambda / EGT readings are very nice tool for tuning overall maps.....it is very difficult/ next to impossible however to detect single cilinder faults when measuring at a point in the exhaust where all six cilinders dump their gases! Accordingly, at this very moment it probably won't help you too much.

A $25 boost gage and some vacuum hose can perform the same boost checks your $500+ datalogger can perform. What is more, you don't want to register any boost to begin with, with the way your engine is now running!!!!!

I think your garage have done a professional job to the best of their knowledge up to now. IMO the time has come however for someone truly specialised in electronics/Motronics to have a look at things....

Best regards,

Harald

dkcaims

Great insights Harald....Thank you

dkcaims

Sending the TPC ecu to the original manufacturer for testing today.
Also... the 7th injector spray pattern was not so much a spray, but rather just a stream.
One of the members here upgraded the 7th injector, anyone have details? I've read so many threads, it's just a blur now.
Will take notes from now on.

evoderby

Cool, hope the piggyback people can find anything wrong.

Perhaps stating the obvious:

As far as replacing/upgrading the injector goes, please make sure a new injector is rated at the same flow and impedance of your current injector......otherwise your injector either won't fire at all or at best mess up your air / fuel ratio.

sabehtaayon

dear all, i need help for installing TPC supercharge for 964 1991,