Motronic 1.3 and auto TPS

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careysd

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Recently, someone brought to my attention that when using M1.3 with an auto harness and auto TPS, the computer will net get a wide open throttle signal without having an auto trans ECU installed? Can anyone verify?

Scott C.
 
There are 2 TPS units from BMW for the Motronic ecu 1.3
5 speed and auto cars used different TPS units.
5 speed unit has 3 wires and auto has 6 wires.
5 speed TPS will show idle, cruise and WOT throttle to the ECU with switches in the TPS unit
Auto shows the same as above and also continuously variable load which is sent to the auto tranny computer to tell the valve body how hard to shift gears.

If you are installing a 179 ecu into a manual- buy the manual TPS.

If you are installing a Megasquirt ecu into a manual- you will need to get the auto TPS and swap wires in the harness with the manual wires.
Black and Yellow wires will swap with Brown/Blue and Brown/Black

You don't need the tranny computer
 
I have an auto harness and auto TPS. Harness is from an '89 735i. 179 ECU. My car does run fine. This is thread is in reference to another person's problems, but I am now wondering if my car is seeing WOT?

To clarify, I should be able to run a B35 with an auto harness as long as I use the auto TPS (which I am) and the ECU should have no problems seeing WOT when the throttle is opened, correct?

To clarify further: the difference between auto and manual (besides the obvious wire count) is that the auto TPS is 100% variable, where the manual is not.

This is what I thought, but was being told this wasn't true.

Thank you, SFDon.

Scott C.
 
Let me see if I can do better...

The manual TPS has 3 wires. It is all you need. Two wires go directly to the ecu [pins 52 and 53 and 1 wire to ground.
A 3 wire TPS tells your ECU if you are at idle, cruise or WOT.

An auto TPS has 6 wires. The same 3 that the manual has and 3 more that go to the automatic transmission module. There is no connection with your engine ecu with those extra wires. They are usually cut out of the harness as the have no function for any car without an auto tranny with electric shift controls.

You only need the manual TPS for your car to run perfectly.
Lots cheaper too.
 
Thanks, Don, I understand what you are saying.

Let me see if I can be clearer... :-D

There is no penalty for running an auto harness and auto TPS in the conversion compared to the manual harness and manual TPS. They both, in the end, function the same.

I got my harness and TPS together from the same car in the junkyard, as I am sure most do.

Once again, Don, thank you!

Scott
 
Don i have 2 harness , the one on my car has 4 wires + a shielded wire.. the extra wire is Brown is its a ground.

My other harness has just the 3 with the shielded.

and there are 2 plugs - round and Sq any diffrance?

car runs great
 
Sorry for the semantics. Please replace "auto trans ECU" with "TCU" or "tranny computer". Whichever may be the most correct in this situation.
 
Please, if I may, let me re-ask the question in a clear and concise way, I am not sure if I am getting across the right information.

In my 1973 Bavaria, I transplanted a B35 with M1.3 out of a '90 535i automatic. The harness and of course, TPS from the E34 are automatic. My Bavaria is a 5-speed. I made zero modifications to the M1.3 harness, including leaving all automatic tranny wiring intact.

1. Can I plug and play this auto harness and auto TPS in my car without making any adaptations to the wiring of the TPS?

2. Is there a change in wiring using the auto TPS that needs to happen for the 179 ECU to see the proper values including WOT?

3. Do I need to install a special jumper from the automatic part of the harness to the 179 ECU to get it to work properly?

Thanks again,

Scott
 
#1 yes

#2 no

#3 no

Good questions- well written!

There are a few mods that CAN be done on a auto harness- you can cut out the oil level, purge valve, auto TPS and a few other wires to make it neater. You don't have to do any of that if you don't want to.

If you want to save money you can install a manual TPS and plug just because they are cheaper. You don't have to do that either.

What you really need to do is to test your TPS for proper adjustment and proper function.
Personally I won't touch a used TPS because I have tested so many bad ones. Usually it is corroded WOT connections inside.

To test- pull the rubber boot off and test for continuity between the brown/blue and brown/orange wires for your idle signal.

test WOT circuit by checking for continuity between brown/black and brown/orange.

This test is done with the plug OFF! If it makes it easier for you- with the plug off, 12:00 pin is brown/black, 2:00 pin is brown/blue and 10:00 pin is brown/orange.
 
Don, you are much appreciated! I have been running a B35/M1.3 in my car for well over 1000 miles. It runs very well, but does seem to not be quite as peppy as I would have thought, so I am diagnosing to see if there are any problems.

Following a thread on another forum, a member was adding M1.3 to his E28, a B34/manual car. He was concerned that the computer would not see WOT without an extra wire added from the auto harness to pin #3, I believe.

Thanks for your time!

Scott
 
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Are you running a 3 bar fuel regulator?
Have you hooked up a wide band o2 sensor to test for air/fuel ratio at WOT?

BTW- pin 3 is the ground signal wire to the fuel pump- it is twined to the tranny control module which is not connected.
 
Yes, I am running a standard B35 manifold, fuel rail, etc. I think that it may be my O2 sensor, as it is of unknown quality. I tested it as it dithered a while back and the low voltage wasn't as low as it should have been (can't remember off of the top of my head).

I also had a problem with sediment in my tank clogging my filters and destroying a pump. The gunk didn't reach the injectors or fuel rail, though. I cleaned the tank and installed a pre-filter between the low-pressure tank pump and the high-pressure pump. So far, I have had to change it once. I am planning on having the tank boiled and epoxied, but haven't had a chance to do so.

Scott C.
 
I was doing some maintance on my car 3.5 1.3 motronic , i removed the Throttle Housing.
When we talk about FPR ,Don speaks about a 3bar.
I was looking inside the cyl of the housing and noticed the vacuume hole is a tiny pin-hole.Has anyone enlarged the hole to draw more vacuume to the FPR or is the hole just the right size? It can get oil or dirt in it and will that change your FPR pressure?

Just a thought
 
you should have 2 vacuum nipples- with both blocked off if it is early style throttle body.
Early throttle bodies are ported for vacuum advance and retard.
Vacuum to the fuel regulator should be continuous and not use the throttle body. Use the vacuum nipples at the plenum for the fuel regulator.

BTW- I sent you a pm re the TPS ...
 
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