3.4 DOHC Swap Couple Questions (Page 1/2)
355Fiero JUL 11, 01:44 PM
Good day all;

I am finally at that point of final touches on the engine swap into my very much modified and updated 308 replica on an '86 Fiero. Pic to show the work that has been done over the past 12 years.... way too long but it is what it is....

Overview, and yes I have searched the archives and obtained some info but a couple items left that still outstanding. Actually finally down to just a few which is amazing for me.... (List doesn't seem to work for me today so hopefully my indenting will show up OK)

* Speedo
** I have a VDO aftermarket gauge and I have both high and low wires. I have set the gauge to 4000 pulses and used the setup in the instructions for a controller. Essentially high hooked to the appropriate pin with power and ground as well. I believe the Low Speedo wire is what used to come from the gauge cluster to the ECM and it had an output of 2000 pulses that the ECM needed. I have a '93 ECU and the VSS wire, already goes to the appropriate ECU pin. (I will double check again tonight but pretty sure)
** When starting, the gauge does the test and then no speed registered when driving.
** Do I need to hook up the Speedo like a Hall Effect or other type of sensor?

* Temp gauge
** I had the harness built by Erik on here many years ago and he had the temp wired to the sensor on the front head just beside where you hook up the coolant hose. Single wire sensor.
** When running, the gauge works but only hovers around the 100* mark when on TunerPro, I am seeing 200-212*. The gauge does go up and down a bit when fan kicks on etc. so it is getting a variable voltage.
** These work on 0-5V so I can't see the gauge caring between *F or *C. The engine is a crate engine and in Canada but the sensor is voltage driven and clusters manage the display I have to think.
** I plan to set up a volt metre tonight and watch the volts and Tunerpro as the engine warms to see what the voltage is but from past attempts, it seemed to work between 0-5V. Will confirm again tonight.
** I have read in other threads that there is a second sensor in the lower intake manifold on these engines but I have not seen one.
** Any ideas from anyone on any other possible reasons for the low reading?
** I also want to lower the temp that the fan gets kicked on at as I don't like being up at the 200-212 mark. That is ecm setup though so another topic.

Thanks very much and hope to hear some ideas.
Don
olejoedad JUL 11, 04:42 PM
Don, I think I can help you.

I sent you a PM.
marc-alan JUL 11, 06:36 PM
We just completed a 3.4 dohc swap.

The coolant sensor should be a 2 wire under the area naround the throttle body. The sensor you hooked up to is not correct. We believe it is used for coolant level.

We used a megasquirt pro to set up our wiring and we used the stock speedo so I won't be able to help you with the speedo question
355Fiero JUL 12, 12:50 PM
Update:

I found the two wire water temp sensor last night and confirmed that it only goes to pin C16 in the ecu and nowhere else. That means I need to splice the water temp gauge into that wire and run a new wire up to the gauge. Relatively easy fix. I also found that the original wire going to the gauge goes to the water temp switch in the front head so I moved that over to my water temp idiot light.

Now I have a left over wire that was supposed to be for the water temp light that runs into the engine bay and I have no idea where that goes yet.... Not to either water temp sensors so I have something else misconfigured. Wish I had found these before the engine went back into the car... Way more room before.

I believe these are all my issues not Erik's who made my harness as when I had him do it, I had a 94/95 engine so wired for that and then I switched to a '96 engine so quite a bit different. I thought I caught all the differences but obviously not.

Speedo is next and going to call Joe tonight to see where I am going wrong there....

Thanks for the help everyone. This community continues to impress me with the amount of help everyone is willing to give out.
Don
olejoedad JUL 13, 12:40 AM
Don, in reading your last post, you may need to do some more work on the temp gage.....
355Fiero JUL 13, 03:57 PM
A big shout out to Joe who walked me through some trouble shooting on the speedo last night. Very much appreciated and I now have a plan of attack.

One item that came up in our conversation though is that I need to splice into the buffered out put from the ECU and neither one of us were sure what the PPM would be in that stream? I am searching the net now as well but I am going to take a wild guess that the chip burn that was put into the ECU for the build would probably have the 4000 ppm set since it is going into a Fiero and could well have used a stock dash cluster. Big assumption I will need to confirm.

Does anyone know the name of the internal ECU setting for the buffered output? I can log in and look with TunerPro tonight if I know the setting name. The water temp will be traced tonight as well.

Thanks again all
Don

[This message has been edited by 355Fiero (edited 07-18-2022).]

olejoedad JUL 13, 08:10 PM
Don, if you could post the Part Number and Service Number of the ECU utilized in you swap it would be very helpful.

It should be on a label on the outside of the ECU.
355Fiero JUL 18, 01:33 PM
OK, Confirmed with Ryan (Sinister) that the PPM should be 4000 as he did my flash update and the ECU is 16149396. I traced the wires for the VSS and confirmed that the VSS is getting to the ECU and registering correctly as I saw mph in Tunepro on a test run. I have also attached the B8 wire and connected to the Speedo but I have not had it out to test run yet so hopefully the speedo is done.

Per Joe's comment above, looks I still have work to do on the water temp. I spliced in the signal wire to the vdo temp gauge from C16 and moved my single wire head switch over to the water light on the dash. Problem I have now is that when I turn the key on after plugging in the vdo water temp signal, I get an error code, the engine light comes on and the fan starts up full and doesn't shut off. sigh..... I also connected a completely new wire, attached to nothing else from the C16 to the water temp gauge and same behaviour so I know it is not the existing wire.

Possible items causing issue:
* Temp sensor wired incorrectly
** Not sure of this as the ECU shows both C and F temps and they move so would assume the sensor wired correctly?
** Come to think of it, I am not sure if I confirmed the ground side of the temp sensor, only the signal wire. Will check that tonight

* Gauge wired incorrectly
** Checked manual and the working really is simple. Switched 12V, Ground and Signal. Hard to get that wrong but I checked...

* Gauge faulty
** I tested last night by pulling 12V off gauge and connecting signal wire. No fault code but the temp gauge also did not work without the 12V

Thoughts from any of the gurus out there??? I don't see an output temp signal from the ECU (something I could connect to the gauge)

Thanks much
Don

[This message has been edited by 355Fiero (edited 07-25-2022).]

355Fiero JUL 21, 01:23 PM
The adventure continues.

I could not get the speedo to work after putting the seedo buffered output from the ECU to the VDO gauge. Anyone know where the buffered output ppm setting would be when looking at a tuner program? I have tunerpro.

I saw one setting but it was set at 95 so pretty sure that wasn't it. ECU number is above. I thought it was 4000 ppm but maybe not?

Also, I still don't have water temp. In talking to Joe, I need a three pin water temp sensor that will fit in the lower intake manifold so that two wires can continue to the ECU per design and the third can go to the gauge in the dash. Anyone have a part number or model year that has the three pin in the confg I am looking for? I can find a boat load of two pin but can't track down a three pin so far...

Thanks
Don
marc-alan JUL 21, 09:29 PM
We are only running the 2 wire for the water temp.