ALDL (OBD1) to OBD2 - PCM upgrade 3800 turbo (Page 1/1)
Frenchrafe MAR 08, 02:48 AM
I got my new (to me) PCM in the post (mail) this weekend.
I've put this post up because I'll maybe need some help to get it all OK, and just to share the joy of trouble free (hopefully?) running!
Thanks to Darth Fiero (Ryan) for the custom tune and thanks to La Fiera (Rei) for shipping the thing out to Europe!

Old PCM ('95 ALDL) and new PCM ('98+ OBD2):




I like the fact that Ryan puts a little label on the PCM case so we know it's custom!

Ryan sent some used PCM connectors as well that had to be thinned out in terms of number of usefull wires. Look at all the wires that won't be used!


So then it was just cut-n-splice all weekend:



I will make a "Turbo Slug" video to go on Youtube but I need to sort through hours of watching me do wiring. It's not the most exciting viewing!

I added the purple wire to the OBD2 port for the class two serial data link, but I don't have the little connector pin in all my elecrical spares! M**de!!


I also added all the harness wires missing from a '95 application. All that should be needed to make the '98+ PCM work; seperate earth for the ECT sensor, second knock sensor and the MAP sensor wiring. I still havn't received the 2 bar MAP so the wiring won't be routed properly untill then:


So there we go for now. I'll keep you posted on the progress...
Regards,
Rafe


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"Turbo Slug" - '87 Fiero GT. 3800 turbo. Sticky tyres. Driven hard!
https://www.youtube.com/cha...1wZvWQlkYxTjivW_0XNg

olejoedad MAR 08, 11:56 AM
OBD 2 DLC pins are the same as found in the 88 Oil Pressure connector.

The OP connector style is used on dozens of GM models.

[This message has been edited by olejoedad (edited 03-08-2021).]

Frenchrafe MAR 08, 03:06 PM
I've ordered a whole new J1962 connector with 16 unused pins for a "whopping" 1€17 from Ebay!
Even at $1.40 thats a good price just for the 1 pin that I need.
Probably will get here at the same time as the 2 bar MAP.... (he hopes!)

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"Turbo Slug" - '87 Fiero GT. 3800 turbo. Sticky tyres. Driven hard!
https://www.youtube.com/cha...1wZvWQlkYxTjivW_0XNg

Frenchrafe MAR 14, 04:47 AM
Got the new 2 bar MAP sensor this week end. Made a little bracket and fitted it:


I finished up the wiring in the engine bay and pushed the harness back through the firewall. Apart from the ICM / ignition coils cooling fan (my aftermarket mod), the engine bay is back together:


The PCM is loosely in it's place and I haven't yet wrapped the wires, in case there are some last minute changes (mistakes!) to be made good:


Still haven't got the one missing pin end for the OBD2 connector so I can't plug in the diagnostic tool for the moment:



OK. So I fired the car up last night after all this and it started 1st time and idled perfectly. I didn't run it for more than 2 minutes; neighbours after 9pm!!
The engine service soon light came on pretty quick, but since no scan tool for the moment we'll have to see that later...

However, I noticed that the fuel pump stayed on quite some time after shutting off the engine. The pump stayed running for a good 30 seconds after the contact was switched off. Is this normal?

Thanks,
Rafe

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"Turbo Slug" - '87 Fiero GT. 3800 turbo. Sticky tyres. Driven hard!
https://www.youtube.com/cha...1wZvWQlkYxTjivW_0XNg

[This message has been edited by Frenchrafe (edited 03-14-2021).]

olejoedad MAR 14, 08:02 AM
Disconnect the oil pressure sending unit plug and see if that stops the fuel pump run-on issue after key OFF.
Frenchrafe MAR 20, 04:52 AM
Update here:

https://youtu.be/GNyocekcXvg


It's running! Still waiting on the pin for the OBD2 plug.

On a second test run the fuel pump shut down promptly. My oiling system is probably too good keeping pressure even when the motor is stopped!

I may even get round to driving the car this week end!

See you soon,
Rafe

------------------
"Turbo Slug" - '87 Fiero GT. 3800 turbo. Sticky tyres. Driven hard!
https://www.youtube.com/cha...1wZvWQlkYxTjivW_0XNg

[This message has been edited by Frenchrafe (edited 03-20-2021).]

Frenchrafe MAR 29, 03:23 AM
OK, I took the car out for a run yesterday.
Running reasonably well (compared to before) but hesitating à little.

First code to show up was a P0102 MAF circuit low.
The MAF didn't seem to read on the scan tool? No change in values.

Back in the garage, I swapped in an older part and the readings came back through the scan tool.

Second time out and running OK'ish but did cut out twice!
After running for some time and getting up into opperating temperatures, it threw a 2nd code P0171 System too lean (bank 1 - I only use 1 O2 sensor).
The P0102 showed up again as well.

So these 2 codes could be showing a lean condition, especially when well into closed loop fonctioning.

The car starts and runs correctly when cold but starts to play up when at opperating temps. My guess is fuel starvation when everything is nice and hot and has been running for a while.
I'll have to test the fuel pressures, not only static (easy) but also on the move when hot (less easy).

I'll keep you posted... but I think I'm in for a fuel tank drop and entire fuel line check with a bench test of the fuel pump!

------------------
"Turbo Slug" - '87 Fiero GT. 3800 turbo. Sticky tyres. Driven hard!
https://www.youtube.com/cha...1wZvWQlkYxTjivW_0XNg

olejoedad MAR 29, 06:28 AM
What oxygen sensor are you using?
Fuelj pressure should rise as boost rises and can be tested by revving the engine.

I'll wager you already knew that.
Frenchrafe MAR 31, 09:33 AM
Tested the static fuel pressure and at idle today.
Seems a little low to me:
Static doesn't seems to go above 3.5bars.
While running at idle=3.0bars
Vac line disconnected at idle= 3.3bars.

Will go up to 3.5bars when blipping the throttle and on overrun, but never wants to go to the 3.8bars (55psi).

Once shut down the pressure drops to 2.8bars and then stays there.

What do you think? Fuel pump or just the regulator.

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"Turbo Slug" - '87 Fiero GT. 3800 turbo. - The fastest Fiero in France!
https://www.youtube.com/cha...1wZvWQlkYxTjivW_0XNg