1985 Buick 3.8L Turbo First Fire Up
 

http://youtu.be/fpaPtUXHDxs

Special thanks to...
Jimmy Gorecki
Competition Fabrications
Precision Engine Rebuilders
Bob Hebert

No ECM codes. :lock:

More to come....

Re: 1985 Buick 3.8L Turbo First Fire Up
 

VERY cool! Congrats!

IAC needs to be relearned? Reset? Or is it something in the chip?

Re: 1985 Buick 3.8L Turbo First Fire Up
 

I've reset the IAC a few times. I tried the IAC in the car, it seems to work, but the ECM threw a code that I attribute to my lazy approach to calibrating it to that engine. My buddy Jimmy's got a tool to set them, I'm not sure what that will be. I'll look elsewhere for the problem if he can demonstrate that it works.

I get the same poor idle with Casper's 42lbs chip and some other 42lbs mystery chip. I have one more chip to try, a 42lbs Turbo Tweak chip meant for alcohol injection. I intend to use the Turbo Tweak chip with Razor's alky system. The instructions with the Turbo Tweak chip state that it will run the system in open loop at idle. I'd rather use closed loop until I get everything sorted out.

One issue I've got is the alternator I began with is putting out about 12.2 volts. (You can see the "volts" idiot light is dimly lit). I've got a known good replacement teed up for Tuesday night testing.

Another issue that I've got is the fuel pressure is cranked up to 48 lbs to keep the engine running at a barely decent idle. That's way too high.

I tested three LT1 MAFs, the engine idles poorly with all three.

The O2 system is showing lean, the MAF Translator is showing lean and Turbolink is showing lean. Hmmmmmm I guess it's running lean at idle. The spark plugs are clean, just a hint of color. Yeah, it's running lean.

At a steady RPM of 1500-2000 the AFR is around the ideal of 14.7. It runs smooth at most everything above idle and there is no stumble getting there. It's when I bring it back to idle that it goes lean, 16.5, 17 and 18 AFR.

I'm happy to report that Turbolink is working well with this ECM. This is not the case for the ECM that's currently in the car. But that's another story.

I'm running a 206/206 cam and 1.65 ratio roller rockers on mildly ported stock heads. The EGR is blocked off.

This is the fun part.:winkgrin:

Re: 1985 Buick 3.8L Turbo First Fire Up
 

Hmmm... lean at idle and low RPMs hints at some sort of vacuum/air leak downstream of the MAF, to me?

Re: 1985 Buick 3.8L Turbo First Fire Up
 

Yeah, that's good advice. It occurs to me that I've got one of the vacuum hoses hooked up wrong. I didn't think of it last night. I'll block them all off except the fuel pressure regulator and see what happens.

We tested the IAC and it seems to work properly. The test device is a hand held tool that plugs into the IAC. It has up and down membrane buttons to change the IAC position. The idle speed would follow use of the buttons.

IAC counts are low, 4-10. The idle speed hunts around between 700 and 900. I could see the IAC counts go up as I closed the throttle blade.

We switched out the alternator, now I've got decent voltage.

It seems that it took the ECM awhile to sort out the idle AFR. At first the AFR was 16.5 to 18, then over time, 10-15 minutes it dropped down to 15 and 16.

I dialed back the fuel pressure and it's now at 38lbs and jumps up to about 45 lbs when I remove the vacuum hose.

I may not be able to get back at it until next week, the shop may be closed Saturday while the owner dynos a customer's motor.

Re: 1985 Buick 3.8L Turbo First Fire Up
 

Can you see the BLMs (I wish these older ECMs had LTFT and STFT) ...?

I wonder if the reason you saw it adjust is the BLMS skewed all the way to rich?

Re: 1985 Buick 3.8L Turbo First Fire Up
 

Sent you a PM.

Re: 1985 Buick 3.8L Turbo First Fire Up
 

The table below shows the number of frames and the BLM values. The percentage is the number of frames having that BLM value divided by the total frame count. The 85% at the bottom is the percentage that the BLM is above 128.

BLM Total Percentage
110 4 5%
128 8 10%
131 6 7%
137 13 16%
138 8 10%
139 6 7%
140 37 45%
Grand Total 82 85%

What is LTFT and STFT?

Thanks for the advice, much appreciated.

Re: 1985 Buick 3.8L Turbo First Fire Up
 

LTFT (long term fuel trim) and STFT (short term fuel trim) are used by modern ECUs as a way to adjust the strategy for fueling based on sensor feedback and are basically a very sophisticated way to adjust the VE map on the fly. More precise and tells you more than BLM in the older ECUs.

That said, the high numbers seem to indicate to me that there is an air leak somewhere behind the MAF (maybe the intake manifold didn't seal well? ... bad EGR gasket?)

Re: 1985 Buick 3.8L Turbo First Fire Up
 

Roughly what sort of number should I see for MAF at idle?

Thanks for the help.:hail: