ac tune help

[dhworkin]

Installed new ac system on my 95 gmc pickup and when I come to a stop with the compressor on the engine tries to stall and I get a map code. Can I make changes in Tunerpro RT for this problem?

[MAC]

If you added ac to a truck that never had ac then yes, you could probably make some changes in tuner pro that would help. BUT... if you replaced/repaired an old ac system with new parts then tuning is not going to be the problem. There is some other problem.

[dhworkin]

Thanks Mac, your right. It's not the a/c, I think it's the dual fans that I installed. I disconnected the fans and used water to keep the condenser cool, turned the a/c on and didn't have any problems with the engine trying to stall. With the fans,lights and blower motor on high, all is good, but with the a/c compressor and fans running the idle drops below 600 rpms and the alternator doesn't charge. I've idled it up at the throttle body, but it only keeps it from shutting down. Is there a way to tune for the extra amp draw? I really don't want to put the propeller back on. I've installed a 140 amp alternator and upgraded the cables.

[myburb]

Being as your truck is a 95 the pcm should be a 6395/7427 vintage and should have idle speed settings that use the iac. If your rpm's are dropping below min a place to look would be the settings and if the iac is working properly.

[sturgillbd]

You need to connect the ac clutch positive wire to pin E12 on the PCM. The PCM needs to know when the AC clutch is engaged. It also has rpm tables in the tune to compensate for the AC engagement. See the pictures below:

[dhworkin]

Thanks for the help. I checked wires to ecm and the settings on memcal and all is good so I decided to start from beginning with the throttle body setup. I checked the timing before the procedure and it's jumping around from 14 to 18, then I shut it down and disconnected the tan/ blk and it's steady at 16. Shouldn't it go back to 10 with the wire unkooked?

[myburb]

I think with tan disconnected 5.7 is 0 and 7.4 is 3.9 in stock setting. I haven't read your bin but would guess with tan connected you should see in 20's on the lite.

[sturgillbd]

On TBI trucks, the base timing is usually set at 0. With you adding the extra load on the electrical system, you will have to compensate in the tune. Here are some parameters in $0D yon can try. There are some airflow parameters for A/C also. See screenshots below. Use the parameter finder in tuner pro to search out settings in the bin.

[dhworkin]

Yes, that's right. I should have mentioned that I put a lunati 20080660 cam in a 5.7 L31r and the timing in the bin is set at 9.5. I installed motor, unhooked tan/blk, started and set time at 10 which put it at 18-20 with wire hooked up, then drove onto trailer and went to muffler shop. After that the problem started with the timing. The timing doesn't change if the wire is connected or not (it jumps around when connected and is steady when not). Truck starts and runs good except for low idle and a slight surge at low speed.

[myburb]

When you say you changed it in the bin did also change it in the xdf/adx setup. If not it won't read rifgt on data logs or dash. I have a bunch of extra cam in my bbc and still use the factory initial and do what ever extra I need for the cam in the bin spark table.

[dhworkin]

myburb, I bought a harris chip and found the changes by comparing with a stock bin that dave W sent me. Other than the EGR delete I found differences in max spark retard for torque management and initial spark adv. I didn't know to change xdf/adx to match the bin and have looked to see that it is not the same as in bin. Sounds like I need to load the stock bin and start there and see if the timing bypass works like it should. Thanks for that info, here is the bin that I bought.12066

[myburb]

It looks like they didn't do much for the tune. I am pretty sure you could get it running much better tuning it yourself. It takes some time but well worth it. I am assuming you are able to burn chips. I mostly only do $OE but if none of the $OD guys chime in I can probably help. I helped on a $OD conversion to a 454 so have fooled with it a bit.

[dhworkin]

Thanks myburb, I have a ostrich 2 w/G1 adapter and will get a chip burner just to help out friends with there trucks. I'll load the stock bin to the ostrich and set timing at 0 degrees later today and post the results. All help is greatly appreciated.

[myburb]

I did a compare with your stock bin and the harris bin. You couldn't jump to the conclusion that the harris tune was bad. They gave you more timinhg in the high throttle area. less timing in the idle area (don't know why ) and more fuel in higher throttle and accounted for the possibility your cam will produce torque at higher rpm. When you get your burner I would first try taking the harris bin and setting initial to 0 in the bn and on the distributor and start from there or import those spark and ve tables into a stock bin.