pcopp

Want to help son finishing tuning of his LG4 with the Electronic QJeton 1986 IROC 5 Speed

We had an overheat issue but after much back and forth and help from the forum, figured out I installed the intake manifold gaskets backwards. (ooph - my bad). That is behind us.

So, we finished installing the new AC system (converted to R134 with all new parts) and that works well. The ACD OEM R4 compressor is a pig and puts a lot of load on the motor when cycling at idle.

So here are my questions:

1. AC Idle stop solenoid

It is engaging properly but it not strong enough to kick up the throttle at idle. If son gooses the throttle, it will extend and hold the throttle up. Is this the way this thing works? The car is a 5 speed so it definitely stumbles when starting/idling with AC engaged. Is it the "procedure" to start car with AC off? Can someone explain how this thing is supposed to work? Was wondering if it was weak and we should replace. Part is $70+ bucks so don't want to buy if not needed. I can extend/retract plunger with 1/2 wrench. What is the procedure for setting the plunger length? I assume I set the curb idle screw with AC off so that I am happy. Then set the plunger length with AC on after goosing idle to get it to fully extend. Should it be strong enough to push the throttle open? Should son shut off AC before shutting off the car to prevent dieseling run-on by throttle being held open or on shut off, does solenoid quickly release?

2. Timing

We tried various timing settings. The "stock" is 0 BTDC at 700 curb idle. But car is not happy there as we installed COMP CAMs RV Cam. When we broke in CAM, we were at 10 BTDC and currently at 6 BTDC as we have played with it. I feel when we are on highway and punch it, there is a "rattling" acceleration but I would not call it pinging. Thinking it could be the HOOKER headers which collect to a 3" (!!!) main pipe and we stepped down to the stock 2.25 exhaust. Currently no CAT installed. Any guidance on how to dial in the best timing setting for these CCC carbs with ESC? Is there a total timing advance we should be looking for at 2500 or 3000 RPM?

We backed off from 10 to 6 BTDC in hopes to quell the rattling but no change. I think the car might even want more timing than 10 but dont want to go overboard.

The exhaust has a very rich smell to it. The Carb has been rebuilt and set/checked to all specs and checked with a complete set of vintage dealer tools for setting up the carb. TPS is new and was set to the FSM voltage.

As for the rattling, I had similar issue with a C4 L98 Vetter and I was never happy with the sound but the car pulled well and I only ran 93 Octane in that. I felt the rattling on that started when my pre cats went bad and I installed a wye pipe with pre cats and a flow master low restriction main cat. Should I just ignore the ratting on acceleration and chalk it up to the lower restriction exhaust??

3. OBDI Lights

We are currently getting intermittent SES for two codes:

a. 24 - VSS - the stock gauge cluster is installed. The odometer stopped working (I have seen fixes for that) and the speed is a little jumpy at acceleration. We changed the rear gear from stock 3:23 open diff to a 3.77 posi when we swapped in a gen 4 disc brake rear. Now, the shift light comes on in every gear including 5 th gear when we hit plus 65 on highway. We changed speedo gear and the speedo is accurate to an Iphone speed app so we did that right.

I dont necessarily want to rebuild the cluster as son wants to swap to a T56 that he picked up and he may be changing entire cluster for digital.

My question is whether the CODE 24 would impact the ESC system and screw up the electronic spark advance.

It cleared when we disconnected battery but came right back soon after car was idling for a few minutes in garage yesterday.

b. 53 EGR Vac Pressure Error - the EGR system is currently disabled. I understand this code is set by the Vac Pressure Senso which is connected to the Carb. It set on the highway last weekend and cleared when the battery was disconnected. It has not come back but we have not taken car on road since weekend. Is this anything that we should follow-up on? We have not gotten the code before. Only change was we installed the AC system this weekend but can't see how that would effect the VAC Pressure Sensor.

Any tips on how to proceed to put the final tune on this car would be much appreciated.

Thanks.

Vader

1. The throttle kicker solenoid typically does not have sufficient strength to open the throttle by itself, but only provides a higher idle stop position once the throttle is released.
   
   
   
2. The A/C compressor should be shut off before the engine is shut off, not only so the engine doesn't start with the compressor engaged, but so the evaporator has a chance to dry off just a bit and not promote growth on it while sitting. GM actually provided a service kit to address this problem in some climates, and it included a timed relay to operate the interior fan for a minute or two after shut-down to dry the evaporator. Not that it ever gets humid in Jersey.
   
   
   
3. The ECM needs to know the throttle position in order to invoke the lookup tables for spark advance at a given engine RPM. If the TPS signal is out of range, it is probably operating in Backup Fuel / Test Mode ("limp-home" mode) and there is no spark advance. This can be verified with a timing light. Backup Fuel mode also defaults to a more rich mixture.
   
   
   
4. A functioning EGR system is not a bad thing. It is typically defaulted to closed at WOT, so there is no penalty for performance. A working EGR system can keep chamber temperatures lower, so it decreases the tendency for detonation/preignition.