Tampa 928s

I was looking at the idle and saw the line showing a pulse don't remember when but it looked like a small square wave. I just went through all the grounds do you think it's a inj wiring issue maybe shorting or a lifting of the ground?

AO

It could be either, but I would suspect a ground from the harness. There are two harness grounds that bolt on the rear of the V on the top-side of the block. I had a bolt back out on me there that caused a similar issue - like someone turned the car off.

Tim Murphy

Good spy AO, I think you are on to something with the injectors cutting out.

Tony

I cant recall if the both injector banks ground on one post...or if its one on each?

AO

On 89+ it one each. No idea on 85/86 or other early S4's.

Tampa 928s

Working on Shadow Knights car adding an X-pipe right now. We found his main harness rubbed through it was hitting the air pump valve, does not look real good but it was caught before a short took the car down.

I removed and cleaned both grounds on the rear of the block.

What I am finding is the ISV is also connected to the Inj circuit, I need to get into it, if the Isv is shorting it will effect the Inj I believe. Since all my testing does not change the idle it could be held open and if it is shorting this could be the cause of the cut out. I need a little more time to ID the three wires I know Pin 10 and 20 goes to the LH. I think they reverse the voltage on the Isv to open and close it but I am not sure, feel free to chime in"!

And yes really good call on the injectors.

Tampa 928s

I can see this happening on all my logs although randomly! Any way to check between a lifted ground or shorted 12V by looking at the logs?

Brent

For almost two year now I have had the shudder issue. Just as Tampa describes. Seems everyone I've talked with points to the MAF, leaks, etc. All good tough. I just caulked it up to the Eaton SC'er, what do I know? Bad ground and injectors cutting out, make sense to me. I'll be going after those ground points now.

Tampa 928s

OK, Spoke to Paul and I tried the following.

Looking at the circuit the 12 V is shared with the Pass side Injectors.
The ground for both open and closed is using pin 10 and 23 providing ground.
I disconnected my Lh bridged the FP relay and had 12 V on both pins.
I used my power probe to ground each pin and no clicking of the Isv.
Now I need to get into the intake, it could be that the coil on one side of the Isv is shorting causing my drop out, will check back but not today!

Tampa 928s

Idle control valve is dead so I need to replace it!

Partial number is 0-260 xxx 509 the xxx is worn off. I called Napa there part is N-69471 from Bosh is $209.00 and takes 5-Days.

Anyone have a used one or provide all the numbers to do a search or a place to purchase it?

Tampa 928s

I did a bench test and the ACV is pulling 1/2 amp this maybe due to it being bad.
Has anyone tested or know the current draw on this?

Since my injectors were going to 0 randomly and it is hooked to the 12-V passenger bank I am hoping to solve both these problems when I replace it.

Tampa 928s

1986
Thought I might attach the circuit:
Pins 10 and 23 are ground pulsed from LH
12 volts is shared from the passenger injector bank.
Shorting B&C at tester port takes the ACV out and allows to adjust the idle.

To test ACV in car remove Lh cable
Bridge Fuel Pump Relay
Ground Pin 10 then Pin 23 and listen for clicking of the acv as you ground each pin.

Tampa 928s

New ACV and new Inj wires.
With the S/C not connected I was able to get the idle spot on using the bypass on the diagnostic connector and adjusting the idle screw.
Once everything was connected I use the bypass it the idle fluctuates wildly. I can adjust the Idle screw and get it with in a window but not stable. When I remove the bypass it does stabilize but at about 825. If I set it any lower the idle will fluctuate until it gets time to stabilize. Seems the Lh only has a window to work in and I cannot get to that window.
I took the car for a run seems good but not enough time to fully check everything out.
Is this normal with out S/C cars or do I still have some issues?

Bill Ball

I had one instance where I could not get stable idle with a supercharger kit and I came to the conclusion it was because of turbulence in the air going into the MAF due to abrupt changes in tube diameter and direction close to the MAF. Car idled fine with the SC intake tubing disconnected from the MAF but not with the intake installed whether the SC was belted up or not. I did find I could alter this somewhat by "clocking" the MAF differently, which might have changed the way the airflow hit the MAF center. Others that encountered a similar issue solved it by replacing the MAF. Most appear to never encounter this and Murph could not duplicate my observations and did not agree with my suggestion. Still, a few seemed to think that the flow direction and diameter changes near the MAF could be the issue. If this is a NEW problem with an OLDer SC kit install, then my comments are probably not relevant. I saw this problem from day one of the kit install on this car.

Tampa 928s

Well this is the one and only 86 stage one out on the market.

Tim is sending me some type of honeycomb filter to try and see if this takes care of it!

The idle is stable but not with the ACV bypassed. It acts jittery when I try to get it to the normal range after an adjustment; so 820 or so seems to be where it likes to stay.