Quest to identify hesitation and smog test prep (2 Viewers)

[IslandJ]

Made some progress. Traded out my old smog pump that was seized with one from @RodrigzCrzr. Replaced my old Air Injection system with one from @FJ60newb. Looks like my smog octopus is now functioning per the FSM.

As far as the hesitation, I have had no such luck. Replaced my EGR modulator with a new oem alternative, no changes. Then replaced the EGR valve with one from the pieces pulled from @FJ60newb and no change either. Yeah I did clean the the valve.

For now I'll see how the rig does at the smog station and live with the hesitation. If I do block off the vacuum hose from the EGR valve what else might have to adjust to compensate?

 

[fjc-man]

So now maybe it’s time to see if ignition advance is working correctly. Too much or not enough advance. The centrifugal advance may have a damaged or missing stop ( too much, too soon ). The vacuum advance unit may be doesn’t work ( leaking diaphragms). Any of these things could also be the cause of your hesitation. This has been covered extensively here. Who would like to chime in?

 

[IslandJ]

Probably worth while mentioning that previous to switching out the air pump and air injection components the 60 rpms fluctuated slightly at idle, between 600 and 700. Seems to be steady now.

 

[ravenplague]

I wish someone could remake EGR valves or make an electronic air valve control doo-dad spliced in the vacuum line ..I would pay a s*** ton for one

 

[IslandJ]

This morning I went out to the truck to double check some things. One being the VCV as @Beachcomber Bernie had mentioned previously.
It had tested fine from going by the FSM. Air did flow out of pipe Z when doing the inspection but I had no idea on how much it should flow.
Well after comparing it to the VCV that came in the box of goods from @FJ60newb it was obvious that was one of my problems.
The hesitation is only BARELY noticeable in 2nd gear, I doubt some one would even feel it if not looking for it.
What OSS had said about things testing OK but not functioning properly after 35 years kept repeating in my head.

 

[IslandJ]

Spoke too soon. 2nd drive today, after it cooled down for a bit and the hesitation is there. Drove to the post office with hesitation. Return trip i capped the EGR modulator and it drove like a dream.

 

[PescaBaja]

I offer this option to consider on the AI system...

When the two VSV's are "off" or they quit working they "fail" closed. In this configuration the air path through the ABV is "bypassed" to the air cleaner. In the ACV the ABV is the initial determinate of the direction of the air path. With the VSV-2 off there is a vacuum now on both sides of the diaphragm in the ABV (fig. (1) Pg. 3-19. This allows the spring to push the diaphragm up and closes off the airway from the ABV to the downstream connection to the tail pipe. If there is atmospheric pressure on the top of the diaphragm in the ABV then the air path will be to the hose to the downstream connection to the tail pipe (fig. "2 and 3" Pg. 3-20). To configure the air to always go to the downstream connection to the tail pipe, cut a small slit or hole in the top short hose that connects from VSV-2 to the top of the ABV and put a small BB between the slit or hole and VSV-2. This will maintain atmospheric pressure on top of the ABV and force the air to go to the downstream connection to the tail pipe at all times...especially for SMOG tests. BTW... always ask for a "pretest" before the "final" test to see if your likely to pass. By pretest I mean a tailpipe sniff. I have had several pre-sniffs before the final test to make sure I pass. Hope this helps.

 

[Spike Strip]

The above info from @PescaBaja is very good -- Wish we could FAQ it ?

Jason, one other thing to consider, also, is the ICS (deceleration cut out) can sometimes cause the hesitation. Is your ICS connected as stock (emissions computer controlled), or is it grounded?

If it's still connected as stock, you might try disconnecting the Tachometer feed at the coil and see how that affects the hesitation.

 

[IslandJ]

Sniffer test is lined up for this afternoon.

 

[ravenplague]

just sounds like we need to regulate the vacuum from the EGR to reflect a new OEM EGR. Can't we use a valve and adjust the flow until it runs well and doesnt ping?

 

[IslandJ]

Thought I would keep this updated for anyone down the road. Making my way through the FSM some more.
The High Altitude Compensation System checked out.I did notice that the hose leading in to the carb on the driver most side was a little more challenging to push air through. Not sure if that needs attention.
By the time I got to the Automatic Hot Air Intake system the engine was warmed up. Blowing cool air on the HIC valve did not close the cool air intake. It was stuck open. That could lead to hesitation when cold yeah? I still need to pull the HIC and hot water test per the FSM
The Choke breaker diaphragm wasn't functioning but switched out the VTV and that seemed to do the trick. Inspection of the distributor vacuum advanced was good.
The Choke Opener doesn't seem to be functioning 100% I still need to check it when cold but when warm, the diaphragm doesn't budge when i removed the vacuum hose. That said, on first morning start up i do the standard 3-5 pumps of gas and pull the choke all the way out. Turn the key and the truck starts. RPM's go to 1000 or so and then slowly drop till it dies unless i give it a few more pumps. After that the rpms will steadily rise to 1800rpms
After reading and learnin some, this points to a faulty diaphragm yeah?
WHile doing the inspection of the Deceleration Fuel Cut System pg(3-45) I saw that the engine was not effected when i pinch the the vacuum line off the vacuum switch and increase the the rpms to 2000.
The engine does die when when I disconnect the wires to the solenoid vlave. I didnt get a chace to hot wire the switch yet.
The vacuum swithc does check out with the ohm meter.
Thats where I had to cut my diagnosismake yesterday.

The 60 passed its smog test though! I thought it would considering everything but you never know.