real quick - what does this relay do?

[fiater]

What's the relay located between the coil and vac solenoids on the pass side fender wall (85 TI). It's cycling in sync to my horrible rev swing from 500 to 1500, dying and then revving. I hope it's just that, cuz I've been replacing parts like crazy trying to solve this drivability problems.
Thanks.

[The Dude]

Just an educated guess, but I think that's the baro-read solenoid.

[IROCNOROLL]

Sounds like you are chasing a vacuum leak. The cycling solenoid may be the cause or may be the result. Can of carb spray or a little propane and start putting short shots around the all the vac hoses, intake manifold, throttle plate and gasket, egr valve if you have one, injectors into the mani and so on. If you hit a vac leak, the engine will momentarly smooth out, then the surging will start again. Try to pin point the leak this way,

[fiater]

I'm hoping it's the cause, and not the result. I can't really keep it running long enough to even try though. I'm wondering if this is not a fuel related relay that's cycling.

[Marcus86GLHS]

the silver-colored relay on that side is the air conditioning clutch relay.

[ShelbyMopar89]

Not sure if they changed from year to year but on the 89's your Fan and AC (ASD on some) relay are on the drivers side and on the pass side is your purge and boost relay.

[fiater]

It wasn't that relay, I guess it was just cycling as the revs dropped to 500 and then recovered.

[IROCNOROLL]

OK...quick cheat #1. Take a propane torch and feather a little raw propane into the induction system while someone starts the engine. If the engine starts and you can control the rpm cycling by feathering the propane then you are either overcoming a fuel supply issue or covering a vacuum leak.
Remember that the O2 has no bearing on the cold start for at least 2 minutes after start, and the coolant has to pass 60deg F. So you are on the base start program until the engine has run long enough to get the temp up and the O2 warmed up as well. If the engine will start and you can hold it over 2000 rpm with no surge, then suspect a vac leak. Once you pull the throttle open that far, you have made your own vacuum leak that is bigger than the actual leak is and start your search for the leak.
If it starts and is controllable with the propane, then check fuel delivery pressure and volume.
If the fuel pressure is in spec and the volume is at least 20 oz in 15 sec or less then you have a big vacuum leak somewhere. Try putting shots of propane around different areas of the induction system to see where the vac leak might be. Don't forget you have vac operated heater controls on a lot of these cars, as well as a vac line going into the factory boost gauge. A bad diaphragm on the heater box, or a leak in the control assy is also a vac leak to the intake.

Easiest way to do the volume test is to set up a measured bottle on the supply line to the rail and the jump the ASD relay. When you turn the key on the run position, the pump will run and should push the fuel. Time the volume delivery and see what you have.

[fiater]

thanks all. Just wrote a longass post but it didn't take on submit. I'll rewrite tomorrow, but seems like there's a very wierd fuel pressure issue.

I did run quick propane over stuff when it would run, and no change that I could detect.