It's an 88T2
- I've checked for codes - none
- all new vac lines and gaskets, double checked all vac lines, know them intimently

After the cold start assist cam finishes (car is warming), it will begin to idle like my old lawnmower at like 150 - 200 rpm, real low. Then if I give it 70% throttle it will pause, then rev up and I can hold it anywhere above 2k and it sounds fine, but if I let it go below 2k it will bog out and idle at 150rpm, barely alive.

I've been checking voltages @CPU and haven't seen anything out of the ordinary.
again no codes, new plugs, cleaned inj., good battery, set tps, initial set coupler... etc.

Some suggestions please and thank-you

 

vac leak

what is the vacumn (in inches preferably) when it is idling so low(and its probably not really 150 rpm... the starter cranks it faster than 150 rpm).

 

OK can I check vacumn at the nipple which controls the factory BOV?

 

Have you checked and adjusted the mechanical idle peer the FSM yet?

 

I think so. I've started it with initial set coupler, but adjusting the idle on BAC doesn't help.

 

check your TID..might be there..most likely in that area...I take it that this just happened form one day to the next

 

I had everthing off down to the block over the winter, and then re-assembled with all new gaskets and vac hoses.

I initially took it apart to fix a vac leak,

TID is like 2 yrs old. I will check it thanks.

 

then you have an easy fix..go back and check your work..might have forgotten a hose...just hope you did a good job getting the old gaskets off

 

Well, the only gasket I can't really check is the one between the LIM and the block. Everything else has checked out, including vac hoses.

I was thinking it could be a problem with the BAC, is this likely you think?

 

Real low idle there. Usually if you pull the bac's plug off OR install the initial set coupler the idle will drop a touch due to the bac not helping with the idle. On your car, idling at 100-200 rpm, you'd think the engine would die if you removed the bac plug.

Remove the two screws holding the bac on. Turn the key to ON. Touch the bac's innner piston to see if it's vibrating. No vibration. No good bac OR and most probable a bad transistor in the ECU. R square the transistor.

But when you get right down to it, the idle should be set with the bac out of the picture. That's why the fsm installs the initial set coupler..to disable the bac. THEN the idle is set to approx 750. That's hard to do if the bac screw has no effect. Odd that. Pull the bac and see if the passage is open/closed that the screw opens/closes.

You might try what Wayne suggests. Remove the throttle body and see if the throttle plates are set per the fsm. There's a fast idle cam/screw involved with that. As a temp fix you might turn the throttle stop screw a touch to make the throttle plates open a crack to get the idle up to around 750. Idle stop screw being about a quarter inch long with a 8mm wrench size nut (jamnut) holding it in place.

The turbo inlet duct is a good idea to look at first. I had one once that had a crack at the end that mates with the turbo. A common problem. It cracks just under the clamp. Hard to see without removing the duct.

Smooth low idle????? Maybe the timing is set too retarded? Use a timing light to set the timing spot on.

 

Interesting....
HAILERS / Wayne are you guys saying the throttle plates should be cracked open slightly AFTER the car is warm?
I thought the fast idle cam was out of the picture once the car is warm and the plates are fully closed, leaving the BAC to provide air to the motor.

 

did you put new spark plugs?

 

Yes new spark plugs