I'm working on a GC that sat for about a year, northern car with substantial lower body rust, and a pesky rough idle I can't get to the bottom of. The current symptoms are:

Induction:
-19 in. idle vacuum at the plenum
-clean air path/TB/plenum
-MAP/TPS test good voltages
-new EGR/clean tube
-new upper(plenum) gasket

Fuel Delivery :
-48 psi at the rail, key on; 50 psi running
-injector terminals all show 12 ohms
-all injectors clicking(via stethoscope) with engine running
-all injectors click and squirt pressurized carb cleaner on the bench

Ignition:
-coil driver circuits pulsing at (new) coil pack connector
-new wires and plugs
-good battery/charging voltage

Additionally;
-swapped in new IAC (no help) due to weak or no idle up at A/C on
-new VSS (my book says it and TPS send PCM signals for IAC modulation)

The van is not setting any DTCs at this time. The engine doesn't stall, but drops to 450-500 RPM with A/C on in gear. With the vacuum I'm reading, I'm thinking I shouldn't have a vacuum leak (gasket et al) or exhaust obstruction (CAT or muffler fail).

Hope this isn't too much info for one post; any advice is greatly appreciated.

 

Compression?

 

Haven't checked that, yet. Shoulda/coulda/woulda when I had the plenum off doing the plugs. Any issue cranking for that rear bank with the plenum off ?

 

Uh-oh.

#2-175psi
#4-180
#6-180

#1- 52
#3-188
#5-190

I dumped 1/2 cup of oil into #1; after 3 sets of cranking (@5 revs ea), I only got a bump up to about 58 psi. I've never removed the head(s) on a 3.3/3.8 , anything to look out for ?

Thanks again for your advice.

 

Yup, that's an uh-oh. Can't help with the head pull. Never pulled these and the last head I removed was 15 years ago. There's plenty on this forum who have.

 

Kinda wondering if that might be a bad valve; not loosing any coolant. Oh well, I'll find out when the head comes off.

Thanks again.

 

CYLINDER HEAD
REMOVAL
Drain cooling system. Refer to COOLING SYSTEM for procedure.
Disconnect negative cable from battery.
Remove upper and lower intake manifolds. Refer to procedure in this section
WARNING: INTAKE MANIFOLD GASKET IS MADE OF VERY THIN METAL AND MAY CAUSE PERSONAL INJURY, HANDLE WITH CARE.

Disconnect coil wires, sending unit wire, heater hoses and bypass hose.
Remove PCV system hoses, evaporation control system hose and cylinder head covers.
Remove exhaust manifolds. Refer to procedure in this section.
Remove rocker arm and shaft assemblies. Remove push rods and mark positions to ensure installation in original locations.
Remove the nine head bolts from each cylinder head and remove cylinder heads Cylinder Head Bolts Location and Tightening Sequence
INSTALLATION
Clean all sealing surfaces of cylinder block and cylinder heads.
Install new gaskets on cylinder block Head Gasket Installation
The cylinder head bolts are torqued using the torque yield method, they should be examined BEFORE reuse. If the threads are necked down, the bolts should be replaced Checking Bolts for Stretching (Necking)
Necking can be checked by holding a scale or straight edge against the threads. If all the threads do not contact the scale the bolt should be replaced.
Tighten the cylinder head bolts 1 - 8 in the sequence shown in Cylinder Head Bolts Location and Tightening Sequence Using the 4 step torque turn method, tighten according to the following values:
Step 1: Bolts 1 - 8 to 61 N·m (45 ft. lbs.)
Step 2: Bolts 1 - 8 to 88 N·m (65 ft. lbs.)
Step 3: Bolts 1 - 8 (again) to 88 N·m (65 ft. lbs.)
Step 4: Bolts 1 - 8 turn an additional 1/4 Turn. (Do not use a torque wrench for this step.)
NOTE: Bolt torque after 1/4 turn should be over 122 N·m (90 ft. lbs.) If not, replace the bolt.

Tighten head bolt number 9 Cylinder Head Bolts Location and Tightening Sequence to 33 N·m (25 ft. lbs.) after head bolts 1 - 8 have been tighten to specifications.
Inspect push rods and replace worn or bent rods.
Install push rods, rocker arm and shaft assemblies with the stamped steel retainers in the four positions, tighten to 28 N·m (250 in. lbs.) Rocker Arm Shaft Retainers
Place new cylinder head cover gaskets in position and install cylinder head covers. Tighten to 12 N·m (105 in. lbs.)
Install exhaust manifolds and tighten bolts to 27 N·m (20 ft. lbs.) and nuts to 20 N·m (15 ft. lbs.)
Install upper and lower intake manifolds. Refer to procedure in this section.
Connect ignition cables, ignition coil connector, and sending unit connector.
Connect heater and coolant by-pass hose.
Fill cooling system. Refer to COOLING SYSTEM for procedure.
Connect negative cable to battery.

 

Thanks a lot for that, master. Is there a definitive way to diagnose between valve and gasket leakage before removal ? Mine went right to 52psi on the first compression stroke and never increased.

Much abliged.