When you had everything apart, did you renew all the vac lines under the passenger's manifold?

I also suggest just buying a new CTS. They're only $20. If no difference, then you've got a spare for when it DOES die.

Did you replace the plug wires yet? That could be an issue.

I dunno...I know you've already replaced it but I'm leaning towards ECU.

 

The coolant sensor resistances are normal for cold and operating temp. Did you verify the readings at the ECU or just the sensor?

The 15" of vacuum was it steady?

Well when the engine is at operating temp the O2 sensors should go into closed loop. Did you measure the O2 sensor volts?

If you unplug the TPS you can rule that out too.

Warm up the engine let it die. Then remove a spark plug. Is it wet?

Here is a list of possible causes based on your symptom description. I listed the test(s) to verify and rule out the items.

Firing order- verify

Timing- TDC check and set with van gauge

Rotor- close inspection for burn through to shaft

Cap- carbon tracking

O2 sensors- when at temp the voltage should fluctuate between .1v(lean) and .9v(rich)
if it is running real rich but reads .1v that can be a problem

Low compression- compression test

Valve timing-remove cam covers and check camshaft timing per manual

Plugged/restricted exhaust- rev the engine to 3000 rpm and watch vacuum gauge it should stay steady, not drop

Coolant temp sensor-verify readings at sensor and ECU connector, pin 5 and 19

Wiring - use DVOM to verify every wire between ECU connector and input/output

enrichment pot on ECU- center the adjustment pot

injector wiring- is the correct group of 3 firing at the right time

Fuel pressure - connect fuel gauge to inlet hose while car is running or fuel pump is running

ECU- substitute known good ECU

TPS - verify voltage set correctly at idle and recheck at ECU connector with ECU plugged in

Ignition module- cool off with freeze spray or cold water

Engine ground - use jumper cable to add redundant ground as a test


This is all I can think of. If I have more I will add to it.

 

Firing order- verified

Timing- checked

Rotor- closely inspected

Cap- checked

O2 sensors- ~.7v

Low compression- not checked

Valve timing- not checked

Plugged/restricted exhaust- good flow... really REALLY loud.

Coolant temp sensor- verified at sensor, not at ECU

Wiring - not checked.

enrichment pot on ECU- centerered

injector wiring- pulses are correct.

Fuel pressure - not checked.

ECU- this is my 3rd one... so it just can't be the ECU.

TPS - .38v at idle. 3.98v at WOT. steady increase across the board.

Ignition module- not getting hot.

Engine ground - good ground from passenger manifold to chassis.

 

As far as I know, at tickover the vacuum in the intake manifold should be a very high value. Therefore, if the ECU is connected and the vac is low, there is a leak. Either a leak between the engine crossover pipe vac take-off and the ECU; or a leak into the manifolds.

This must be worth investigating.

1. If you disconnect the vac take-off from the crossover pipe, and pull a vacuum at the ECU end of the pipe, does it hold?
2. Go carefully round both intake manifolds and block off every single pipe except the vac advance pipe.

Then see what happens. By the way, if you disabled the AAV, what did you do about blocking the entry into the rear of the B bank airbox and the other air connections there? I tell you this, when it does run properly, I'll fax you a drink!

Greg

 

it holds vacuum nicely.

and i blocked it with a coolant bottle cap. lol

 

To clarify, was it the AAV tube at the backside of the left air filter housing that you blocked off with a coolant bottle cap?

Is the elbow to the rear of the intake manifold still in place? Is the hose to the distributor vent still in place?

If the answers to all these questions is "yes" you'll want to disconnect the distributor vent hose from the AAV hose...or you'll end up with a distributor cap full of engine oil!

Cheers
DD

 

my distributor cap hoses are already disconnected. thanks to the previous owners engineering prowess. the elbow from the AAV to the manifold disitigrated in my hand, so i blocked the manifold with the only thing i had. a coolant bottle cap. i was planning on either replacing the hose to the AAV or bypassing it alltogether and having it plugged professionally.

 

Ok, good. I found out the hard way about the oil-in-the-distributor thing :-)


Cheers
DD