3SGE 2ND GEN MANIFOLD VACUUM SPEC?

[straulf]

Hey guys, I'm trying to find out what my vacuum should be at idle within the manifold of my 3sge 2nd gen engine? She constantly idles high and smells like she is running lean, but I'm getting 19 in-hg at the manifold. And to my knowledge this is perfect indicating no engine air leaks.
So if that's the case, what could be cause my idle to be high ( engine hot and cold) and smelling like it running lean? Unless the measurement is meant to be higher?

Thanks guys...

P.S I've had one ECU burnt out because of this high idle issue so far... I've replaced the throttle body with the idle control valve, coolant temp sensor and new ECU. Checked all the common issues with wiring and earths with the complete wiring harness from engine and to ECU. I have no faults codes. She has plenty of power, no power loss. Runs absolutely perfect, apart from idling high, close to 1k.... I've visually inspected all the vacuum lines and check all solenoids within the engine, they are all 100%.

Next ideas are, MAP sensor possible? A/C idle up solenoid? oxygen sensor?

Anyone else experience this before maybe?

[Cruser]

The repair manual says at idle 17.7.
I don't think an air leak is likely to be the issue.
Nor do I think the issue had caused an ECU to fail unless something was back feeding into the idle speed control valve. But I would expect the idle speed to be higher like 1,500rpm and also very unlikely assuming things are standard.
Have you checked that there is good coolant flow to the idle speed control valve? Both hoses the same temperature and about the same as other hoses? Poor coolant flow could cause this.
Other possible is the idle speed control valve has carbon buildup and is sticking. I know you have replaced it but given the age it isn't impossible for two to be the same. The valve needs to he removed and dismantled to clean it. It won't come right without doing this, trust me I've tried short cutting it and it doesn't work!
The other possible is the wires from ecu to the valve. The repair manual says with the plug disconnected the idle speed should rise from 850 to 1,000 rpm. This higher rpm is what you have?
The middle terminal should have battery voltage. The outside two I'm trying to figure out as the manual doesn't say. I'm picking they will earth via the ecu depending on if idle speed needs to go up or down.
I can send you a picture of the pin outs and standard outputs if needed, just need to confirm which engine your running, that assuming you have a standard ECU of course.
Hope something in this helps and it makes sense, I've typed it on my phone!

[straulf]

Thank you very much for your reply, and DW because all of that makes total sense....

So I will be checking my coolant flow to the idle valve to see if both coolant hoses are nice and hot compared to each other once the thermostat has open up... I will take the valve out and clean it up as that could also be a possibility, and I will check the wire from the ECU to the idle valve to make sure they are OK..

So it would be great if you could give me exactly what pin comes from where and what I should expect? I would also like to do a continuity tests on all three wires too .... I know right, I'm not asking for much now ...

I do have a standard ECU along with a 3SGE engine 2nd gen .

Will hopefully get a chance this long weekend to do those tests

Also I'm guessing that is 17.7 in-hg of vacuum at idle when hot?

[Cruser]

Have PMed details. Hopefully the fault finding is or has gone well!!

[GDII]

Just as a note, vacuum levels change depending on altitude. Most of us live near sea level so the number should be pretty close.