Using my new scan tool the ac pressure (line 02) is at 69 lbs with the air off. Is this normal? Can't find this in the FSM. Probably is in there but I have spent a great deal of time searching with no luck. The system was recharged with r134 at some point before I owned the car. Pressure is normal when running, 175-200 lbs. AC works fine but I have been chasing a High Idle issue for weeks now and have eliminated every other possibility other than a bad Throttle Body.
Air conditioning pressure
- Thread starter tmkassin
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93Rubie
Well-known member
Was it about 69 degress when you took this reading? IF it was then yes, that is normal pressure, when the A/C is off the pressures between the high and low sides equalizes and normally that pressure is about equal to ambient temperature.
- Thread starter
- #3
Yes it was. Thank you.
boomdriver
Well-known member
I'm curious, what or how would the throttle body be bad?
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- #5
Vacuum leak at the butterfly shaft. I'm running out of possibilities. When its cold it idles at 1200-1500 rpm. When it's warmed up as I come to a stop it idles at about 1000 rpm till completely stopped then it slowly drops down to about 700. Other than this issue it is running perfect.
G Winter
Well-known member
I have the same problem and am pretty sure it is my throttle body. I can only feel it lose with engine not running. With engine running vacuum is high enough that you can't move it.
Mine is bad enough now that the throttle plates hang open a bit. By bumping the throttle it slows some. Planning on redoing the throttle shaft bore.
Glenn
Mine is bad enough now that the throttle plates hang open a bit. By bumping the throttle it slows some. Planning on redoing the throttle shaft bore.
Glenn
Schrade
Well-known member
Good thinkin' - high idle / A/C relationship (except for TB, I think). A/C request gets read by ECM, and increases idle. Spec RPM increase should be in the FSM. OR, see if you can get user 'sun???' in the other vette forum. He's a wiz on A/C systems.
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- #8
Today I checked the throttle body shaft for play. When closed it seems solid. When open half way it wiggles about .020...not good. Should have checked it better when I cleaned it. New one, 52mm is on order.
boomdriver
Well-known member
That tells me that the idle issues is originating from somewhere else.
Having some slack in the shaft at half throttle is not bad...thats being forgotton as the rush of air thru the bores passes thru. Idle was forgotten about around 1mm of plate opening.
I'd take the IAC motor out and clean the idle ports in the Throttle body as well as the plenum. Those get very dirty and will keep the IAC pintle from seating properly against the seat, allowing air to pass when it should not. a weak or slow motor will do th same. IAC's should be changed every few decades or so. The 52mm is slightly different in operation and you will need a few things off the stock TB.
gmjunkie
Well-known member
Out of curiosity here,Have you Cleaned and Inspected All Grounds???
"I mean ALL of them too,not just the easy ones!":L:L:L
"I mean ALL of them too,not just the easy ones!":L:L:L
- Thread starter
- #11
Yea Junk, every one I can find. And I have the bloody knuckles it required too. 2 by the bell housing,one behind the battery and one from the air conditioning by the passenger inner fender. Do you know of any others?Out of curiosity here,Have you Cleaned and Inspected All Grounds???
"I mean ALL of them too,not just the easy ones!":L:L:L
boomdriver
Well-known member
should have been at least 4 on the bellhousing, one under battery tray, under blower motor, radiator shroud driver side, small strap driver side under brake booster area...another on/under oil temp sensor and I KNOW I'm over-looking a couple. They're everywhere and there are a bunch of them. Plastic car, computer control by grounds....yep, everywhere.
- Thread starter
- #13
OK I missed the one by the heater on the bell housing. Did get the 2 on the other side. How the he.. do you get to that one without pulling the motor?
boomdriver
Well-known member
well,
any way you can?
I know thats not what you wanted to hear!
This is one of those deals where they say "get them all" and you;re lucky to get most. Some are not even visable.
What CAN be done, is to ADD grounds. I added a cable from battery to block, and have another cable to run from block to a good frame section, when I get to it...But since upgrading my grounds I have MUCH better voltage, more stable lites, less drain, and everything just seems to work better. Like it did new.
any way you can?
I know thats not what you wanted to hear!
This is one of those deals where they say "get them all" and you;re lucky to get most. Some are not even visable.
What CAN be done, is to ADD grounds. I added a cable from battery to block, and have another cable to run from block to a good frame section, when I get to it...But since upgrading my grounds I have MUCH better voltage, more stable lites, less drain, and everything just seems to work better. Like it did new.
gmjunkie
Well-known member
LT1/LT4's are just a little different,But Not Much! Should be 1 in the front of engine around coil,Should be 2 behind the battery(Smaller wire from Battery Ground cable to chassis,Ground Strap Chassis to Bell housing (2nd Bolt Up Lt Side),along with 3-4 wires from engine harness!) Larger Ground from Battery to Engine Block just above Oil Filter along with a couple other wires from engine harness!Rt and Left Frame Rail just below Head Lamps and I believe there are 2 wires beside the LT of Radiator,And several inside and in the rear of the car,but they won't effect the ECM,they'll just make Tail Lights,Brake Lights,Turn Signals,Rear Defroster,Radio and Accessory's do Crazy Sh*t!!:L:L:L
gmjunkie
Well-known member
You can add all the ground cables you want from here to there,But if you don't Remove,Clean and Inspect every ground wire including the crimped end on the eyelet,"YOUR JUST P*SSING in the WIND"!!
When you least expect it,EXPECT IT!! I'm Baacckk!!!
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