Plenum Electrical Help Please
Thread Starter
Race Director
Joined: Jun 1999
Posts: 14,924
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From: Merritt Ils Fl
Plenum Electrical Help Please
Cut to the chase: Bought vetmeds 91, had what turned out to be a nonexistant starter issue which did entail pulling the plenum. Had an uncontroble high idle ever since, suspected vacuum leak. Pulled the plenum yesterday, replaced any and all old,hard or cracked vacuum lines. Replacing the plenum with new gaskets I end up with a two pin male connector with tan/black wires for which I can find no home. Using the Electrical Supplement to the FSM I can identify the green/black oil temp circuit and the yellow/black coolant temp circuit. The only tan/black circuit is IAT but it is properly connected on the right side.by the IAC. My mystery connector is on the left side under the plenum. Can anyone give me a clue what this thing is and where it goes?
Team Owner
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There's 2 sensors at the front of the LH injector housing. Both are coolant temp. One for gauge and one for ECT to ECM. I believe that's what you've overlooked. I'll check an FSM in a while but that's what it sounds like! It would be the ECT - the gauge is a single. You seem to mention that you have them covered though!
Forward most section of the IH.
Forward most section of the IH.
Last edited by WVZR-1; Jan 21, 2013 at 11:51 PM.
Team Owner
Joined: Sep 2003
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The other thing that some eliminate is the canister purge system which would have a connector under plenum.
Is there a purge solenoid under there and a secondary port solenoid:
Is this hardware all still under the plenum, the pump of course would be up front in the vicinity of the RH headlamp but mounted low down by bumper impact bar:
Last edited by WVZR-1; Jan 22, 2013 at 12:24 AM.
Thread Starter
Race Director
Joined: Jun 1999
Posts: 14,924
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From: Merritt Ils Fl
Well this is interesting:
There is no vacuum canister.
No canister purge system.
None of the devices in your thied picture are present.
The drivers side plenum vacuum(pic #3) is capped, no vacuum lines.
Obviously I am an LT5 n00b and am tiptoeing my way through all this.
Can you Dick and Jane me through what the absence of these components mean. I absolutely love the machine and am not interested in addind or subtracting pieces and parts. All I want is a correct idle.
There is no vacuum canister.
No canister purge system.
None of the devices in your thied picture are present.
The drivers side plenum vacuum(pic #3) is capped, no vacuum lines.
Obviously I am an LT5 n00b and am tiptoeing my way through all this.
Can you Dick and Jane me through what the absence of these components mean. I absolutely love the machine and am not interested in addind or subtracting pieces and parts. All I want is a correct idle.
Tech Contributor
Joined: Aug 2006
Posts: 9,933
Likes: 103
From: Peoria Arizona.. Resident Gold Cylon
Well this is interesting:
There is no vacuum canister.
No canister purge system.
None of the devices in your thied picture are present.
The drivers side plenum vacuum(pic #3) is capped, no vacuum lines.
Obviously I am an LT5 n00b and am tiptoeing my way through all this.
Can you Dick and Jane me through what the absence of these components mean. I absolutely love the machine and am not interested in addind or subtracting pieces and parts. All I want is a correct idle.
There is no vacuum canister.
No canister purge system.
None of the devices in your thied picture are present.
The drivers side plenum vacuum(pic #3) is capped, no vacuum lines.
Obviously I am an LT5 n00b and am tiptoeing my way through all this.
Can you Dick and Jane me through what the absence of these components mean. I absolutely love the machine and am not interested in addind or subtracting pieces and parts. All I want is a correct idle.
Last edited by Goldcylon; Jan 22, 2013 at 11:31 AM.
Team Owner
Joined: Sep 2003
Posts: 25,413
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I'm going to guess you didn't put it back together until you resolved the connector issue and I thought the images might help. I thought he may have eliminated but I didn't know and images are what is it 999 words, pictures are 1000 LOL.
I'd say tidy it up, button it up check the MAP at the extreme rear center underneath 1 single very short hose and see what you've got. Then I guess I would start at the booster and work towards the engine, the check valve etc.
Enjoy - your not a plenum noob that's for sure!!
I'd say tidy it up, button it up check the MAP at the extreme rear center underneath 1 single very short hose and see what you've got. Then I guess I would start at the booster and work towards the engine, the check valve etc.
Enjoy - your not a plenum noob that's for sure!!
Thread Starter
Race Director
Joined: Jun 1999
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From: Merritt Ils Fl
Thanks guys. No didn't button it up, hate to do anything twice. I went over every piece of vacuum hose and O ring. Replaced all I felt were suspect and put clamps on all.Will button it up this afternoon. As a side note The 8 corners of the plenum were bent downward as much as 1/16 of an inch. Know for sure vetmed would not do this, suspect my trusted mechanic. Stoned them all flat and checked with a straight edge and flashlight. With new gaskets it has gotta be better.
Thanks again.
Muffin
Thanks again.
Muffin
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Le Mans Master
Joined: Oct 2004
Posts: 6,314
Likes: 508
From: South-central Missouri
Thanks guys. No didn't button it up, hate to do anything twice. I went over every piece of vacuum hose and O ring. Replaced all I felt were suspect and put clamps on all.Will button it up this afternoon. As a side note The 8 corners of the plenum were bent downward as much as 1/16 of an inch. Know for sure vetmed would not do this, suspect my trusted mechanic. Stoned them all flat and checked with a straight edge and flashlight. With new gaskets it has gotta be better.
Thanks again.
Muffin
Thanks again.
Muffin
As for the torque spec, I believe it is about 19 ft# for the plenum. No way will that little bit of torque bend the ears of the plenum. So, if they were bent, my guess is the screws were driven in with an air impact wrench! And, if true, it is a wonder the threads were not stripped out
BTW, long as you have the plenum off, NOW might be the time to clean up the copper ring connection in the starter solenoid, if you haven't already done so. The copper ring is slammed against the two internal connection posts to complete the circuit to the starter armature.
Over time (at about 35k miles +) the ring becomes pitted and the contact posts need to be changed. A little elbow grease and emory cloth will fix up the copper ring, good as new. And, if the high-current contact posts need to be replaced, I saw them on ebay for about a whopping $6.00 for a pair of them.
Apologies for veering off topic, a little.
P.
Safety Car
Joined: Aug 2008
Posts: 4,344
Likes: 48
From: San Marcos CA
I would guess the gas tank purge solenoid and associated hard vacuum line- the one that goes to the plenum has a big circular loop for stiffness and goes to one side of the solenoid. The car won't idle below 1200 rpm when that one pops off.
Also, you might want to block the air horn with a hard cover book or very thick piece of cardboard. This should stall the engine, but if not, will make the vacuum leak a little louder and easier to find with carb spray or some other form of enrichment gas like propane.
Also, you might want to block the air horn with a hard cover book or very thick piece of cardboard. This should stall the engine, but if not, will make the vacuum leak a little louder and easier to find with carb spray or some other form of enrichment gas like propane.
Le Mans Master
Joined: Aug 2005
Posts: 7,392
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From: Merritt Island, FL
Secondary system plumbing has been eliminated on that car.
purge solenoid is still present and functional, was replaced with new solenoid when charcoal canister failed and blew charcoal pellets into the old solenoid. Solenoid connector is red plastic body, if I recall correctly.
2-wire connectors could only be the coolant temp, AC compressor clutch, purge, and vacuum solenoid for secondaries <--- this would be unplugged since that solenoid has been deleted.
purge solenoid is still present and functional, was replaced with new solenoid when charcoal canister failed and blew charcoal pellets into the old solenoid. Solenoid connector is red plastic body, if I recall correctly.
2-wire connectors could only be the coolant temp, AC compressor clutch, purge, and vacuum solenoid for secondaries <--- this would be unplugged since that solenoid has been deleted.
Thread Starter
Race Director
Joined: Jun 1999
Posts: 14,924
Likes: 9
From: Merritt Ils Fl
Don't really know. Every hose that even looked like it may be bad was changed and clamps placed on all. That and correcting the bent plenum ears fixed whatever was wrong.If I had to select a single fault I would pick the gas tank purge line. I think it was off its outlet from the plenum.