Where do I connect Tach - Page 3
Cadillac
 

Cadillac Forums | Help Us Help You | Advertise | Cadillac Parts | Cadillac News | Cadillac Classifieds / (Old System)

Cadillac Technical Archive | Cadillac Dealers | Cadillac Reviews | Cadillac Dealer Reviews | Cadillac Vendors

CadillacForums.com is the premier Cadillac Forum on the internet. Registered Users do not see the above ads.
+ Reply to Thread
Page 3 of 3 FirstFirst 1 2 3
Results 31 to 42 of 42
HT4100 4.1, 4.5, 4.9 Discussion, Where do I connect Tach in Cadillac Engine Technical Discussion; Repeated the process this afternoon, except this time not using a jumper harness and the green test connector by the ...
  1. #31
    83CADMAN's Avatar
    83CADMAN is offline Cadillac Owners Fanatic
    Automobile(s): 83 Eldorado, 90 Seville, 94 Concours
    Join Date
    Jun 2009
    Location
    Pacific Northwest
    Age
    59
    Posts
    449

    Re: Where do I connect Tach

    Repeated the process this afternoon, except this time not using a jumper harness and the green test connector by the distributor disconnected...
    I cant get that damn plunger to retract!!!!
    Still no codes. Sooooo Close. What am I doing wrong??? Do I need to unplug the TPS before manualy performing the ISC plunger retraction?

  2. #32
    carnut is offline Cadillac Owners Master
    Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
    Join Date
    Feb 2003
    Location
    california
    Age
    66
    Posts
    5,710

    Re: Where do I connect Tach

    No, are you lifting up on the throttle with one hand while depressing the plunger with the other? Thats the proper way. If you dont open the throttle slightly the isc will not retract.

  3. #33
    83CADMAN's Avatar
    83CADMAN is offline Cadillac Owners Fanatic
    Automobile(s): 83 Eldorado, 90 Seville, 94 Concours
    Join Date
    Jun 2009
    Location
    Pacific Northwest
    Age
    59
    Posts
    449

    Re: Where do I connect Tach

    The last time I tried that approch, Still couldnt get it to move.

  4. #34
    drewsdeville's Avatar
    drewsdeville is offline Cadillac Owners Master
    Automobile(s): none
    Join Date
    Oct 2004
    Location
    WI
    Posts
    5,281

    Re: Where do I connect Tach

    Quote Originally Posted by 83CADMAN View Post
    The last time I tried that approch, Still couldnt get it to move.
    Then the "closed throttle" switch inside the ISC is dirty/broken. This also explains the high idle.

  5. #35
    83CADMAN's Avatar
    83CADMAN is offline Cadillac Owners Fanatic
    Automobile(s): 83 Eldorado, 90 Seville, 94 Concours
    Join Date
    Jun 2009
    Location
    Pacific Northwest
    Age
    59
    Posts
    449

    Re: Where do I connect Tach

    Quote Originally Posted by drewsdeville View Post
    Then the "closed throttle" switch inside the ISC is dirty/broken. This also explains the high idle.
    That explains why the plunger would'nt retract. The jumper wire method must bypass the "closed throttle switch" and just runs the motor backwards. The fact that I went thru 2 junkyard units and both were bad is not surprising, and at $3.00 each I’ll go back again. Price new at NAPA, $130.00. They also list a plunger repair kit for $30.00. I think I’ll tear into one and see what’s what.
    What a relief, everything else is OK then. I wonder how many of these cars wind up in the bone yard because of a bad ISC. I’ve been looking and I see a lot of new parts on some, but the ISC’s all appear rather dated.
    I'll get the ISC repaired and post results. Thanks

  6. #36
    83CADMAN's Avatar
    83CADMAN is offline Cadillac Owners Fanatic
    Automobile(s): 83 Eldorado, 90 Seville, 94 Concours
    Join Date
    Jun 2009
    Location
    Pacific Northwest
    Age
    59
    Posts
    449

    Re: Where do I connect Tach

    I disassembled the original ISC I had previously removed. I found no mechanical issues within the ISC, ie: broken gear, burnt/corroded contacts etc. Running a continuity test indicated the switch contacts were OK and that the switch functioned properly.
    I repeated the test on the junkyard ISC and it also tested OK.
    The repair kit I found consist of just the plunger shaft w/ gear and rubber boot.

  7. #37
    83CADMAN's Avatar
    83CADMAN is offline Cadillac Owners Fanatic
    Automobile(s): 83 Eldorado, 90 Seville, 94 Concours
    Join Date
    Jun 2009
    Location
    Pacific Northwest
    Age
    59
    Posts
    449

    Re: Where do I connect Tach

    What if…

    Either the “Manifold Air Temperature Sensor (MAT)”
    Or the “Coolant Temperature Sensor (CTS)”…

    Are weak and the ECM is responding to cold start, hence the fast idle. If the ISC were receiving cold start data, wouldn’t it want to extend and hold the ISC plunger at fast idle?
    Maybe that’s why I couldn’t get it to retract?
    I think the OBD would display a code if the circuit or sensor failed, but what about a weak sensor condition. Wrong temp data to the ECM right.
    The TPS “0 volt” setting can be set either hot or cold, as long as the throttle lever is not impeded and allowed to close completely.

  8. #38
    83CADMAN's Avatar
    83CADMAN is offline Cadillac Owners Fanatic
    Automobile(s): 83 Eldorado, 90 Seville, 94 Concours
    Join Date
    Jun 2009
    Location
    Pacific Northwest
    Age
    59
    Posts
    449

    Re: Where do I connect Tach

    Quote Originally Posted by 83CADMAN View Post
    I disassembled the original ISC I had previously removed. I found no mechanical issues within the ISC, ie: broken gear, burnt/corroded contacts etc. Running a continuity test indicated the switch contacts were OK and that the switch functioned properly.
    I repeated the test on the junkyard ISC and it also tested OK.
    The repair kit I found consist of just the plunger shaft w/ gear and rubber boot.
    I snaped a couple of pictures of the disassembled ISC If any one is intrested.

  9. #39
    83CADMAN's Avatar
    83CADMAN is offline Cadillac Owners Fanatic
    Automobile(s): 83 Eldorado, 90 Seville, 94 Concours
    Join Date
    Jun 2009
    Location
    Pacific Northwest
    Age
    59
    Posts
    449

    Re: Where do I connect Tach

    I took the multi-meter to the temp sensors today after I reassembled and installed the original ISC unit. Cold they tested OK, so I figured in order to get the maximum reading out of the manifold air temp I should install the air cleaner, connect all the hoses including the heat riser.
    Started up and ran it for about five min or so then shut it down. I pulled the air cleaner to get at the sensors, and they tested OK…..WTF?
    Well I hooked up the tach, and multi-meter to the TPS and fired it up again while it was still hot.
    Guess what? This time when I tried to press the ISC plunger IT MOVED!!!!!!!HOT DAMN!!!!!!
    WAS IT THE AIR TEMP ALL ALONG THAT WAS KEEPING IT IN CLOSED LOOP?
    In my previous attempts I had removed the air cleaner prior to warm-up, I merely felt the top radiator hose, when it was hot so I knew the thermostat had opened.

  10. #40
    carnut is offline Cadillac Owners Master
    Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
    Join Date
    Feb 2003
    Location
    california
    Age
    66
    Posts
    5,710

    Re: Where do I connect Tach

    You mean open loop (prior to oxy sensor being activated) You could be right about the air cleaner, I've always waited till engine temp was about 90 cel. before I removed the filter assembly. SO------- Is it fixed?

  11. #41
    83CADMAN's Avatar
    83CADMAN is offline Cadillac Owners Fanatic
    Automobile(s): 83 Eldorado, 90 Seville, 94 Concours
    Join Date
    Jun 2009
    Location
    Pacific Northwest
    Age
    59
    Posts
    449

    Re: Where do I connect Tach

    Wild huh. Every procedure I read involving warm-up noted removal of air cleaner prior.?
    Well it worked; I was able to get the ISC retracted and the TPS adjusted. Idles smooth now. I am experiencing a chugging effect upon acceleration through. I’m thinking weak coil pack maybe.
    Taking a little break from it right now. I need to replace a rear air strut on my 91 Seville, going to do the front brake pads while I’m at it. So I got to move the Eldo out of the shop to make room.

  12. #42
    83CADMAN's Avatar
    83CADMAN is offline Cadillac Owners Fanatic
    Automobile(s): 83 Eldorado, 90 Seville, 94 Concours
    Join Date
    Jun 2009
    Location
    Pacific Northwest
    Age
    59
    Posts
    449

    Re: Where do I connect Tach

    I was able to replace the coil before I had to move the car out of the shop. No difference. I also changed out the EGR valve. I think next I’ll go through the spark plugs again and check the cable routing.

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.
If you do not want to register, fill this field only and the name will be used as user name for your post.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Bookmarks

Cadillac Posting Rules

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
Read about Lincoln | Buick | Kia Forte Forum
Need products for your Cadillac? Check out your options at the links below:

custom floor mats | Cadillac Chrome and Black Chrome Wheels | window tinting