Where do I connect Tach
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 1 of 3 1 2 3 LastLast
Results 1 to 15 of 42
HT4100 4.1, 4.5, 4.9 Discussion, Where do I connect Tach in Cadillac Engine Technical Discussion; Can any one help me? I need to adjust the RPM on a 83 ELDO HT4100 and dont know where ...
  1. #1
    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

    Where do I connect Tach

    Can any one help me? I need to adjust the RPM on a 83 ELDO HT4100 and dont know where to connect the tach lead.

  2. Remove Advertisements
    CadillacForums.com
    Advertisements
     

  3. #2
    the recluse is offline Cadillac Owners Connoisseur
    Automobile(s): 2002 STS, 1991 Eldorado
    Join Date
    Feb 2009
    Location
    Jacksonville, FL
    Posts
    1,016

    Re: Where do I connect Tach

    IF that is the standard HEI design cap. right on the cap itself is a clip spot marked "TACH". Hook there and find a ground...

  4. #3
    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

    Thanks Recluse, I found it.

  5. #4
    carnut is offline Cadillac Owners Master
    Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
    Join Date
    Feb 2003
    Location
    california
    Age
    67
    Posts
    5,736

    Re: Where do I connect Tach

    The RPM is set thru on board diagnostics and is NOT set by simply screwing in the ISC shaft. The minimum idle speed is set on the throttle body once the ISC has been fully retracted. If not done correctly you will end up with a check engine light on upon cold start potentially. Please understand this is not your fathers 57 Chevy!! Do a search for ISC and TPS adjustment procedures.

  6. #5
    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 carnut View Post
    The RPM is set thru on board diagnostics and is NOT set by simply screwing in the ISC shaft. The minimum idle speed is set on the throttle body once the ISC has been fully retracted. If not done correctly you will end up with a check engine light on upon cold start potentially. Please understand this is not your fathers 57 Chevy!! Do a search for ISC and TPS adjustment procedures.
    OK, I adjusted the ICS shaft back to the original setting when I started. The adjustment to the ICS I first made in a atempt to slow RPM, showed a 3 volt change at the TPS low reading. Using this difference I readjusted the ICS back.

    All producedures require the engine be at opp. temp. When first started the RPM is at 2200, and the ICS shaft starts slowly extending a little. The TPS readings remain at .5 volts. At this high RPM I'm afraid to let run for any length of time.
    My book says to use the sticker info. when adjusting.

    The under hood sticker says to "unplug green connector behind distributor, connect tach, loosen distributor, adjust timing to 800 RPM." The books also say use "10 deg. set w/ timing light."Any pointers?
    I do enjoy this car and the condition is excellant, but you are right, This is not my 57 chevy. (project in primer and ready for paint).

  7. #6
    carnut is offline Cadillac Owners Master
    Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
    Join Date
    Feb 2003
    Location
    california
    Age
    67
    Posts
    5,736

    Re: Where do I connect Tach

    Disconnect the green connector behind the distributor and with a timing light, set the static timing to 12 degrees not 10. 12 will make it run better. If its running at 2200 RPM on cold start the ISC is incorrectly set. Again, do a search on ISC, TPS adjustments. The ISC shaft must be retracted first to verify .060 gap between it and the throttle shaft. Then monitor the TPS. Once the ISC is retracted and the car is barely running, you should see a 0 (zero) reading on the on board diagnostics for TPS voltage. If its not zero then back off the TPS till it is. Then verify this ISC gap. Then reconnect the ISC wiring and restart the car A/C off. The ISC must be pressed on rather forcefully for it to retract, then QUICKLY remove its wiring harness to hold it retracted. If you dont quickly unplug the ISC it will damage the ECM.

  8. #7
    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

    OK 12 degrees, done.
    2200 RPM on cold start. YEP

    ISC huh! Been reading up on it, am more confused now.
    How do I access TPS voltage reading thru the OBD? How do I monitor the OBD climate control unit and adjust the TPS at the same time?
    Iíve been using a multi-tester to monitor TPS readings thru the harness connection near the alternator. Is this OK? I thought the low idle reading for the TPS is supposed to be .5 volts.

  9. #8
    carnut is offline Cadillac Owners Master
    Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
    Join Date
    Feb 2003
    Location
    california
    Age
    67
    Posts
    5,736

    Re: Where do I connect Tach

    I assume the 12 degrees was set with the green connector unplugged? You are monitoring the TPS correctly. The zero spec is at minimum idle( 400 to 450 RPM) ISC retracted and unplugged. 0.5 volts is the reading with ISC plugged in after the proper air gap has been set. You need the factory manual to access the read out on the climate control head. If the screws on the TPS are loosened but snug, you can tap on it with a screw driver handle then glance into the car to read the results. I've always done it with a friend behind the wheel. My experience is the TPS rarely needs adjusted. Most all ISC's are misadjusted because of years of tinkering. Just do the ISC retraction, then set gap. Turn off engine and reconnect the wiring to it. wait 30 seconds and restart the car and report back. AND after all that, I would recheck static timing once again to verify 12 degrees with green connector unplugged. Again, not your fathers 57 Chevy!

  10. #9
    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

    You assume correctly.

    I do not have a FSM, but I do have a couple of other manuals. The procedures defined in them are a little ambiguous regarding DFI-ICS adjustment.

    In one manual it advises:
    1. Ground the test connector near the alternator.
    2. Run engine to temp.
    3. Check/Adjust timing. (Refers to timing procedures)
    4. Remove air cleaner, plug vacuum hose.
    5. Retract ICS plunger.
    a. Disconnect connector at ICS (recommends using a jumper harness)
    b. Connect 12-volt supply jumper wire at terminal C.
    c. Jump terminal D to ground while manually depressing the ICS plunger completely, then immediately disconnect the ground lead. (Donít want to damage the ICS)
    d. Check throttle lever to ICS plunger screw adjuster clearance.
    6. Adjust the ICS plunger screw until 375-500 RPM is achieved.
    7. Disconnect test equipment and turn off ignition for 10 seconds.
    8. Turn engine on, check ICSís operation and check for codes. Perform diagnostics.
    9. Disconnect battery for 10 seconds to reset TPS value in the ECM.

    First question:
    1. Is the connector referred to in step 1 above, the TPS green test connector? Ground it? Wire colors are dk-blue and gray.
    2. I understand a warm engine for timing but does the engine have to be running while the ICS plunger is retracted? With it unplugged and all. (At 2200 RPM itís a little nervy, I donít want to damage the engine.
    3. By the way, what is considered redline for these engines?
    4. Do I fine adjust timing to under hood lable?


    The other manual recommends the following:
    1. Warm engine.
    2. Connect tach.
    3. Open the set timing connector. (Refers to timing procedures)
    4. Disconnect TPS.
    5. Turn off ignition for 10 seconds, check ICS plunger position (should be extended)
    6. Disconnect connector at ICS. Connect a jump wire between terminals A and B. (top two slots on ICS connector)
    7. Reconnect the TPS and start engine and adjust ICS plunger to 1500 RPM.
    8. Reconnect the ICS and adjust ICS plunger to 1500 RPM. If RPM fluctuates re-check TPS adjustment.
    9. Disconnect test equipment and reconnect the green ďSet timing connectorĒ. Turn off engine. Observe the ICS plunger operation (should be extending).
    10. This adjustment may kick a code in ďC3 systemĒ along with a check engine light. Thru the OBD clear the codes.
    11. Re-install air cleaner.

    More questions:
    1. Disconnect TPS? Step 4
    2. jump wire T-A to T-B? step 6
    3. 1500 RPM? Step 7
    4. Clear codes thru OBD? Step 10

    WTF! Which one to use? Any one have a 83 FSM and can check this out for me?

  11. #10
    carnut is offline Cadillac Owners Master
    Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
    Join Date
    Feb 2003
    Location
    california
    Age
    67
    Posts
    5,736

    Re: Where do I connect Tach

    I've owned 3 Cadillacs of this era and have NEVER seen these procedures?? I sold my 84 3 months ago but kept the FSM. I'll review it tonight. The red line? probably 5000 RPM. Keep in mind we are retracting the ISC plunger with a warm engine so the hi RPM should be less, not 2200, right? Simply press on the ISC shaft long and hard enough to feel it sink away and retract or bottom out.( engine running) Then quickly disconnect its wiring ( or it will short out the ECM not the ISC ) At that point the engine should barely run, 400 to 450 RPM. get a feeler gauge and set .060 gap to throttle lever. Shut off engine. Count to 10. Reconnect ISC wiring. restart engine and allow 20 to 30 seconds for it to stabilize. A/C off. Then set the climate control to 70 degrees in AUTO mode. Watch the ISC, you should see it extend a half second before the A/C clutch engages, then retract the second the clutch disengages. Erase all codes if one has set. This car did not require a learning procedure for the TPS as later early 90's Cads did. I've never disconnected the TPS or grounded any leads on my cars nor was instructed to do so in the factory manual. The OBD display can be set to be a tach but short the last digit. It will show 65 for 650 RPM ETC. I've never connected a tach to my HEI because of this.

  12. #11
    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

    Maaan I sure appreciate the help.
    Procedures? Let’s just say C and H has been providing the how to’s.
    Isn’t the 84 is almost the same as the 83?
    So lets see if I get this right;
    With tach. connected, air cleaner off and vacuum line plugged, Green set timing test connector connected, TPS connected, (no jumper wires at the ICS), run engine 5 min to warm up.
    With engine running press the ICS plunger until it seats then quickly unplug the ICS.
    Use a feeler gauge and adjust the ICS plunger so there is a .060 clearance to throttle lever.
    Shut off engine allow 10 seconds to pass then reconnect the ICS.
    Restart and run engine with the A/C off for 20 –30 seconds, then set climate control to AUTO and temp to 70 deg.
    Observe ICS operation.
    Clear codes thru OBD.

    Hmmm, Not so complicated.
    I'm sure looking forward to driving this car.

  13. #12
    carnut is offline Cadillac Owners Master
    Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
    Join Date
    Feb 2003
    Location
    california
    Age
    67
    Posts
    5,736

    Re: Where do I connect Tach

    GREAT SCOTT, I THINK HE"S GOT IT!!! I just move the air cleaner to the passenger side leaving the one vacuum hose connected. And yes the 83 and 84 are virtually identical. And if the minimum idle screw is at spec, 400 to 450 RPM I dont even hook up a tach. When you're done it should idle in gear at 625 to 650 A/C on or off and the static timing should be 12 degrees.

  14. #13
    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 carnut View Post
    Simply press on the ISC shaft long and hard enough to feel it sink away and retract or bottom out.( engine running) Then quickly disconnect its wiring ( or it will short out the ECM not the ISC ).
    Thanks for the information carnut but try as I might, I could not get the ICS plunger to retract. I trolled my local U-PULL-IT yard and found an 84 someone had thrown a lot of new parts at. I pulled the cap/rotor, wires (new), temp sensor, TPS, EGR (new) and a ICS along with a good length of their respective wiring harness. I changed out the ICS and tried again with same results. I just could not get the ICS plunger to retract. I used the electrical connector and wires scored from the donor car and tried jumper wire approach at the bench, still unable to retract the plungers.
    The RPM did settle down a bit, 1500, and after clearing the codes I took it for a test drive to check for any new codes. No codes! Did seem to have a little more pep and wanted to stall when first shifting into drive or reverse. Also after it was good and warmed up it was sort of sluggish on acceleration.
    Back in the shop while it was hot, I pulled the EGR hose and there was no vacuum. OK, I replaced the hoses some time ago and I may have gotten it wrong at the control unit. Also there is an extra port on the control unit and no hose that I can find for it, (note it was sucking air at the extra port).
    I looked at the junk car for guidance but my 83ís EGR control unit is different in having that extra port. Now I may have gotten the EGR hose connected to the wrong port but whatís up with this extra port! See attached photo. I currently have the top hose routed to the EGR, the one below it is a jumper to the lower half of the valve. You can clearly see the open port. If I swap the EGR hose I will still have an extra tap.
    Not seen is the hose from the lower part of the control unit to a tee fitting connecting it to the vacuum tap and the purge valve at the charcoal canister. Could this be causing The RPM problem? When I plugged the extra port there was no noticeable change in RPM.
    Itís not my fathers 57 Chev.
    Attached Images

  15. #14
    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
    whatís up with this extra port! See attached photo. I currently have the top hose routed to the EGR, the one below it is a jumper to the lower half of the valve. You can clearly see the open port..
    PHOTO 1:
    Another view of the EGR solenoid and regulator. The Regulator below has the open tap in question and a hose on the oppisite side, (toward the rear of car), connecting to the manifold tap. A jumper hose connects regulator to the soleniod. The top hose routes to the EGR.
    PHOTO 2: There are two taps on the oppisite side of the solenoid, (toward the rear of car), the lower one has a small foam filter with the upper one open.
    Does anyone know excactly how this thing hooks up?

  16. #15
    ehall's Avatar
    ehall is offline Cadillac Owners Connoisseur
    Automobile(s): 1985 Sedan DeVille
    Join Date
    Aug 2007
    Location
    Southern Maryland
    Posts
    1,487

    Re: Where do I connect Tach

    The open port on the solenoid is a blow-off port. The solenoid passes vacuum to the valve when open, and needs to eliminate vacuum when closed or else the valve will use the captive vacuum and stay open. The open port allows the solenoid to discharge vacuum from the valve. It needs to stay open.

    You really need to get an FSM. There is a huge amount of information in there about these systems

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