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HT4100 4.1, 4.5, 4.9 Discussion, Where do I connect Tach in Cadillac Engine Technical Discussion; Thanks ehall. I understand that, but isn’t that blow-off port you speak of provided by the tap with the small ...
  1. #16
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    Re: Where do I connect Tach

    Thanks ehall. I understand that, but isn’t that blow-off port you speak of provided by the tap with the small foam filter on the solenoid? (see post 14, photo 2) And what about the open tap above it with no filter? My guess is one is intake (filtered) and the other one exhaust (not filtered).
    The open tap I question is one of three on the regulator (little round thing below the solenoid), vacuum must pass thru this regulator in order to get to the solenoid. I presume there is a spring and diaphragm in that little bastard that keeps vacuum to the solenoid at a constant value, so a bi-directional relief port behind the diaphragm makes sense, but should there be full vacuum at this pressure relief port on the regulator?
    Using a hand vacuum pump I am unable to get any readings across this device. Could the diaphragm be damaged? Result, no vacuum to the EGR solenoid or to the EGR valve for that mater. In that event I most certainly have the hoses connected correctly. Conformation would be nice.
    Ya I wish I had one of those FSM’s but I don’t. I’m asking anyone in caddy land that does for help. All I’m asking is how are the vacuum hoses suppose to connect to the EGR regulator and solenoid. All it would take is for someone to take a look underneath the hood of his or her 83 Caddy, maybe take a picture and post it for the world to see. Isn’t that what we are all here for? Help and be helped. I can get all the “could be this, or maybe its that, from my neighborhood shade tree armchair mechanics.
    This project started out chasing a really hard engine miss, so hard I thought it was my transmission. Someone on this forum recommended looking at the TPS and I did. All it accomplished was my RPM went up to 2200.
    While visiting the junkyard I was talking to a guy about it, (he was part scrounging also) He suggested I look at ignition. Boy was he right, what I found was a fried rotor and cap. Suprising it ran at all.
    Simple job I thought, cap, rotor and a set off plug wires. I think not! With TPS / ICS adjustments in the mix, althrough it should be, with help from you guys out there.
    I could have just gone to the shop and spent a couple hundred and be cruising right now! As it is I might have to do just that in regards to that f@#%*ing ICS.

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    Re: Where do I connect Tach

    A couple more shots of the EGR vacuum regulator. Which tap should the hose connect to? Are both taps suppose to deliver vacuum? There appears to be a small breather hole in the center of the round metal face.

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    Re: Where do I connect Tach

    your 83 is different from my 85 so I can't comment on what you've got

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    Re: Where do I connect Tach

    Here is a photo of an 84 doner car, as you can see the EGR regulator and solenoid are similar. I guess the 83 is unique. I don't see why it wouldn't work on my 83. Any thoughts?

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    Re: Where do I connect Tach

    Git er dun

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    Re: Where do I connect Tach

    CHAAA! I got the ISC retracted. I used a procedure outlined in ch**** manual. I scrounged a junkyard electrical plug and with the engine running, I unplugged the ISC and plugged in my jumper, which I had the wire from the “C” terminal connected to the positive battery post. (Look really close at the plug and you’ll see markings A, B, C & D)
    Touching the wire from terminal “D” to ground runs the ISC motor backwards thus retracting the plunger. Made adjustments to 0.6 and plugged in the ISC. Then I rechecked the TPS and readjusted. Its running smooth but the idle is still a little high at 1000 RPM. And stalls when put in gear. I rechecked time timing and it is a tad advanced. Starting to get tired, I'll take a stab at it tomarrow.

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    Re: Where do I connect Tach

    Quote Originally Posted by 83CADMAN View Post
    ...the idle is still a little high at 1000 RPM. And stalls when put in gear.
    Sounds like a vacuum leak

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    Re: Where do I connect Tach

    Timing would explain it--same thing happened with me after the intake gasket was replaced. If he knows it's a little far forward then that's just confirmation.

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    carnut is offline Cadillac Owners Master
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    Re: Where do I connect Tach

    SET THE GAP TO .060 THOUS NOT .6. Once retracted, verify the TPS is at zero, not .5 volts. What does it idle at when fully retracted? should be very low 400 to 450 RPM.

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    Re: Where do I connect Tach

    I haven’t been back to it yet, started to give me a headache. Man I need to replace valve cover gaskets, I tightened all the bolts but the passengers side is still seeping a little onto the exhaust manifold kicking a bit of smoke.
    The engine stalled at the low idle before I could read the RPM’s. I quickly adjusted the ISC plunger ISC gap to .060 (typo in previous post) as well as adjusting the TPS to 0 volts. I then removed my jumper, plugged back in the ISC and turned off the key. After 10-15 seconds I checked for and cleared any codes. When I turned the key on, the ISC plunger pulsed the throttle 3 or 4 times and then set with it extended slightly. When restarted the engine’s RPM was 2200 so I adjusted the plunger and got the RPM down to 1000. When I checked the timing, the mark was advanced beyond the degree tag. I adjusted the timing to 10 degrees and got it down to 800 RPM. I rechecked the TPS readings and it was at .29 volts so I adjusted to .5 volts. When I checked the timing again it was at 6 degrees, so I adjusted, checked the TPS again, .5v, (cool) RPM back up to 1000….Put it in gear and stall….this is where I tired / choked out!

    Vacuum leak huh. (see post #13, 14, 17, 19) could the EGR vacuum regulator be it?

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    Re: Where do I connect Tach

    deleted

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    Re: Where do I connect Tach

    Once you screwed in the ISC shaft to lower the idle from 2000 to 1000 RPM you lost the .060 gap. What gap if any, did you have before when you first retracted it? The zero TPS reading is measured with the ISC fully retracted and the throttle body min. idle screw is turned to get there. Was the 6 degrees timing showing with the green connector unplugged? The distributor cannt advance or retard if that is unplugged so I dont understand the different readings. You say the engine stalled once you retracted the ISC. Did you do all these adjustments with engine off then? If so, then they are not accurate. Frustrating not being there. You MUST have the engine continue to run at a very low RPM to set the ISC accuratly. The min. idle screw should probably be turned in a quarter turn prior to retracting the ISC. The most common vacuum leak on this car is the base gasket under the throttle body. I've not mentioned it before because ISC and TPS settings are the first items to confirm. And yes, a vacuum leak on a fuel injected engine will cause a faster idle whereas a vac. leak on a carbed engine will cause a rough unstable idle.

  13. #28
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    Re: Where do I connect Tach

    Fully retracted the gap was maybe ¼ inch with the adjuster screwed all the in. That’s when the engine stalled. With the key still on (engine stalled) ISC still fully retracted, a good ¼ inch of gap, the throttle lever closed at its limit, this is when I adjusted the TPS to 0 volts. I then screwed out the ISC adjuster to achieve the .060 gap, unplugged my jumper from the ISC and reconnected it. I then turned the key off. When restarted The ISC extended causing the throttle to rev.
    Yes the green connector was unplugged.
    I’ve been looking for any leaks, the throttle body was a little loose, tightened it, no change. Checked all hoses with hand pump. The vacuum regulator mounted under the solenoid that controls the EGR valve seams to have two feeder ports, one of which supplies the solenoid, the other sucks about 24 on vacuum gauge all the time.
    Well I just start over again and hope I get it right.
    Thanks

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    Re: Where do I connect Tach

    Spray some carb cleaner around the TB base, see if it affects the idle, stay away from the throttle shaft when spraying, they always leak just a little. Stalling when retracted tells me the min idle is too low. As I said above, turn that screw in slightly and recheck zero once it idles slowly, and reset the gap. Adjusting with key on, engine off will not be accurate. The EGR gets no vacuum at idle as you know so I doubt thats an issue. The ISC extending and retracting 3 or 4 times prior to restart tells me the TPS is off slightly. Normally as the key is rotated to start the ISC extends allowing a bit of air to be drawn in, then once started, it retracts to stabilize at about 650.

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    Re: Where do I connect Tach

    OK, I started it up this morning, after installing another ISC and plugging that nagging EGR vacuum regulator port, like I’ve stated before it was a constant vacuum loss.
    So…
    With Green connector connected (near distributor),
    Tach connected to distributor,
    Air cleaner removed and vacuum hose plugged,
    Multi-tester connected to green TPS test connector near the alternator (pos lead to blue & neg lead to gray)…
    I let it idle until the top radiator hose was warm, (RPM held at 1500 from start and TPS reading was .5).
    I tried to push the ISC plunger and couldn’t budge it….
    Well I unplugged it and plugged in my jumper harness, (T-C to power source).
    Touching jumper wire from T-D to ground just enough to retract the ISC plunger.
    The RPM settled down to about 450-500 when the plunger fully retracted.
    Next I adjusted the TPS to 0 volts and the ISC adjuster to .060 gap….
    The engine was running very smoothly throughout…
    So with everything adjusted, the engine still idling, and the ISC still unplugged…
    I turned off the key, plugged in the ISC ( 10 seconds or more) and turned the key back on. Cleared codes, turned the key off again for 10 seconds, then restarted the engine.
    Roar! 2500 RPM Holysh**!! Shut er down!!!
    Again with that damn ISC!
    OH ya, no sign of vacuum leaks at throttle body.

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