83 FWB Idle Problems
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HT4100 4.1, 4.5, 4.9 Discussion, 83 FWB Idle Problems in Cadillac Engine Technical Discussion; Helping a friend diagnose a rough idle and Black smoke. Started today with Seafoam, new EGR valve, PCV valve, a ...
  1. #1
    biggeazy-e is offline Cadillac Owners Member
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    83 FWB Idle Problems

    Helping a friend diagnose a rough idle and Black smoke. Started today with Seafoam, new EGR valve, PCV valve, a few rotted vacuum lines, carb cleaner. He left my house with no black smoke, but ran codes and got 13, 30

    13- O2 sensor not ready
    30- ISC out of range

    The O2 sensor I am starting to think it may be carboned up, and not getting up to "Operating temp", but the ISC (idle speed ctrl) circuit, I am at a loss.. I am fresh out of school, so no Alldata for me....

    Can anyone get me in the right direction?? Provide ISC circuit diagram/schematic?

    thanks a lot..

    eazy

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  3. #2
    awadecki is offline Cadillac Owners Enthusiast
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    Re: 83 FWB Idle Problems

    Definitely change the 02 sensor. Each and cheap. The ISC error is likely due to a stuck EGR valve. If the motor moves when you turn the steering wheel or turn the air on, it's probably fine, what the error is saying is that the ISC is having to extend farther than it should to maintain the correct idle speed. Check your EGR diaphram to see if it moves freely. If not, replace the EGR.

  4. #3
    biggeazy-e is offline Cadillac Owners Member
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    Re: 83 FWB Idle Problems

    Quote Originally Posted by awadecki View Post
    Definitely change the 02 sensor. Each and cheap. The ISC error is likely due to a stuck EGR valve. If the motor moves when you turn the steering wheel or turn the air on, it's probably fine, what the error is saying is that the ISC is having to extend farther than it should to maintain the correct idle speed. Check your EGR diaphram to see if it moves freely. If not, replace the EGR.
    Replaced the EGR yesterday, seemed to help a lot actually, less black smoke, but the idle was still erratic..

    We also ran some Seafoam through a vacuum line, cleaned the TB, replaced PCV valve... I really would like to fix the first time rather than guessing and replacing parts, so.. O2S next?

    Also, his service engine light was on when he drove the car to my place, but went off after replacing EGR valve and driving it a mile or so. Can I erase codes through the CCM?

    Thanks..

  5. #4
    Po Pimp is offline Cadillac Owners Fanatic
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    Re: 83 FWB Idle Problems

    Do you know how to use a voltage meter?

    I would get a voltage meter and check and adjust the TPS if necessary. If not adjustment is necessary then move to checking the ISC. The ISC could have a burnt circuit or striped gears (they are plastic). Using a voltage meter will give you a definative answer as to what is going on and what if anything needs to be replaced. If you need help or do not have a book that shows you these things I can help.

  6. #5
    biggeazy-e is offline Cadillac Owners Member
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    Re: 83 FWB Idle Problems

    cool, i didn't even think to check the TPS while the car was here, where exactly is the ISC??? is it tested the same as a potentiometer??

    thanks...

    eazy

  7. #6
    Po Pimp is offline Cadillac Owners Fanatic
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    Re: 83 FWB Idle Problems

    Turn the key in the "On" position but not running. Get on the passanger side of your car and locate the the TPS. It should have three wires running into it and be mounted to the throttle body. You will need to know which wire is what. If you are on the passanger side looking right at it they will be like this |SIG|GND|REF|.

    The first test will confirm that the TPS is getting the right power. Unhook the harness. Apply the positive to the REF and the negative to the GND you should get a reading of 5v.

    The next check is for the adjustment. You will have to hook the harness back up. Now back probe the SIG with the positive and the GND with the negative. With the throttle closed you should get a reading of 0.44-0.55v pretty close is okay. If you have a partner or something to wedge the throttle all the way open you should get a reading of 4.0-4.5v.

    Now if the closed throttle reading is close I would not suspect this of being the problem. If it is out of adjustment you will have to slightly loosen the two bolts (torx heads) and swivel the TPS in whatever way it takes to get the right reading. Swiveling it toward the radiator should bring the numbers up, swiveling towards the firewall should bring the number down.

    The ISC will be on the other side of the throttle body. It is pretty big and black. You can turn the key off. There should be a four wire harness that runs out of the back of the ISC. Follow it back where it connects with the rest of the wiring spool and unhook it there (about 10-12" away). This is important. These should be marked with letters. They are written very small. They will be on the harness or the ISC make sure you see them and know which is what.

    I use some speaker wires for this part. Apply 12v to the C terminal and ground the D terminal. You can simply cut some speaker wire and run one from the battery for the positive and touch one to the intake. Doing this should retract the ISC plunger. If it does not retract replace the ISC. Now once it is fully retracted check terminals A and B to see if there is any continuity. If there is replace it.

    You will do the opposite on this one. Appling 12v to the D terminal and grounding off the C terminal. This will fully extend the plunger. If it does not extend all the way replace it. Once fully extended check the A and B terminal for continuity. If there is replace it.

    It is important never to apply 12v over the A and B terminal. Try to extend or retract the plunger as quick as possible and then unhook it. At this point with all the checks you have ruled out the ISC completely.

    Try to remember about where the plunger was and after preforming the last test try to retract as close as possible to where it was. If you do not it should adjust itself but will be a little weird. I start it once and let it run for a minute and then turn the car off. Start again let it run for another minute or so the ISC should adjust when it gets turned back off this second time.

    If you do have to replace the ISC just do a search when you are in the 4.x catagory on this forum and you should be able to find good information so you do not have problems. Really only the 3rd and the 6th paragraph are the test that need to be preformed with what you are describing.

  8. #7
    biggeazy-e is offline Cadillac Owners Member
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    Re: 83 FWB Idle Problems

    Po Pimp; thanks..

    I already knew how to test a TPS/potentiometer, but I just printed out the rest to read.. Will adjust the TPS and test the ISC tomorrow morning..

  9. #8
    biggeazy-e is offline Cadillac Owners Member
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    Re: 83 FWB Idle Problems

    Po Pimp, Thanks for the good info- I just went outside and checked mine, Continuity between A&B at fully extended ISC, no continuity between A&B at fully retracted.. I'll pull the ISC off a spare 4100 I have... Until then- tomorrow is the day I'll be testing the 83 FWB in question..

    thanks again for the info..

  10. #9
    biggeazy-e is offline Cadillac Owners Member
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    Re: 83 FWB Idle Problems

    Back with more problems!!..lol

    Got the car back over here this morning, started with a new O2 sensor (old one was covered in a blanket of carbon)

    Tested and inspected the TPS, checked out fine, set it back to 0% throttle= .54v

    Checked out ISC, checked out fine

    Started changing plugs and wires(in the process, knocked some dirt/oil off the old plug "surrounding" onto the exhaust manifold), got the odd bank done (owner bought Bosch Plat. 2's.. I usually try to use delco on anything GM, but the owner had already purchased the platinums)

    Noticed that the distributor was PLENTY loose (not enough to bounce around, but could be moved easily by hand), so I decided to tackle the small task of tightening the distributor.... I was in for a suprise.... about 45 minutes later, I had a bunch of shit pulled apart, and still couldn't reach the distributor hold down... Decided to leave it as it was, and put everything back together, see if the TPS/o2s/ISC had any effect on anything...

    started up, no smoke, but the idle was lower than before- checked timing, it was retarded a few degrees, played with the timing, 8BTDC had the idle pretty high, idle only sounded good with timing at TDC/2-4*BTDC

    sent the car home, save it for another day with the following problems..

    code for TPS Shorted (probably just from messing with it so much when testing/adjusting it, must've tapped it on the ground t pin)
    and code for MAP signal high, I guessed maybe from playing with the timing so much, low vacuum, high vacuum, low vacuum......

    also, the drivers side bank is smoking, smells and looks like burning oil, but no visible oil leaks/wet spots(i thought MAYBE from when pulling the old plugs... the owner recently had a valve cover gasket done on that side, so MAYBE residual oil/dirt?????)

    and the owner complained about the car running shitty on the way home, high idle, but quickly drops when put in gear... and he complained about the oil..

    ANY input is greatly appreciated, I'll look in my haynes book in a minute, but what do I disconnect when setting base timing??

    anybody have this same problem before????

    the car will be back this week to finish up the even plugs/wires, and to diagnose the timing problem.

    also- has anyone had any luck with a "regular" distributor wrench on a 4.1 distributor?? what size is the hold down nut?? feels like bigger than 13mm/1/2 in

    thank you again..

  11. #10
    biggeazy-e is offline Cadillac Owners Member
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    Re: 83 FWB Idle Problems

    ttt

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