Rough Idle w/ Brake Booster Loss - Page 2
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 2 of 2 FirstFirst 1 2
Results 16 to 30 of 30
HT4100 4.1, 4.5, 4.9 Discussion, Rough Idle w/ Brake Booster Loss in Cadillac Engine Technical Discussion; What about the pick up in the distributor? Somebody else chime in and correct me if I'm wrong, as I ...
  1. #16
    the recluse is offline Cadillac Owners Connoisseur
    Automobile(s): 2002 STS, 1991 Eldorado
    Join Date
    Feb 2009
    Location
    Jacksonville, FL
    Posts
    1,016

    Re: Rough Idle w/ Brake Booster Loss

    What about the pick up in the distributor? Somebody else chime in and correct me if I'm wrong, as I haven't play with the 4100, but the 4.5/4.9 have pick ups in the distributor that go bad and don't always through a code...this could be the rough idle/hard start problems...

    The last time I'd seen the vacuum running all over the place like that, I had cam lobes wiped off...

  2. #17
    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
    5,890

    Re: Rough Idle w/ Brake Booster Loss

    Whats the fuel pressure? At idle and while driven. With a fuel pressure gauge taped to the windshield tell us what the pressure is running.

  3. #18
    cadillac_al is offline Cadillac Owners Connoisseur
    Automobile(s): Cadillac 78 Seville, 78 Coupe de Ville, 92 Sedan de Ville
    Join Date
    Feb 2007
    Location
    Maine
    Age
    53
    Posts
    2,746

    Re: Rough Idle w/ Brake Booster Loss

    It does sound like the ISC isn't working right for some reason.

  4. #19
    Kiriken is offline Cadillac Owners Member
    Automobile(s): 1985 Eldorado, 2008 STS
    Join Date
    Mar 2009
    Posts
    26

    Re: Rough Idle w/ Brake Booster Loss

    I haven't gotten around to checking anything new. There was an unexpected death that I had to leave town for, I started a new job and a lot of things just happened really fast. I want to thank everyone for the tips and apologize for not getting around to checking them out yet, I do appreciate the suggestions though.

    I was going to follow up on carnut's tip this afternoon and see if the autoparts store had a loaner fuel pressure gauge. Problem is I never made it, the car didn't start because of a dead battery. I replaced the battery around 2 months ago as it was dying more and more frequently. Many times when I'd get to the car and the battery would be dead, I would hear a clicking coming from under the hood but I never pinpointed what it was exactly (I could hear it as I approached the car). All belts were tightened and re-tightened as I know there are issues with slippage between the pulleys. Now that I have a new battery and tight belts I'm wondering if the battery dying could be relevant to all of this. My understanding is that the ISC kicks the fuel pump on when the ignition is on but car is off so that pressure is built up to start the car more easily. If the ISC was malfunctioning or misadjusted I'm guessing it might keep power running to the pump perhaps drain the battery or wear out the fuel pump.

    I have found the ISC adjustment procedure in the manual under a TPS section and it doesn't look as intimidating as I thought so hopefully I can check that soon (I am missing one of the two sections the index points to for the ISC and I thought it was there) as well as the fuel pressure. I'll post back when I have more info.

  5. #20
    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
    5,890

    Re: Rough Idle w/ Brake Booster Loss

    The ISC is "idle speed control" It will not drain the battery if the car is off. The ISC does NOT "kick" the fuel pump on, the key does that. If the computer sees oil pressure thru the oil pressure sender, it keeps the fuel pump on. If the key's turned on and the car is not started, the pump shuts off in about 10 seconds. Relays under hood will click if the battery is very low because there's not enough voltage to fully engage them.

  6. #21
    Kiriken is offline Cadillac Owners Member
    Automobile(s): 1985 Eldorado, 2008 STS
    Join Date
    Mar 2009
    Posts
    26

    Re: Rough Idle w/ Brake Booster Loss

    Thanks for the info, looks like I had it wrong.

    I went ahead and tried to adjust the ISC today using the manual instructions. Since I haven't seen an exact, word-for-word copy of the instructions on the forums I thought I'd go ahead and transcribe them below for accuracy.

    Quote Originally Posted by FSM
    3. Remove the air cleaner, start the engine, and warm the engine up to normal operating temperature (parameter .0.4 greater than 85C). Turn A/C off. Check engine timing using fixed spark mode as described. Adjust to specification if needed.

    4. Turn off all electric accessories. Place steering wheel in its center position. Place the transmission in Park.

    5. Retract the ISC motor plunger using the following procedure.
    a. Unlock ISC motor connector but do not disconnect it from the motor.
    b. Open the throttle and hold at approximately 1500RPM. With the same hand close the throttle switch by depressing the ISC plunger.
    c. When the ISC plunger is fully retracted, continue to hold the throttle open and the throttle switch closed while disconnecting the ISC motor connector with the other hand.
    Notice: Do not power the SIC motor in the fully retracted position for more than 4 seconds or ECM damage may occur.
    d. After the connector is removed release the throttle switch and return the throttle to idle.

    6. Under these conditions, the ISC plunger should not be touching the throttle lever. If contact is noted, adjsut the ICS plunger (turn in) with pliers or suitable available special tool so that it is not touching the throttle lever.

    7. Enter diagnostics and depress the "outside temp." button to turn the "A/C Clutch" status light off. Display engine data parameter .1.1 and observe "engine speed" at minimum air. If the vehicle has under 500 miles and the displayed "engine speed" is "30" to "50" then proceed to step 9. If the vehicle has over 500 miles and the displayed value is "40" to "50" proceed to step 9.

    8. If the "engine speed" value does not fall within the above limits, then connect a tachometer to the engine and adjust the throttle stop screw to obtain 450RPM. If the engine speed cannot be correct, check that the throttle is not held off the minimum stop screw because of linkage binding or interference with the ISC motor plunger.

    9. With the vehicle at ignition on (engine off), enter diagnostics and display engine parameter .0.1. Open the throttle and let it snap fully shut against the throttle stop screw. If the displayed "throttle angle" value is "0", proceed to step 15.

    [10 - 14 Removed; TPS adjustment procedure using voltmeter]

    15. With the ISC motor fully retracted and the throttle fully shut against the throttle stop screw, turn the ISC motor plunger adjustment screw to obtain a 0.060 inch (1.50mm) gap between ISC motor plunger and the throttle lever.

    16. Disconnect all test equipment and reconnect all connections. Turn ignition off for at least 10 seconds. Start engine and check the ISC motor for proper operation.
    I did the prep work in steps 3 and 4. In step 5 I became confused. I held the throttle open at 1500-1540RPM with a small rope (tied it and went back inside the car to check parameter .1.1 (RPMs) in the diagnostics, when satisfied I exited diagnostics). Then I pressed the funny looking ISC screw (I'm assuming this is the plunger) in as far as I could and then quickly disconnected the ISC connector. So far so good, at this point though I released the throttle (disconnected my rope) and it dropped back to the ISC plunger/screw but the throttle was low enough to kill the engine pretty quickly.

    The procedure didn't mention the engine stopping and step 7 mentions checking the RPMs after doing this so that tells me this shouldn't happen... I wasn't sure how to procedure and I ended up probably messing with it in ways I shouldn't have... After screwing around with it I'm seeing it now retract when I turn the ignition (I think that's correct), but turning the ignition off it stutters back out twice and makes an odd clunk noise (probably very misadjusted now...)

    Anyway, any idea what's going on here? Should it be dying when I release the throttle after retracting the screw and unplugging the connection? Do I just need to screw it in more and retry (I tried screwing it in and then redoing the procedure but it never got to the point where the throttle didn't touch the plunger, perhaps I just didn't screw it in enough)?

  7. #22
    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
    5,890

    Re: Rough Idle w/ Brake Booster Loss

    The 1500 RPM parameter is not an exact spec. Just simply hold the throttle lever as stated up at a hi idle, then depress the ISC plunger. It will slowly retract with constant pressure applied. You will feel it bottom out. Once you feel its retracted and the connector is off, it should idle at a very low RPM, like 450. There should be an air gap between the ISC plunger and the throttle lever. If it wont idle at 450 theres something else going on? You are correct about the ratcheting ISC. Its doing that because either the TPS or the ISC is out of range and the ISC is searching to keep the engine running. You are getting there, How about removing the ISC from the throttle body and see if you can get the engine to idle very low. Both my 4100's would idle dead smooth at 450 RPM during the air gap adjustment. You do have the A/C off, correct?

  8. #23
    Kiriken is offline Cadillac Owners Member
    Automobile(s): 1985 Eldorado, 2008 STS
    Join Date
    Mar 2009
    Posts
    26

    Re: Rough Idle w/ Brake Booster Loss

    Yeah I figured the 1500RPM was just so you'd lift the throttle high enough to get it out of the way. I wanted to follow the procedure exactly in case anything unexpected happened (and it did). A/C is off.

    I just went out and redid the procedure to be sure I wasn't crazy. This time I did the procedure and after the part where I release the throttle and it dies, I screwed the ISC screw in until it was no longer touching the throttle. The factory service manual said the throttle and ISC screw shouldn't touch during this step so I thought I'd see if that made a difference. I then reconnected the ISC harness and started the car. It ratcheted back up but kept clicking non-stop (probably could have expected that). I then held the throttle open and pressed the ISC screw back in and disconnected it once it was retracted fully. I released the throttle this time and.... the engine died. I'll have to tie the throttle up again to verify the RPMs it's dying at. Whatever it is, it must be very low, it doesn't die immediately, it drops and kinda bumbles along slowly until it gets to the point where I can count the individual combustions. Then if I don't lift the throttle a few millimeters it dies. Is that what you meant by removing the ISC, just to get the throttle as low as it would go?

    For now I unscrewed the plunger a bit and redid the procedure just to make the ratcheting stop and ensure I'll be able to start it in the morning.

    Let me recap what the current status is because some things have changed since I started this thread and I'm sure I probably haven't mentioned everything (a lot of it I'm not sure is related or not):
    • Idle is no longer surging. I'm not sure if the vacuum pump replacement cured this, or perhaps the tuneup I gave it but that seems to have gone around that time.
    • Idle when the car is first started is not too terrible now. It does sound off and I've noticed the airflow coming out of the exhaust seems overly strong. If the catalytic converter is in fact plugged, would the pressure of the air exiting the exhaust be higher or lower? The air exiting the exhaust is odorless. The air comes out in fast, hard puffs which is part of the reason I thought the engine might be missing but this air pattern could be normal, I'm obviously not experienced enough to tell
    • After a short drive the idle becomes rougher. There is a rhythmic clanking-type noise coming from the driver's side. When I replaced the valve cover gasket a few weeks ago I wiggled the pushrods and rocker arms just to make sure nothing was loose (everything was tight).
    • The car was having issues starting after a short drive. A light press of the gas peddle while cranking and it would start up. I might've needed to press a little bit more just to even the idle out (sometimes it would start up with a high idle that felt like it was going to be over-corrected down and kill the engine, it had happened before). If the car has been sitting for at least 30 minutes it will start with no problem.
    • I could be imagining it but after a short drive the exhaust's airflow/pressure seems a lot higher but if I remember correctly the RPMs were normal (~750). (Still fast puffs) I could also be imagining it but it seems like the steering wheel is harder to turn after a short drive as well. Before I replaced the vacuum pump I was having the issue of the car having very hard steering and stalling when parking after a short drive.
    • I have noticed some hesitation. This started before the ignition tuneup and is part of the reason I did it. The hesitation isn't predictable or bad.
    • Shifting doesn't seem terribly responsive/good.
    • Poor fuel economy. I'm reading around 12MPG average with around 70% freeway 30% city. When I first acquired the car a few years ago it averaged about 19-20MPG. That lasted about 2 years but declined to about 15MPG where it remained until just recently.
    • Brand new battery following in the old one's footsteps by dying randomly with no apparent explanation.
    • Torque converter shudder when the transmission harness is connected. I've gone back and reconnected it a few times just to see if anything I've done has influenced it. Nope. Doesn't seem to happen in the first few minutes of the car running. Gets worse as the car heats up. Probably unrelated but thought I'd mention it.

    That's everything that comes to mind right now.

  9. #24
    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
    5,890

    Re: Rough Idle w/ Brake Booster Loss

    Disconnect and remove the ISC. Turn the minimum idle screw in so the car just barely runs. Shut the car off and reinstall the ISC. Do the retracting of the ISC shaft again and if no air gap, you have the shaft too far out. Turn it back in till the 60 thousands air gap is there. Strong air flow from the tailpipe means that your cat converter is probably OK. Restricted cat, less air flow from the tailpipe. All of these adjustments are done with the assumption you don't have internal engine problems! A flat cam comes to mind! The air from the tailpipe should not pulsate but be steady and very hot.

  10. #25
    the recluse is offline Cadillac Owners Connoisseur
    Automobile(s): 2002 STS, 1991 Eldorado
    Join Date
    Feb 2009
    Location
    Jacksonville, FL
    Posts
    1,016

    Re: Rough Idle w/ Brake Booster Loss

    Quote Originally Posted by carnut View Post
    All of these adjustments are done with the assumption you don't have internal engine problems! A flat cam comes to mind! The air from the tailpipe should not pulsate but be steady and very hot.
    Glad to see I'm not the only one....

    Quote Originally Posted by the recluse View Post
    The last time I'd seen the vacuum running all over the place like that, I had cam lobes wiped off...
    weren't these motors notorious for that?

  11. #26
    Kiriken is offline Cadillac Owners Member
    Automobile(s): 1985 Eldorado, 2008 STS
    Join Date
    Mar 2009
    Posts
    26

    Re: Rough Idle w/ Brake Booster Loss

    The ISC is still a bit off so I'll make another attempt to adjust the ISC when I find the time but for now it's starting up alright and the idle just feels too high, but not bad.

    Thanks for trying folks. My gut reaction to the noticeable decline of my car was internal failure. I had instinctively considered a flattened cam earlier on, but had no idea how to confirm if it was that or some secondary component throwing things off. I'm becoming more convinced that it's something internal that I don't have the tools, time or space to tackle (although I really wish I did).

    I may make a few more attempts at saving this thing but right now I'm beginning to look for a newer Cadillac. The fuel costs, time spent and parts purchased are really starting to outweigh any financing charges I'd pay on a ~5 year old model. If anyone's in the market for a parts car or an ambitious fixer-upper in the Santa Barbara area, as much as it pains me, I may be listing my Eldorado on the CadillacOwners classifieds in the next few weeks.

  12. #27
    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
    451

    Re: Rough Idle w/ Brake Booster Loss

    Quote Originally Posted by Kiriken View Post
    The ISC is still a bit off so I'll make another attempt to adjust the ISC when I find the time but for now it's starting up alright and the idle just feels too high, but not bad.

    Thanks for trying folks. My gut reaction to the noticeable decline of my car was internal failure. I had instinctively considered a flattened cam earlier on, but had no idea how to confirm if it was that or some secondary component throwing things off. I'm becoming more convinced that it's something internal that I don't have the tools, time or space to tackle (although I really wish I did).

    I may make a few more attempts at saving this thing but right now I'm beginning to look for a newer Cadillac. The fuel costs, time spent and parts purchased are really starting to outweigh any financing charges I'd pay on a ~5 year old model. If anyone's in the market for a parts car or an ambitious fixer-upper in the Santa Barbara area, as much as it pains me, I may be listing my Eldorado on the CadillacOwners classifieds in the next few weeks.
    I replaced a flat cam in my 83 eldo 4100 and the car has run like new since . The project didnt cost that much and I was able to get parts easy enough. I did have to search for a GM intake manifold reseal gasket kit. If the overall condition of the car is good...

  13. #28
    the recluse is offline Cadillac Owners Connoisseur
    Automobile(s): 2002 STS, 1991 Eldorado
    Join Date
    Feb 2009
    Location
    Jacksonville, FL
    Posts
    1,016

    Re: Rough Idle w/ Brake Booster Loss

    Remove the valve covers and pull on the rockers...even with the valves all the way closed, the rockers shouldn't have a whole lot of free space...turn the motor 90* and try again...then another 90* and try again...

    In the motors that I have had with wiped lobes, the rods almost fell out of the rockers, they had that much space in them...

    With the removal of ZDDP and the like from all motor oils, I always take a bottle of Lucas engine break-in and pour half of it(about 8oz) in to an empty crankcase (after oil changes) and then top of with motor oil of choice.

    It puts back a lot of what they took out.

    One 16oz bottle lasts me 2 oil changes and is well worth the $10-$12 dollars per (only $5-$6 an oil change)....

  14. #29
    Kiriken is offline Cadillac Owners Member
    Automobile(s): 1985 Eldorado, 2008 STS
    Join Date
    Mar 2009
    Posts
    26

    Re: Rough Idle w/ Brake Booster Loss

    Well I guess this is it. I purchased a 2008 STS yesterday. Everyone is excited "for" me but I feel more anxious about driving it and sad about leaving behind the Eldorado. I hear the STS is a great car (I chose it based on a lot of the threads in the more modern area of this forum) but it's going to be hard to get rid of the Eldo. Spending so much time working on that car has created a "bond" that's hard for most people to understand. If I had a garage I'd probably keep it and work on it whenever I had moments of free time. I imagine it's a lot easier to "restore" a car you're not constantly driving and depending on. Housing is expensive here and garages are a luxury. I even looked into larger storage units and random residential garages being rented out; still around $300-400 / month which would add up quickly. I'll be selling it soon

    -But some day I'll buy another, when I have the space and the time and the money to do it all properly. Having driven the STS for a day I still prefer the Eldorado. Maybe I just need to get used to modern cars but I really think Cadillac was onto something. I don't think anyone can argue that these cars weren't way ahead of their time. Sorry to lament here, I know this thread isn't exactly the place but just wanted to express myself.

    @83CADMAN: Just in response to your comment, the condition is decent in that it's too nice for Pimp-My-Ride but probably not worth a full restoration. it has scratching on the leather in the back seat from a prior owner's dog (nothing torn through). The dash cap is cracked in the middle in a V-shape. There are some spots where the paint has worn completely through, I've been rubbing wax over those areas to prevent rust (it works). Torque converter shudder. Evidence points to the engine being near its end. Little bit of oil burning or leaking (maybe 1qt / month). A/C doesn't seem to work although a few times I've gotten it to randomly blow cold air and engage the clutch, most times it doesn't even attempt to spin.

    @the recluse: Thanks for the tip, I might add a bit of that when I change the oil on the STS. The used car dealership I bought it from said they just changed the oil but the information panel said "Oil Change 43%" (or something close to that). Likely they just didn't reset the meter but I'd like to play it safe and change it sooner than later. About the Eldorado, when I had the driver's side valve cover off a few weeks ago there was absolutely no play between the pushrods and the rocker arms. Possible it was either the passenger side or something else entirely.

    Thanks carnut, cadillac_al, the recluse, 83CADMAN for all of the advice. I feel a bit like I've failed here by "giving up" and not quite getting to the bottom of it, but I really appreciate the wisdom you guys put forth

  15. #30
    the recluse is offline Cadillac Owners Connoisseur
    Automobile(s): 2002 STS, 1991 Eldorado
    Join Date
    Feb 2009
    Location
    Jacksonville, FL
    Posts
    1,016

    Re: Rough Idle w/ Brake Booster Loss

    Quote Originally Posted by Kiriken View Post
    @the recluse: About the Eldorado, when I had the driver's side valve cover off a few weeks ago there was absolutely no play between the pushrods and the rocker arms. Possible it was either the passenger side or something else entirely.
    You would have to rotate the engine 90* 4 times and check each time you did...you are looking for the valves to be completely free of compression...on my son's Firebird (2.8 V6) a few years back, the #5 exhaust lobe was gone causing rough running conditions that were hard to diagnose. Last week I pulled apart a 3.4 out of a Camaro (same motor, just bigger bore and stroke) and the same lobe was wiped off of it (odd)...various motors over the last few years have been suffering same failures, which leads me to...

    Quote Originally Posted by Kiriken View Post
    @the recluse: Thanks for the tip, I might add a bit of that when I change the oil on the STS. The used car dealership I bought it from said they just changed the oil but the information panel said "Oil Change 43%" (or something close to that).
    The Lucas Oil add-in tip was really for just flat tappet cams...your new Caddy has roller cam and lifters...no need to spend the extra cash on it. On older cars with flat tappet cams, I would definitely do it....

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