Rough Idle After Retiming.
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Northstar Engines and System Technical Discussion Discussion, Rough Idle After Retiming. in Cadillac Engine Technical Discussion; Gentleman/Ladies, I have a '96 DeVille with just over 80,000 miles. This past spring I performed a head gasket job ...
  1. #1
    joeycap is offline Cadillac Owners Member
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    Unhappy Rough Idle After Retiming.

    Gentleman/Ladies,
    I have a '96 DeVille with just over 80,000 miles. This past spring I performed a head gasket job using time-serts and, do to my mother coming into town, hastily reassembled the engine etc. Car started on first turn of key and ran fine but was showing the P0340 - camshaft position sensor no activity, code. Since I tried everything possible and in one of my September posts, ManicMechanic, suggested something mechanical. So, about 3 weeks ago I removed the right camshaft cover and sure enough I put the camshaft sprockets on wrong. They were reversed hence the code. Anyway, I dropped the cradle, removed the front cover, retracted the tensioner and proceeded to switch the sprockets align the pin 90 degrees reset the crank timing marks and reassembled. When attempting to restart a huge backfire, I actually saw a spark by the battery from the drivers seat and the P0300 code showed up. After thinking about is for awhile, I slapped myself in the head and realized I should have timed both sides, at least with reference to the crank. I removed the left cam cover and sure enough the left side and right side were out of alignment. So I dropped the cradle, removed the front cover, relieved the tension on the right side, realigned the crankshaft/intermediate shaft points to coincide with the 90 degree pins on the right side then realigned the left side to 90 degrees in accordance with the other timing points and reassemble.

    So...now I clear PCM codes and restart. It started right up, but idles very rough. Almost chugs. No codes are present. I also changed the fuel filter. FPR is fine. What on earth did I screw-up and what is my next move? I almost didnt post because I feel really, really stupid. Sorry to bother everyone for my haste and stupidity.

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    vincentm's Avatar
    vincentm is offline Cadillac Owners Connoisseur
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    IAC or Plugs?

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
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    Re: Rough Idle After Retiming.

    WORST case is bent valves - The Northstar is an interference engine and if you had one or more cams out of proper time then the risk of engine damage is great.

    Compression test to start, then purposeful diagnosis to find the offending cylinder(s).

    (You are not the first to have cam/chain timing horror stories, and you will definitely NOT be the last - it's a learning curve. Measure twice, cut once.)

  5. #4
    stoveguyy is offline Cadillac Owners Connoisseur
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    Why did u remove cam sprockets to begin with? Oh well, what's done is done. I did my 96 also and nowhere do I recall anything about sprockets being 90 degrees out of time? All 4 timing marks are pointed up at 12. U rotate motor 1 rev and all marks are at 6. Rotate again and marks are all at 12. Never changes, ever.

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    joeycap is offline Cadillac Owners Member
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    Re: Rough Idle After Retiming.

    @stoveguyy,

    I removed the cam sprockets to clean them...I cleaned everything as long as I had it apart. Regarding the timing marks, they are all at 6,12 etc. but to time correctly they need to be at 12 with the marks on the crank/intermediate shaft opposing each other which takes, if I recall correctly, four revolutions. Anyway, it was a pain.

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    stoveguyy is offline Cadillac Owners Connoisseur
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    I may have misread ur 1 post about sprocket marks. I have commented on intermediate sprocket mark over the yrs and never really have gotten clear answers. Crank is aligned. Cams are aligned. Who cares about inter sprocket? Motor is 4 stroke so u rotate crank 360 and now cam sprockets should all point down or 6. Rotate crank 360 more and all 4 cams are pointing at 12 again.

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
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    Re: Rough Idle After Retiming.

    Might as well time it by the book -

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    joeycap is offline Cadillac Owners Member
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    Re: Rough Idle After Retiming.

    @Submariner and stoveguyy,
    I performed the timing per the service manual in accordance with the diagram seen in the latest post. Right now I am testing compression and so far, my values are as follows: 1-230 psi, 2-208 psi, 3-?, 4-203 psi, 5-?, 6-210 psi, 7-?, 8-205 psi. I could not obtain a value on 3,5,7 because I can't get the car to crank as I did on the 1,2,4,6,8. Yet, when I went to start it too warm it up for the compression test it started right up with the plugs and wires installed. Without plugs and wires, now I didn't have the problem with first set of cylinders, it just whines when I hit the key. I checked battery = OK, checked alternator=OK.

    Also, when it get warm smoke starts coming from under the right side cam cover area. I can't see where its coming from. In addition, smoke also came out of the #5 piston tunnel when I removed the plug. More and more issues are arising and I'm not sure I will have the car for the holidays. Thanks gents.

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    stoveguyy is offline Cadillac Owners Connoisseur
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    If u think cams were mistimed and ran motor than u probably did damage. Bent valves? Cam opens valve and piston closes it? Ugh.

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    maeng9981's Avatar
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    Re: Rough Idle After Retiming.

    Sounds too much like internal engine damage. If your timing was off that much, it's almost a guarantee to have some damage due to the design.

  12. #11
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    Re: Rough Idle After Retiming.

    Quote Originally Posted by joeycap View Post
    @Submariner and stoveguyy,
    I performed the timing per the service manual in accordance with the diagram seen in the latest post. Right now I am testing compression and so far, my values are as follows: 1-230 psi, 2-208 psi, 3-?, 4-203 psi, 5-?, 6-210 psi, 7-?, 8-205 psi. I could not obtain a value on 3,5,7 because I can't get the car to crank as I did on the 1,2,4,6,8. Yet, when I went to start it too warm it up for the compression test it started right up with the plugs and wires installed. Without plugs and wires, now I didn't have the problem with first set of cylinders, it just whines when I hit the key. I checked battery = OK, checked alternator=OK.

    Also, when it get warm smoke starts coming from under the right side cam cover area. I can't see where its coming from. In addition, smoke also came out of the #5 piston tunnel when I removed the plug. More and more issues are arising and I'm not sure I will have the car for the holidays. Thanks gents.
    The compression numbers you did get are way too high. I think your cam timing must be off. When I did my 98, I took a cold cranking compression test to confirm timing was right and the numbers were about 140 psi, if I remember correctly. You numbers are almost what my S&S engined motorcycle are.

  13. #12
    joeycap is offline Cadillac Owners Member
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    Re: Rough Idle After Retiming.

    Thanks for all the input..bigtone...the compression test was completed at operating temp.. If that makes a difference I don't know and according to alldata anything below 140 psi is an issue. Anyway, I'm going to sit on it for a while and go from there. I am fairly disgusted right now. Just spent a bunch of time doing the 3M Perfect-It system to almost a mirror finish and it doesn't run. Oh well.

  14. #13
    stoveguyy is offline Cadillac Owners Connoisseur
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    Well u are good at pulling motor! Should be easy to find a core motor with good heads. Junkyards almost give them away. So many folks junk cars due to bad head gaskets and those cars have good heads.

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    joeycap is offline Cadillac Owners Member
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    Re: Rough Idle After Retiming.

    I was at a Christmas party last night and someone told me about a "protection port" on the intake manifold that will come out in the case of a large misfire. Is anyone familiar with it? If so, is it possible the rough idle is caused by loss of vacuum?

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    Ranger's Avatar
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    Re: Rough Idle After Retiming.

    It's called the over pressurization relief valve. It's a spring loaded flapper door, so to speak in the tunnel behind the P/S pump on the pre-2000 engines. It's a small poppet valve under the TB on the 2000+ engines.

    Pre-2000 valve


    Post 2000 valve (Courtesy of Submariner409)

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