Stutter, Engine or Trans?
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Northstar Engines and System Technical Discussion Discussion, Stutter, Engine or Trans? in Cadillac Engine Technical Discussion; Well I guess it's my turn. '97 Deville. This afternoon I was on my way to work and as I ...
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    Stutter, Engine or Trans?

    Well I guess it's my turn. '97 Deville. This afternoon I was on my way to work and as I was on the toll road entrance ramp I slowly accelerated from about 45 mph, not enough to downshift. I felt what I thought was a misfire. Somewhat like a coil breaking down under load. It still accelerated albeit slowly. When I got to work I put it in park and lightly brake torqued it and could not duplicate the symptoms. On the way home I tried it with a cold engine and all was normal. After normal operating temps were reached the same symptoms appeared. I thought maybe a weak fuel pump but WOT ran smooth though maybe not quite as much power. When cruising at 50 mph and a light throttle acceleration I can feel a pronounced stutter and hear an occasional pop or bang. Hard to tell for sure if it is coming from the tail pipe or under the car but I swear I can feel something bumping the floor board. I can also feel this stutter or slip when accelerating normally from a stop. I tried holding it steady and light brake pressure. No RPM jump. Once on a county back road with no traffic I stopped and brake torqued it again. This time I ran the RPM up to about 2000. At about 1600 I could feel an occasional stutter or slip again but I was standing still with my foot on the brake. I am starting to fear a transmission problem rather than an engine problem. Maybe this WOT stuff is not such a good idea after all. NO codes, temp normal 212f, no warning lights. What do you guys think?

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    Thumbs up Re: Stutter, Engine or Trans?

    I too had the same problem with my SLS running fine at times but missing/stuttering at driving speeds. It would give a little slip right when you take off, made me wonder if the tranny was slipping for a second. It got more noticeable as the car became warmer. Pulled all the plugs, they looked great. The problem was that the wire caps were not down all the way on the plugs on 2 of the back cylinders. I guess as it warmed up, the expansion caused the bad connection. Reseating them got rid of the problem. My plugs and wires were only 30K old, so I didn't think they were the problem, but sure glad I checked. Good luck!

    Jim from WY

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    Andrew M. Franklin is offline Cadillac Owners Member
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    Re: Stutter, Engine or Trans?

    I have this same problem with my '94 N* and described it on this forum several weeks ago. Was counselled to check the EGR ports in the spacer plate between the head and intake manifold - I guess these can clog and cause poor part-throttle cruising performance. I thought it at first kind of felt like the TC was switching in and out of lock or something trans-related, but advice from some excellent forum members directed me toward the EGR ports first. Don't know if this applies to your year vehicle. I haven't done the work on my car yet, but will this winter. Please post your experience. Sincerely, Andy.

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    Re: Stutter, Engine or Trans?

    In the limited time I have before I have to get ready for work I was able to pull the front plugs and one of the rears. Most of the platinum tips were gone and the gaps were .060 or close. I cleaned them and regapped them. If that was the problem 5 out of 8 should make a difference and I'll replace them all ASAP. I'll report my findings when I get to work. Looks like I'll have to remove the ignition module and coils to get at the last 3. The one thing I found though was that the manuals (owners and shop) both call for 41-900 plugs and I found 41-947's in there. ???

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    Re: Stutter, Engine or Trans?

    Well, there was no change. It really has me confused. When I start from a stop it feels like the tires are slipping as if on patchy ice (slip, grab, slip, grab) which make me think trans. When I am at cruise and I lightly press the throttle it will studder or chuggle and and I can hear and feel an occasional pop or bang that sounds almost like a backfire which makes me think ignition. When I get on it hard it seems to run smoother. Maybe I'll change all the plugs to eliminate that and see what happens. This really has me baffled.

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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Stutter, Engine or Trans?

    Isn't there a manual override code for the tranny pressure? You could just tell it to put on max pressure, and see if it stops slipping... That would rule out clutch packs at least. But it sounds like you have multiple problems.

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    Re: Stutter, Engine or Trans?

    Ranger - How old are the plugs and wires? Did the plugs look like they were burning o.k? Light Brown / tannish coating? It could be a coil pack.

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    Re: Stutter, Engine or Trans?

    Plugs and wires have 92K on them. They did not look too bad other than what was described. Coil are another possibility I'll have to check out along with the wires. They were untouched til the fuel rail replacement a couple of weeks ago. .

    I just got home from work and noticed another symptom. I normally run 1950 RPM @ 70 MPH. Tonight I was running about 200 RPM higher with minor fluctuations Also I could not feel the normal TCC engagement at 41 MPH. I am starting to suspect the TCC.

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    Re: Stutter, Engine or Trans?

    Making progress. I just went out in the garage and misted the wires (though I did not remove the conduit that the dealer put on) and coils. Nothing, engine was as smooth as a babies bottom. Then I did a brake torque with the hood up so I could watch the engine. Brought it up to about 2000 RPM and held it. It began to shudder a little bit (not real bad). I held it and let it continue for a few seconds. Then I noticed the SES light on. Sure enough there was the P0300 code. So I think I have it narrowed down to ignition, not tranny. Needless to say I am feeling much better about this. I picked up a new set of Delco 41-950's this morning so I will tackle the plugs tomorrow morning before work and eliminate that.

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    bigred is online now Cadillac Owners Fanatic
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    Re: Stutter, Engine or Trans?

    Brake torquing this powertrain, especially when it's hot, is not conducive to long transmission life. Stop doing that!

    The thump in your floorboards is from the engine/transmission mounts. I totally agree your problem is almost certainly ignition. Hopefully the plugs will be all it takes.

    I wonder what the dealers are doing that screws up our ignition systems on these fuel rail recalls. Yours is the fourth car I've heard develop this problem soon after the recall. I wonder if some of the plug wires get really bent enough to cause stress fractures in their conductors.

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    Re: Stutter, Engine or Trans?

    Quote Originally Posted by bigred
    I wonder if some of the plug wires get really bent enough to cause stress fractures in their conductors.
    That is one of my suspicions. I'll know more after I change the plugs.

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    Re: Stutter, Engine or Trans?

    With 92K on the plugs/wires, it would be a good thing to get out of the way. I'll bet it helps in one way or another. Please keep us abreast of the progress.

    JIM FROM WY

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    Re: Stutter, Engine or Trans?

    I needed to replace the wires on my N* at 70,000 miles. I could feel a miss or stutter and an occasional pop or low level backfire. The 0300 code was never set. The best I could figure was the spark was jumping from one wire to the other in a place where they touched each other or ran in parallel then traveled on to fire the wrong plug causing a slight pop or backfire. When I changed the wires it all went away. I did change the old plugs at the same time even though they still looked good.

    As to a problem of missing or skipping caused by the ignition wires after the new S/S rail install, think about it. The wires are not replaced under the recall and if they are old you may have a problem of the spark jumping from the wires to the nice new S/S fuel rail and on to ground. The plug wires lay down on the rail in many places. That means many places to ground the old wires. Remember the old fuel rail was plastic and the intake is plastic about the only metal the wires used to touch was the valve covers and now they touch the metal fuel rail. I didn’t have any plug wire arcing problems with the new fuel rail because my wires are new.

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    Re: Stutter, Engine or Trans?

    Well I changed the plugs this morning and I am glad to say she now purrs like a kitten and runs like a Thoroughbred. I have never seen a bad plug or plugs give such conflicting symptoms. As I said, I always think the worst. Gotta stop doing that. I think it is partially due to spending too much time here . Out of 8 plugs only one had a slight remnant of a platinum tip. In fact, most were slightly eroded where the platinum tip had once been. All gaps were in the .060 range. I can now feel the torque converter lock up again at 41 MPH and RPM at 70 MPH is steady at 1950 RPM.
    Thanks to all for the help, suggestions and moral support. Oh yeah, and apologies to the dealer for what I was thinking.

    Haymaker,
    When the dealer replaced my fuel rail, they also installed plastic conduit on the plug wires to prevent shorting out on the new rails. I think that is part of the recall as I have heard others mention that as well.

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    Re: Stutter, Engine or Trans?

    They didn't on mine.

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