joeb Posted January 22, 2009 Report Share Posted January 22, 2009 96 sts. random miss. only noticeable at idle. plugs are 1yr old delco single platinums. 5yr old delco wires. replaced coil pack/icm with used assy today and idle is the same. intake was replaced last fall with new gaskets. no change in idle. i am going to say wires since the plugs are so simple. all they do is spark but the dbl plat tips might make a difference. i really want a smooth idle. Link to comment Share on other sites More sharing options...
navion Posted January 22, 2009 Report Share Posted January 22, 2009 96 sts. random miss. only noticeable at idle. plugs are 1yr old delco single platinums. 5yr old delco wires. replaced coil pack/icm with used assy today and idle is the same. intake was replaced last fall with new gaskets. no change in idle. i am going to say wires since the plugs are so simple. all they do is spark but the dbl plat tips might make a difference. i really want a smooth idle. I had a similar problem on my 94 SLS. I replaced the plugs, wires and intake gaskets. Still had the problem. Some days it was worse than others. At about 55 MPH, the engine would surge or miss on two cylinders in quick succession. At times, it was almost undriveable. (Probably the miss coupled with bad motor mounts.) An ex Cadillac mechanic suggested that I clean the high tension towers of the coil packs. He said that they were susceptible to corrosion which would add resistance to the high tension circuit, causing intermittent misfiring. After cleaning the contact areas of the high tension towers, the engine ran smooooth once again! Good Luck, Britt. Britt Link to comment Share on other sites More sharing options...
joeb Posted January 22, 2009 Author Report Share Posted January 22, 2009 high tension towers? like on a suspension bridge? i guess there is the low voltage input and high voltage output to the plugs. maybe thats what you are referring too? well, since i changed all the coils than would that mean i have addressed that issue? oh, and how did you determine that it was missing on 2 cylinders? a single coil doe control 2 plugs but 1 is on the power stroke and the other is not. Link to comment Share on other sites More sharing options...
BodybyFisher Posted January 23, 2009 Report Share Posted January 23, 2009 high tension towers? like on a suspension bridge? i guess there is the low voltage input and high voltage output to the plugs. maybe thats what you are referring too? well, since i changed all the coils than would that mean i have addressed that issue? oh, and how did you determine that it was missing on 2 cylinders? a single coil doe control 2 plugs but 1 is on the power stroke and the other is not. yes on our 96, each coil has two spark plug wires attached to it at the 'towers'. Each coil fires about 40,000 volts and the sparks will jump 4 to 6 inches unbridled. They will certainly knock you across the room. Britt is recommending pulling each plug wire off the coil, look in the tower on the coil and see if you see any corrosion white or green, if you can get a small round brass brush clean the contact in there. Make sure that when you snap the plug wire back in, you have a positive solid contact 'SNAP". If not you might need to adjust any contacts on the wire to make it more 'positive' solid. At 5 years your ignition wires might be grounding out, due to heat and leaning up against metal. The new style fuel rail caused the ignition wires to drape over it, when the vanity cover is screwed down it puts pressure on the wires pushing the wires against the fuel rail. Pick up the wires and look for high voltage burns on them, they might even be aching between each other. Keep in mind that with high voltage like this, aching can occur. If these were aftermarket wires I would be looking them over carefully. Look at the spark plug end, if you pull the plug out and you have OIL on the boot, your well is full of oil from bad seals on the cam cover. Look in each plug well for oil. If you want to get nuts check each wires resistance with an ohm meter, measure their length and see if any appear out of range, indicating a bad wire. Divide the resistance figure by the wire's length in inches to get a 'equalized norm', any out of the 'equalized norm' you found a possible cause. Mike Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
joeb Posted January 23, 2009 Author Report Share Posted January 23, 2009 i checked each wire for resistance. they are all within range depending on length. i have tried rerouting the wires as a test to separate them and cross/uncross them. no difference. do i want to put in a set of dbl plat plugs for $50? maybe another set of wires? i did put in 1 new motor mount when i pulled the motor last year. the 2nd mount looked fine. maybe its the trans mount? or dogbones? Link to comment Share on other sites More sharing options...
WarrenJ Posted January 23, 2009 Report Share Posted January 23, 2009 Each coil fires about 40,000 volts and the sparks will jump 4 to 6 inches unbridled. They will certainly knock you across the room. Britt is recommending pulling each plug wire off the coil, look in the tower on the coil and see if you see any corrosion white or green, if you can get a small round brass brush clean the contact in there. Make sure that when you snap the plug wire back in, you have a positive solid contact 'SNAP". Is there any "cleaning fluid" whose use might be advisable, or do you just do it "dry?" Regards, Warren There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises Link to comment Share on other sites More sharing options...
BodybyFisher Posted January 23, 2009 Report Share Posted January 23, 2009 Each coil fires about 40,000 volts and the sparks will jump 4 to 6 inches unbridled. They will certainly knock you across the room. Britt is recommending pulling each plug wire off the coil, look in the tower on the coil and see if you see any corrosion white or green, if you can get a small round brass brush clean the contact in there. Make sure that when you snap the plug wire back in, you have a positive solid contact 'SNAP". Is there any "cleaning fluid" whose use might be advisable, or do you just do it "dry?" Regards, Warren I suppose you could use electrical contact cleaner. Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
BodybyFisher Posted January 23, 2009 Report Share Posted January 23, 2009 i checked each wire for resistance. they are all within range depending on length. i have tried rerouting the wires as a test to separate them and cross/uncross them. no difference. do i want to put in a set of dbl plat plugs for $50? maybe another set of wires? i did put in 1 new motor mount when i pulled the motor last year. the 2nd mount looked fine. maybe its the trans mount? or dogbones? You have one year old plugs in your car, they are fine Test the resistance of your coils, remove them, test the primary and secondary resistance of each of the four coils. When you have them out, look for cracks in the towers and corrision on the contacts. Post the resistance here, we have a thread some place where we have norms for resistance. You have drifted off into thinking this is a mechanical problem, please explain your mis better. When does it happen, does it happen idling or under load?. Is it random, or constant? If you can not find it, you might measure the resistance of your injectors. Id hate to think you are having a leaky or burned valve. Didnt you do a timesert job? Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
joeb Posted January 23, 2009 Author Report Share Posted January 23, 2009 yes, i did the headgasket task about 18 months ago but only 5k miles. i did not touch the heads. just a combustion chamber cleanup/gasket removal. i really only feel the stumble at a stop. i like to throw the car into neutral. since the motor is not connected to the trans, the uneven pulse/stumble is not felt thru the chassis. the stumble is random, maybe every 10 sec or 15 sec. it is never constant like the motor is bogging down. smooth idle, 10 secs later stumble, smooth idle, stumble. seems to be slightly better with the new coil pack but i only did that yesterday. Link to comment Share on other sites More sharing options...
kens96 Posted January 23, 2009 Report Share Posted January 23, 2009 I had the same issue the other day when the temperature in Jacksonville FL. dropped into the 20's for 3 days. While I had the engine idling in the garage looking under the hood for errant sparks and searching for vacuum leaks, noticed a large amount of water dripping from both muffler weep holes. Problem ended up being condensation in the gas tank. Some dry gas and a fill up fixed the issue. Might want to check for this. Link to comment Share on other sites More sharing options...
BodybyFisher Posted January 24, 2009 Report Share Posted January 24, 2009 I had the same issue the other day when the temperature in Jacksonville FL. dropped into the 20's for 3 days. While I had the engine idling in the garage looking under the hood for errant sparks and searching for vacuum leaks, noticed a large amount of water dripping from both muffler weep holes. Problem ended up being condensation in the gas tank. Some dry gas and a fill up fixed the issue. Might want to check for this. Good idea Ken! Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
joeb Posted January 24, 2009 Author Report Share Posted January 24, 2009 my tank is usually 1/2 or less. i might try some fuel system moisture remover. but i have had the issue since last year. not a recent problem. when the heads were off, the exhaust valves on cyls 5,7,6,8 were all white while the other cyls valves were black. seems the driver side of the motors heads had lifted or the gaskets had started to fail. both heads had the same discoloration. i took some pics but they are too large to post here. i really did not want to tear down the heads and do a valve job but i thought with only 100k miles i would only have average wear. it could be a valve issue? Link to comment Share on other sites More sharing options...
kens96 Posted January 24, 2009 Report Share Posted January 24, 2009 Couldn't hurt to keep the tank full and add some methanol or isopropal based dry gas to see if it makes a difference. I would think that keeping the tank1/2 full all the time creates an environment for moisture to collect especially with gasoline now having higher ethanol content. The other thing that comes to mind is a lean condition that does not set a code. I had a "fishbite" issue at highway speeds that also felt like a miss at idle. It ended up being the flex pipe from the EGR to backside of the engine that had pin holes in it. The dealer found it after 2 days of diagnistics. Keep chasing the simple stuff and knocking it off the list. You will find the problem! Link to comment Share on other sites More sharing options...
joeb Posted January 24, 2009 Author Report Share Posted January 24, 2009 the picture i posted shows that flex pipe. it appears to be double wall. ugh. i remember how tight that area was when i pulled my motor. i would hate to have to change that pipe. i am sure the manifold nut has to be loosened from underneath. it is -4F outside now and my garage is 30F. i just checked this afternoon. i do not want to crawl under my car in january. Link to comment Share on other sites More sharing options...
kens96 Posted January 25, 2009 Report Share Posted January 25, 2009 Nothing surprises me any more about the my Eldorado. However at 157K, I've come to appreciate guys like BBF and Ranger who will point you to the simple stuff first before tearing down an engine. Link to comment Share on other sites More sharing options...
BodybyFisher Posted January 25, 2009 Report Share Posted January 25, 2009 the picture i posted shows that flex pipe. it appears to be double wall. ugh. i remember how tight that area was when i pulled my motor. i would hate to have to change that pipe. i am sure the manifold nut has to be loosened from underneath. it is -4F outside now and my garage is 30F. i just checked this afternoon. i do not want to crawl under my car in january. That pipe is really not too hard to change, I was looking at mine the other day as it looks like exhaust is leaking from it at the crossover. Thanks Ken, Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
Ranger Posted January 25, 2009 Report Share Posted January 25, 2009 I would suspect the wires. It sounds a lot like the miss I fought with right after the fuel rail recall. I think I posted about it. I think it was titled "Stutter, Engine or Trans?". Might find it if you do a search. Turned out to be the wires. Link to comment Share on other sites More sharing options...
joeb Posted January 25, 2009 Author Report Share Posted January 25, 2009 wires could mean 1 is suspect or maybe more. what are the odds you could found the bad wire and change it out? can you even buy 1 wire/boot? probably easier to just get a new set. 100 for delco or 50 for generic. don't bother with generic since its throwing money at substandard stuff? same with delco dbl plat plugs. stick with the preferred factory quality stuff. Link to comment Share on other sites More sharing options...
BodybyFisher Posted January 25, 2009 Report Share Posted January 25, 2009 wires could mean 1 is suspect or maybe more. what are the odds you could found the bad wire and change it out? can you even buy 1 wire/boot? probably easier to just get a new set. 100 for delco or 50 for generic. don't bother with generic since its throwing money at substandard stuff? same with delco dbl plat plugs. stick with the preferred factory quality stuff. Yes but, you tested the wires with an ohm meter right? Plus you determined that both ends are snapping in with a strong connection correct? Do you recall if you used dielectric grease when you installed the wires? Have you pulled the plugs and looked for carbon tracking? What was the result of checking the wires for high voltage burns from grounding? Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
joeb Posted February 2, 2009 Author Report Share Posted February 2, 2009 khe, thanks for the tip about routing the wires close to the hvac fan housing. i had a nice pic of another NS motor with proper plug wire routing and i redid my wires with zipties and i think the miss might be gone. i notice each bank has the wires routed separately or in 2 bundles. i did that and made sure they as far from the blower motor as possible and the motor seems to idle better. maybe it is fixed. Link to comment Share on other sites More sharing options...
BodybyFisher Posted February 2, 2009 Report Share Posted February 2, 2009 khe, thanks for the tip about routing the wires close to the hvac fan housing. i had a nice pic of another NS motor with proper plug wire routing and i redid my wires with zipties and i think the miss might be gone. i notice each bank has the wires routed separately or in 2 bundles. i did that and made sure they as far from the blower motor as possible and the motor seems to idle better. maybe it is fixed. That is not the reason to keep them away from the HVAC motor, the high voltage transients damage the controller on the motor.. If you have improved your miss, its likely related to the wires, routing, etc.. Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
joeb Posted February 3, 2009 Author Report Share Posted February 3, 2009 i admit the wires were somewhat tangled but were routed from the proper coil # to the proper plug #. the firewall plug wires are really the only ones i rerouted and yet it seems to run better. with pulling the motor, taking off the intake twice, i have had many chances to tug on the wires. maybe one or more has a bad connection or crimp. Link to comment Share on other sites More sharing options...
adallak Posted February 3, 2009 Report Share Posted February 3, 2009 i admit the wires were somewhat tangled but were routed from the proper coil # to the proper plug #. the firewall plug wires are really the only ones i rerouted and yet it seems to run better. with pulling the motor, taking off the intake twice, i have had many chances to tug on the wires. maybe one or more has a bad connection or crimp. Bad connections on the PCM and PROM can make it too. Try to remove and reinstall those items to "refresh" the contacts. Easy job. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
Texas Jim Posted February 3, 2009 Report Share Posted February 3, 2009 i admit the wires were somewhat tangled but were routed from the proper coil # to the proper plug #. the firewall plug wires are really the only ones i rerouted and yet it seems to run better. with pulling the motor, taking off the intake twice, i have had many chances to tug on the wires. maybe one or more has a bad connection or crimp. This may sound stupid...but... If the wires are touching.. see if you can separate them from each other. Sometimes when they are running parallel to each other and touching, you can get some inductance from one wire to another, which will cause the plug to fire at the wrong time. If the wires must cross each other, try to have them cross at as close to a 90 degree angle as possible. Can't hurt anything...may help. Link to comment Share on other sites More sharing options...
BodybyFisher Posted February 3, 2009 Report Share Posted February 3, 2009 SORRY i did not mean that they were going to wrong coils I meant that they were ROUTED WRONG, meaning they were TOUCHING each other, a no no with 40000 volts. The 96 has a specific routing. The new fuel rail screws things up, I used 3/8 hose over the wires where they hang over the fuel rail. They must not touch and where they do they must be separated by loom or hose Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.