Ion Posted October 14, 2012 Report Share Posted October 14, 2012 Ever since pulling off the cover to replace the MAP sensor, the engine started running rough. I have experienced similar situations with other vehicles due to vacuum issues and was told by more than once source this might be an issue with my Eldo as well. I have attached a diagram of the top of the Northstar with a vacuum related part circled in red. This part is leaking, because the housing on one side has cracked. Question: could this one leak on it's own, be the source of the rough-running issue? BTW, there are no PCM codes present since I reset them after installing my MAP sensor and I have driven the car to a service guy and back. I can only assume that during that time, if there was going to be a new error code, it would have been generated by now. Side Note: said service guy has a diagnostic gizmo that can detect more than my OBD1 can. He stated to me that his device detected "random misfire" and to replace plug wires. I did and this had absolutely no impact on the rough running issue. Link to comment Share on other sites More sharing options...
BodybyFisher Posted October 14, 2012 Report Share Posted October 14, 2012 Any vacuum leak at all can cause a misfire because of a lean mixture If you had removed them check your ignition wires for proper seating and damaged contacts are connectors. You may have damaged a plug wire on removal or reinstallation or the boot is not seated right 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...
Cadillac Jim Posted October 15, 2012 Report Share Posted October 15, 2012 The plug wires was a good guess, but plug wires don't cause a random miss. If your plug wires are bad, you will have one, two, or three cylinders that consistently miss. A random miss is not likely the ignition, unless it's something like a bad ground on the ignition module, very high mileage on a set of spark plugs, etc. One thing that is very important with all modern cars is the lay of the plug wires when you install them. You *must* put them back exactly the same way that they came out. Use a diagram from a manual if you didn't take note (or take a cell phone photo!). If you don't, you will have plug wires cross-firing, pinch them against the guides in the beauty cover, or, worst of all, hook the wrong coils to the plugs. Check *all* the vacuum hoses to the manifold and the throttle body. Also, make sure that the PCV valve is seated firmly, that the PCV valve boot is still OK (if you need a new one, NAPA Auto Parts sells them for $2, but I had a dealer once charge me $200 for one), make sure that the oil dip stick is OK and firmly seated, and likewise the oil filler cap. After this little Autumn driveway exercise, please clear the codes, drive the car, run the OBD codes after you get back but before you turn off the key, and post all of them here. We can work with you to clear them all. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
Ion Posted October 18, 2012 Author Report Share Posted October 18, 2012 UPDATE: Just finished installing the vacuum harness pictured in my attachment (one of the parts was mounted on top of throttle body), to fix obvious vacuum leaks and...absolutely no impact on the rough-running issue! I hate having to say "well, the harness I replace needed to be replaced anyway", as if it were some sort of consolation... I checked all other vacuum lines and PCV is seated firmly. Plug wires are seated firmly into the plastic harness on the driver-side of engine, while the ones closer to the 4 cylinders closest to firewall are kind of willy-nilly, as there is no plastic harness for them. After taking it for a spin, the only code was in history P070 (intermittent tps). One curious thing: for fun, I started pulling plug wires from their respective coilpacks (and spark plugs) and all but one, arced like crazy as soon as wire became disconnected. Is it normal for one coilpack AND the wire's respective spark plug connection to NOT arc when disconnected? Might this be the cause of my ongoing issue? Link to comment Share on other sites More sharing options...
BodybyFisher Posted October 19, 2012 Report Share Posted October 19, 2012 I just worked on a 95 Eldo with a bad miss (ala rough idle) and it was a bad coil. Replaced the coil and she purrs. You can confirm this by testing the coil's primary and secondary resistance, my bad coil was very obvious when I checked the resistances. Write down the primary and secondary readings and your bad coil will stick out like a sore thumb. BUT... if you do not have an ohm meter, it sounds like you have zero'd in on the bad coil, and I think its safe to replace it, they are about $35 to $50. By the way, in order to test the primary coil winding, I used a narrow knife connector with a wire soldered to it, just slip the knife connector into the primary. The secondary is where the plug wire attaches. 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 October 19, 2012 Report Share Posted October 19, 2012 Here is a nice article on coil testing and coils http://www.aa1car.co...ition_coils.htm You will notice this statement, never let sparks jump around like that, it can damage local electronics or coil damage can result WARNING: Never pull off a plug wire or the coil's high voltage output wire to test for a spark. Besides risking a severe shock, an open plug wire or coil wire will increase the voltage demands on the coil to the point where it may damage the coil. The only safe way to test for spark is to use a spark plug tester tool. 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...
Ion Posted October 20, 2012 Author Report Share Posted October 20, 2012 I just worked on a 95 Eldo with a bad miss (ala rough idle) and it was a bad coil. Replaced the coil and she purrs. You can confirm this by testing the coil's primary and secondary resistance, my bad coil was very obvious when I checked the resistances. Write down the primary and secondary readings and your bad coil will stick out like a sore thumb. By the way, in order to test the primary coil winding, I used a narrow knife connector with a wire soldered to it, just slip the knife connector into the primary. The secondary is where the plug wire attaches. Can you show me on the attached image of a coil, where the "primary" is? If I understand you correctly, the "secondary" is where the plug wire connects. Link to comment Share on other sites More sharing options...
Cadillac Jim Posted October 20, 2012 Report Share Posted October 20, 2012 The coil shown is one for the 1993-1999 models. The two exposed lugs are for the plug wires with boots. The primary is between pins on the connector under the bolt and ground, which is another pin. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
BodybyFisher Posted October 20, 2012 Report Share Posted October 20, 2012 The reason why I posted that article on testing coils is that it explains the primary and secondary parts of the coil The primary is underneith, you will need to remove the coil, its the feed side of the coil, where the ignition wires attach is the output side or the secondary. If you don't want a big hassle check the secondaries (between the towers) real quick and see what you find, write down the results and compare the 4 coils 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...
Ion Posted October 21, 2012 Author Report Share Posted October 21, 2012 If you don't want a big hassle check the secondaries (between the towers) real quick and see what you find, write down the results and compare the 4 coils After testing the 4 coil packs (between the towers), 3 had an almost identical reading, while the 4th was drastically different. Is is safe to assume the one that stood out needs to be replaced? Link to comment Share on other sites More sharing options...
Cadillac Jim Posted October 21, 2012 Report Share Posted October 21, 2012 It sounds likely. Give us the numbers and we can tell. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
Ion Posted October 21, 2012 Author Report Share Posted October 21, 2012 WOO-HOO! Replaced the one that was way out of range and finally...the engine runs properly! One last question re: this whole mess...could the bad coil have triggered MAP and TPS error codes? Link to comment Share on other sites More sharing options...
BodybyFisher Posted October 22, 2012 Report Share Posted October 22, 2012 I dont know about the TPS code but it definately can cause a MAP code. Good for you! Glad we were able to help, 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...
Cadillac Jim Posted October 22, 2012 Report Share Posted October 22, 2012 Congratulations on your success. I would expect that a bad coil could cause the PCM to throw a TPS code, by putting the idle speed out of the range for the TPS reading. The simplest way to tell is to reset the codes and see what comes back, which is a good idea whenever you complete a repair that threw a code. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
Ion Posted October 22, 2012 Author Report Share Posted October 22, 2012 Thanks Jims_97_ETC and BodybyFisher 4 helping me diagnose this problem. Link to comment Share on other sites More sharing options...
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