ocdave Posted January 11, 2009 Report Share Posted January 11, 2009 Hopefully someone can help. I have a chance to buy a 1998 Deville very cheap. The car has only 36,000 miles on it. The head gasket has been replaced. The car drives very smooth and doesn't seem to have any power loss. There are problems though! Once the car is warm, when you have been driving and come to a stop it idles very rough. If I put it in neutral the idle smooths out a bit but once it goes back into drive it is rough again. I also noticed when I came to a stop one time there was a very bad exhaust smell. There is also, I want to call it a grinding sound but that doesn't quite describe it. It comes from the engine on the passenger side, sounds almost like a belt is too tight or something. It changes its pitch as the engine revs. Very hard to describe. Also at idle in park there is a pop or misfire sound coming from the tail pipes. The "service engine soon" light in the dash is on. The owner, who is an old lady, took it to the cadillac dealer and they supposedly did a 55 point inspection and said that the idle was something in the enging that they couldn't diagnose without tearing it apart. What kind of problems am I looking at and what is it going to cost to fix it?? Link to comment Share on other sites More sharing options...
Texas Jim Posted January 11, 2009 Report Share Posted January 11, 2009 Pull the codes from the DIC and post them here. The car will tell you (up to a point) what is wrong with it. From your description...the first thing i would check would be the plugs and wires. A bad plug or a bad wire will cause ALL of the things you mentioned. If a plug is fouled or misfiring, it will be running rich..which will turn on the CHECK ENGINE light. A bad plug will also cause it to run rough and have a bad exhaust smell and cause the noise you are hearing at the tail pipe. It could also be something REAL SERIOUS like a burnt valve, but start with the simple stuff first. The grinding sound could be a tensioner pulley for the serpentine belt. Link to comment Share on other sites More sharing options...
ocdave Posted January 11, 2009 Author Report Share Posted January 11, 2009 Thanks so much for your reply! How do I pull the codes?? Link to comment Share on other sites More sharing options...
BodybyFisher Posted January 11, 2009 Report Share Posted January 11, 2009 You will probably have a P0300 misfire code 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...
Texas Jim Posted January 11, 2009 Report Share Posted January 11, 2009 Thanks so much for your reply! How do I pull the codes?? http://www.caddyinfo.com/readingcodes.html Link to comment Share on other sites More sharing options...
Ranger Posted January 11, 2009 Report Share Posted January 11, 2009 Also check for a leaky FPR. It will not set a DTC. Link to comment Share on other sites More sharing options...
ocdave Posted January 13, 2009 Author Report Share Posted January 13, 2009 I just got home from the car and was able to pull the codes. I also checked the FPR and it seemed to be ok. There was vacuum and no sign of any fuel. I also found out that the plugs and wires were all changed out in July 07 and only have a couple thousand miles on them. The codes are as followed....... P0300 - Engine Misfire Detected P0463 - Fuel Level Sensor Circuit High Voltage P1376 - Ignition Ground Circuit P1381 - Misfire Detected - No communication with Brake Control Module U1255 - Class 2 Communication Malfunction (Serial Data Line Malfunction) B1147 - Driver Side Air Bag System Malfunction B1148 - Passenger Side Air Bag System Malfunction B1552 - Keep Alive Memory (KAM) Error Any ideas where I should start???? Something tells me I'm going to find a bad o2 sensor or catalytic converter!! Thank you! Link to comment Share on other sites More sharing options...
BodybyFisher Posted January 13, 2009 Report Share Posted January 13, 2009 Look at the plugs and ignition wires for their manufacturer name. If NON platinum plugs were thrown in there, the tips are blown off, if cheap ignition wires were used that could be the problem. Look in each spark plug well to see if its full of oil. A bad O2 sensor would set a code. I think the ignition ground circuit needs to be looked into 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...
MAC Posted January 13, 2009 Report Share Posted January 13, 2009 It could be something like an ignition coil pack. I believe, however, you cannot replace just one in a '98 and would have to by the whole coil pack assembly if this is the problem? or I would guess the possibility that the PCM is bad. A bad PCM can cause erratic idling. I don't want to emphasize too much a bad PCM because there is something else less major that can be causing the problem or perhaps there are multiple issues like a bad O2 Sensor and coil pack. The grinding sound could be a bad pulley. That would be an easy replacement. Just my 2 cents. Link to comment Share on other sites More sharing options...
DJRATEDR Posted March 21, 2009 Report Share Posted March 21, 2009 It could be something like an ignition coil pack. I believe, however, you cannot replace just one in a '98 and would have to by the whole coil pack assembly if this is the problem? or I would guess the possibility that the PCM is bad. A bad PCM can cause erratic idling. I don't want to emphasize too much a bad PCM because there is something else less major that can be causing the problem or perhaps there are multiple issues like a bad O2 Sensor and coil pack. The grinding sound could be a bad pulley. That would be an easy replacement. Just my 2 cents. you CAN buy seperate coil packs for '98 devilles. i got one at advance auto for around $25. Link to comment Share on other sites More sharing options...
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