epricedright Posted December 5, 2006 Report Share Posted December 5, 2006 Drove around today, ran great. Then went into Best Buy and came out 20 minutes later, started it up, and it noticed right away the miss. It feels like it's running on only 6 or 7 cylinders. Runs really bad! No codes though. Driving home going up a hill was really taxing on the motor...bogs down with drastic reduction in power and the miss more pronounced. Punching it, you really feel the miss. Then I was driving along at about 45 or so and heard pinging/detonation(?) when it shifted in OD. Runs rough at idle as well in PN & D, idle was jumping between 575 to 675 RPM's. Giving it gas in P/N misses bad. Starts up fine. What do you suppose is going on? Still has the original plugs and wires, approx 91K. It was really cold today (coincidence?) and it's been kept in a fairly warm garage, so maybe she caught a cold? Anyhow, where should I start trouble shooting? First time I've had this problem. I'm no expert, but it seems to be electrical/ignition related...bad plug/wire? What about the coil? I guess it could be fuel related, but it feels more like an electrical miss. Strange how it was running perfect earlier today, then come out 20 mintes later and BAM! Strange too how it can run so bad, but throws no codes. I'm really dreading working on it as it's gonna be cold all this week. The plugs and wires look like a nightmare to access too, especially the rears. Thanks in advance for any help/advice! Link to comment Share on other sites More sharing options...
PAUL T Posted December 5, 2006 Report Share Posted December 5, 2006 Eliminate the FPR first by checking for gas at the vacuum side. Could there have been some water in the gas? Condensation from inside the tank? Link to comment Share on other sites More sharing options...
epricedright Posted December 5, 2006 Author Report Share Posted December 5, 2006 Eliminate the FPR first by checking for gas at the vacuum side. Could there have been some water in the gas? Condensation from inside the tank? Ok, I'll check the FPR tomorrow. Water in the gas? No idea. Gassed up at Speedway. Ran out about 5 gallond before today. Link to comment Share on other sites More sharing options...
Ranger Posted December 5, 2006 Report Share Posted December 5, 2006 Since you are due for plugs & wires anyway, that might be a good place to start. Link to comment Share on other sites More sharing options...
epricedright Posted December 5, 2006 Author Report Share Posted December 5, 2006 Since you are due for plugs & wires anyway, that might be a good place to start. Larry, you're probably right, but I really didn't want to hear that...It's really cold out and my blood hasn't thickened up yet. I take it the rear plugs are accessed from the top, correct? Link to comment Share on other sites More sharing options...
adallak Posted December 5, 2006 Report Share Posted December 5, 2006 I am with Ranger. Might be a bad contact of wires with plugs. I would first play with connections without pulling the boots (just turning the boots a little bit). The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
Ranger Posted December 5, 2006 Report Share Posted December 5, 2006 Since you are due for plugs & wires anyway, that might be a good place to start. Larry, you're probably right, but I really didn't want to hear that...It's really cold out and my blood hasn't thickened up yet. I take it the rear plugs are accessed from the top, correct? Yeah, when I did the plugs on my '92, I went in from the top. The rears were a @#$^%. By the time I got through my arms looked like a road map. Link to comment Share on other sites More sharing options...
BodybyFisher Posted December 5, 2006 Report Share Posted December 5, 2006 I agree this is a good place to start but why did this start spontaneously? I would lift the hood in complete darkness and see if you have any arching, pay attention to the coils, maybe one cracked or you developed a carbon track. Unless a plug cracked, plugs go bad gradually. 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 December 5, 2006 Report Share Posted December 5, 2006 If you put in gas and everything was fine until it got under a quarter tank, then you made a suddent stop or hard corner or other maneuver, and suddenly it acts like it has water in the gas, then it probably does. You might fill it up ASAP with "top tier" gas or the closest equivalent you can find and see if it doesn't immediately et a little better. If so, water in the gas is the most likely culprit and you have 3/4 of a tank to get a can of GM Fuel System Treatment, P/N 88861011 (in Canada, 89020804) or Techron. -- 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...
GreenMachine Posted December 5, 2006 Report Share Posted December 5, 2006 I found it easiest to reach the rear plugs by removing the coil pack and strut tower brace. With those out of the way you have a lot more room to work with. The Green's Machines 1998 Deville - high mileage, keeps on going, custom cat-back exhaust 2003 Seville - stock low mileage goodness! 2004 Grand Prix GTP CompG - Smaller supercharger pulley, Ported Exhaust Manifolds, Dyno tune, etc 1998 Firebird Formula - 408 LQ9 Stroker motor swap and all sorts of go fast stuff Link to comment Share on other sites More sharing options...
Ranger Posted December 5, 2006 Report Share Posted December 5, 2006 I think he is talking about a 4.9. Northstar is a piece of cake. Link to comment Share on other sites More sharing options...
mmarinov Posted December 5, 2006 Report Share Posted December 5, 2006 I found it easiest to reach the rear plugs by removing the coil pack and strut tower brace. With those out of the way you have a lot more room to work with. He's got the 4.9 though - not the Northy. As I understand it the plugs on the 4.9 are a bear, but I've never had my hands on one. I agree with your own assessment epricedright - ignition (sorry!) That's weird how it was so sudden but then again like BBF said you may have wires that have finally worn to the point where arcing is happening. Mark <!--fonto:Arial--><span style="font-family:Arial"><!--/fonto-->2007 DTS Performance - 50K <!--fontc--></span><!--/fontc--> As a matter of fact, I <i>am</i> driving 70 MPH in a phone booth. Link to comment Share on other sites More sharing options...
epricedright Posted December 5, 2006 Author Report Share Posted December 5, 2006 Where are the coils on the 4.9? I'll check for arching tomorrow night. The pain changing the rears as far as I can see is the very small gap between the valve cover and firewall, and just getting back there going over the engine, never mind all the crap in the way. And it doesn't appear I'll be able to see what I'm doing either, looks like it'll be more of the "brail" method perhaps? I'm a big guy. I wish I had the time, weather and room to make some scaffolling to go over the engine for me to lie on, that would sure help. Gas: I filled it up to about 16 gallons and now have 11 gallons left. Being water is heavier than gas, and if I do indeed have water in my tank and/or lines, I can see that possibly being the cause for the engine running rough. And being I went from a warm garage to the cold outside today, I could see how condensation could form....perhaps? But it sure seems like it's ignition related. Link to comment Share on other sites More sharing options...
adallak Posted December 5, 2006 Report Share Posted December 5, 2006 Where are the coils on the 4.9? I'll check for arching tomorrow night. The pain changing the rears as far as I can see is the very small gap between the valve cover and firewall, and just getting back there going over the engine, never mind all the crap in the way. And it doesn't appear I'll be able to see what I'm doing either, looks like it'll be more of the "brail" method perhaps? I'm a big guy. I wish I had the time, weather and room to make some scaffolling to go over the engine for me to lie on, that would sure help. Gas: I filled it up to about 16 gallons and now have 11 gallons left. Being water is heavier than gas, and if I do indeed have water in my tank and/or lines, I can see that possibly being the cause for the engine running rough. And being I went from a warm garage to the cold outside today, I could see how condensation could form....perhaps? But it sure seems like it's ignition related. Rear ones actually easier than front plugs... Plenty of room up there.Just lay on the engine. You do not need to see the plugs, just follow the wires. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
MAC Posted December 5, 2006 Report Share Posted December 5, 2006 This is where it would be good to have the Factory Manual so you could use the PCM Override feature to test system functions. For example, each fuel injector can be disabled individually with the PS04 code in order to note the effect on engine performance. Link to comment Share on other sites More sharing options...
epricedright Posted December 5, 2006 Author Report Share Posted December 5, 2006 I am with Ranger. Might be a bad contact of wires with plugs. I would first play with connections without pulling the boots (just turning the boots a little bit). That sounds like a plan...and easiest. I will do that after I check for arching. Then I'll check the FPR. Then I will fill up with Shell Premium, although I always use premium, and try that GM fuel treatment. I'm concerned though to try that and not burn it all out. I certainly can't run out a tank with the way it's running. I would hate for that treatment to eat up my fuel pump windings. What about trying some gas dryer? If all that doesn't help, I'll change out the plugs and wires with new OEM. Link to comment Share on other sites More sharing options...
adallak Posted December 5, 2006 Report Share Posted December 5, 2006 Gas drier is harmless, and you can easily calculate the necessary concentration based on the gas in the tank. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
epricedright Posted December 5, 2006 Author Report Share Posted December 5, 2006 Where are the coils on the 4.9? I'll check for arching tomorrow night. The pain changing the rears as far as I can see is the very small gap between the valve cover and firewall, and just getting back there going over the engine, never mind all the crap in the way. And it doesn't appear I'll be able to see what I'm doing either, looks like it'll be more of the "brail" method perhaps? I'm a big guy. I wish I had the time, weather and room to make some scaffolling to go over the engine for me to lie on, that would sure help. Gas: I filled it up to about 16 gallons and now have 11 gallons left. Being water is heavier than gas, and if I do indeed have water in my tank and/or lines, I can see that possibly being the cause for the engine running rough. And being I went from a warm garage to the cold outside today, I could see how condensation could form....perhaps? But it sure seems like it's ignition related. Rear ones actually easier than front plugs... Plenty of room up there.Just lay on the engine. You do not need to see the plugs, just follow the wires. Huh? How is that? I didn't look real close, but aren't the front plugs easily accessible....they're right there, no? Is there something in the way I didn't notice? I know we have the same motors - '91 & '94 4.9's, but is everything the same under the hood....proximity of the rear valve covers to the firewall, etc. I can see those wires being a pain up front though. Rears too for that matter. They were buried and covered under something I believe. I'll have to look at my FSM. I definately didn't see "plenty of room" for the rears. There has to be a difference between the 91 and 94 then. Have you done the plugs and wires on the 94 before? Link to comment Share on other sites More sharing options...
Ranger Posted December 5, 2006 Report Share Posted December 5, 2006 Then I will fill up with Shell Premium, although I always use premium, and try that GM fuel treatment. I'm concerned though to try that and not burn it all out. I certainly can't run out a tank with the way it's running. I would hate for that treatment to eat up my fuel pump windings. What about trying some gas dryer? Use 10% ethanol if you have it in your area. 10% alcohol should dry up any amount of water in the tank. If like us, that is all you have, then water is unlikely unless the tank was full of it and you pumped in gallons of it, but then I doubt it would run at all. Link to comment Share on other sites More sharing options...
adallak Posted December 5, 2006 Report Share Posted December 5, 2006 Where are the coils on the 4.9? I'll check for arching tomorrow night. The pain changing the rears as far as I can see is the very small gap between the valve cover and firewall, and just getting back there going over the engine, never mind all the crap in the way. And it doesn't appear I'll be able to see what I'm doing either, looks like it'll be more of the "brail" method perhaps? I'm a big guy. I wish I had the time, weather and room to make some scaffolling to go over the engine for me to lie on, that would sure help. Gas: I filled it up to about 16 gallons and now have 11 gallons left. Being water is heavier than gas, and if I do indeed have water in my tank and/or lines, I can see that possibly being the cause for the engine running rough. And being I went from a warm garage to the cold outside today, I could see how condensation could form....perhaps? But it sure seems like it's ignition related. Huh? How is that? I didn't look real close, but aren't the front plugs easily accessible....they're right there, no? Is there something in the way I didn't notice? I know we have the same motors - '91 & '94 4.9's, but is everything the same under the hood....proximity of the rear valve covers to the firewall, etc. I can see those wires being a pain up front though. Rears too for that matter. They were buried and covered under something I believe. I'll have to look at my FSM. I definately didn't see "plenty of room" for the rears. There has to be a difference between the 91 and 94 then. Have you done the plugs and wires on the 94 before? I believe the engine bays look pretty much the same. Easily accessible... LOL You'll get a lot of scratches doing front ones. Do the job and you'll see I was right! Rear ones actually easier than front plugs... Plenty of room up there.Just lay on the engine. You do not need to see the plugs, just follow the wires. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
epricedright Posted December 5, 2006 Author Report Share Posted December 5, 2006 Adallak, I'll take your word regarding the fronts. But I still can't see the "plenty of room" you see for the rears. You must have "E.T." hands and arms. And I just know I'm gonna break something if I lay across that motor, with my big ars. I'll let you know how it goes - if I have to go there. Link to comment Share on other sites More sharing options...
BodybyFisher Posted December 5, 2006 Report Share Posted December 5, 2006 I think he is talking about a 4.9. Northstar is a piece of cake. Good point, I suggested looking at the coil packs.. my mistake. The coil is in the distributor cap on the 4.9. I would pull the cap and look for carbon tracking or a crack. This started spontaneously that bugs me. Check the Resistance of each wire and check for vacuum leaks. I think if you were getting an EGR problem (open and not seated) you would get a code. The rear plugs were not too bad on the 4.9, wear gloves there are a lot of sharp edges to get ripped up on. If you have the proper length extensions and universals its not bad. 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...
epricedright Posted December 5, 2006 Author Report Share Posted December 5, 2006 OK, after sitting in the warm garage all night, I started it up just now and it ran perfct. Drove it to the bank and back....no missing at all. This is weird!! I guess that rules out water in the tank/lines. Also the plugs and wires being bad, but I guess there could have been a bad connection between the plugs/cap and wires. Maybe a vaccuum hose that split open when it got cold perhaps? But why is it ok now? It has to be related to something acting up when it got cold. It was pretty chilly yesterday (no more than 20 F) and the wind was gusting really hard in the Best Buy parking lot. It sat out there for 1/2 hour or so. What electronics could be temp sensitive? Could the EGR valve stick due to the cold, and would that produce the symptoms I had? I replaced my EGR valve and vacuum switch less than a year ago. I'm telling you, yesterday it ran like dookey! Link to comment Share on other sites More sharing options...
PAUL T Posted December 5, 2006 Report Share Posted December 5, 2006 I would not rule out water in the gas just yet. Water freezes at 32 degrees F. Water could be freezing in the tank after so long out of the garage in extreme temperatures. Have you checked the FPR yet? What about new codes? Link to comment Share on other sites More sharing options...
epricedright Posted December 5, 2006 Author Report Share Posted December 5, 2006 Hi Paul, No I didn't check anything today. No codes though. Hmmm, you make a good point about the possibility of water in the gas. I'm a little apprehensive about putting the drier in now though. I'd like to fix what's wrong, but would also like to KNOW that it's fixed. I'd hate for this to happen again and be far from home. I guess I could leave it out overnight in the drive when it's freezing and see if it acts up again. Atleast that would tell me it's temp related,(and probably water in my gas) and wasn't a fluke or glitch. Link to comment Share on other sites More sharing options...
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