BodybyFisher Posted October 7, 2011 Report Share Posted October 7, 2011 Pulling the vacuum hose is creating a vacuum leak. Same as pressing on the throttle. An RPM increase is exactly what I would expect. Ahh, good point Ranger!, my thinking didnt go there, I am so frustrated with this problem, I am looking at anything positive 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 7, 2011 Report Share Posted October 7, 2011 You have stuck with this, and have done a lot of diagnosis and work. Good for you. It is surprising that we have not come across the problem given the amount of work you have done here. I want you to keep in mind that you feel that you can cause the misfire by hitting bumps and you feel you can make it better by hitting the coil area. I think the problem is right in front of you. If you had the ability to see real time info, I'd love to know which cylinders have the misfire again. Answer me this question, did you have this exact misfire before the head gasket 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...
donljacobs Posted October 7, 2011 Author Report Share Posted October 7, 2011 Yes, same issue started just before the HG repair. The mechanic who did the HG, put on his computer and said 2468 were misfiring, told me to buy a coil pack and it would be healed....nope.....went back to him......told me to put on a coil pack harness....nope. He told me to come in on a certain day....no show.....I have not been back I have a one year warantee on the HG....but he forgot to put freon back in system, my brakes are extremely squirrely ripping the wheel out of my hands, he bled the brakes, same issue, and he is telling me I need new lower control arms. That is on my list; however, the car stopped perfect before he dropped the cradle. So, you can see where I am reluctant to go back to him. He charged $1150 for head gaskets with new tap out inserts and bolts....no overheat since. The thing that drives me crazy is that you start the car with touch of key(takes away from fuel pressure issues?) Idles fine for a minute or two, then goes into rough idle.....and then smooth without touching it. sometimes it takes off rough (ses flashing) and all of a sudden it takes off (no ses) sometimes it takes off perfect. On highway, I feel, not certain, that with every bump, it changes, but mostly I guess because of speed, it is smooth. I am getting a priest to exorcise it! I agree with you that this must be something simple, but I can't find it.....my gut is telling me it is intermittent with the computer????????? The wife is getting very testy with me about throwing money at. I have always fixed most issues with out cars, she has never seen a dealer bill and this HG is the largest bill she has seen on auto's in our 30 years of marriage! Very frustrated but willing to try more, do over, whatever, thanks again Oh, I only have 0300 code and once a #4 misfire and that is why I replaced #4 injector. That code doesn't show anymore...only 300 Link to comment Share on other sites More sharing options...
BodybyFisher Posted October 7, 2011 Report Share Posted October 7, 2011 I think you need to find out exactly what cylinders are misfiring before continuing. For the record, I don't think you are 'throwing' money at it or 'parts replacing You replaced the coil pack, those coil packs are problematic and we have seen the problem, plus your mechanic said it was bad I think what you should do is to check the continuity between the ICM and the PCM for the front bank. You said you saw a nicked wire. I would focus on that. Do you have an ohm meter with a buzzer for continuity? I would as an example put your meter leads on one end say Terminal C at the ICM end of the connector and put the other lead on Terminal 9 at the PCM and then manually move the harness to see if you can induce an intermittant. I would do that for every terminal between the ICM and the PCM. I would also make sure that none of the connectors at the ICM plug are damaged (did you replace that plug?) 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...
donljacobs Posted October 7, 2011 Author Report Share Posted October 7, 2011 I do not have a buzzer on my ohm meter, but I will try tests, I will try anything. I went ahead and re-did the coil pack harness again. This time I went up the harness 8 inches way past that nick and spliced in soldering connections and then plastic coating. I also took the airbox completely out and checked the wiring unterneath and it all was very good. Oh, while splicing in all the original wires were shinny bright no corrosion. I have been over all connectors and wiring that I can get my hands on. I am telling you it is crazy to start up this car with the touch of a key......get out.....watch it go rough.....and then smooth.....and then rough........without touching! I am finding that when it starts to go rough while I am driving, sometimes I can grab a lower gear and it goes smooth, sometimes I can feather the gas peddle and it will go smooth. That may have nothing to do with it. Also, sometimes at a light when it starts to go rough, I will put in neutral and feather the peddle up to 1500 rpm, shift when it is dropping, but not to 900 and she will take off smooth. Crazy! I personally have never seen anything like it. I will run these new tests and let you know what I find, thank you again!!!!!!!!!!!! I am starting a new job, been off work all summer, on Monday and it is a pretty fair commute and I don't want to drive this baby like it is, but I have no choice! I did find a shop that will check the computer for $65 and if I am unsuccessful tonight, I will be there first thing in the morning and at least get that done plus see what code his computer comes up with. One thought I have had is that it is the back bank instead of front? Another 200 plus, but I would dance if that fixed it! ...........Hey, what if I disconnected that back bank while it is rough, if it did not die, or change.....would that be proof that it is bad??????? Link to comment Share on other sites More sharing options...
BodybyFisher Posted October 7, 2011 Report Share Posted October 7, 2011 DO NOT leave the connector connected to the PCM when you do that continuity test I described above 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 October 8, 2011 Report Share Posted October 8, 2011 If you disconnect the rear bank you'll be running on the front 4 cylinders only, but it would not hurt to wiggle the connector while it's running. Have you considered a junkyard cassette instead of $200 for a brand new one? Generally speaking, they are pretty reliable. One more thought. There is a way to enable "snap shot", where the PCM will store all the engine parameters when a fault occurs. The only problem with that is I believe you'll need a Tech II to retrieve that data and of coarse will need a FSM to decipher it. Link to comment Share on other sites More sharing options...
airmike Posted October 8, 2011 Report Share Posted October 8, 2011 If you disconnect the rear bank you'll be running on the front 4 cylinders only, but it would not hurt to wiggle the connector while it's running. Have you considered a junkyard cassette instead of $200 for a brand new one? Generally speaking, they are pretty reliable. One more thought. There is a way to enable "snap shot", where the PCM will store all the engine parameters when a fault occurs. The only problem with that is I believe you'll need a Tech II to retrieve that data and of coarse will need a FSM to decipher it. Not being familiar with the cassette you are dealing with here I will make a suggestion that I hope is feasible. I would try taking the front coil pack/cassette and temporarily mount it to the rear, even just laying loose but grounded, just to use a known good part. If your miss continues on that bank you have absolutely eliminated the cassette as the cause. Link to comment Share on other sites More sharing options...
donljacobs Posted October 8, 2011 Author Report Share Posted October 8, 2011 Fun City, I just got home from the hospital, Gall Stones, ouch! Front and rear cassettes are different. The mechanics computer said misfire 2468 front bank, but after everything, I think he is unreliable....and it feels like it is running on 4 cylinders! So when it goes rough and I pull rear connector, in theory, it should die? but if the rough doesn't change does that mean it is the rear misfiring and the front are firing????? Does that make sense? Link to comment Share on other sites More sharing options...
Ranger Posted October 8, 2011 Report Share Posted October 8, 2011 No, if you pull the connector from either cassette it's like pulling the center cable from a distributor cap. No power to the coils or plugs. The only difference between the front and rear cassette is the color. Link to comment Share on other sites More sharing options...
donljacobs Posted October 8, 2011 Author Report Share Posted October 8, 2011 Well, I have the original front bank which I believe is just fine! I have the new one in the car and when I swapped no change. So this should be quite simple......well, the back is a bit more trouble to do than the front, but I did it before when I put in new plugs. Now that sounds like a great test. Again with this thing doing its automatic correction, it is almost impossible to tell if your wiggling, proding, tapping has anything to do with it! Thanks again I will report findings. Link to comment Share on other sites More sharing options...
BodybyFisher Posted October 8, 2011 Report Share Posted October 8, 2011 Misfiring does not mean that its NOT firing. It just could be weak spark, so pulling the rear would have an affect but may not kill it. I am not one for pulling connectors though. This FN problem is annoying. If his scanner says 2, 4, 6 & 8, it is, you don't have to be too competent to get that correct, I have an autotap that gives misfire counts its a no brainer So MEMBERS, lets help this fellow out, what in the hell can cause the FRONT bank to misfire like this? PLEASE 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...
donljacobs Posted October 8, 2011 Author Report Share Posted October 8, 2011 I talked to a friend of a friend today who is a Cadillac Mechanic and he said often after a HG job you have carbon on the valves and it causes sticky valves. He said try seafoam spray.........which I did once, but will try again. Went to try to get computer checked, too busy today. Not feeling well, so will try tests tomorrow, Thanks again! Link to comment Share on other sites More sharing options...
BodybyFisher Posted October 8, 2011 Report Share Posted October 8, 2011 Feel better I am sure gall stones are no picnic. What are the symptoms? Lets see what other members think. We have some pretty deep thinkers on this forum. I hope they are looking in on this thread and can come up with some ideas. I don't buy the sticking valves reasoning, just 2,4,6,8? Too coincidental, and odd that ALL valves on the same bank would 'stick' I considered that maybe, just maybe, the front timing chain is off a tooth, and that is why I asked if you had this before the head gasket job and you said yes you did. Let me ask in more detail, did you have the misfires scanned before the head gasket and did they actually say 2,4,6,8 was misfiring? Are you 100% sure you have the EXACT same misfire now as you had before the head gasket job? It is VERY important to know if this is the EXACT same problem before and after the head gasket job, we can eliminate mechanical issues caused by the mechanic. Did your mechanic replace the intake manifold gaskets?, that is important to know, if you still have the same problem you had before the HG job. The intermittant nature of this problem leads one to conclude that its electrical, but as we know an electrical problem can lead to a fuel pump wacking out or a fuel pump can have an intermittant balky motor. In addition, you seem to feel that it is affected by vibration, road or otherwise. We tried a tap test on the PCM and you could not induce the problem, but the PCM still could be the problem and it just not be sensitive to vibration (although your observation, tells you the misfire seems to be sensitive to vibration). When you did the PCM tap test, did you reset the electrical connections to it by unplugging and plugging them? You changed a couple of injectors with no change and you changed the o-rings on the fuel rail and made sure its seated good. You changed the Fuel Pressure Regulator. You changed the connector at the coil pack and rechecked it. You changed the coil pack, and swapped in another one for good measure and the problem continued. You checked power to the coil pack is constant, and the ICM ground is constant and it exists. I asked you to check for continuity in the wiring between the ICM and the PCM to make sure you don't have any issues. Do you have any scrap yards near you?, if you do, you might attempt to get a used PCM and swap it in. Did you check the ICM ground with your ohm meter? I DO NOT want you to go out and buy a PCM, but I am leaning toward a PCM problem. I really need the membership to stop in on this one, they seem to have avoided this thread (and I don't blame them ) What have I missed above? Feel better man, the problem can wait to be solved 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...
donljacobs Posted October 8, 2011 Author Report Share Posted October 8, 2011 No symptoms......blood appeared and a minute later the pain hit me like a truck! I could not speak, my kids saw me and rushed me to the hospital. On the way there, the pain greatly abated, today I am just real sore and experiencing "after shocks". Shock to me, I am blessed with great health otherwise, a few old war pains, but I get around well for my age. I still need to do electric tests. I ran another can of seafoam spray through it, very simple. Took car on the highway for a 40 mile trip.......It ran perfect no SES light....third light off the highway, it started stumbling at traffic light. Just ran an errand still stumbling! I will run electric test again. I got to take a little rest now, my nerves are shot. Thanks for sticking with me. I have a computer on watch on Ebay. I still don't know if vin makes a difference. The owner said no it did not? I have not taken the connectors off, but I wlll and spray with contact cleaner. Thanks again! Link to comment Share on other sites More sharing options...
airmike Posted October 8, 2011 Report Share Posted October 8, 2011 I am not sure reading this if you have changed the front coil pack to the rear yet. I would like those results to rule that out. Link to comment Share on other sites More sharing options...
donljacobs Posted October 8, 2011 Author Report Share Posted October 8, 2011 Yes, did that, I pulled computer connectors and cleaned them with contact spray. It is crazy, but appears to run a little better. Here is another crazy thing there are two cables by the TB......one is gas pedal...is other for shifting? It appears that when I put tension on that the car runs better, the cable appears to be very loose and while pulling it, it came out of its little rubber pulley. Anyway, I put it back and the car ran better???? Maybe I am loosing my mind now???? I still have not run test on computer. Uh, that cable I mentioned has a big spring underneath. At other times messing with hoses, wires near that cable, the car ran smoother. but again, it will run smooth on its own. Often coming to a stop at a light, i will shift into neutral, feather it to 1500 rpm on the drop shift into gear and it will take off properly. It also appears that the power steering pump is leaking now. When it misfires the belts don't run fast enough and perhaps I put too much pressure on it while it was running rough???????? Thanks again! Link to comment Share on other sites More sharing options...
BodybyFisher Posted October 8, 2011 Report Share Posted October 8, 2011 If you have a digital photo, take a photo and post it here On the TB there are connections for the IAC (Idle Air Control) and the TPS (throttle position sensor) 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 October 9, 2011 Report Share Posted October 9, 2011 The intermittant nature of this problem leads one to conclude that its electrical I agree. Here is another crazy thing there are two cables by the TB......one is gas pedal...is other for shifting? Two cables, side by side. One is the throttle cable and the other is the cruise control cable. Uh, that cable I mentioned has a big spring underneath. The shift cable beneath the TB has a spring around it just before where it mounts and attaches to the shift rod that controls the gear selector on the top of the trans. Link to comment Share on other sites More sharing options...
BodybyFisher Posted October 9, 2011 Report Share Posted October 9, 2011 Oh, I took cables to mean electrical wires, sorry. Those cable connections to the throttle body are the pedal and the cruise control as noted 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 9, 2011 Report Share Posted October 9, 2011 Check the IAC connector for corrosion and tightness. You might want to pull the IAC and clean it and the port. Make sure its seal is intact. It is held in place with torx screws. Look at all vacuum hoses to make sure they are not cracks and listen for a vacuum leak also. Make sure the throttle body is tight. Rock the throttle plate rod and see if you have play or if it induces the miss. 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...
donljacobs Posted October 9, 2011 Author Report Share Posted October 9, 2011 That makes sense! I took pictures saved to my docs.........how do I attach to this message. Don't need now, but for future reference. Could the idle get so low as to cause a misfire?? I did clean the IAC forgot about that and it was dirty, did not make a difference though. ELECTRICAL make sense to me, again, it sits there and goes back and forth bad to good. Kind of like a wave! Because it automatically corrects itself, it is hard/impossibe to tell if something you are doing is affecting it. I still need to do test on PCM which I will do tomorrow. Link to comment Share on other sites More sharing options...
Ranger Posted October 9, 2011 Report Share Posted October 9, 2011 Look at all vacuum hoses to make sure they are not cracks and listen for a vacuum leak also. Be sure to check the PCV dirty air line connection in the rear cam cover. Link to comment Share on other sites More sharing options...
donljacobs Posted October 9, 2011 Author Report Share Posted October 9, 2011 PCV is fairly new and rattling freely. TB is tight. I have been all over connectors twice. IAC was dirty and I cleaned it very well. the shaft moves left to right about 1/4 inch......is that OK. Could it cause misfire if bad??? Thanks! Link to comment Share on other sites More sharing options...
BodybyFisher Posted October 9, 2011 Report Share Posted October 9, 2011 What shaft?, the IAC or the throttle plate shaft? 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...
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