Deciphering the P03xx series misfire codes - please help!?
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Cadillac Catera and Cimarron Forum Discussion, Deciphering the P03xx series misfire codes - please help!? in Past Cadillac Vehicle Discussion; Bought a used '98 Catera, 96k miles -- cheap, cheap, cheap. I've only had it for two weeks. Love the ...
  1. #1
    catman'98 is offline Cadillac Owners Member
    Automobile(s): Cadillac Catera '98
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    Deciphering the P03xx series misfire codes - please help!?

    Bought a used '98 Catera, 96k miles -- cheap, cheap, cheap. I've only had it for two weeks.

    Love the car, but hate the parts prices. Geeez! But, this thing has all the gadgets! I find new little contraptions on this thing almost every day. Great thing is that everything works (knock on wood).
    I pray that the catalytic convertor isn't fouled. No bad O2 sensors, so I must have caught it in time. Seller told me they replaced the front sensor already -- took a peek, looks new. Passed GA emissions test in May '08. Car sat for a few months, then all this (well, that's what SHE said....right!). I can tell it was dumping unburnt fuel into the exhaust. But, I could also tell that the valves were okay!

    Symptoms: Low power and acceleration, slight rough idle. I'm not sure how the car should feel, but I know something is wrong in the fuel/air or electrical! It's a DOG right now. 200+hp should feel much better than this.

    Check engine light on - OBD codes:
    P0300 - Random misfire
    P0302 - #2 cylinder misfire
    P0305 - #5 cylinder misfire
    P0304 - #4 cylinder misfire (this one cleared after all the work below)

    Replaced the valve cover gaskets. Oil leaks settling down around the spark plugs. Had to pull the entire intake manifold and injector housing to have good clearance for removing the valve covers. Did not replace the gaskets on the manifold or injector housing (o-rings and shaped seal rings), but will do that later. I cleaned the old seals and the manifold seat/facings really good and used a little silicon grease to lube them up before putting it all back together. I'm pretty sure it's sealed up good, but haven't checked the vacuum yet. I can't hear any leaks. Replaced spark plugs with Bosch Platinum 4 (had 3's in it). The old plugs were in really bad shape. I mean BAD! Serviced the injectors (flushed w/Gumout). Added a can of Gumout cleaner to a new, full tank of Super Premium. Cleaned the old plug wire covers with some acetone to get the oil out of them. They look good, but who knows.

    Next step (I think) is to replace the plug wires, then the distributor pack, in that order.
    Anything else I should check first, before buying that stinkin' $135 set of plug wires, and then the $209 distributor pack?
    The service flow chart would be awesome. Can anyone help me with the service flow charts on this issue?


    (((( Previous owners need some serious spankins'. I know this little car is a gem, despite all the bad PR...it just needs some TLC. And, it seems, based on all the horror stories that I have read in the past few days, that us Catera owners should take extra precaution to keep them serviced right! ))))

    Brad -

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  3. #2
    catman'98 is offline Cadillac Owners Member
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    Cool Re: Deciphering the P03xx series misfire codes - please help!?

    No knowledge or experience out there for this one?

  4. #3
    catman'98 is offline Cadillac Owners Member
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    Thread Starter

    No Cat Experts lurking? Deciphering the P03xx series misfire codes - please help!?

    Huh?

  5. #4
    frank moran is offline Cadillac Owners Fanatic
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    Re: Deciphering the P03xx series misfire codes - please help!?

    Quote Originally Posted by catman'98 View Post
    Bought a used '98 Catera, 96k miles -- cheap, cheap, cheap. I've only had it for two weeks.

    Love the car, but hate the parts prices. Geeez! But, this thing has all the gadgets! I find new little contraptions on this thing almost every day. Great thing is that everything works (knock on wood).
    I pray that the catalytic convertor isn't fouled. No bad O2 sensors, so I must have caught it in time. Seller told me they replaced the front sensor already -- took a peek, looks new. Passed GA emissions test in May '08. Car sat for a few months, then all this (well, that's what SHE said....right!). I can tell it was dumping unburnt fuel into the exhaust. But, I could also tell that the valves were okay!

    Symptoms: Low power and acceleration, slight rough idle. I'm not sure how the car should feel, but I know something is wrong in the fuel/air or electrical! It's a DOG right now. 200+hp should feel much better than this.

    Check engine light on - OBD codes:
    P0300 - Random misfire
    P0302 - #2 cylinder misfire
    P0305 - #5 cylinder misfire
    P0304 - #4 cylinder misfire (this one cleared after all the work below)

    Replaced the valve cover gaskets. Oil leaks settling down around the spark plugs. Had to pull the entire intake manifold and injector housing to have good clearance for removing the valve covers. Did not replace the gaskets on the manifold or injector housing (o-rings and shaped seal rings), but will do that later. I cleaned the old seals and the manifold seat/facings really good and used a little silicon grease to lube them up before putting it all back together. I'm pretty sure it's sealed up good, but haven't checked the vacuum yet. I can't hear any leaks. Replaced spark plugs with Bosch Platinum 4 (had 3's in it). The old plugs were in really bad shape. I mean BAD! Serviced the injectors (flushed w/Gumout). Added a can of Gumout cleaner to a new, full tank of Super Premium. Cleaned the old plug wire covers with some acetone to get the oil out of them. They look good, but who knows.

    Next step (I think) is to replace the plug wires, then the distributor pack, in that order.
    Anything else I should check first, before buying that stinkin' $135 set of plug wires, and then the $209 distributor pack?
    The service flow chart would be awesome. Can anyone help me with the service flow charts on this issue?


    (((( Previous owners need some serious spankins'. I know this little car is a gem, despite all the bad PR...it just needs some TLC. And, it seems, based on all the horror stories that I have read in the past few days, that us Catera owners should take extra precaution to keep them serviced right! ))))

    Brad -
    first, were the plugs you took out wet with fuel? if not you can probebly rule out a leaking injector. Next, did you have these codes before you lifted the plenum? it's doubful you would have 3 bad wires or plugs. Let us know...

  6. #5
    catman'98 is offline Cadillac Owners Member
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    Thread Starter

    Re: Deciphering the P03xx series misfire codes - please help!?

    Thanks for responding, Frank.

    The car had misfire issues when I bought it. It was very obvious. I limped it home and immediately went to work on it. I didn't check the codes before pulling the plenum and replacing the valve cover gaskets and spark plugs. Most of the spark plug wells had oil in them. The two cylinders misfiring now definitely had oil in the wells. When I pulled the spark plugs, the oil drained down into the cylinder...and got oil all over the spark plug electrodes, so I'm not sure if there was fuel in those cylinders (#2 and #5). The car seemed to run a little bit better after replacing the plugs.
    Then, I limped it over to a local oil change / tune-up shop a few days later, and a mechanic checked the codes for me there, after cleaning the fuel injectors. I asked him to try clearing the codes. The cylinder #4 misfire cleared and didn't come back. I suspect that I fixed that one.

    I think you make a good point about the spark plug wires. I've been working on my own cars for 20 years, and I've yet to see plug wires just 'quit', without some sort of visible damage. The plug wires look fine, although I did have to clean the oil out of them. I know that visually looking okay is no real test, so I'm thinking about purchasing one of those inline 'spark' checking devices for $15...rather than trying to use a spare spark plug to check the spark. Do you think I could just skip the plug wires and move straight to the distributor/coil pack, if I don't get a good spark? I wish that I had a known good, spare plug wire laying around. I'd check it that way. I'd try swapping a couple of them, but these wires are cut specific lengths, for each cylinder. I don't want to buy a $135 set of plug wires, if I don't have to.

    I've seen a bunch of Catera posts describing how this exact same problem (valve covers leaking / oil in the wells) had fried the coil pack. Does the coil pack have anything in common for cylinders #2 and #5?

    Also, I've seen other posts here that tell me the entire cause this cascade of events -- the cranckase breather path is plugged -- causing excess pressure to build up. I'm not completely sold on that yet, because it seems that the oil fill tube should start venting before blowing the valve cover gaskets. I've seen instructions on how to clean that vent path. Any thoughts about that?

    Brad -

  7. #6
    frank moran is offline Cadillac Owners Fanatic
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    Re: Deciphering the P03xx series misfire codes - please help!?

    Yes, 2 and 5 are opposite one another in the coil. First check that 2 and 5 are in the correct location on the coil, the coil is on the rear of the DS cyl head. Locate the primary wire connector on the coil, from this connector location wires 2-6-4 are on the head side,5-3-1 are opposite . Before you do anything, confirm the wires are in the correct location, if OK replace the plugs assuming they are oil fouled, they may look OK but that can fool you. Next check the wires with an ohm meter..point, before you start buying anything get the cheap stuff out of the way first.
    For clarification 2-5 are opposite, 3-6 opposite and 1-4 opposite on the coil. Hope this helps. From your note, I think you still have a plug problem.?



    Quote Originally Posted by catman'98 View Post
    Thanks for responding, Frank.

    The car had misfire issues when I bought it. It was very obvious. I limped it home and immediately went to work on it. I didn't check the codes before pulling the plenum and replacing the valve cover gaskets and spark plugs. Most of the spark plug wells had oil in them. The two cylinders misfiring now definitely had oil in the wells. When I pulled the spark plugs, the oil drained down into the cylinder...and got oil all over the spark plug electrodes, so I'm not sure if there was fuel in those cylinders (#2 and #5). The car seemed to run a little bit better after replacing the plugs.
    Then, I limped it over to a local oil change / tune-up shop a few days later, and a mechanic checked the codes for me there, after cleaning the fuel injectors. I asked him to try clearing the codes. The cylinder #4 misfire cleared and didn't come back. I suspect that I fixed that one.

    I think you make a good point about the spark plug wires. I've been working on my own cars for 20 years, and I've yet to see plug wires just 'quit', without some sort of visible damage. The plug wires look fine, although I did have to clean the oil out of them. I know that visually looking okay is no real test, so I'm thinking about purchasing one of those inline 'spark' checking devices for $15...rather than trying to use a spare spark plug to check the spark. Do you think I could just skip the plug wires and move straight to the distributor/coil pack, if I don't get a good spark? I wish that I had a known good, spare plug wire laying around. I'd check it that way. I'd try swapping a couple of them, but these wires are cut specific lengths, for each cylinder. I don't want to buy a $135 set of plug wires, if I don't have to.

    I've seen a bunch of Catera posts describing how this exact same problem (valve covers leaking / oil in the wells) had fried the coil pack. Does the coil pack have anything in common for cylinders #2 and #5?

    Also, I've seen other posts here that tell me the entire cause this cascade of events -- the cranckase breather path is plugged -- causing excess pressure to build up. I'm not completely sold on that yet, because it seems that the oil fill tube should start venting before blowing the valve cover gaskets. I've seen instructions on how to clean that vent path. Any thoughts about that?

    Brad -

  8. #7
    catman'98 is offline Cadillac Owners Member
    Automobile(s): Cadillac Catera '98
    Join Date
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    Thread Starter

    Re: Deciphering the P03xx series misfire codes - please help!?

    Okay - think I have it isolated to the coil pack. All plug wires checked okay with my digital meter -- between 10-12k Ohms. Pulled the plug wire from #1 cylinder and stuck a spare spark plug into the boot, then grounded it on the plenum. Plenty of spark on #1! Did the same thing on #5 wire, and NO SPARK! Next step -- replace the coil pack!

    Just for a sanity check, I started the car with the #5 boot off and on -- either way, it made absolutely no difference.

    I'll post the results after I find a reasonably-priced coil pack and install it. I'm not paying $209 bucks for a damn coil.
    One more thing. I thought I had found a real problem while I was taking the wiper unit out. I found what looked to be a disconnected vacuum line. After searching an hour for the destination port, it turns out that it HAS NO home. It's a vent line from the transmission, and it just vents to atmosphere. Geez -- what a wild goose chase!

    Thanks Frank!

  9. #8
    gunther1000 is offline Cadillac Owners Fanatic
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    Re: Deciphering the P03xx series misfire codes - please help!?

    I'm very interested in how this turns out for you.

    I have been messing with the same exact issue but with my #1cy. it says misfire codes for 1-4-5 but only #1 has no spark. Replaced coil pack tonight with no change... maybe Ecu? I'm Throwing money at it like a freaking moron... This time once its running its for sale and parked I swear! My cold hard $3000 I get for it will be a nice loss and a paid for learning lesson.

    Maybe crank sensor? I'll just get out the check book again... catera = Cost Alot To Eventually aggrivate.

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