98 Suburban-How to remove ignition coil / get it to fire up / idle better

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by ticad, Feb 19, 2013.

  1. ticad

    ticad New Member

    I just got a 98 Suburban and am going through the steps of getting it all as close to ship shape as possible. Right now it is running well when driving, but is a little off sounding/puttering slightly at idle. It does not fire right up either, rather it turns for a few soconds before turning over. Check engine light has returned the PO300 code, multiple misfires... I have replaced the plugs and plug wires. The next day, after resetting the code, the light came back on, I did not have it checked to verify it was the same code. A day later the check engine light turned off, but the idle and starting issues remain. I am now attempting to replace the ignition coil.

    I have the new ignition coil ready to install, but can't figure how to get the original off. I haven't found anything real useful online, so far. I did find from this site that there is another 1/2" bolt somewhere on the driver side of the manifold, I think it said, in addition to the 2 bolts at the bracket. It also seems I may have to drill the rivets to remove it, but then will be able to use the bolts that come with the new coil to reinstal. Is there anyone that may have images of the bolt locations to remove the coil and maybe a good process for removing and replacing this critical part of the ignition system in my fine piece of machinery? I also imagine that when drilling the rivets I should use a bit that will still allow me to use the new coil bolts, they look to be 1/4", if I remember right.

    If anyone can think of any other areas I could replace/fix/kick to get the errors fixed feel free to let me know. I'm hoping the issue is not a major thing, but it very well may be. Either way I love the vehicle and am having a great time driving it.

    Sorry about the length, just trying to paint a good picture.

    Thanks in advance either way.
  2. ticad

    ticad New Member

    I have found the third bolt on the bracket. It's behind the distributor towards the back of the engine block. There's a wire harness conduit that is tied to it that follows the bracket sort of hiding it. If I remember correctly it runs under, or by the distributor cap and towards the firewall then bends down and there it is, that Hoffa bolt, as I started calling it. I haven't had a chance to get out there and try to remove the coil yet, so I haven't had a chance to see what the deals is with the rivets that may or may not be holding the ignition coil to the bracket. I'm still up for any advice on how to tackle these rivets and getting the new coil back on. Thanks in advance to this issue and any others that I'm sure I'll be having.
  3. Billy D

    Billy D Rockstar

    This happened to me last summer. The truck was running perfect but at times would just shut itself on and off at highway speeds usually under a load, but always click itself back on when coasting. I was going nuts trying to figure it out and assumed it was more a fuel issue than coil due to it always starting and idling nice. Anyway, it broke down on the side of the road and I had to climb under the hood and fix it. Sounds like you located all the bolts, etc. The rivets you will have to drill out, and just use the new screws that came with the coil to mount it back on the bracket. I am not a mechanic by trade by any means, but the job was not all that bad, maybe 45 minutes once I had the coil. It looked scary starting off because I had to take a bunch of things off to get to the coil, but it was pretty simple.

    Now have you checked the voltage coming from the coil? What makes you think the coil is the culprit? I always figured a coil either works or doesn't (mine eventually totally stopped working with no voltage coming out), but learned that it can act strange and still run as I saw for a while. Do not forget the ECU in the vehicle can add to these gremlins sometimes. Have you changed the cap & rotor with the plugs, etc? I also recommend getting a real decent set of wires, plugs, cap, & rotor when doing that stuff...the cheap stuff never turns out to be worth the savings.
  4. ticad

    ticad New Member

    Thanks for the info and advice.

    I just ran through some basics for a tune up, and started with the simpler items that I could do myself. A mechanic friend mentioned the coil, so I figured why not try to change it, and if I remember correctly the PO300 code had that as one of the possible problems. I've only changed the plugs and wires so far (and oil & filter change), and didn't go the cheapest route, since I've heard about that too. Cheaper is not always better on just about anything. I went with some mid grade wires, based on price at least, Bosche, and AC Delco plugs (think these are on the lower end, but came decently recommended and were OE). Maybe in the near future I'll look into some better plugs, wires and cap. My tank now idles and runs much better, but the funky start issue is still there.

    I have mechanic coming to tackle most of the larger items that are out of my low skill level. I'll make sure he checks the voltage on the coil, since I do not know for sure if its going up. I think I'll go ahead and take your advice and get him to change the cap & rotor while he's doing everything else, that way I know its all new and good to go. One of his tasks is fixing the fuel gauge which bounces back and forth from empty to full for no reason, so he'll most likely have to drop the tank. If he does that I'll have him replace the fuel pump, since he'll have the tank dropped anyway, because if I don't, my luck he'll fix the gauge then a week later the fuel pump will go up and he'll have to drop the tank again. If the ignition system is mostly all replaced and a new fuel pump, hopefully the starting issue will be no more. I've called in the big guns and hopefully he'll get it all taken care of. If it still remains then I'll chalk it up to being an old tank that just takes some extra cranks to turn over. As long as he gets the engine light to stay off and gets it to pass inspection, It'll be a good weekend. I'll chime in when its all said and done, and post what he fixed and if it all worked.

    Thanks again for the info, I'll put it to good use.
    Last edited: Feb 27, 2013
  5. bazar01

    bazar01 Rockstar 100 Posts

    Coil can be tested if it is producing the high voltage output with a timing light. Clamp the probe to each spark plug wire and if it flashes, coil is good or at least the ignition system is good.
    As for the fuel, get a fuel pressure tester. Fuel pressure must be t least 50 psi. If low, regulator or fuel pump are suspect.
    Also do not forget to do a compression test to check the engine condition,
  6. Billy D

    Billy D Rockstar

    One other things I wanted to ask and make comment on - when you stay it sputters or gives a hard time starting, it is happening more often during damp weather? If so, new plug or not, check the plugs. I have another car that I chased that gremlin for two years. Turned out a plug was cracked out of the box and the car would not want to start in damp weather. A shop did not even figure it out. Someone recommended starting the car and spraying the cap, wires, plugs, etc. with a spray bottle containing water and salt (guess the salt for being a better conductor?). As soon as I hit that one plug the car would die, so I finally found the culprit...and it was a new plug out of the box that I personally installed too the last tune-up before the issues started.
  7. ticad

    ticad New Member

    Thanks for the info.

    The starting / low puttery idle is all the time, damp and dry conditions. My mother is having a similar problem, on her Explorer, so I'll let her know to check into the cracked spark plug issue, and check mine as well. I can see how that problem can be overlooked very easily.

    I have found out a couple things. When checking the distributor, we found it had been siliconed down, because one of the bolt holes was craked and didn't hold it down properly. I need to get a new distributor, so I'll have a new cap and rotor done as well. I also found that the fuel pump is going up, and as you mentioned bazar01, the pressure is low. I was told that this is what is causing all the problems, from starting to idle to engine light. I think the starter is alright, but I will look into checking it as mentioned above.

    The fule pump is fairly close to its end I believe, so I think I will have to have it done very soon. I'm keeping my finger crossed on this taking care of the problem, but if it doesn't I'll keep moving forward on fixing it.

    I also just got new tires. Pepp Boys' Definity Dakota A/T 2's. So far they are very nice. They have a smooth, rather quiet ride for A/T, and have some beefy tread that should make it hard, well harder, to get stuck, at least in a majority of the messes I should find myself in.
  8. Quikfire

    Quikfire Member

    I just fixed a starting, sputtering, and low idle problem by cleaning the throttle body. Mine was filthy, it took less than 30 minutes and about $4.00 for a can of throttle body cleaner. So far that has fixed my issue.

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