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HT4100 4.1, 4.5, 4.9 Discussion, 4.5 distributer 180 out? in Cadillac Engine Technical Discussion; Check/change fuel filter and pump. I had the same problem in a throttle body Chevy van; come to find out ...
  1. #16
    the recluse is offline Cadillac Owners Connoisseur
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    Re: 4.5 distributer 180 out?

    Check/change fuel filter and pump. I had the same problem in a throttle body Chevy van; come to find out it was the small tube that went from the fuel pump to the delivery line in the tank. It would idle and run 5 mph, but try and gas it and you could forget it.

  2. #17
    daniel58 is offline Cadillac Owners Fanatic
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    Re: 4.5 distributer 180 out?

    Fuel pressure is good 38psi and shoots up in the 40s when I disconnect the regulator, no gas leaks there either. I just replaced the fuel pump (Bosch) sending unit and rusty fuel lines from the tank to the eng compartment. The stumble feels like just one or 2 cylinders are missing under load. Doing the cylinder balance test is not really informative although it does idle rough I cannot isolate one cylinder. We pulled the distributor and rotated the gear 180 degrees on the shaft last night to no effect. Pulling the plugs and wires tonight, not a fun job to do over and over!

  3. #18
    daniel58 is offline Cadillac Owners Fanatic
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    Re: 4.5 distributer 180 out?

    Pulled the plugs and wires today. The wires ohmed out good, and the plugs looked good with the exception of #5 which was black with carbon. The distributor cap looks good inside. I was only able to check compression on #5 and #7 and they are both showing 200 psi and since we checked compression before that can probably be ruled out. I will certainly replace at least that one plug as I know you can get new plugs (even AC) that are bad. I plan to check each wire with a timing light after it is back together. Not much confidence this will ever run right at this point. There are 2000 Devilles on Craigs list in our area selling for less money than we have recently put into this 90!!!

  4. #19
    drewsdeville's Avatar
    drewsdeville is offline Cadillac Owners Master
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    Re: 4.5 distributer 180 out?

    OK, I'd hang on here and take a breath.

    Don't start throwing parts at it on recommendations here. You should still properly diagnose the ideas given here to prevent wasted time and money.

    Do you know how to use the onboard diagnostics? If not, get a manual. If so, this is the perfect time to put them to use.

    A running issue can almost always be partially narrowed down by looking at how the computer is trimming the fuel. The computer is always dynamically adjusting the fuel trim and can be effected by just about anything inclduing poor ignition, vacuum leaks, sensor malfunction, etc.

    Take a look at the Block Learn and the Integrator values through the onboard diagnostics. These will tell you which bank(s) of cylinders the problem is occuring on. It will also tell you if you are dealing with a rich or lean condition on the affected bank(s). Then you can move on from there.

    If you know how to do this, post the values that you find here. Then we can continue to help.

    Hopefully you have a manual...

  5. #20
    daniel58 is offline Cadillac Owners Fanatic
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    Re: 4.5 distributer 180 out?

    Yes I do have a FSM and am familiar with the on board diagnostics and have a scanner as well. There is nothing out of the ordinary that I can tell, but will admit to not having much knowledge about those specs mentioned. I will post the specs as soon as I get it back together.

  6. #21
    drewsdeville's Avatar
    drewsdeville is offline Cadillac Owners Master
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    Re: 4.5 distributer 180 out?

    Well, I'll be leaving for a trip in the morning, so I'll be unable to help again until Monday. But here's what you are looking for...

    You must check these values under different conditions. Hot/Cold idle, acceleration, coast, etc.

    Your integrator counts are the short term fuel trim, or a fuel trim based on temporary conditions. Using data from various sensors during a short time frame, the pcm changes the integrator to achieve the correct fuel/air mixture. A value of 128 is neutral with no adjustment made, higher than 128 indicates that the PCM is adding fuel, lower than 128 indicates that the PCM is lessening the fuel. It does this by lengthening or shortening the injector pulse.

    By the way, the PCM uses the integrator only when the O2 sensors are ready and it's in closed loop. The integrator should sit at 128 until the engine is warmed.

    This same system applies to the Block Learn values as well. However this is a long term fuel trim... For lack of better words, it averages the integrator counts and stores this value for the PCM to use as a baseline when calculating fuel trim. It compensates for long term conditions and applies under both a hot AND cold engine.

    Pay attention to the values. You should be able to tell if the engine, as a whole, is running rich or lean by looking at how the PCM is trying to compensate. For example, if you have a Block Learn value of 145, you can assume that the PCM is adjusting for some irregular condition by increasing fuel since this value is well above 128.

    Also, compare the values between banks. Regardless of the actual value, the right and left bank Block Learn values should be quite similar, same with the integrator counts. If they aren't, you may have a problem on only one bank of cylinders, as the PCM only detects an irregular condition on the one bank.

    Sorry for the in-depth post. Hopefully this helps gets you started. This method won't pinpoint the problem but it SHOULD help lead you on the right path, preventing you from throwing more parts at it.

  7. #22
    daniel58 is offline Cadillac Owners Fanatic
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    Re: 4.5 distributer 180 out?

    We replaced the new AC plugs again, ohmed out the wires. Still has a rough idle and what feels like one cylinder missing under acceleration and lack of top end power. Checking each plug wire with a timing light shows a nice even spark increasing to a solid light with increasing rpm. Cylinder balance test shows rpm drop in all cylinders. Fuel pressure is 38 psi increasing a bit with increased rpm (hot eng) Moving on to the on board computer specs,

    P.0.2 TPS 1.7 responds to rpm increase
    P.0.2 Map 47 and goes down with rpm increase
    P.0.3 baro 98
    P.0.4 coolant temp 90
    P.0.5 mat 85
    P.0.6 spark advance 17 at idle up to 40 with increased rpm
    P.0.7 batt vt 12.7
    P.0.8 rpm 630
    P.0.9 veh speed 0
    P.1.2 injector pulse w 4.7
    P.1.4 ox sensor vt .85
    P.1.8 integrator 90 at idle up 128 with rpm increase
    P.2.0 block learn 108 at idle up to 128 with rpm increase

    Scanner readings (closed loop)
    baro (HG) 27.74
    baro (v) 4.45
    blm cell 25 down to 7 with increased rpm
    blm enable no
    blm L 118, blm R 118
    exh o2 L rich exh o2 R rich Occasionall flickers to lean but usually reads rich
    inj pulse w L 5,R 5
    integrator L 86, R 86 up to 128 with increased rpm
    map (v) 1.88
    map (hg) 15.00 to 15.30
    O2s L mv 850 O2s R mv 850

  8. #23
    daniel58 is offline Cadillac Owners Fanatic
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    Re: 4.5 distributer 180 out?

    $2500 worth of new parts, distributor has been out several times, 3 sets of plugs, good compression, good fuel pressure, no bubbles in the coolant, no coolant in the oil, tested the intake for leaks with lots of oil no change still runs rough, misses and has a lack of power. I have had Cadillacs since I started driving, my first car was a 56 coupe deville I have 4 cads now and am ready to give up on FWD cadillacs. With all of these new parts I may be able to recover some of my losses by parting this GM junk out on craigs list!!!

  9. #24
    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: 4.5 distributer 180 out?

    I'm stumped too and I feel your disappointment. It sounds like you have covered all the bases and everything checks out perfectly. I was raised on Big GM RWD Oldsmobiles and Caddys and I hated all FWD drive cars until I got my 92 Deville. I think GM finally got it right with the 4.9. I never remember the differences between the 4.5 and 4.9 so I don't usually comment on 4.5 issues. One little tid bit that comes to my mind that I'll run by you is that I don't believe that GM's HEI ignition can fire a .060 spark gap reliably. At idle it may be misfiring because the spark can't jump that gap. I try to close up that gap some on my HEI cars. Sometimes it may require investigating a different spark plug because you can't just close a wide gap because the tip won't be parallel to the electrode. I don't remember how I did it on my 92 because it's been a few years but I do remember doing something about it.

    How is the engine vacuum? Have you tried a different MAP sensor yet? I usually recommend trying a new one just for diagnostic purposes. I would assume that would have been one of the parts replaced on that $2500 list of parts but if not, try it.

  10. #25
    daniel58 is offline Cadillac Owners Fanatic
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    Re: 4.5 distributer 180 out?

    Well yes the map sensor has been replaced, eng vacuum is 16" teed into the map sensor vac line. I did take your advice Al and tightened up the plug gap a bit to .055 on the 3rd set of AC plugs to no effect. This car does have material (rusted stainless steel?) rattling in the cat, but its welded on and that would mean more money should I take a sawzall to it to check that. I might be able to pull the new oxygen sensor out and run it that way to check it. I am very disgusted with this car at this point and not inclined to throw more money away on it.

  11. #26
    daniel58 is offline Cadillac Owners Fanatic
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    Re: 4.5 distributer 180 out?

    I pulled the O2 sensor, with that out ( its not the cat) it still has the miss and lack of power/ rough idle. There are a lot of these in the junkyard... ANYONE have any ideas before this car gets junked???

  12. #27
    daniel58 is offline Cadillac Owners Fanatic
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    Re: 4.5 distributer 180 out?

    The better half has been driving this car, she thinks it runs better as it heats up through out the day as she makes her garage sale rounds. It did run hot a while back though not so hot as to make the stop eng. light come on, the leak was fixed and it did run fine for a while. With this much money in it can't afford to give up. Intake leak... head gaskets??? That should show up as coolant in the oil or bubbles etc. in the coolant right? What else could it be???It actually seems to be running rich, scanner shows rich most of the time, O2 sensor is black, fouling #5 plug (black) and blowing carbon out the exhaust when revved, so a heat crack or intake leak dosn't make sense because that would make it run lean??Any one with any ideas??

  13. #28
    the recluse is offline Cadillac Owners Connoisseur
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    Re: 4.5 distributer 180 out?

    Wow, man, I haven't been on here in a awhile and your sill having problems with that car?!?!

    The rattling in the cat, however, is a clue to me. Too much back pressure will lead to overheating, crappy performance, and a general lack of power. The front should bolt right off and if you cut the back in the right spot, you can slide a 2" or 3" exhaust sleeve over both sides of the cut and bolt it back together with U bolts for about $10.

    Inside the cat will be a ceramic "honeycomb". Take a tire iron, large spike, or pipe and bust out the stuff inside; just drive it right through. It won't be easy and you should do it in an empty trash can (to collect all of the stuff falling out).

    Avoid breathing the "smoke".

    If it works, you can use your discretion as to whether you want to replace with aftermarket cat or just leave it open. It will give your car a MUCH throatier sound as it becomes a rather large resonating chamber.

    Your about about where I was 6 months ago, I spent the same amount and eventually had to pull the motor...

  14. #29
    daniel58 is offline Cadillac Owners Fanatic
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    Re: 4.5 distributer 180 out?

    Recluse, this cars cat is welded on and would have to be cut off. I did remove the o2 sensor (easier way to reduce the backpressure) and it still runs the same.
    To recap, we have replaced the plugs (AC) 3 times, cap, rotor, wires (they ohm out good), ign module, pickup coil, EGR, o2 sensor (only one on this car), map sensor, fuel pump, fuel sender pickup assy, fuel lines and hoses, injectors, timing chain and gears (didn't need it), ECM 2 times, removed and inspected throttle body it was clean, vacuum lines are good as most have been replaced, fuel pressure is good, fuel regulator is working and no leaks, compression is good, vacuum is good at the map sensor. Injectors are clicking as they should and noid light tests show a good signal from the ECM. No codes. I don't have a scope but I did check for spark at each wire with a timing light and they are all getting spark. No coolant in the oil, no bubbles in the coolant, oil and either testing show no external leaks. It idles rough and feels like 1 or perhaps 2 cyls are missing under accleration and lack of top end power. A scanner shows it is running rich most of the time, the last time I had the plugs out #5 was black with carbon and the new o2 sensor was carboned up as well. This car has been maintained well, we bought it from a Cad dealer when it was 3 years old, 114k now. I just went through the cooling sys last fall, new rad, hoses, waterpump, etc. and it ran fine afterwards. At this point the only thing I can think of is a leak or crack in the intake or heads though I would like to see proof before I tackle that nightmare of a job! We are probably just going to run it till it blows up and find out what is wrong that way! Thanks to all those offering advice, a little sympathy makes a person feel better even if it dosn't fix the car.

  15. #30
    drewsdeville's Avatar
    drewsdeville is offline Cadillac Owners Master
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    Re: 4.5 distributer 180 out?

    By looking at the fuel trim numbers you posted earlier, it wouldn't appear you have anything like leaking intake/heads.

    This may sound silly, but I'm running out of suggestions. You only had 1 or 2 bad plugs when you pulled them out the second time...are you sure you don't have any crossed plug wires?

    EDIT: nevermind, I re-read the first page and see that you are certain you haven't.

    Go back to the beginning. How/when did this problem begin showing symptoms? What's the background to this problem?

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