4.5 hesitation, stumble, poor mpg; smog pump bypassed
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HT4100 4.1, 4.5, 4.9 Discussion, 4.5 hesitation, stumble, poor mpg; smog pump bypassed in Cadillac Engine Technical Discussion; okay guys newbie caddy owner here. my issues are: stumble upon take off followed by hesitation to accelerate. When I ...
  1. #1
    jenniandphil is offline Cadillac Owners Member
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    4.5 hesitation, stumble, poor mpg; smog pump bypassed

    okay guys newbie caddy owner here. my issues are: stumble upon take off followed by hesitation to accelerate. When I got the car the smog pump and hvac was bypassed, assuming both doesn't work.... keep getting e49 which is the air fault management. checked all vacuum lines, reading 19 on vacuum gauge drops to 14 when the throttle is pressed and doesn't go back up. we have replaced the water pump (unrelated) spark plugs with champion, and wires with oriellies cheapies, i'm running 100% gas 87 unleaded, tried changing seeing no difference. we have cleaned the t.b. (used carb cleaner) it's sparkling clean! not sure what is going on and i hope someone can help. it does okay on mpg 14-17 in city (stop and go traffic), but the stumble has me mystified. PLEASE HELP!!!

    fyi its a 1990 fleetwood fwd with the 4.5.

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    jenniandphil is offline Cadillac Owners Member
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    Re: 4.5 hesitation, stumble, poor mpg; smog pump bypassed

    okay vacuum check now reads a steady 15, replaced pcv valve and rough idle is gone, checked for vacuum leaks didn't find any... still have the hesitation on take off and car seems to not have pick up unless you floor it. no error codes as of yet. we disconnect battery and then reconnected and drove for 30 minutes under normal "city" traffic. still no ses light, mpg according to display is 15.4 on 100% gas. i've read and reread the sticky on code 49, and i'm not getting anywhere. check exhaust output via placing hand over tail pipe and the air seems to be exiting just fine, don't hear a stumble or miss or anything. mistified by the hesitation on take off or from a lower speed acceleration.

  4. #3
    dennis93coupe's Avatar
    dennis93coupe is offline Cadillac Owners Connoisseur
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    Re: 4.5 hesitation, stumble, poor mpg; smog pump bypassed

    Have you cleaned the intake tubes in the manifold under the throttle body? Open your throttle wide open and look down in there, sometimes they get plugged and need cleaned out. You might want to consider changing the cap and rotor. I have never been a big fan of champion plugs in these cars, prefer AC plugs part number 41-902

  5. #4
    jenniandphil is offline Cadillac Owners Member
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    Re: 4.5 hesitation, stumble, poor mpg; smog pump bypassed

    yes, we've cleaned the intake tubes in the manifold under the tb, they were really goopy! i was mistaken on plugs they are even worse lol... autolites. thinking about changing them out to see if that helps. could it have something to do with the smog pump being bypassed? or possibly the o2 sensor? i'm not getting a code for the o2 sensor tho.

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    Re: 4.5 hesitation, stumble, poor mpg; smog pump bypassed

    You might try doing a search in the 1985 to 2005 FWD Deville forum. I'm not that well versed on the AIR on these 4.5's. I have read quite a few threads regarding the diverter valve. Have you checked your fuel pressure? Have you replaced the fuel filter? Have you checked timing? There is a procedure to do that. Have you checked for back pressure in your exhaust. You can do this by removing the O2 sensor and get a pressure reading from the port where the O2 sensor is, it should not be 2 lbs. or more. Do you have a FSM, (factory service manual)? Lot's of good information in there, diagnostics and trouble shooting, everything you could want to know about your car. Check out ebay for some good deals. Here is avery good deal right now.

    http://www.ebay.com/itm/1990-Cadilla...rature&vxp=mtr

    BTW, don't waste your money on a Chiltons or the others, they have very little useful information on these cars.

  7. #6
    jenniandphil is offline Cadillac Owners Member
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    Re: 4.5 hesitation, stumble, poor mpg; smog pump bypassed

    [QUOTE=dennis93coupe;2934856]You might try doing a search in the 1985 to 2005 FWD Deville forum. I'm not that well versed on the AIR on these 4.5's. I have read quite a few threads regarding the diverter valve.

    Diverter valve is good.

    Have you checked your fuel pressure?
    no.

    Have you replaced the fuel filter?
    yes

    Have you checked timing? There is a procedure to do that.
    no.

    Have you checked for back pressure in your exhaust. You can do this by removing the O2 sensor and get a pressure reading from the port where the O2 sensor is, it should not be 2 lbs. or more.
    not getting code for 02 sensor, so i assumed it was good.

    Do you have a FSM, (factory service manual)?

    no haynes read it and re-read it lol.

    Lot's of good information in there, diagnostics and trouble shooting, everything you could want to know about your car. Check out ebay for some good deals. Here is avery good deal right now.

    http://www.ebay.com/itm/1990-Cadilla...rature&vxp=mtr

    thanks will order now

    another issue might fall into play with all my issues is;
    1) parking brake won't disengage when put in reverse or drive. (inspecting in the am for a vacuum leak)
    2) air won't blow through vents, just defroster (double checking for vacuum leak)
    3) driver window won't roll up or down anymore (it was rolling down with a little push, and up with a little pull)
    it "clicks" so i know the switch works, you can hear the motor running and what sounds like a grinding or clicking noise. had to replace the window regulator guide on passenger window because it fell down by itself while driving on the highway! would i need to replace the motor? or the window motor regulator? i don't know the difference between the two.
    4) possibly related there is a line capped off with a screw coming from the cruise control, it would be the lower line... cruise control work, can't find any diagram anywhere that would help and i refuse to take it to a mechanic so i can get screwed over.

    i had a 3.5 v6 mercury sable with a knocking sound and was lead awry being told everything from a lifter, a push rod, bearing, to a piston and it still isn't fix as the last time i was told i just needed a new motor. argh, the nerve of shade tree mechanics trying to screw a female over. i took a 3800 apart piece by piece because it slung a main bearing at 260,000 miles with no problem, ahem, the car is in the junk yard because i didn't want to buy a new motor. but i learned what part was what and how it worked. i can just about diagnose a problem by the sound of a motor i am familar with. a cadillac i know nothing about but i'm learning, after a lot of learning.

    5) i entered the obd dtc and was fidding around (probably shouldn't have) and found some settings i could change. p0.1 - p1.2 all are set at 128. what's that mean? thanks so much for your help!!

    ----------

    AND I forgot that my abs light is on as well

  8. #7
    dennis93coupe's Avatar
    dennis93coupe is offline Cadillac Owners Connoisseur
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    Re: 4.5 hesitation, stumble, poor mpg; smog pump bypassed

    Quote Originally Posted by jenniandphil View Post
    Have you checked your fuel pressure? no.
    you can rent a fuel pressure gauge from parts stores.

    Quote Originally Posted by jenniandphil View Post
    Have you checked for back pressure in your exhaust. You can do this by removing the O2 sensor and get a pressure reading from the port where the O2 sensor is, it should not be 2 lbs. or more.
    not getting code for 02 sensor, so i assumed it was good.
    You don't need to get a code for O2 sensor, you just want to check backpressure as in the cat might be plugged or exhaust is restricted. A cat can plug up if a leaking injector has been let go for an extended amount of time. Not common but we have had posters report that problem here.

    Quote Originally Posted by jenniandphil View Post
    Do you have a FSM, (factory service manual)? no haynes read it and re-read it lol.
    Haynes and Chiltons, same not much information. You got the FSM on order, GOOD. You will not be sorry, maybe shocked over the amount of information in there.

    Quote Originally Posted by jenniandphil View Post
    another issue might fall into play with all my issues is;
    1) parking brake won't disengage when put in reverse or drive. (inspecting in the am for a vacuum leak)
    2) air won't blow through vents, just defroster (double checking for vacuum leak)
    Yes, sounds like you have vacuum leak. Get a can of starting fluid or throttle body cleaner and spray on connections with engine idling, hoses wherever you think it might be leaking. When you hear the engine RPM increase, there's a leak. You car has 20 years age on it, vacuum hoses begin to crack and fall apart.


    Quote Originally Posted by jenniandphil View Post
    3) driver window won't roll up or down anymore (it was rolling down with a little push, and up with a little pull)
    it "clicks" so i know the switch works, you can hear the motor running and what sounds like a grinding or clicking noise. had to replace the window regulator guide on passenger window because it fell down by itself while driving on the highway! would i need to replace the motor? or the window motor regulator? i don't know the difference between the two.
    There is a block at the rear of the window, that part has been known to fail. I had one that broke quite a few years ago in the past, about 10 years ago to be exact. I didn't have the time to fix it as I was working 80 hour weeks, took it to the dealer back then so I can't tell you what was involved. You will need to take the inside door panel off first to see what is wrong before you buy or order parts.

    Quote Originally Posted by jenniandphil View Post
    4) possibly related there is a line capped off with a screw coming from the cruise control, it would be the lower line... cruise control work, can't find any diagram anywhere that would help and i refuse to take it to a mechanic so i can get screwed over.
    Oh, that is likely why you have problems inside the cab. Is this where you are talking about the line? If this is line you are talking about, plastic, they have a tendicy to crack and break in the area between the master brake cylinder and valve cover of the engine. I think it is from the heat coming off the exhaust that crosses over from the front of the engine. Look at this picture and let me know if this the area you are talking about. There should be a smaller vacuum line under the bigger one you see in the picture.



    Quote Originally Posted by jenniandphil View Post
    i had a 3.5 v6 mercury sable with a knocking sound and was lead awry being told everything from a lifter, a push rod, bearing, to a piston and it still isn't fix as the last time i was told i just needed a new motor. argh, the nerve of shade tree mechanics trying to screw a female over. i took a 3800 apart piece by piece because it slung a main bearing at 260,000 miles with no problem, ahem, the car is in the junk yard because i didn't want to buy a new motor. but i learned what part was what and how it worked. i can just about diagnose a problem by the sound of a motor i am familar with. a cadillac i know nothing about but i'm learning, after a lot of learning.
    Completely different animal.

    Quote Originally Posted by jenniandphil View Post
    5) i entered the obd dtc and was fidding around (probably shouldn't have) and found some settings i could change. p0.1 - p1.2 all are set at 128. what's that mean? thanks so much for your help!! AND I forgot that my abs light is on as well
    "P" codes are parameters that you can check. Best to stay out of those until you get your FSM. The best scan tool you can get for your car to diagnose engine and body electronic functions is built into the dash. As far as the ABS light, wait for the FSM. You might need a special tool for that, otherwise check all of your speed sensors at the wheels, all of the wiring harness to the wheels, harness and connectors to the ABS pump module (I believe is at the front drivers side on frame between radiator and transmission on a 1990). There are fuses to check, lots of stuff for the ABS. Usually it is something minor.

  9. #8
    jenniandphil is offline Cadillac Owners Member
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    Re: 4.5 hesitation, stumble, poor mpg; smog pump bypassed

    it is the smaller line under the big vacuum line in the picture! no idea where it goes.... as i stated it is capped off with a screw. will take picture in the am and post it.

  10. #9
    dennis93coupe's Avatar
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    Re: 4.5 hesitation, stumble, poor mpg; smog pump bypassed

    Is your cruise solenoid in the same location as the picture I posted?
    Edited to add pictures and make corrections to text:
    Both of the lines that connect to the cruise control go across the valve cover, one of them has a tee that has a line coming from your vacuum source which is at the throttle body, they go into a loom where one of them connects to your vacuum reservoir mounted to the firewall and the other goes to the firewall where it goes through and to your lines inside the cab.

    Here are some pictures hopefully I can get them in this post.








  11. #10
    jenniandphil is offline Cadillac Owners Member
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    Re: 4.5 hesitation, stumble, poor mpg; smog pump bypassed

    yes, that's it! thanks a million, i'm going to try to track this booger down tomorrow. i understand it goes through the firewall, but where does it go exactly after that? i'm sooo lost i might just take it to the shop after all. i don't want to take the dash apart to track it down and it's so hard to stand on your head to look under and behind the steering column just for a stupid vacuum hose, but i'm assuming this could be why i'm only reading 15lbs of vacuum on a gauge and have the miss or stuble or what ever it is. It doesn't do it when the car is under load, which is why i'm mistified.

    i'm also going to check the distrubitor cap and pick up wire tomorrow.

    oh and your car is really clean! i've got a lot of work ahead of me, as mine you touch and your covered in oil... heistating on cleaning it as i will probably find a lot of leaks here and there lol, the oil is covering all the holes in the vacuum lines.

  12. #11
    jenniandphil is offline Cadillac Owners Member
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    Re: 4.5 hesitation, stumble, poor mpg; smog pump bypassed

    okay so it rained all day yesterday and i have to work today, so i guess i'll try to get to it this weekend when i'm off again. hopefully my fsm will be in!

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