4.9 switched to 87 oct., hard starts, re-time?
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HT4100 4.1, 4.5, 4.9 Discussion, 4.9 switched to 87 oct., hard starts, re-time? in Cadillac Engine Technical Discussion; Hello. I own a '92 El Dorado Touring Coupe. The car has poor gas mileage to begin with. The best ...
  1. #1
    LikeaDream is offline Cadillac Owners Member
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    4.9 switched to 87 oct., hard starts, re-time?

    Hello. I own a '92 El Dorado Touring Coupe. The car has poor gas mileage to begin with. The best I've ever gotten out of it without drafting on the highway is 15 mpg highway and 10-12(cold season 9-10) in town. Up until about a month ago I was using 93 octane mobile gas since September when I started driving it.
    It has about 173k miles on it.
    I checked codes and only code of any consequence might be the power steering pressure switch code. The switch is hard to get to and the wiring looked slightly damaged. Wondered if this can effect fuel economy at all. It does send a "check engine" signal when it's still open after 40 mph, I've tested that after a code clear. Could this kind of open pressure be so great as to hurt fuel consumption?

    I recently changed the cap and rotor and it looks like it had never been changed(green corrosion.) No fuel economy gains whatsoever, though. I have had new plugs and wires in my possession for months, but not installed during the harsh NY winter we've had. Although I'd swear the wires look original(they have numbers on them.) I see no arcing and the engine runs smooth as a button to the ear. I will change these soon anyhow. I've delayed because of what was lacking after the cap and rotor change.

    No fuel leaks, no sputtering. But I've noticed since even before I changed octanes that I was getting hard starts, if I had to start the car more often in a day. At first I thought it was a starter going. But now I can clearly hear it's the timing. Now I know that the car's ignition system will retard timing with the use of 87 octane. I also found out the guy I bought it off of always used 87. I can hear this is clearly off and probably resulting in some of the poor fuel economy other than age or possible compression loss with that age.
    The question is: do I try if possible to manually re-time the engine/and or replace the timing chain(I heard some manual re-timing is possible even on this type of ignition. Will re-timing make things worse with 87 octane? Will this risk detonation? I don't speed or push the car. Will it help the fuel economy, or should I maybe re-time but make sure it is still slightly retarded from normal anyway?

    Other info: I replaced the gas tank and I noticed the fuel gauge isn't usually accurate until it's past the half way point. I don't know if the sender went bad or is tilted wrong in the process. I record every tank exactly with trip mileage and fill ups.

    Power steering pump has an occasional leak I noticed in the winter. I will probably change this very soon unless it is just a seal. Can this result in off timing with the serpentine system or poor fuel economy?

    Left side bearing has been going bad for months, will change this soon. Can this added resistance on the axles give poorer fuel economy?

    E-break likes to get stuck when I leave it on during a repair. I have to drive sometimes and slam the brakes to get it off. However, it makes me wonder if there might be rubbing and that's what's contributing to poor fuel consumption. No smell though.

    Sorry so long, but I've been reading these forums for months, and now it's spring time/fixing time and I need helpful direct answers if possible. Any help will be greatly appreciated. Thank you!

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  3. #2
    lenny lincoln is offline Cadillac Owners Fanatic
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    Re: 4.9 switched to 87 oct., hard starts, re-time?

    New plugs and clean erg tubes and get the e-brake/ back brakes redone. I get 13.5 city short 2.5 mile daily trips and 27 hwy 73mph. the hard starting is the bad plugs and wires. the power steering switch is easy, $35 bucks at napa 20mins under the car. If your not sure where the power steering switch is just ask.

  4. #3
    kdcing is offline Cadillac Owners Fanatic
    Automobile(s): 1993 Eldorado, 4.9L, 200k miles
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    Re: 4.9 switched to 87 oct., hard starts, re-time?

    Quote Originally Posted by LikeaDream View Post
    But I've noticed since even before I changed octanes that I was getting hard starts, if I had to start the car more often in a day.
    ....hmmm....poor fuel economy and hard HOT starts are classic symptoms of a bad Fuel Pressure Regulator. More info here:

    http://www.cadillacforums.com/forums...-pressure.html

    I've been using 87 octane in my '93 Eldorado (4.9L) for 7 years...no hard starts and acceptable fuel economy (21 mpg w/ combined city and highway). 205k miles on the original engine. I doubt that the 87 would cause any of the symptoms indicated in your post.

  5. #4
    LikeaDream is offline Cadillac Owners Member
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    Re: 4.9 switched to 87 oct., hard starts, re-time?

    Concerning the psps I bought one at NAPA a few months ago. Never put it in myself because it looked pretty tough. To find the switch I had to pretty much climb on top of the engine and look in between the firewall and the middle section of the engine. My mechanic who originally inspected it said to leave it be, but I think it was more like saying "it's a pain in the @ss to fix." In fact I'm doing most of the repairs myself because they don't want to get too involved with a Cadillac. You say 20 minutes from the bottom? Do I need a lift? To me it looked like bottom access was restricted and I'd have to pull the engine just to fix this. I also need to go out and probably buy new wires to resolder the connectors because they look bad and even the mechanic pointed that out. I have the the facotry manual but I can't find anything so far on the gauge of wire needed for that.

    As far as the FPR, I read about it on here a few months back and obsessively believed that to be the problem. However, I don't see the signs like a gas smell or leaky fuel with the air intake filter assembly taken off and the car running. So I'm not so sure about this being the problem yet.

    About the The EGR tube. About 3 months ago I broke it in between the valve and the computer sensor. However, when this happened it broke right where the tube meets it's farthest point against the base of the valve not after the connection, so I duct taped it for now. No loss in gas mpg and no codes. I was taking it off to clean it and it was so dry rotted this is what happened. I've been told I can buy the tubing in the store, since there's no specific tube part available for replacement and make one myself. Not sure about what rating the tubing should be, though. Thanks guys, I will definitely fix the plugs and wires at this point. Then I guess see how it goes. If anyone wants to give a quick run down about the easiest way to get to the psps, I'm all ears.

  6. #5
    kdcing is offline Cadillac Owners Fanatic
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    Re: 4.9 switched to 87 oct., hard starts, re-time?

    Quote Originally Posted by LikeaDream View Post
    As far as the FPR, I read about it on here a few months back and obsessively believed that to be the problem. However, I don't see the signs like a gas smell or leaky fuel with the air intake filter assembly taken off and the car running.
    I haven't had a bad FPR myself, but from everything that I've read, a fuel smell will NOT accompany a bad FPR. It is my understanding that the fuel will leak internally...past the internal diaphram...then it gets sucked into the engine and burned. To test, simply take the vacuum line off the FPR while the engine is running....look for fuel dripping from the FPR's nipple.

    Note: another member did not see the fuel drip from the FPR's nipple, but had to supply vacuum (via a hand vacuum pump) to determine that the FPR would not hold a vacuum and was therefore defective. He replaced the FPR and gas mileage and hot starts returned to normal.

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    LikeaDream is offline Cadillac Owners Member
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    Re: 4.9 switched to 87 oct., hard starts, re-time?

    Yeah I remember reading about applying hand vacuum. I'm going to probably wind up just replacing this thing eventually after I change the plugs and wires. Seems to me if I just keep fixing things I'm bound get this engine in order. From what I'm reading on some people's avg. mpg it has to be some fixable problem and not a compression loss/and or age which requires a rebuild. I think I will give this car a second chance.

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    Murphyg's Avatar
    Murphyg is offline Cadillac Owners Connoisseur
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    Re: 4.9 switched to 87 oct., hard starts, re-time?

    With my 93 SLS 4.9, It specifically recommended the higher octane.

    And there is a reason for that recommendation. Its not because they wanted me to spend more money on fuel.
    Its because that is what my Cadillac needed to run efficientally.

    You have a Cadillac.
    You must maintain it properly and do so by GMs recommendations. You cant let things slide and get to it when you get to it. That will only result in a snow ball effect.

    If you want to treat it like a Taurus, then you will be lucky if it lasts half as long as one.

  9. #8
    awadecki is offline Cadillac Owners Enthusiast
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    Re: 4.9 switched to 87 oct., hard starts, re-time?

    4.9s have no knock sensor. The computer will NOT retard the timing with lesser grade fuel--unlike a Northstar.

  10. #9
    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: 4.9 switched to 87 oct., hard starts, re-time?

    The 4.9 is a very docile and tame engine with a whopping 9.5:1 compression ratio and a whopping 200 hp. I think the premium fuel recommendation is for snob effect and not really required. It might have been a cya move for the dealers; if a fussy person complained of pinging, the dealer could tell them to run premium like it says on the gauge and send them on their way. Any low performance engine will carbon up after many miles of high octane fuel and then it will "require" the high octane fuel to keep it from pinging. There are many 4.9's running 87 octane with no problems so it shouldn't be causing your hard starting. Change your plugs and wires and check the fpr with hand vacuum and you should be getting closer. I'm not clear on the EGR tube you are speaking of, I may have to take a look at mine out of curiousity. It would be helpful to check your vacuum too. Good luck.

  11. #10
    awadecki is offline Cadillac Owners Enthusiast
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    Re: 4.9 switched to 87 oct., hard starts, re-time?

    This all depends on your altitude, and many other factors. Yes, you can use 87. But make sure you hear no pinging. The timing on 4.9s--and all older GM cars for that matter--is set conservatively for emissions reasons (when you increase the timing, combustion temperatures increase, and emissions increase).

    On all my 4.x cars (both 4.1s and 4.9s), I have my base timing advanced to 12 degrees, and I always fill up with premium. By advancing my timing, I have around 10% more power, and 10% better mileage. So, I'll pay the extra 30 cents per gallon for a wash on total fuel cost and more power. I'd guess my 4.1 now makes around 140hp (vs. 125hp), and my 4.9 makes about 215-220hp instead of 200hp. In any case, it's worth it!

    Both engines are considerably more "peppy" with the timing advanced. This especially helped my 4.1 engine.

  12. #11
    92EldoTC's Avatar
    92EldoTC is offline Cadillac Owners Enthusiast
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    Re: 4.9 switched to 87 oct., hard starts, re-time?

    Always run premium. The engineers who built these engines recommend 91/93 octane for a reason, not to make you spend more money on gas, and right, its only like $2.xx more a tank.

    Speaking of 92 touring coupes, I HAD a 92 TC that had 173,xxx when I got rid of it. Still ran great except when I would WOT grayish black smoke came out the exhaust and someone told me it was the FPR but I got rid of the car before I had a chance to look into it. One time I got it up to 130 mph.
    I always ran premium in that car and in the 91 Deville I have now.

    What color is your Eldorado? Mine was burgundy with 95 or 96 chrome wheels.

  13. #12
    LikeaDream is offline Cadillac Owners Member
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    Re: 4.9 switched to 87 oct., hard starts, re-time?

    Mine is also burgundy, it has what I believe to be original wheels, 16" which seems kind of big compared to some deville owners I spoke to. I think some people have 15s on devilles from earlier and slightly later years.

  14. #13
    92EldoTC's Avatar
    92EldoTC is offline Cadillac Owners Enthusiast
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    Re: 4.9 switched to 87 oct., hard starts, re-time?

    yeah, the devilles came with 15's and smaller tires of 205/70 while the eldorados came with 16's and 225/60 tires.
    I hope thats not my old car you're driving. I doubt it though because I got rid of mine in Las Vegas and it had all windows tinted and there was a dent by the gas filler door. Not really a deep or noticeable dent though

  15. #14
    LikeaDream is offline Cadillac Owners Member
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    Re: 4.9 switched to 87 oct., hard starts, re-time?

    For the heck of it I did check but, nope, no dent there. Actually the car came from a neighbor who sold it very cheap because he was in need of money fast, and he bought a new gas tank but hurt his back and couldn't replace it himself. He bought it off a dealer who used it to travel and one day when my neighbor was at the dealer he saw someone back into it and ding in the quarter panel just behind the passenger door. So they sold it cheap to him.

    My neighbor fixed the ding but forgot to take the prep tape off fast enough it left a mark.

  16. #15
    92EldoTC's Avatar
    92EldoTC is offline Cadillac Owners Enthusiast
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    Re: 4.9 switched to 87 oct., hard starts, re-time?

    Does your automatic level system work?
    The compressor on mine used to run all the time and you could actually hear it running.
    The dent on mine came from somebody backing into it and it messed up the air compressor for the rear suspension so the car was a little low in the back but it was cool because it looked like it had been lowered.
    The rear driver side wheel was a little bent also, the top of the wheel was in more than the bottom so it looked like the car was carrying too much weight on that side in the rear. That tire though didnt wear uneven and didnt affect the way the car drove.
    Here are some pics, check it out!

    http://www.cadillacforums.com/forums...some-pics.html

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