HT4100, no power uphill
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HT4100 4.1, 4.5, 4.9 Discussion, HT4100, no power uphill in Cadillac Engine Technical Discussion; My brother in law has a 83 Fleetwood with HT4100. It only has 67,000 original miles and was well kept. ...
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    gene512 is offline Cadillac Owners Member
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    HT4100, no power uphill

    My brother in law has a 83 Fleetwood with HT4100. It only has 67,000 original miles and was well kept. It starts fine, runs well but crawls uphill. We hollowed out the cat and tested fuel pressure, timing and codes. Everything was fine. Any suggestions??

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    Night Wolf's Avatar
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    Re: HT4100, no power uphill

    nope, nothing seems wrong.... actually the fact it is still running is pretty good...

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    Edahall's Avatar
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    Re: HT4100, no power uphill

    These engines have something like 135 hp for a 4000 lb car so the hp to weight ratio is very low. You can get a little more power by advancing the timing 2-3 degrees as long as it doesn't ping too much. Another thing you can do is install smaller diameter tires such as 50 series tires to get the engine rpm's up. The tall gear ratios were used to attain good fuel economy so you might be able to find a 3.73 rear axle off a Chevy Caprice.

    On the other hand, just down shift the transmission to 2nd gear when you need more power going up hills. It's good to about 70 mph in 2nd. Don't be afraid to spin these engines up. I do it all the time.

    Make sure you change the coolant every two years and add the coolant supplement tablets (bars leak) if you're interested in keeping this engine going.

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    Night Wolf's Avatar
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    Re: HT4100, no power uphill

    actually, IIRC for the RWD DeVilles... they were a more pathetic 125hp...

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    Re: HT4100, no power uphill

    Edahall,

    I can confirm the HT being good for about 70 in 2nd. My '85 Brougham has the 135hp HT with a 3.42 rear axle. It does fine until it sees hills...on I-68 here in WV where speed limit is 70, the downshift to 2nd happens often.

    ONE THING TO WATCH: I just had the transmission rebuilt in my '85 (it's a 200R4 overdrive). I have a feeling this was because of the downshifts from 3rd to 2nd at highway speeds. In RWD Caddies, the tranny computer was designer to allow a LOT of "slip" when shifting. This creates "smooth" shifts, but also wreaks havoc on the guts of the transmisison.

    The shop where I had work done put the "fixes" in that firm up those shifts when they rebuilt it; it still shifts very smoothly, but just doesn't slip so much.

    Just an FYI...I think an HT that's maintained properly and is in good tune will run the 70mph in 2nd no prob, but just keep in mind your transmission health, too...maybe drop it into 3rd on hills?

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    Night Wolf's Avatar
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    Re: HT4100, no power uphill

    yeah, the 200R4 isn't a very strong tranny either... I would treat it nice

    They probably put a shift kit in it, thats all...

    ... my mothers '89 Brougham has to be downshifted all the time too.. even though it has the 307 and 700R4(?) still has no power...

    '79 on the other hand will push top gear... 3rd, up a medium grade hill at 30mph...2.28 final drive too...

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    85eldodude is offline Cadillac Owners Member
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    Re: HT4100, no power uphill

    Ok everyone, listen careful to this one. I will post this in my thread I started about my problem too... I did what you did with the cat and that helped get riid of the smoke and made my gas milage go to 23 instead of 9... I then had a power problem like you... well, I changed the fuel filter, pump and sock in the tank, and I knew I had fuel pressure but it got worse and worse the more stuff I fixed from the engine back!!! Know what is was? The TBI unit was chock full of rusty corrosion!!! I had to take it apart in little pieces and clean it, but when I did, holy cow!!! I think everyone's 4.1's should have this treatment done, because my 85 Eldo now has no problem on hills, and is more than fast enough to overtake and pass at 85 mph. CLEAN YOUR THROTTLE BODY!!!


    To be more specific, Clean the injector body... I didnt even take the TBI off the car... just the piece the goes from the fuel line to the injectors. Note: I had to take off the fuel inlet adapter to get it off the TBI, and I did break the bottom gasket.... however I placed it back anyway and lined it up, and it works fine. Getting the injectors out id kind of hard too, I used one of those all in one screwdrivers without a tip on it to press them out, and when I tightened them down, used the body itself to do it, evenly spacing out the screws as I tightened them. Worked great, used the original gaskets, no leaks. Probably got lucky there, you may need a kit.

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    gene512 is offline Cadillac Owners Member
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    Re: HT4100, no power uphill

    The last post finally gave an answer worth while. I understand that it is a heavy car with a pathetic motor but I mean crawl uphill I mean CRAWL!! When it is running it also seams to be running extremely rich and O2 sensor was changed. I suspected the trottle body or injectors but thought I'd try here first. Thank you for the useless answers and the one that helped.

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    Re: HT4100, no power uphill

    '85eldo,

    Just wondering if you can clean that without taking anything apart (other than taking off the air cleaner, etc.) Just curious...also, could it be done with a chemical spray-in or fuel tank treatment? Just wondering. I don't notice mine being down on power that much, though.

    Night wolf,

    Yeah, I think it's probably just a shift kit, too...if I'm lucky, maybe it got whatever the Buick GN Regals had...their 200R4 was supposed to be really strong.

    I know about the 425's power...I don't care what anyone says, they pull! I test drove a '78 Eldo Biarritz with a 425...that's even heavier than the 77-79 RWDs and it still pulled like a mutha. It may not have 400hp like a 70 Eldo, but you're still running about 320 lbft of torque...nothing to sniff at, even in a car that weighs upward of 4000 like yours probably does.

    But it's alright...my consolation is that I like the 80-89 RWD styling better

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    85eldodude is offline Cadillac Owners Member
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    Re: HT4100, no power uphill

    No, you must take the injectors out to clean it fully, and that requires taking it apart, it wasnt very hard, just dont loose the big spring in the regulator My problem was that it had so much crap in it, that the more I did like change filters and fuel pump, it packed it in worse!!

    And you're welcome, glad I could help.


    also.. if it is running rich, that could indicate another problem like the vacuum line to the Barometric sensore being bad... aint that funny? a car that runs rich AND lean, lol

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    thepitboss is offline Cadillac Owners Member
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    Re: HT4100, no power uphill

    Just in case you were wondering that spring and gasket as well as a few other small items are included in the fuel pressure regulator kits and they for some weird reason run about 20-35 bucks at your local auto parts store. Same goes for a TBI rebuild kit. Also I use a product called Sea Foam every 6 months in my car through the TBI and that seems to keep things clean.
    jk

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    Fords_12345 is offline Cadillac Owners Member
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    Re: HT4100, no power uphill

    I always get a run at the hills that I go up but when you come back down watch out. These motors just get you where you want to go no more no less.

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    Re: HT4100, no power uphill

    Quote Originally Posted by gene512
    The last post finally gave an answer worth while. I understand that it is a heavy car with a pathetic motor but I mean crawl uphill I mean CRAWL!! When it is running it also seams to be running extremely rich and O2 sensor was changed. I suspected the trottle body or injectors but thought I'd try here first. Thank you for the useless answers and the one that helped.


    You have to take the good with the bad.....LOL....answers that is....

    It might be rust and gunk in the throttle body...certainly worth checking. You definitely have to take the injector pod apart to do that. Just cleaning outside is useless.

    Have you put a fuel pressure gauge on the shraeder valve fitting at the throttle body and monitored the fuel pressure WHEN THE PROBLEM OCCURS?? It almost sounds like fuel starvation to me. Checking the fuel pressure at idle or in the driveway is somewhat pointless. You need to check for a constant 10 PSI when the problem is occurring.

    The HT4100's from that era were somewhat prone to coolant intrusion into the oil at the head gasket/deck surface interface. The contaminated coolant would eventually lead to internal engine wear of the cam lobes and distributor gear. The engines , when new , received fresh coolant, the coolant supplement/sealer and that would take care of any concerns like that. Unfortunately, the coolant needed (needs...) to be replaced every 2-3 years/24-35K miles to keep the corrosion inhibitors fresh and the coolant supplement/sealer also has to be replaced with the coolant as it looses it's effectiveness over time/miles also....and it is removed when the coolant is drained at service intervals. Even though the miles are low the engine should still be on it's 7th or 8th coolant change due to time alone.....bet it has never been changed or if it has only recently. The coolant supplement installed back in 1983 (22 years ago) losts it's effectiveness about a decade back.

    If the fuel pressure is OK I would pop the valve covers off and look at the rocker arm motion to ascertain that all the cam lobes are intact. My bet is that there are worn cam lobes in the engine causing the problem. Also, you can pull the distributor and check the distributor gear for wear/scoring on the gear contact pattern. It should just be a nice shiny spot. Any perceiveable wear or scoring indicates contaminated oil from coolant and almost certainly a worn cam lobe.

    That package does not perform as bad as everyone makes out. I have driven those 82 and 83 HT4100's thru very hilly and mountainous terrain and they manage it fine. They will easily run the speed limit even in the mountains. By todays standards they are slugs but they will still move the car along. A performance concern like you state obviuosly inidcates something wrong. Worn cam lobes will act exactly like you describe. The engine idles perfectly and actually has good driveaway feel and is very smooth. It just has absolutely no power and it is very very evident on hills and grades. The engine will run very rich under those conditions because the speed density fuel injection system is seeing high manifold pressures and is fueling for the anticipated flow of air thru the engine based on properly operating cam lobes and valve lift. Since the lobes are worn and the air flow is dramatically reduced the fueling being delivered is way to rich which just adds to the sluggishness.

    Rich operation is not usually caused by debris in the throttle body resticting fuel flow unless it sticks the injector open all the time and that should be obvious....and it will not idle and run good at low speed with an injector stuck open. My bet is on the chronic worn cam lobe.

    All is not lost if that is what it is. Replacement cams are readily available, it is not that difficult to do and it is a sure fix. For an older car that nice it is a simple and easy thing to do. While in there, buy the service parts "reseal" kit with the upgraded head gasket material, intake gaskets, stronger head alignment dowels, etc..... Put it back together with a fresh filter, new oil and a quart of GM EOS. The EOS (engine oil supplement) is a GM product that is engine oil heavily fortified with ZDP to help stop any incipient wear on other components and it is very usefull in a situatio like you describe on the repair. Replace the distributor drive gear that mates with the cam and you have a nice car and one that will perform well.

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    cl1986's Avatar
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    Re: HT4100, no power uphill

    wow ive never heard of this additive for the coolant, what is it, where do i get it, and does my new gm motor have this problem. I guess the motor was changed in 96 or something, brand new gm motor, bill was $4800. Some other idiot did this, then i bought it. He showed me reciept.

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    cl1986's Avatar
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    Re: HT4100, no power uphill

    oh shit, i didnt see the end of your post till later, are u telling me i need a cam?? im only at 80k on the new gm motor

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