Hesitation persisting in 88 Brougham(NODIH)
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5.0 and 5.7 Discussion, Hesitation persisting in 88 Brougham(NODIH) in Cadillac Engine Technical Discussion; NODIH wrote in June, "Check EGR for proper operation, you can remove the vacuum line where the old ported distributor ...
  1. #1
    Orph is offline Cadillac Owners Member
    Automobile(s): 88 Brougham, 90 Brougham, 84 Eldorado
    Join Date
    May 2005
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    10

    Hesitation persisting in 88 Brougham(NODIH)

    NODIH wrote in June, "Check EGR for proper operation, you can remove the vacuum line where the old ported distributor port was that is on the drivers side front middle of the carb, in the Float Bowl section. Plug hose to carb, see if drivability is still poor, if not, reconnect." I have done this and now the engine runs fine with good power and no hesitation. My question is what do I do now? I really don't understand what I did, because the tube from the carb connected with a multitube unit on the driver's side, which in turn sent one tube to the EGR, as well as tubes to some other distant places. Does this make the new EGR valve unfunctional? This is a California 88 Caddy Brougham (5.0 L). Shall I let the tube blocked on both ends the way I have it now? Does this mean the new EGR valve was faulty or the electronic multitube unit (no idea what it is called) that connects with the carb and EGR is faulty? On the under-hood emission diagram it is called "SOL ASM".
    Thanks for leading me in the right direction.

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  3. #2
    N0DIH's Avatar
    N0DIH is offline Cadillac Owners Master
    Automobile(s): 94 Fleetwood Brougham
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    Re: Hesitation persisting in 88 Brougham(NODIH)

    I honestly haven't seen all the mess California does on the 307's. I'll nose through my 85 Olds FSM and see what it has. Likely it is something that keeps EGR working at WOT. EGR is disabled at WOT on fed emission cars.

    If you change the backpressure on the exhaust, the EGR will open at the wrong time. Positive backpressure won't open with less backpressure, or it will open late. No biggie, but can invite pinging on some timing sensitive engines like the 307. Negative backpressure valves really get goofy. The less backpressure makes them open earlier. I think California got more of these than Fed emissions cars. My LT1 has one even.

    See if you can get a non backpressure EGR from a 76 or older Olds that will bolt on the 307 intake. You will have to look at a few from the part store, most of the time they will let you look at them side by side. The 76 Olds 455 EGR was a backpressure type, but with a ported valve. It used a transducer to sense the backpressure so they could use a std valve.

    I would take a look at a 301 Pontiac valve, an 76 Olds 350 and 455 valve, Toro included, sometimes Toro's got weird stuff that was better.

    Send some pictures if you can under the hood, I might be able to figure it out. Emissions aren't a tricky as they look, it is more of figuring out what they did and why. CA likes to have emissions on as soon as possible (hence reduced timing when cold and stuff like EGR functioning at WOT) and even milder cams with less overlap to prevent as little raw fuel from going out the exhaust port when both valves are open for that short time. Likely cams with less than 50 degrees overlap. Fed cars try to keep it under 55-58 degrees. Hence why roller cams became std. faster ramps, better emissions, and a side benefit, less friction, so slightly better fuel economy.

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