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I am searching for answers to why my S4 auto wont downshift into 3rd when I pull the shifter to 3rd.
I am suspecting a broken spring in the valve body but not 100%sure
Bad fuel pressure regulators and or dampers would not likely cause a high rev to occur. They most likely would lead to an irratic rev, as if the engine were hunting for the right balance to idle smoothly. YMMV.
My rear regulator and damper failed recently - the engine would not start at all.
I'd check out the ignition control computers up in the front by the hood latch. On 87+ they retard timing based on input from the hall coils mounted to the engine for knock detection as well as gating +12 to the ignition coils. When one goes the car goes *weird* in a big way. You can buy one for $50 bucks or so, swap it in on one side, then swap it to the other side. Just have a bit of heat sink compound around for the back.
Fixed my car from a barely running mess to a purring kitten.
All good suggestions...
i suggest essentially investigating ALL of these possibilities before you button it up, but do so in an organized fashion.
You might have a rennlister swap in your MAF, EZK and LH, (one at a time) and check for operation. Ohm our ALL of your coils, spark plug and coil wires. Check the vacuum nipples of all your fuel regulators/dampness for fuel idor. Do a reasonable check of your vacuum network holding vacuum (including pesky HVAC register control vacuum valves). Check all of your multi-pin, ring and spade terminals under your hood. Check for chafed wires on the MAF connector harness. Like any owner of a decades old car, you’ll find there is plenty to refresh and worth doing it. Oh, been there and done all of it 2 years ago.
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