87 TurboII loss of power
 

Hey all, picked up a 1987 turbo2 with 80k miles for a good deal, engine was bad and already out, I put a "good" s5 swap in and I'm having some issues now. The fuel system was compromised and in really bad shape so I cleaned the tank the best I could, flushed the lines, replaced the sock filter on the pump and the inline filter, removed the injectors and flowed them both forward and backwards to clean them and make sure they were working (without being able to properly check flow/volume) I am running a s4 rtek 1.7 with s4 550 primary's and 550 secondary's, premix fuel, racingbeat turbo back exhaust and cone filter intake. When I first test drove the car it has a jerking under acceleration and got worse as engine temp rose to operating temp. Timing doesnt seem quite right as it doesnt want to run well at all when i set the timing to the "correct" position. It seems to want to run better if the timing is slightly off. Also I checked fuel pressures look correct at both speeds and did a compression test and it looks good as well. Any help would be greatly appreciated. Thanks in advance guys.

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Did you pull the components off the S4 and put them on the S5 block or are you using all the S5 components? You are premixing have you blocked off the OMP? What if any block off(s) on the emissions are you utilizing? Which engine emissions harness are you using? The reason I ask is there are differences between the two series- harness/wiring, emissions, turbos, OMP....
Let us know

Onlly s5 components used are engine, turbo and manifold, intake manifold and distributor. Omp and all emissions are blocked off. All other components are s4.

If you believe the timing is correct I would check the grounds on the engine harness especially at the fuel injectors and check the AFM

Try something simple and unplug the TPS. If no difference then unplug the TPS and boost sensor. And your injectors might still be clogged.

and make sure the trailing ignition wires are going to the correct rotors.

tried 2 afm but thats assuming that 1 of 2 are good lol re-calibrated tps, haven't looked into the boost sensor yet but i will do that next. triple checked spark plug wires and theyre definitely going to the correct plugs/rotors. Just unplugged the leading coil pack and fired it up and seemed to make no difference at all. going to check the resistance of the coil pack and ignitor then having an engineer bench test it at work tomorrow. hoping this is it. fingers crossed

can anyone please tell me if the black bullet connector is supposed to be hooked up to anything? i did some research and all signs point to NO but i'm just double checking.

no, it is for an auxiliary tachometer for testing purposes in the engine bay.

thank you very much. Ohm meter is dead so I'm diagnosing the leading coil in the morning.

leading coil resistance reads
Primary windings: 0.8 ohms
Secondary windings: Open
Secondary to B+ post: Open
Seems as if the leading coil is indeed bad. Ordering the coil and hoping to have it in by the weekend

Got spark to the leading coil now and replaced plugs again assuming they're fowled and it is running smoother at higher rpm (2500+) but won't idle. I'm checking vacuum leaks after work and timing.

compression test and check for vacuum leaks

Compression test on a cold engine checked 120 psi on both rotors and 90 psi on all 3 phases of each rotor

I see old dry rot vacuum caps so I'm gonna replace them and set timing then giver another shot

Had quite a few vacuum leaks. Timing is close but I'm not certain it is correct. I have both an s4 and an s5 timing pulley. The timing marks are slightly different and one is slightly larger than the other. Can someone please tell me which is the correct one I should be using on the s5 engine?

neither, never mess with the main pulley on an FC. the pulley and hub are a matched set, once you mix that up there is no way to know if the timing is accurate or not. all you can do is play with the timing to see how it affects the idle and performance.

I did find that the S4 inner pulley with timing marks is smaller than the S5. So the one I currently have installed is the correct pulley.

the pulley doesn't match the engine, it matches the hub it was machined and stamped for. unfortunately there is a bit of variance in this manufacturing process so a hub and pulley should never be separated permanently from one another.

my original how to thread is dead as the pictures are defunct but the pictures in this one will explain what i am referring to:
https://www.rx7club.com/2nd-generati...-973214/page2/



with a turbo engine, this can cost an engine once people start tossing unknown parts that are critical to engine function onto a rebuilt engine. i check all the engines i build due to this issue.

i have seen timing marks up to 35 degrees off.

is there a good aftermarket timing pulley you would recommend that isn't underdrive? I see racing beat has one but it is underdrive and isnt recommended for the TII. I'd like to just get an aftermarket one.

if you are unsure if you got the pulleys placed back on their original hubs or question whether or not they were original in the first place then you can replace them. i have a degree wheel for checking pulley timing, restamping them or pairing the correct ones together.

i don't know of any aftermarket sets that aren't underdrive. if you want me to check it then you can send me a PM regarding it.


i sell reconditioned, paired hub and main pulley sets for $65 plus shipping, $30 if a core is provided. these days it's almost impossible to trust that they are properly matched anymore, rebuilders for years pulled the hubs from a box and mixed these parts all up.

put the s4 timing hub and pulley on and still had issues. after removing the injectors to check flow again i ran the numbers and found i had 3 460cc inj and 1 550cc. installed 560 primary's and 760 secondarys that i had layin around and boom, she runs and idles smooth. timing is dead on and power is smooth. cuts out at high rpm but im assuming that is a fuel tank issue as it is still very very rusty. doing a electrolysis cleaning on it tomorrow and see how good a job that will do. hopefully all goes well and i can be driving this gem to work on monday. thanks everyone for their help, i am over the moon happy with the progress on the car.