oregano

iTrader: (1)

Well, I just bought an 89 gxl. It has an s4 block with s5 everything else (ECU, intake manifolds, etc). Only engine mods are pineapple sleeves (claimed by seller but i hvant inspected this), header + no cat 2.5" exhaust, K&N cone filter. I just got the car running after putting a tranny in and am starting to drive it now.

The car is sloooooooow. Please, before you start laughing and leaving comments like (N/A are slow do a TII swap, etc), you have to understand that I realize that these cars were not blazing fast. My engine setup new would have made ~160 flywheel HP, and right now it has ~85 compression front and ~65 rear (have to check again myself). I know low compression kills the power but it should still make like 120 - 130 flywheel HP i think.

Well, something is wrong. It feels like its making maybe 70 - 80 HP. its like there is no difference between full throttle and half throttle. also it does not get faster at high rpm. it feels like it hits peak power at 3500 rpm and stays flat all the way up from there. I need some ideas on what i should check when i get a chance to look at it (when it gets warm outside again : s).

So far, i know there is a fuel leak on the engine somewhere (but i doubt its big enough to drop off fuel pressure). also i have a defi air/fuel gauge but its not connected right now so i have to get that worknig and see what my air/fuel ratios are as i rev up the motor. Things i know to check:
- exhaust clogged (theres no cat though. how could i check? blow with my mouth?)
- intake clogged
- Variable upper intake manifold thing not working
- 5th + 6th ports stuck closed
- secondary fuel injectors clogged, leaking, unplugged (all fuel related items will become obvious once air/fuel gauge works)
- fuel filter, pump, or sock clogged
- ignition timing way off, plugs fouled


any other ideas on what i should be checking?


oh and i checked the secondary throttle butterflies that sit in front of the throttle body and are opened by a diaphragm. they seem to work fine and also i tried wiring them open and no difference.

88redturbo2

pretty new to rotary's but that compression definitly seems low and the % difference between the two is pretty significant, what have you done maintinence wise? plugs? wires?

for the fuel leak you better figure out where that is coming from and make sure its mot leaking out of the pulsation dampner otherwise you wont be happy when you have a engine fire

check your timing! fuel filters are cheap and might as well buy a new one anyways, for the AFR guage make sure its a wideband, narrow band is not in anyways accurate at all. do a fuel pressure test, having the injectors sent out and cleaned is very cheap as well

Brodie121

iTrader: (8)

That compression is really low. How many miles on the engine?

oregano

iTrader: (1)

no idea how many miles on the engine : s

i will check compression today. the numbers i gave before are based on what someone else told me and are not my own findings.

Also, i will change ignition wires for sure cuz i know how much a difference that makes when they are old. I will change fuel filter soon as i can too and get the injectors cleaned. Timing i will also adjust today.

The AFR gage is designed for one O2 sensor wire signal between 0 and 1 Volt. Any idea what signal a wideband sends and can i still hook up a wideband to this AFR gage?

oregano

iTrader: (1)

crap, the defi AFR gauge is pretty useless. i did some research and it is designed for a narrowband O2 sensor. Only way i can get it to read wideband O2 signal is to get a wideband controller unit like the LC-1 which will let me control analog output signal to the defi AFR gauge. oh well, im off to get plugs, wires, and fuel filter.

my buddy said his FC had a high rpm issue and it turned out to be some resistor/sensor that is mounted on the front right fendor right behind the front strut tower. i took a look at what he was showing me but i have no idea what that thing does. i will try to figure it out in the FSM but if anyone know what im talking about and what that thing does let me know please.

Thanks for the help and input : )

oregano

iTrader: (1)

it turns out my leading coil/igniter pack is not firing at all. it has 12V though and coil resistance is .7 Ohms. i think its ECU signal but im not 100% sure.

i did compression test too and got 95 front, 85 rear (holding down pressure release button on tester). car should be much much faster once coil is firing lol.

calpatriot

Pull the O2 sensor; leave the hole open; test drive. If the power is increased, your exhaust has a restriction, i.e. clogged cat, or some other...

Get a fuel pressure test set from HF (<$20). Check the fuel pressure per the procedure in the online FSM (see FAQ section). If the fuel pressure does not fall off at high power/high rpm operation, the filter, pump and sock are likely ok.
Yes... I see nothing here that indicates you have checked for trouble codes. There is a procedure in the FSM to get trouble codes by grounding a connector and then counting pulses of the check engine light.

I also like to verify that the ECU is going into closed loop operation. The factory test set calls this the monitor lamp. On the 86-88 cars, the lamp is on when there are 12v between the upper and lower center connectors on the 6 pin test connector. I *presume* that is the same in the 89-91, but you will have to verify the circuit. The lamp should flash on and off about 8x per 10 sec when tested at steady cruise (not idle) rpm. That verifies that the ECU can see and interpret the O2 sensor, and is successfully controlling the mixture by modifying the injector pulse width.

After warm up, the lamp should be on at idle, on during acceleration, off during deceleration, and flashing during steady cruise.

Aaron Cake

iTrader: (1)

If your compression really is 65 PSI on one rotor, that engine is done. There is no point trying to make it work properly.

oregano

iTrader: (1)

compression is 85/95 holding down pressure release button on tester.

i havnt checked codes cuz i dont have a check engine light on. i will try checkiong codes now.

but im pretty sure the issue is just the leading coil pack.

thanks for the ideas : )

pd_day

iTrader: (6)

I think when aaron had the car, he was using an electric air pump to actuate the aux ports and vdi, make sure that pump is still working.