orangekid
04-22-2011, 06:02 PM
First off, I have a 1980 cressida with a 4me, but it's really just a celica supra in disguise. The engine is completely rebuilt, but i haven't been able to take it on the road yet, because i can't get it to run right. Anyway, here's the situation...
The car will start reliably. But it the engine idles very rough, shakes around a lot, and from the muffler, it sounds like a harley. When I throttle up, the engine revs up very well, but if I hold the throttle open, there still seems to be a slight hiccup (This may be imaginary). Sometimes when I start the engine, it idles smoothly for about 5 seconds, then it starts getting rough as described above. When I pull spark plug wires, All seem to have an effect on the engine, but it's hard to tell exactly, because the engine is running so rough in the first place. I should also mention that the engine had trouble idling before I tore it down, so I'm pretty sure nothing went wrong with the rebuild. I used a block from another 4me as well.
The exhaust and cats are new. I cleaned and resealed the gas tank as well, and there is a new sock filter inside the tank. The lines were also removed, and i blew air through them before re-installation. Everything on the engine was cleaned during the rebuild. Fuel filter is new as well.
Things that i've checked:
-Timing (12 degrees BTDC)
-Spark plugs (new, all are similar in appearance)
-Plug wires (new)
-Distributor cap (new)
-Compression (all within range)
-AFM (the first one checked out, but i messed with the idle mixture screw in an attempt to set the idle, so i swapped a California spec AFM in it's place, which has not been tampered with)
-CSI (great spray pattern. The CSI time switch works too)
-Vacuum and air leaks (sprayed brake cleaner around, no change in idle. Replaced iintake manifold gaskets just in case, but it didn't help)
-ECU (I checked the resistance and voltage values at the ECU as best I could. They seemed to check out)
-Main Injectors (resistance checks out, and they do click as heard through a stethoscope)
-Injector resistor box (checks out great)
Some things I am concerned about:
-The fuel pump is the original, judging by the dirt buildup, which matches the rest of the underside of the car.
-During the rebuild, I had the cylinder head skimmed flat to avoid a BHG. The replacement block also appeared to have been skimmed before (The car it came out of had a BHG, but the block was perfectly flat). This has resulted in a slight cam timing issue. The cam sprocket pin is in alignment when the crank is at 5 degrees BTDC, meaning the the cam is about 2.5 degrees off from where it should be.
-When I pinch the fuel return line, the idle smooths out as the fuel pressure builds up. I got this idea from these forums. Some thought it might be the FPR, but that wasn't always the case.
My plan is to check the fuel pressure next, possibly the coil after that. I also may want to check the vacuum advance mechanism, as it's part of the "Spark Control System" according to my FSM's. Does anyone have any other suggestions or ideas? If I'm an idiot, please inform me...
The car will start reliably. But it the engine idles very rough, shakes around a lot, and from the muffler, it sounds like a harley. When I throttle up, the engine revs up very well, but if I hold the throttle open, there still seems to be a slight hiccup (This may be imaginary). Sometimes when I start the engine, it idles smoothly for about 5 seconds, then it starts getting rough as described above. When I pull spark plug wires, All seem to have an effect on the engine, but it's hard to tell exactly, because the engine is running so rough in the first place. I should also mention that the engine had trouble idling before I tore it down, so I'm pretty sure nothing went wrong with the rebuild. I used a block from another 4me as well.
The exhaust and cats are new. I cleaned and resealed the gas tank as well, and there is a new sock filter inside the tank. The lines were also removed, and i blew air through them before re-installation. Everything on the engine was cleaned during the rebuild. Fuel filter is new as well.
Things that i've checked:
-Timing (12 degrees BTDC)
-Spark plugs (new, all are similar in appearance)
-Plug wires (new)
-Distributor cap (new)
-Compression (all within range)
-AFM (the first one checked out, but i messed with the idle mixture screw in an attempt to set the idle, so i swapped a California spec AFM in it's place, which has not been tampered with)
-CSI (great spray pattern. The CSI time switch works too)
-Vacuum and air leaks (sprayed brake cleaner around, no change in idle. Replaced iintake manifold gaskets just in case, but it didn't help)
-ECU (I checked the resistance and voltage values at the ECU as best I could. They seemed to check out)
-Main Injectors (resistance checks out, and they do click as heard through a stethoscope)
-Injector resistor box (checks out great)
Some things I am concerned about:
-The fuel pump is the original, judging by the dirt buildup, which matches the rest of the underside of the car.
-During the rebuild, I had the cylinder head skimmed flat to avoid a BHG. The replacement block also appeared to have been skimmed before (The car it came out of had a BHG, but the block was perfectly flat). This has resulted in a slight cam timing issue. The cam sprocket pin is in alignment when the crank is at 5 degrees BTDC, meaning the the cam is about 2.5 degrees off from where it should be.
-When I pinch the fuel return line, the idle smooths out as the fuel pressure builds up. I got this idea from these forums. Some thought it might be the FPR, but that wasn't always the case.
My plan is to check the fuel pressure next, possibly the coil after that. I also may want to check the vacuum advance mechanism, as it's part of the "Spark Control System" according to my FSM's. Does anyone have any other suggestions or ideas? If I'm an idiot, please inform me...