96 corolla engine missing - 4AFE

[killbox916]

Hello everyone...I am at wits end with this little car and if I had hair I would pull it out......lol

1996 Toyota Corolla
1.6L DOHC EFI
Standard transmission.

I was driving to work the other day and the engine light come on/flashing and it starting skipping/shuttering really bad. I drove it back to the house, and had the codes pulled from the computer.

The following codes appeared:
P0300 - Random/Multiple Misfire Detected
P0302 - Cylinder 1 Misfire detected
P0303 - Cylinder 2 Misfire detected
P0305 - Cylinder 3 Misfire detected
P0305 - Cylinder 4 Misfire detected
P0105 - Manifold Absolute Pressure or Barometric Pressure Circuit (MAP)
P0120 - Throttle/Pedal position Sensor A Circuit

I have changed so far the Throttle Sensor and the MAP Sensor to no avail.
All plugs look good and all cylinders are getting spark, and all fuel injectors have been cleaned in an ultrasonic bath and seems to be working (I pull the connector off and the engine dies a bit)

So I am pretty much stuck right now.

The computer reader gives the following parameters at idle
MAP (Hg) 9
Ign Adv 8-12 depending on rpm
ST FTRM1 % 0.0
LT FTRM1 % -1.6^
Fuel Sys Open
O2S11 - .140
O2S12 - .060

I shot the Engine Control Module (ECM) connectors and the connectors that plug into it with some contact cleaner to make sure they were clean. And I seem to have noticed an improvement. I also took the cover of of the ECM while it was removed and didn't notice any abnormalities on the circuit board, it looks very clean.
When I drive the car now it still idles rough but now runs good at higher RPM's in first gear and in all other gears it seems to run smooth until I give even a little bit of throttle. Which also makes me think it's lean. I went ahead an changed the fuel filter after I ran the gas tank dry. I put in some fresh 93 octane and didn't notice a difference after the fuel filter R&R.

I checked the MAP sensor and TPS for voltage, both sensors ARE getting 5 volts.

I completed a resistance test of the TPS and the ohm values seem to have come out right. The only discrepancy is was when throttle valve fully open I got 2.9k and the limit was 3.3k-10k, but the reading did climb nicely and steady as I opened the throttle to full.

I check timing with a light and it came out ok, it was 12 but the engine was little above idle. Supposed to be 10 at 700rpm I got 12 at 790.

I still suspect a vacuum leak and I looked again today for like the 10th time and didn't find anything.

Any new ideas would be much appreciated..

[topnotch]

am no pro but i got a hunch that ur distributor could be fooling around. like the dizzy for example.

[killbox916]

Yeah I checked that.........I have a non adjustable distributor and the cap and rotor are worn but functional. I am getting great spark at the plug, and the timing with the TE1 and E1 jumpered on the test connector is right on @ 10. At 700 RPM. It finally idled down to 700. usually it is all over the place.

[Corollajoe]

my car had the same problem yours is having and mine ended up being the coil on the side of the distributor was bad, bought a new coil put it on and it was good as new, if that isnt the case with yours I would also check the intake manifold gasket to make sure it is good, thats about all i know where to start at good luck to you

[killbox916]

Checked the resistance on the coil. Check good
Checked the EGR Valve. - Good
Checked the idle air control valve, cleaned it and noticed some power gain, but still missing a cylinder. ECM says #1 misfire.

I'm gonna do a compression test next and see if I have any compression in the #1.

Would the ECM detect a misfire in the #1 cylinder if it were mechanical like a stuck valve etc.

[zythr]

And if not, are you going to sell?

[Corollajoe]

could have dropped a valve on the number 1 cylinder but usually when this happens it pops the piston and the motor is done but u never know it could have happened without killing the motor

[killbox916]

The mystery continues!

took compression reading from all 4 cylinders dry, and the engine nice and warm.

Cyl 1 = 220
Cyl 2 = 220
Cyl 3 = 180
Cyl 4 = 220

Most seem high I think they all should be around 180, but at least i know I got some compression.

I wonder if carbon build up is creating the high readings and if that could cause the issue I'm having.

If it's not something in my Cyl Head, I either have a loose/broken wire or an ECM problem. I think I have checked everything else on this Engine.

[speedy25]

The only time I got a misfire CEL was when I ran a vehicle out of gas. Hows the flow in your fuel pump?

-SP

[killbox916]

Originally Posted by speedy25

The only time I got a misfire CEL was when I ran a vehicle out of gas. Hows the flow in your fuel pump?

-SP

That is really the only thing I haven't checked is fuel pressure. I cant figure out a creative way to get a pressure gauge inline in the system. This car doesn't have a fuel pressure test port.

According to the Haynes manual, they want you to tie into the beginning of the fuel rail with a special fitting, with isn't really practical.

The pump does run, and if i unplug it the car dies. The only other thing I did was pull off the return line at the pressure regulator and fuel gushed out. But I guess it is possible that I have a weak pump and/or a bad regulator that is bypassing to much fuel. Although I squeezed off the return line to make sure there was no fuel bypassing and it didn't make a difference. Engine still skipped.

Does anyone know the size threads Toyota used that attach to the fuel pump? It's the same size as the bottom of the fuel filter. I may be able to tap in there if i could get my hands on some fittings.

[killbox916]

Originally Posted by speedy25

The only time I got a misfire CEL was when I ran a vehicle out of gas. Hows the flow in your fuel pump?

-SP

Ok, finally checked the fuel pressure I got 40psi at idle which is pretty good I think. So with the high compression readings Im going to pull the head, unless someone can talk me out of it.......lol

[speedy25]

Pulling the head will not fix your problem. CEL codes are ELECTRONIC and need to be diagnosed that way. While your fuel pump can give adequate pressure at idle it may not have enough flow for maintaining constant running. There can be other causes too. Another good bet would be to spend the money for someone with a scanner that can monitor engine function while driving and see if you can get reasons for the codes.

-SP

[TroyTrumpet]

I know this might seem too simple but I had a miss on one cylinder and checked everything, there was fuel, spark at the plugs, good compression and the distributor/coil was fine as well. I then noticed that the when I put the plug wire (from the cylinder with the miss) closer to the block, it would stop sparking at the plug and would jump about half way up the boot and arc out the side.... Thus causing the miss. I replaced the plug wires and all was fine.

[zwartyvogeltje]

Did you finaly found the answer? I got this as well.

[killbox916]

I changed the plug wires and it was fixed. Even though they tested good with an ohm meter, they were arching to the cylinder head just before the spark plug. (insulation had a pin hole in 2 wires) Only way I seen it is I drove it for a while and the wire finally started getting a burn mark where the arching occurred. I had inspected them before but I couldn't see the mark since it hadn't arched enough to produce a burn mark.

Did you change the wires already?