jazzmanbob

The problem I am having is that it is difficult to start and once it starts it runs for about 10 seconds and then stalls out.

All of the external components that were on the car prior to swapping the motor have been reinstalled with the exception of the factory air cleaner which was replaced by a bonez intake. (Yes the AFM is installed in its original position, I did not follow the instructions supplied with the intake, instead I fabricated a bracket to correctly position the AFM).

My new motor is a rebuilt with new turbo housings. new seals and street port.

I drove the car into the garage prior to pulling the motor so I am assuming everything was ok at that point in time other than the blown seals in the front rotor.

Crank angle sensor has correct resistance on both the G and N connectors.

BAC valve has correct resistance.

New Battery and fully charged.

Gas tank was near empty so I put in 3 gal. new gas.

New O2 Sensor

When the motor starts (usually after going thru the unflooding steps of pulling the injector fuse and turning over to clear unburned fuel) it will freely rev up to 2500 rpm at which point the tach drops to zero and the motor continues to run for 3-5 seconds then dies. No sputtering, it just dies as if I shut of the motor.

The fact that the tach drops to zero makes me believe the problem is somehow caused by the ECU shutting off fuel and ignition.

I tried disconnecting the AFM, no difference same for TPS.

What would cause that to happen. I want to drive this a few times before it goes back into storage for the winter.

Can anyone help?

Thanks

Bob

RX7Racer46

Did you check your vacuum lines? Thats the only thing that would cause it to die like that. Besides AFM not plugged in, but you have that so...Double check the vacuum lines and then check them again.

jazzmanbob

All vac lines are connected, I may have two that are switchd locations but according to the service manual diagrams I have connected every thing up correctly.

Anyhow from what I have read in the archives on this problem it would take a huge vac leak to stall out. A small disconnected hose would most likely cause a rough idle or uneven running.

Doea anyone know what the TPS resistance reading should be between the 3 pins?

Also what should the coolant sensor read?

There is the possibility that even if the sensor is OK maybe the wiring is broke somewhere in the harness.

I dont look forward to finding that problem!!!

Aaron Cake

iTrader: (1)

If the tach drops to zero, then it means the trailing ignition is no longer firing.

First step is to verify that both ignitions (L and T) continue to fire after the engine revs to 2.5K.

Do the injectors continue to fire (check with a stethescope)?

Is the AFM securely plugged in and is the connector in good shape?

Does it continue to run if you jump the fuel pump test connector (yellow connector under air box)?

jazzmanbob

Thanks Aaron,

I checked the Trailing coil resitance and found it toi be within spec of around 1 ohm.

The AFM is securely plugged in and the connector is in good shape. Other than changing the Air filter for a Bonez and following your intructions on your web page to do so nothing is different with the AFM from before the motor swap.

Just went and got an inductive timing light to test the secondaries.

Need to get a stethoscope to test the injectors.

Next thing to do is the fuel pump test.

Also judt got som 12V leds so I can read the error codes from the ecu.

I will let you know what results I get.

Bob

jazzmanbob

Ok here is an update: After 2 weeks of various tests I finally got the car started today. It wont idle but I just had to take it around the block as I got it to run for about 5 minutes in the garage and was able to restart when it stalled when i let off the gas.
Turns out there was a problem with the AFM after all and Aaron's suggestion to see if it would run with the fuel pump connector jumped (I got it started and it ran for about 30 seconds) is what let me to do more checking.

The flap in the AFM seemed to bind as i gently tried to push it open. So I dissassemble the AFM and found that the contact for the fuel pump switch was interferring with the contact arm. So much so that the fuel pump switch was not making contact. Testing the other contacts with an ohm meter revealed that there was no contact between some of the terminals. Closer inspection showed that the small conductor between the PC board and connector were broken.

DUH! I did that. When removing the afm I unscrewed the connector from the afm instead of removing the connector plug from the connector body. Even though I did not pull very hard on the connector before realizing that was not the way to remove the plug I unknowingly managed to break the small conductors. Of course I did that about 1 year ago so you think I could remember that?

After repairing that f*ck up, I tried and tried to get the beast started with no joy to be had. Pull the plugs, clean the plugs, pull the fuses, clear the combustion chambers, at least 6 times before it caught once, and ran for about a minute and stalled the moment I took my foot off the gas.

It seems to flood very easily, At least now I know it runs. So I will pull the Top manifols and check my primary injectors to see if they are leaking. and also look for a possible vacuum leaks that may be the cause for the hard starting and shitty idle.

It appears the non functioning tach is due to the fuse removal proceedure to clear the flooding issue as once I got the car started. stoped it and restated the tach started working. I see I have a small oil leak near the oil filter and my oil pressure reads 0 so I think IO need a new oil pressure sending unit.

Any input at this point greatly appreciated re my idling problem.

Thanks,

Bob