4runner Runs and Dies. Extensive diag. Running out of options.
 

1997 4runner will start, stumble for a few seconds, and die. Give it gas while stumbling, dies.
Things done:
Compression test: 165-170 psi
New NKG double ground plugs
New wires
New coils
Checked and double checked wiring, plugged in correctly.
Injectors were sent out and rebuilt
New fuel pressure regulator
ECT ohmd to spec
CPS ohmd to spec
Cam PS ohmed to spec
Knock sensors and harness from dealer
Timing checked and lines up (both cams aligned to crank)
Reluctor ring on crank checked for missing teeth
Verified knob on cam gear is intact for sensor
Fuel pump tested, wiring checked, shorted relay pump is in good order
All fuses replaced (why not at this point) and relays checked
Ignitor on fender under MAF replaced with good one from my other truck. No change
MAF replaced from other truck, no change. Other truck runs with it just fine.
ECU replaced from other truck, no change.
O2 sensor removed in case cat clogged, no change.
Vacuum lines checked for cracks, have new lines I can put in.
Started and sprayed with starting fluid before and after throttle body, engine dies.
IAC removed and cleaned. Seemed to move fine.
Grounds removed, cleaned, added two more for rule-out.

Only issue I have now is that since it cuts out spark, plugs are fouled and so is 02 sensor, but the plugs clean up nicely and have a good spark.

Not sure what else I can try at this moment. Im assuming I have an electrical gremlin somewhere.

The only area I had of concern was corroded and shorted wiring to fuel pump, which I have sautered new wiring and fixed. Truck did not start prior to me fixing wiring. Perhaps there is another short somewhere along that loom that leads to ecu not firing the coils? Im stumped!

Sounds like it's starting for the initial cranking... have you tried to leave the fuel pump jumper in the diag port in place while trying to start?

At initial cranking it will supply fuel but if there are no ignition events it will either cut spark or fuel (depending on vehicle)... it's a safety feature to shut the engine down (and fuel pump) down in the event of am accident.

I would also try the starter relay... and check your ignition switch. Certain circuits work different whether 'on' or 'start'.

Fuel pump has power for about a second after the engine dies, checked with diode on positive lead on fuel pump plug. Spark plugs are dark black and wet when pulled so assuming its cutting spark. Is there a safety switch somewhere in an event there was an accident that's stopping it from running? I know Fords have an inertia switch not sure about Toyota.

Pretty sure these trucks pump fuel no mater what if the engine is turning over and everything is working fuel system wise, I assume it's the crank sensor or cam that signals the pump to run but don't know. Sounds like he's getting fuel but losing spark, I'd suspect alarm system but it's starting? I'd say start swapping more spark related components if your sure it's fuel soaked and not firing. Might help to let us know what trim you have, what alarm system, limited had it own setup and USDM got that RS3000 system under the seat, any aftermarket alarm/shoddy wiring, compression isn't great but I think it's suppose to be between 210-145 so your good there. I'd start swapping all spark related sensors from donor truck including Cam and Crank sensor even though they spec'd out ok, and even new wires and coil boots incase you happen to get a defective part, it happens. And yes you might have to start pulling the wiring harness apart to all spark related components and look for a severed wire or start swapping wire harness sections.. And no CEL codes?, I realize it won't run long enough for pending sensors but you'd think it would throw a code acting like that right away

1997 sr5 v6. No black box under the drivers seat. There was some viper aftermarket system that was half cut out when I bought the car and I removed the rest once I bought it. I will scan the car tomorrow.

Also should ask when did this problem first appear, driving down the road, off-roading or after working on it, or just one day you started it and it did this?, I'm thinking maybe the old dried out wire harness got disturbed and severed a wire, they are pretty thin gauge wires going to all electricals and getting pretty old and brittle, could have also been rodents chewing on wires you never know, a lot of the wires routed around the bottom edge of the oil pan and on the intake are not in the best environment. No CEL ever showed up, does the CEL illuminate with keys turned on, just trying to understand all possibilities.

Removal of the viper is almost guaranteed to be the problem. As I said, check your ignition switch wiring. Run and ignition have different functions - ecu start sequences vary as well for the first couple hundred cycles after start and then into run mode.



It sounds like you bought it and trying to fix problems it has.

The compression I wouldn't worry about.... there are a variety of factors that will vary the figures (examples... throttle wide open or not, temperature, when last run, if the rings are washed with fuel, etc) as long as all cylinders are within 10% of each other you're fine.

Was the Viper system installed correctly from the initial install? Probably not. Something has probably been wired wrong for sometime. Was the Viper system installed with wire half taps? Half taps can induce problems like dirty opens (partially connected).

Removed all of the half taps and checked wiring. Finally got the engine to run on enough cylinders to throw codes P0340 and P1300. Checked Cam sensor ohm again and pulled on ignitor wiring to see if anything was loose. I will check wiring between ignitor and ecm, think I saw a test procedure somewhere online.

I have a similar issue. Did you figure out your problem(s)?