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Discussion Starter #1
Ok, I would like some thoughts here. I have a double cab 2004 3.4 with s/c, 90k, URD's fuel mods (injectors, fuel pump, thermostat, plugs and 2 piggy back computers). It is tuned to a t and has run perfectly since 2006 until I did a rebuild last year (suspension) and it sat for about 6 months. I got it back on the road and have had this random stalling issue for a few months. I get dtc 0101 and 0102 codes. It will stall with absolutely no warning and sometimes hard to re-start. It takes 4-5 tries then fires back up like nothing happened and runs fine sometimes for 15 minutes, sometimes a few days. I have put in 2 new mafs, did plugs and wires (had a misfire code). Fuel pressure is good, stock intake, good battery, all vacuum lines are intact, grounds are good and the electrical is all stock ie no aftermarket alarm. I have had my wideband hooked up and watching it and noticed that it will get real rich right before the stall. I am in the process of hooking up my obd software so I can data log as well. I have searched for the past few days with no solid answers. Thanks for any ideas in advance!
 

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Discussion Starter #2
Ok, did a quick look at my 02 sensor. Upstream sensor follows throttle response, down stream is a constant up and down top to bottom of the graph with no relationship to the front o2 sensor. So I would assume the rear sensor is shot or cat is malfunctioning? Need to read more. My understanding is ther rear sensor is just for the ecu to monitor the cat. It should be pretty much a flat line to show what the cat is doing. Anyone know if the rear o2 sensor could cause my stall??
 

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Actually that says the cat is operating as it should be. That is a normal reading from a rear O2. If it were following the front sensor you'd likely get a CEL and a failed cat code. You are correct as to the purpose of the rear sensor. It's only there to indicate that the cat is working as it should be. If it isn't you'll get a code for sure and that would not be stalling your engine.
Look for something having to do with fuel, spark or engine intake. More likely fuel or ignition. It's also worthwhile to check that the ECU ground on the engine intake is clean and well connected. Bad ECU grounds cause all sorts of wierd things to happen that usually come and go out of the blue without warning.

Ok, did a quick look at my 02 sensor. Upstream sensor follows throttle response, down stream is a constant up and down top to bottom of the graph with no relationship to the front o2 sensor. So I would assume the rear sensor is shot or cat is malfunctioning? Need to read more. My understanding is ther rear sensor is just for the ecu to monitor the cat. It should be pretty much a flat line to show what the cat is doing. Anyone know if the rear o2 sensor could cause my stall??
 

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Discussion Starter #4
Thanks, good information to know. I did a visual inspection of the manifold ground. I'll give it a good clean tomorrow just in case. The truck is dangerous right now, will shut down with no warning, no brakes, power steering etc.
 

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Since you have some SC mods on your truck I'd give the wiring to the fuel map modification stuff a very close and good look see. If the power to the ECU or the fuel mapping stuff is interrupted it would do just that. Make sure you solder all that stuff and are not relying on butt splices and or other rat wiring techniques. You want everything having to do with the ECU rock solid and nothing sketchy or questionable. Belt and suspender approach here.
 

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Discussion Starter #6
Dick,
Went over all my connections, ground on manifold is good and clean, heat shrink and soldered all of piggyback connections and they still look perfect. Today I moved it 150 feet, ran fine, went to drive it 1 hour later and it starts, shuts off 5 or 6 times then finally starts and seems to be dumping fuel while trying to start (wideband doesn't have time to warm up before stall so I can get a reading). One thing I did notice is I tried running my tuning software (br4 I think) to look at my maps and it wont connect, it says to check ecu power. I'm not sure if this is a connectivity problem or ecu problem. This is driving me nuts. Could one of my urd boxes be going bad?
 

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Discussion Starter #7
One more thing. I noticed that this problem coincided with the gas gauge no longer going below 1/2 tank. The light will still come on though when its close to empty. Could a sending unit problem cause anything like this?
 

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Could be. But if it's saying ECU power then you're on the right track because that's what it sounded like to me from the getgo. Odds are 9 times out of 10 the ECU is fine and it's something else so resort to an ECU swap dead last. Try to scrounge one like your's to swap in before you spend a lot of money to buy one. Likely your's is just fine.

BTW I thought most if not all O2 sensors were headed these days so you should be good readings right off the bat or close enough to it anyway.

Dick,
Went over all my connections, ground on manifold is good and clean, heat shrink and soldered all of piggyback connections and they still look perfect. Today I moved it 150 feet, ran fine, went to drive it 1 hour later and it starts, shuts off 5 or 6 times then finally starts and seems to be dumping fuel while trying to start (wideband doesn't have time to warm up before stall so I can get a reading). One thing I did notice is I tried running my tuning software (br4 I think) to look at my maps and it wont connect, it says to check ecu power. I'm not sure if this is a connectivity problem or ecu problem. This is driving me nuts. Could one of my urd boxes be going bad?
 

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Discussion Starter #9
This is getting more complicated. I, just in case, replaced the maf again to rule out a faulty new maf. Now the symptoms have changed, I appear not to be getting fuel. It will barely start with holding the gas pedal down, then it wont rev past 3k, like a rev limiter if I can get it to stay running at all. If I give it a squirt of starting fluid it will rev all the way up no problem burning the fluid, then it stalls. So now I am not getting gas to motor. I can hear the fuel pump running and the filer is free flowing. I am now going to drop the tank, and check the pump and sending unit. I noticed the tank is severely dented from my last trip to Gore. I am wondering if I deformed the tank enough to cause a problem with the pick up tube and mess with the sending unit as well. I am going to drop it tomorrow and see. Any thoughts? I do have a fuel pressure gauge, does a "t"
have to be put in to tap into the fuel line or is there a port somewhere?
 

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Sounds to me as if it's becomeing more of a hard failure instead of the much harder to pinpoint intermittant problem. If it breaks and stays broke then it's a lot easier to find. Fuel pump, clogged injectors, fuel filter etc. Anything having to do with fuel delivery can usually be checked and ruled out. However one clogged injector would likely toss a code for a single cylinder misfire so I'd look at the pump and wiring for same.

This is getting more complicated. I, just in case, replaced the maf again to rule out a faulty new maf. Now the symptoms have changed, I appear not to be getting fuel. It will barely start with holding the gas pedal down, then it wont rev past 3k, like a rev limiter if I can get it to stay running at all. If I give it a squirt of starting fluid it will rev all the way up no problem burning the fluid, then it stalls. So now I am not getting gas to motor. I can hear the fuel pump running and the filer is free flowing. I am now going to drop the tank, and check the pump and sending unit. I noticed the tank is severely dented from my last trip to Gore. I am wondering if I deformed the tank enough to cause a problem with the pick up tube and mess with the sending unit as well. I am going to drop it tomorrow and see. Any thoughts? I do have a fuel pressure gauge, does a "t"
have to be put in to tap into the fuel line or is there a port somewhere?
 

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Discussion Starter #11
It started great this am after not running last night. Took the tank down, straightened the bottom out, replaced the fuel pump just in case. Still no change, ran great for a while then started stalling. I'm going to power the fuel pump with a separate circuit today and see if that stops the stalling. I still only get 0101 and 0102 codes. I've got a buddy who is a master Toyota tech coming over to help out today. This is getting frustrating.
 

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Discussion Starter #13
Update. I monitored ground and power to the fuel pump. It powers up during crank, and continues 12 volts until after the trucks stalls (about 3 to 5 seconds). So, ecu is not cutting fuel to the truck. I does, while its in this stalling mode, act like the rev limiter is at 3k. My buddy, the toy tech is coming over tomorrow. I am going to go after wiring next.
 

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Update. I monitored ground and power to the fuel pump. It powers up during crank, and continues 12 volts until after the trucks stalls (about 3 to 5 seconds). So, ecu is not cutting fuel to the truck. I does, while its in this stalling mode, act like the rev limiter is at 3k. My buddy, the toy tech is coming over tomorrow. I am going to go after wiring next.
Sounds like fuel pump power is as it should be. The ECU must see engine rotation to allow the pump. Just "ignition on" will not do it.
This might help, from 99 FSM.


This is the "actual" diagram from an 03 FSM (2 pages).


 

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Discussion Starter #16
Man, thank you for that diagram. I am going after continuity of the wires going from my maf to the ecu tomorrow since I keep getting maf codes. My toy tech couldn't make it by today. Next week he is coming. He promises he will find the problem in a few minutes. I will feel like an moron if he does.... Anyways on a side note the pump I put in on friday was out of a 2007 Yamaha fxho jetski. I dable in personal watercraft and had it on the shelf from one I pulled apart. It is a identicle match to a walbro pump. Same pump size and design, actually looks better built, harness plugs in, flow is the same. So, you think my truck is amphibious now?????
 

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roktaco, just a bit more on the Toyota's "Circuit Description".

The description seems to imply that the ECU must see both the "STA and NE" signals to initiate the pump. I have a hard time believing this due to the fact that us man trans folks can push start with out using the starter at all. I am thinking that the ECU will power the relay/pump with the "STA" signal and/or the "NE" signal from the crank sensor then maintain it until engine rotation ceases and "NE" drops out (for fire safety reasons).
So my thinking is the book is just flat wrong or lost something in translation and frankly both are very common with Toyota FSMs.
Maybe you could bounce this off your toy tech bud.
 

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Discussion Starter #18
My toyota buddy has it and is leaning towards the tuning add on signal modifier. I hope not, that could be another bag of worms. I need to get in touch with Gadget and see if he has any ideas or ways to determine if there is a problem with the add ons for the tuning the super charger.
 

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Discussion Starter #19
The more I read up on my URD calibrator the more it sounds like it is the problem. I am throwing maf codes and thats exactly what the calibrator modifies is the maf signals. Man I hope I can pull my map out of the calibrator, I have a bazillion hours tuning this thing any my original laptop that it was tuned on crashed taking down the saved maps with it.... Going to try and get in touch with gadget now.
 
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