whiteyota93

New truck and my wheeler

the wiring mess

all cleaned up

sad ride home
Alright, Ill try to keep this a short as possible. Back story on the truck. Bought as a project to drive as a daily. Was in the process of being restored by a father and son, they got about half way. They ran out of time and or money, and sold it to a friend of theirs, he needed the cash so I ended up with it for cheap.
Truck ran well but was half ass put together and needed a solid weekend of clean up to make it substantially better to drive. Ripped out more wiring than id like to admit, and cleaned up the vaccum lines and engine bay a bit along with a few other small things. It loved it and was running perfect! Over the next while I continued to work on the truck and prepping it for daily commuting. Did a compression test along the way and got a solid 195 across the board. Did plugs and wires shortly after buying it. I did adjust the valves as they were a bit loose and I've done it a few times before and had a knowledgeable friend help me to confirm I'm not an idiot. Checked timing and it was bang on.


Fast forward a few months, my girlfriends takes the truck for a 50km drive to visit a friend. On the way, no issues at all. Goes to leave, starts fine and runs fine, then it started. Stopped at a light, it dies. fires it back up and it ran but wouldn't accelerate without bad hesitation and felt like it was trying to die. Stops for another light and the truck dies on her, and would just crank over and not fire. Long story short, it got limped to a friends house who happened to be very close by, then the next day picked it up with a friends trailer.

K so I got it home and stripped the truck down to bare bones, doors off, fenders off, box off, interior out. time to investigate. The just of the issue is....It will fire up and run, not for long though. Sometimes it will be good for 5 minutes, sometimes only a few seconds. while it is running, it runs perfectly. But it does have a stumble on throttle.. and can cause it to die faster if you try to give it gas.. Got tired of the basics and wanted to get into this thing since it was in need of the basics anyways and they are cheap to get parts for.

Did a full intake clean up, new injector seals, fuel filter, coolant temp sensor, IAC cleaned, New PCV, Throttle body cleaned, egr delete, new intake gaskets, block off plates for egr, looked over harness for failures, none visible at the time and was unaware of the poor injector crimp that i now know i should of just re done. Put it all back together carefully to ensure i didn't miss anything important that could of caused it to die. no obvious issues on the intake side of the motor electrical or vaccum related, I have 2 vac lines left, fpr and evap. Everything else was removed for reasons lol

I very familiar with the 90s Toyota EFI as I've had a 93 3.0l for 5 years now and I've taken some time to try to understand how all the systems work together. So I decided it was time to tackle pinning out the ecu and sensors along with a full test of all the components in the EFI system. Since i wasn't driving it when it died, I really had no definitive starting point as the last time i had it out, it was running perfect. And getting a solid description can be difficult from some..

Things tested and points of interest, (ever sensor I tested, I did a continuity check on all wires associated with the circuits)
EFI Relay - Good Ohm reading from 1-2 and infinite at 3-4 as per the manual
COR - Continuity in ever wire, B has 2 corresponding wires, one in the ecu and one in the efi relay. Fp has power from BATT pin on ecu as it should for ecu memory- 12.9 v
Coolant Temp Sensor- Test @ sensor 1.57 after running for a second and 3.79 after cool down, Wires have continuity as well.
AFM - All Ohm readings were in spec, tested at ecu as well as sensor, same readings +or- 1-2 ohms.
Solenoid Resistor- B+ - no.10 and no.20 - 3.3 ohms ...spec is 2-3 ohms . Now i realize 0.3ohms is minimal but its not within spec so its been put on the watch list for now. I did test for continuity and everything checks out so i suspect it probably fine.
Distributor Pick-up - 155.8 ohm - acceptable
Coil primary - 0.7 ohm - acceptable
And finally..
TPS - VTA-E2 - 0.5 (good)
- IDL-E2 - Nadda .. like nothing at all at any range of throttle
- VTA-E2 - 5.12 (good)
- Vcc-E2 - 5.57 (good)

Tested at ECU as well and got the same results, including the fail for IDL. Now .. I haven't started to adjust the TPS in any way and I haven't touched it since I owned the truck .. It has the factory paint pen marks are still in the original spots. So this is where my questions begin ..
Yes they fail, and sometimes suddenly but can they really cause it to die at idle. My 3.0l had a bad TPS and it caused all kinds of fun issues and a long night learning about the TPS circuit. Anyhow, I was under the understanding that all the IDL-E2 circuit is a switch. It tells the ECU when the throttle plate is opening up passed its resting idle position which 0.57mm or something like that. I also know that its not very picky with when this happens and it doesn't mind if the resistance is low or high as long as its less than 2.3kohms. And I also know it doesn't really care what that base throttle position is as long as it close to make the ecu happy and doesn't give a slow throttle response due to having to open the throttle plate to far to get out of the idle circuit.

So .. would this really cause a no run issue? I even unplugged the tps and tried to run it, but that plan didn't work as i experienced the same symptoms, runs perfect for a minute then dies slowly like its not getting fuel. This has led me to believe that there's a strong possibility that this is my issue, but like I said I'm unsure if that could really be the only factor at play here causing it to die.

Other diagnostic testing I did was,
Tried the Fuel pump tester jump. It turns the pump on and I can hear the COR click while jumping it. So pump has power and is working. Tested voltage and got 12.5, battery was at 12.6 or something close. While doing this I tried to start it, When I had it jumped, it was much easier to start and ran longer, but seems like luck to me, because its not constant and I can only get it to run a few times before it will just crank and not run.

Then with no jumpers, just key on I moved the Afm door by hand and the pump turns on as it should when the door is opened. Again after doing this it was very easy to start. So I got an idea .. What if I used a screw driver to move the door to control how much air the ecu thought it was getting. I figured this will adjust on the fly how much fuel is being injected because, the ecu would rely on the afm signal and the tps signal to figure out how open the throttle is and how much fuel it needs, along with timing and other things i'm sure. So I did this, start it up, and used the afm door to control how it ran. To my surprise... every time it stumbled and tried to die, I opened the door a bit more, and it cleared up and ran nicer. After getting the truck to warm up to a more normal operating temp, it seemed to be running just fine on its own. I then tried to identify any major vaccum leaks or obvious shorts in the sensor harnesses by moving everything around a bit to see if it was just a bad connection. No luck on that, but hey it was still running! Well that happiness came to an end quickly as it began to stumble and I didnt have time to make it back to the afm to help it recover. So this confused me more than before and left me with some thinking to do. I know the afm is testing fine, so why can I keep it running by playing with the door opening?

I checked over all the lines in the engine bay visually and some have been replaced because they were questionable at best. Intake plumbing seems to be alright, I taped up a few spots in question but it doesn't have any large holes to cause massive leaks. I pulled the valve cover again to make sure the timing marks were lined up and that i still had a timing chain, which all seemed good as far as I can tell. Guides still seem to be in place and i can see anything that strikes me as odd or that would cause something like this.


Now I haven't done a fuel pressure test yet, as I'm trying to find the correct adapter banjo that will work, and or deciding if i just want to put a more permanent one on the rail at all all times. I'm also going to do another compression test to ensure I didn't have some kind of catastrophic failure, but id really hope not lol. Tomorrow I will be trying to reset the TPS to see if I can get a IDL-E2 reading out of it and hopefully that will shed some more light onto my issue or maybe lack there of. I will hopefully have time to do a compression test also and continue looking for a bad wire.
I'm not sure what direction I want to go next with testing or replacing parts as I have the luxury of some time to figure this out while I do body work and other things to get this truck back in shape and ready to be driven again...

But any input is appreciated, as I'm just trying to go through all the options and don't want to leave something silly that could be causing me problems.