Test it: http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml



Yep, read the autoshop101.com technical articles on the EFI system. Or throw an Air/Fuel meter on and you can see when the system is in open or closed loop by watching the O2 sensor output.

The problem is still happening like clockwork. One day last week, the problem lasted the whole day and didnt go away even after driving awhile. But, after it sat awhile and completely cooled it was fine again. Here is a quick summry of where Im at with the problem.
Changed out the AFM with a unit from an 1982 supra. It has more power through the rpm range, but the problem is still there. When you turn it off, let it sit several minutes, fire it back up idles rough and pops and bogs when you push the gas. When the pedal hits the floor it jumps up and runs fine untill you back it off a bit, it bogs again. After several minutes of this it runs fine untill you shut it down for several minutes.
I have also tested the TPS and the coolant temp sensor and the egr valve, coil, pickup coil and found all to be with in spec. Even unplugged cold start injector while the problem was occuring to see if maybe it was stuck on. It made no difference. Im all out of ideas. Last thing I know to check is fuel pressure at time of problem. Where and how can I mount a fuel guage on these trucks?

Supposedly you can get an assortment of parts at Napa to make up an adapter for the cold start injector line for a gauge. Or I plumbed an electronic sender into mine. I drilled and tapped the back end of the fuel injector rail (steel cap) for 1/8" NPT and then soldered in a brass elbow and screwed the sender into that. Wires run to a 0-100psi gauge inside the cab.

Anybody know what that assortment of parts would be? Any other ideas, if its not a fuel pump problem?

As far as what parts would be needed, I would probably approach that as follows. Get a fuel pressure gauge and find out what fitting it needs. Pull the cold start injector and find out what size bolt it uses. Then see what parts you can get to mate up the two points and go from there.

Also, stick on an Air/Fuel meter and see what that can tell you. I find having both the fuel pressure and A/F gauge in the cab is quite handy for troubleshooting:
- http://www.4crawler.com/4x4/CheapTricks/Gauges/index.shtml

thanks.
The problem does seem to be evolving a bit and getting worse. When the problem is occurring and your pushing down hard on the pedal, but not full down, its begining to do nothing but sit there and pop and jump more, hardly moving. And the problem seems to be occurring now even when the engine is mostly cooled off.
Its seems like when your pushing the gas one of two things is happening, spark is cutting in and out and when it does respark it pops and jumps, or the gas is cutting in and out. Gotta get a fuel pressure guage on there and see whats going on.

Another update. I pulled the plugs while the problem was occuring, I did turn it off first, The plugs where very white and glazed shiny. This changes things. I expected very black and gas soaked plugs, since I assumed it was running pig rich when it was messing up. Its running very lean, could this indicate the fuel pump is at fault.?

I would think so, but at the same time, theoreticially the o2 sensor and the ecu should try and keep the mixture correct regardless of fuel pressure, since the ecu has no idea what the fuel pressure is. If the ecu sees a lean mixture it would increase the duration of the injection, so even with low fuel pressure it should work, but i'm certainly not an expert on the system so hopefully someone with more knowledge can chime in. As a thought, how many miles are one your o2 sensor? and if its aftermarket is it the kinda you crimp on to the old connector or direct oem style?

The O2 sensor probably has about 20k or less miles on it. Im pretty sure it was a name brand, Bosh I think, but it is the crimp on style.

The Denso sensors work best on the Toyota engines. Folks have had issues with the Bosch sensors.