I've had intermittent/random misfiring, poor fuel economy, and moderate loss of power for some time. Recently I lost power and have a no-start condition. There is fuel, spark, and air, but no firing.

OBD1 codes are 14 (Ignition Signal), 24 (Air Intake), 31 (Volume Air Flow), and 41(Throttle Position Sensor).

As all codes point toward ECM and wiring as the common denominator, and the wiring looks clean at a glance, I replaced the ECM with a plug and play unit from Flagship (tested and pre-programmed to match the VIN), but I still have a no-start/not firing condition.

Thoughts? Thanks in advance!

 

Welcome to YotaTech.

How do you know you have fuel, spark, and air? code 14 points to a distributor/igniter problem. The code by itself will shut off the injectors, but it takes a few turns so shouldn't cause no-start.

Codes 24 and 31 point to a problem with the VAF (or even more likely, a problem with the connector). If the problem with the connector extends to the FC pin, the fuel pump won't run.

Have you checked ignition timing? You'll only be approximate without it running, but it will confirm spark and tell you if the distributor is completely messed up.

Contrary to your initial guess, it is very, very unlikely to be the ECM.

 

Hi Scope - thanks for the reply.

The fuel pump is running and fuel comes out of the line when disconnected. Spark was visible in daylight with a wire disconnected from the distributor. Air, well...I'm going off of what a mobile mechanic in Livingston, Montana told me.

He did an hour and half of trouble shooting/diagnostic (without a code reader) and suspected ECM. I did some goggling and used a jumper to read the codes. Based on his information and the code indications I assumed ECM.

I have not checked the timing yet, but will look into it tomorrow, as well as VAF connector.

Thanks again for your insights!

 

Keep in mind that even with fuel getting to the rail your injectors may not be squirting it into the cylinders and just because you see a spark at a plug wire doesn't mean it is a strong spark at the right time to fire the cylinder.
My suggestion would be to check some basics, check all of your grounds, check that you are getting over 12 volts to the ECM, check your timing marks and timing belt condition.
If you still don't find an issue you will probably need a wiring diagram and a voltmeter to test components/wires. A field service manual (FSM) is your best friend when trying to diagnose issues like this.
Don't just throw parts at it!!! TEST! you can waste a lot of money going with someone's guess and just buying parts.

 

I'm checking the VAF with a multimeter, based on specs shown here: http://www.teamtoyota4x4.org/archivi...e/volumeai.pdf

I'm finding that no matter which combination of terminals I'm contacting the readings all drop to 1 (same reading as when the circuit is not closed on the meter) i.e. E2 - Vs jumps to ~149, then drops to 1 in a second or less. Other circuits are either similar or show no change from the 1 ohm reading when not connected.

Does this sound like a bad VAF or like I'm doing something wrong? The meter gives different resistance readings on other items, like a screwdriver compared to a utility knife and the voltage readings appear accurate on various batteries. When checking resistance between the meter's probes I'm getting .3 at 200 ohms.

Thanks again for any input!

 

maybe you should share a picture of your meter, how you have the leads connected to the meter and what setting it is on. sounds like you may be doing something wrong.
here is what my files show for my 95 3VZ (swapped to 3.4 last year):
1–2: CLOSED WITH STARTER RUNNING OR MEASURING PLATE OPEN
4–5: 200–400
5–6: 200–600 (MEASURING PLATE FULLY CLOSED) 20–1200 (MEASURING PLATE FULLY OPEN)
5–7: 10–20 K (–20 C, –4 F) 4–7 K (0 C, 32 F) 2–3 K (20 C, 68 F) 0.9–1.3 K (40 C, 104 F) 0.4–0.7 K (60 C, 140 F)

 

Here's a quick video clip of what my testing (of the VAF) looks like.

 

I'm not familiar with your meter and I can't see the setting on your dial, but it looks like it's on 200 ohm from the readout, so anytime it goes over 200 if faults to a reading of 1 on the far left of your readout.
try a different setting. you need up to 20,000 ohms for one of the tests (20K) and 1200 ohms for one and 600 or less for the others.

 

Thanks so much for the clear directions - I'm learning step by step. It looks like E2-Vc are out of spec. Replace VAF?

Here are my results:VAF Meter Readings

E2 - Vs (20-400) .336 @2k - Closed/.059 Fully Open/Peak .510 Mid Range

E2 - Vc (100-300) .4 @200

E2 - Vb (200-400) .280 @2k

E2 - THA 4.22 @20k ~32F

E1 - FC 1/.6 @200 w/potentiometer open/points contacting

 

See my comments in underlined bold below:

Here are my results:VAF Meter Readings

E2 - Vs (20-400) .336 @2k - Closed/.059 Fully Open/Peak .510 Mid Range This is out of range

E2 - Vc (100-300) .4 @200 This also appears to be out of range, but why would you choose 200 ohm scale for and expected reading of 100-300 ohms?

E2 - Vb (200-400) .280 @2k

E2 - THA 4.22 @20k ~32F

E1 - FC 1/.6 @200 w/potentiometer open/points contacting

Here's a couple of things to keep in mind:
1: I have never performed these tests
2: I no longer have a 3.0 in my truck or even a spare VAF to confirm any test
3: I am no engine control/performance guru.
4: even if you have verified readings out of spec it doesn't mean a new VAF will fix all of your problems
From your first post "I've had intermittent/random misfiring, poor fuel economy, and moderate loss of power for some time" since you "recently" developed a no start condition this means you MAY have more than one issue.
Maybe someone who knows more can chime in, but it looks to me like you should replace the VAF and see what happens. Better yet, find a loaner to try before you buy a new one.

 

If the E2-Vc reading was really on the 200 ohm scale (not 2k), the 0.4 ohms is a dead short. (It is very difficulty to actually measure 0.4 ohms on any scale, as the resistance of the leads is close to that.) Code 31 is triggered by an E2-Vc short. But that wouldn't cause a no-start. If you have messed up wiring to the VAF, you could have a Vc-E2 short there, along with an open in the Fc line (which usually causes a starts-and-runs-a-few-seconds issue, but ...) Also, you shouldn't get your otherwise good readings of Vs-E2 (those should be shorted as well). This suggests an intermittent short, possibly in the wiring rather than the VAF itself.

You could try an end-end test of the COR-VAF circuit by jumpering FC to B+ in the diagnostic connector. If the truck now starts, you have a problem in the VAF-COR circuit. To find it, consider: https://www.yotatech.com/forums/f116...-quits-312747/

 

Thanks guys - the E2-Vc reading was taken at 200 because 2k produced no reading, so I dialed both up and down to see if it was out of range of the 2k setting. When testing the meter on itself resistance is .3, so yes, scope103 I think you're spot on with that.

I'll try the jumper on Fc-B+ and review the link.

 

No start with jumper on FP-B+.

I'm becoming curious to inspect the timing belt. Am I off track here or is it worth opening up for a look?

Thanks again!

 

But did you hear the fuel pump run with the jumper in?

 

I'll have to check once more to confirm, but the fuel pump has been running and fuel is present with pressure when the hose is disconnected from the pipe near the injector.

 

Maybe you should re-read the whole thread again?