88 Pioneer 4.0 runs for 20-30 miles then stalls

[cruiser54]

I'm anxious to see the results of your testing as you gather momentum.

 

This got my attention:

 

"Apparently it liked its ground improvements as I've NEVER had the crisp throttle response from it that I do now AND the chronic hesitation (accelerator response delay) is nearly gone as well...".

 

That's always been my experience also. 

 

Test and adjust your TPS on the Engine side now....Post 8. 

[gogmorgo]

How to post pictures

Comancheclub.com doesn't host images, so you have to link to a third-party site. I've been recommending using imgur.com for hosting pictures as an alternative to photobucket, although I recently discovered they'll only host 225 images for you for free.

[aatcman]

So,

 

I finally got around to building my test rig...

 

Unfortunately, I have not yet been able to reliably duplicate the units behaviour in the Jeep..

 

However, I have been able to make it produce its failed state once...

When it did produce its failed state, it continued to fire the plug even with the trigger signal disconnected..

it did not respond to trigger at all (which means it did not change firing speed with RPM) and I could only stop it by removing power.

Once I hooked power back up, it would not fire at all -- for a few minutes..

Then it went back to working like it should and I have been unable to break it again since..

 

Another thing I noticed was that right before the unit stopped responding, it started killing every other trigger pulse (pulling it to ground).

--I had my oscope connected to the trigger line so I could make sure my input was similar to that of the ECM...

In fact, it was because of the weird effects to the trigger signal that I disconnected the trigger line in the first place -- I wanted to see if something was wrong with my 555 or if this was a symptom from the ICM...

--555 Circuit was fine..

 

For those that want to try this out,

google 555 astable calculator. 

Pretty much any will do as they all show the same basic circuit..

I used a 1 uf cap for C, 12k for R1 and 18k for R2 and just set it up on a perf board...

I ALSO used a diode (ANY small switching diode should work.  I think mine are 1n4004 or 1n4007, but again, it doesn't really matter)

This diode goes in parallel with R2, cathode at the C end.

The point of the diode is to short around R2 while C is charging (while the output signal is high) and thereby allow us to generate a square pulse with less then 50% duty cycle..

With the values above, you will get a square pulse at appx 42Hz and appx 40% duty cycle.  (40% duty cycle means the pulse is high 40% of the cycle). 

This equates to the appx equivalent of 840 RPM and 50 degrees dwell...

For the purpose of the test, making an exact replication of the ECU output for a given RPM doesn't seem to matter -- you could use 10k and 20k to simplify it and still have a valid test..

 

At any rate, I powered the circuit with my 12v power supply and knocked it down to 5 with a simple regulator I got at radio shack.  These look like a large transistor -- but require no extra components.  Just power in, power out, and ground...

This provided 5 volts to my 555 (supplied as marked VCC or +v in the drawings you will find) and produces an appx 4.5v square pulse on the output (my ECU varies between 4-5v on this signal, so this seems close enough)

It should be noted that any source of 12v will work.  Total draw should be 2-3 amps (note, this is appx -- I did NOT measure this...yet...)

 

I then simply grounded a spark plug (mounted in a vice) to my 12v power supply - and also ran - and + from my 12v power supply to the - and + pins on the ICM.

Next a spark plug wire from the coil to the plug

finally a wire from the 555 (pin 3) to the trigger input pin on the ICM (the single wire on the 2 wire plug)

 

NOTE:  DO NOT attempt this test on the vehicle!!! 

This is a bench test!! 

No connection to the vehicle should exist during this test!!

I am NOT responsible for damage to YOU, YOUR VEHICLE, OR ANYONE OR ANYTHING ELSE!!

The coil produces HIGH VOLTAGE!!

if you do this test -- BE SAFE, and understand YOU ARE DO DOING IT AT YOUR OWN RISK AND YOU ASSUME ALL LIABILITY!!

This info is therefore provided for educational purposes only!!

I ASSUME NO LIABILITY WHATSOEVER!!!  Any use of this info signifies consent to this!!

 

Sorry about all that, but we all know how people like to sue each other these days....  :o)

 

I'll post another update if I find a better way to produce the fail I was seeing on the Jeep..