A few things come to mind here....
In open loop, the PCM ignores all oxygen sensor data.
Any fuel trims that you see in open loop are innacurate.
Fuel trim is calculated only in closed loop, using oxygen sensor data.
If an oxygen sensors output voltage ever exceeds 1 volt, it's bad, replace it.
Have you checked camshaft retard? If so, what was the reading?
Have you checked fuel pressure and leakdown? What were the readings?

 

I didn't check camshaft retard as I don't have the tools for it, I will search for a garage for this one.
Fuel Pressure is perfect and no leakdown, I think I mentionned it in my previous thread (blazer not starting..)

Where are situated the O2 sensors ? There are three of them right? What purpose serve the last one ?

THanks!

 

On your 2000: There is one sensor in each side of the "Y" pipe, close to the exhaust manifolds. These are used for fuel control in closed loop operation. The third sensor is in the exhaust pipe, downstream, (after) the catalytic converter. Its sole purpose is to monitor the efficiency of the catalytic converter. It has no effect on fuel mixture.

 

So if fuel trim AND O2 sensors aren't used in OL. I guess my problem is spark advance then!

 

Fuel trim is an indication of how much the PCM is correcting the fuel mixture from what it should be. The PCM's way of double checking itself. The oxygen sensors must be working properly for fuel trims to be accurate.

The problem could very well be ignition advance but, the PCM calculates the amount of ignition advance to apply from the data that it receives. If any of the sensors are not providing correct data, the calculations will not correct. If camshaft retard data is not within specs, crossfire will occur inside the distributor cap. If crankshaft position sensor data is incorrect, every calculation that the PCM makes will be incorrect.

 

So CMP and CPK must be aligned within 2 degrees right? So what prevents me from using a multimeter with engine at tdc on cyl 1 and checking when CMP is at a high volatge level?

* Btw I have an oscilloscope, I can get 2 channels up and running and put CMP on one and CPK on the other. That way I can correlate the phase relationship between the two. My instinct, is that they should be in phase if alignment is at 0.

Am I right ?

 

The CKP sensor creates a magnetic field that is directed in the "general vicinity" of the 3X tone ring on the crankshaft. When the crankshaft rotates, the tone ring changes the magnetic field. The PCM reads the changes and determines exacty where the crankshaft is in rotation. The magnetic field is unique for each sensor, and the crankshaft position sensor relearn allows the PCM to "synchronize" with the sensor. It is all done electronically inside the PCM. The data is stored in the PCM until the next relearn. Not something you can do with a scope, cn only be done with a capable scan tool.


The CMP sensor, (in the distributor) is a hall effect switch. The streaming data is viewed on a capable scan tool. Engine RPM is snapped above 2K and back to idle before the data is accurate. Adjustment is made by slightly rotating the distributor, which aligns the sensor with the camshaft. Again, a scope won't do it.

 

Man, is there a good reason why they did use the most complicated setup in history?

Also, why didn't they thought of simply keying the distributor housing so it is always in the correct orientation? What the hell!

I don't understand why you say it's not possible to see a phase relationship with the CMP ..
The CKP being learnt by the ECU, why can't I learn the pattern as well? I mean, what is so unique about it??

Do you have a waveform you can send me so I can deduce what to do? I don't want to find a shop that will do this stupid job for me, they will certainly empty my pockets!!

Btw, I have a STN1110 Chip which is supposed to be much better than a ELM327, do you think I can get the crankshaft retard information with this? What are the specs of the protocol to get the crankshaft retard info?

It's on the bus, why not sniff it?

 

The system is not all that complicated, the proper equipment is necessary to test it though. The crank and cam sensors are extremely accurate, possibly as high as 20K rpm. The crank sensor is not adjustable, during the relearn the PCM learns how the sensor reacts when the tone ring interrupts the field. The cam sensor must be adjustable to compensate for component tolerance errors. As for a waveform and protocol, no clue, I just use the scan tool. Camshaft retard and the crank relearn can both be done in well under an hour. For the average DIYer, it's much cheaper to hire the work done. The options are: Pay the labor to someone that is familiar with the procedures, or buy a scan tool capable of viewing the data. From time to time there are some decent used ones on Ebay, starting around $2K.

 

Some news and info!

This week I decided to use the truck as it is, I wanted to see what more info I can grasp.
So today I've decided to look at the stored codes, I only had random misfires before, but now I have System Too Lean Bank 2! Which I guess points to a vacuum leak, which would describe my issue pretty well I think!

And the problem just got worse, now it stumbles on idle when hot as well.

I tried to find the leak myself and failed. I took a cigar and sent the smoke through the pcv tube on the intake, I don't know if it's a good method to find vacuum leak, probably not.. I may have to find a better way or send it to a shop, but if I can do this myself it would be nice.


Where are the possible vacuum leaks on this engine?

Btw, my temperature sensors are all good within 0 degrees celsius. So it's NOT a temp sensors issue.