2.8 stalls under load?

[CNCguy]

Bimdub... I agree with your analysis so far.

Will the engine restart immediately after it dies? If not, does it still have spark? How long will the engine run if you don't rev it?

You could connect a scanner to monitor RPMs, injector pulse width and voltage at the ECM as the engine dies. A better alternative would be to use an ALDL cable and free software on a laptop to record the data while the ECM is on. You can even make your own ALDL cable.

[robertisaar]

heres a question: did the car ever get the recall work done to disable the MAF?

[bimdub]

Bimdub... I agree with your analysis so far.

Will the engine restart immediately after it dies? If not, does it still have spark? How long will the engine run if you don't rev it?

You could connect a scanner to monitor RPMs, injector pulse width and voltage at the ECM as the engine dies. A better alternative would be to use an ALDL cable and free software on a laptop to record the data while the ECM is on. You can even make your own ALDL cable.

the car will restart most of the time, sometimes I have to try several times to get it to start, the noid also flashes dimmer when it it struggling to start.

as for ALDL....I am unsure as this is an 88 and there is only two pins in the connector. yeah free software....where? is this software available for OBD2 Vehicles as well? come on....hook me up! I have built my own megasquirt ECM for another car so fabricating my own cables it not that big of a deal to me.

heres a question: did the car ever get the recall work done to disable the MAF?

I have no friggen idea, I searched and could not find any indication on the car, the MAF is brand new though as well as the MAP. the car will run exactly the same without the MAF connected.

[robertisaar]

i just recently made the ADS necessary to read those cars for tunerpro. that would work out fine for you.

recall: post the car's BCC (four letter code on the sticker of the PROM inside the ECU) and i'll look it up to see if it got the work done.

[pocket-rocket]

Freescan (can be buggy):

http://www.andywhittaker.com/ECU/FreeScan/tabid/70/Default.aspx

Tunerpro RT (free, but has a 10 second nag screen if you don't donate)

http://www.tunerpro.net/

OBD2 stuff (I haven't tried any of it):

http://www.obdpros.com/obd_software.php#free_software

http://www.obdallinone.com/sc/pages.asp?pageid=60

For the OBD2 stuff you will need one of those ELM357? base scan interfaces if you want to use a laptop. I got mine on ebay for around $20 shipped from Hong Kong I believe (took about 2 weeks to get here).

[bimdub]

i just recently made the ADS necessary to read those cars for tunerpro. that would work out fine for you.

recall: post the car's BCC (four letter code on the sticker of the PROM inside the ECU) and i'll look it up to see if it got the work done.

thanks I will get to that today, since I have the ECM pretty much out of the vehicle.

Freescan (can be buggy):

http://www.andywhittaker.com/ECU/FreeScan/tabid/70/Default.aspx

Tunerpro RT (free, but has a 10 second nag screen if you don't donate)

http://www.tunerpro.net/

OBD2 stuff (I haven't tried any of it):

http://www.obdpros.com/obd_software.php#free_software

http://www.obdallinone.com/sc/pages.asp?pageid=60

For the OBD2 stuff you will need one of those ELM357? base scan interfaces if you want to use a laptop. I got mine on ebay for around $20 shipped from Hong Kong I believe (took about 2 weeks to get here).

kewl beans!

I also forgot to mention the car always has spark. and will idle indefinitely once started.

[bimdub]

ok the four digit code is 1727

[robertisaar]

need the letters.... but i'm going to guess they are ASWH?

[60dgrzbelow0]

This is a long shot... but I only just recalled that I read something somewhere about a late 80's Buick having a similar problem... and it turned out to be a fractured (cracked in half...to be exact) Crankshaft Position Sensor that fell out in pieces when the owner was just replacing anything and everything to try and get to the bottom of the problem. Does this sound possible here? I'm not familiar enough with the sensor array on the transverse engines to know if it might be worth replacing the CPS to see if it is involved. I'm assuming that engine has a DIS lobe on the crankshaft, too.

[pocket-rocket]

There is no DIS lobe on the crank. The ICM and ECM both get their signal for the crank position from the CPS. There will be a twisted wire going from it to the ICM, then the ICM "forwards" this signal to the ECM while using it for the spark events. It couldn't hurt to replace the CPS, I don't think they are expensive. If you decide to, its on the rear of the engine, towards the center (when looking from side to side) probably about 2-3 inches above the oil pan. The connector will be a 2 prong, and the plug on the CPS should be at a 90 degree angle. I was always under the impression that CPS either worked or didn't work, though.

[60dgrzbelow0]

There is no DIS lobe on the crank. The ICM and ECM both get their signal for the crank position from the CPS. There will be a twisted wire going from it to the ICM, then the ICM "forwards" this signal to the ECM while using it for the spark events. It couldn't hurt to replace the CPS, I don't think they are expensive. If you decide to, its on the rear of the engine, towards the center (when looking from side to side) probably about 2-3 inches above the oil pan. The connector will be a 2 prong, and the plug on the CPS should be at a 90 degree angle. I was always under the impression that CPS either worked or didn't work, though.

Pocket-Rocket....

This is an excerpt from the link to this post that I found very informative and without knowing how it relates to the Buick, I'm curious as to how the crankshaft in that motor gets its signal for the Crankshaft Position Sensor without either a notched cast iron center section that also serves to balance the motor internally (hence the lighter Flex Plate vs, the heavier cast iron flywheel for the engines with manual transmissions) ...or by some positional magnetic induction method to tell the ECM how fast the crankshaft is turning and at what point to induce any particular injector or spark plug (or bank of injectors or plugs) to fire and function. My point of reference here is poisoned by only knowing how the VIN "S" RWD engines function. Would you please reconcile this so I have a better understanding?

http://www.automotivehelper.com/topic535109.htm

blindeyed
03-13-2006, 10:28 AM
The crankshaft sensor has me interested. I did not replace that. I also did not realize there are two of them. I only saw one when I had the engine apart to replace the timing set. I will check to see if the engine sounds good at 2000 rpms. In my Haynes book, it calls the two crankshaft sensors 'high resolution sensor" and "low resolution sensor" in the wiring diagram. More confusion for me. Could a faulty crankshaft sensor cause the backfiring through the intake manifold?

Yes the Haynes manual is correct, but in technical terms, the crankshaft sensors are known by the 3x crankchaft sensor and the 24x crankshaft sensor.

The 3x (low resolution) crankshaft is located next to the knock sensor and it's signal is mainly used during cranking. The ECM provides three prime pulses at all the injectors based on the 3x signal for start up. It then looks for the falling edge of the can signal to trigger injector number 4. After this the ECM primarily uses the 3x signal from the ignition module to time the sequential firing of each injector

The 24x (high resolution) crank sensor is located next to the crank dampner and has a unique role in fuel control. This is because the 24x contributes to filtering of the MAP signal at speeds below 3000rpm. The ECM reads MAp output at each 24x reference input signals, then averages MAP over every four counts to provide a more stable MAP reading for fuel control. The IAC valve posistion is not longer used to calculate air flow at idle for fuel delivery. So overall, this form of speed density fueling is being used at idle, and at higher engine speeds. This was all done to improve engine starting as well as cranking and idle quality.

As for your question.... Absolutely a bad crank sensor could no doubt cause backfiring. The 3x crank sensor controls fuel delivery at startup, and then takes control of the whole SFI process. While the 24x crank sensor is there to control the fuel delivery at idle and then up to 3000 rpms. And seeing that you've already pulled code 36, which basically means that your 24x crank sensor isnt doing its job for some reason. That would then in turn cause the fuel delivery to each cylinder to still continue operating, but not accurately. Hence, a misfire.

Does the car start up fine with no problem? Have you taken it for a test drive to see if it still misfires/backfires? If it drives fine over 3000 rpm, then that absolutely tells you the 24x crank sensor is the problem.

[pocket-rocket]

What I meant was a separate one from the one used by the ECM. One important thing you have overlooked, his car is an 88. SFI didn't come out until the Gen 3. There is a rong on the crank that does provide a way to trigger the CPS though, either way.

[60dgrzbelow0]

Like I said "poisoned by the VIN "S" Engine" I understand now...Thanks...

[pocket-rocket]

Wow, look at my mad typin skills, yo! I typed rong instead of ring... And I usually read over stuff before I post it...

[bimdub]

ok I dug through some literature today, is it possible in lieu of a signal from the ICM the ECM is just firing the injectors (remember they are not sequential) in pulsed mode (I think that is basically "limp mode" in which case they may not give enough fuel to get above ~2500 rpms anyhow and on top of that the ECM is confused and thinking "decelerate" ie fuel cut? what I need to figure out is how to hook a test tachometer up? is there a way I can test to see if the ICM is even sending a signal to the ECM? the more I read the more I think ICM problem, as for the CPS its doubtful, as I have already pulled it and it is not damaged, remember the coils are firing even after the injectors stop.