Thanks GR !


-Marty

 

I've decided to replace the ignition control module on my 1993 SW2 to see if that solves my intermittent code problem (41 and 42). I'd like to remove or loosen the AC hoses to get more access to the bolts that hold the ignition module and also remove the air intake shroud. I haven't used the AC in years, so I don't think it's under pressure ??

Any advice for removing and installing the ignition module? I watched a couple videos and have the full shop manual. I understand the bolts are long and can be brittle ? I don't want to snap a bolt.
I need dielectric grease on the spark plug contacts? I'm hoping this solves the problem or at least I'll have a new ignition module and then move on the the PCM if that's contributing to the problem.

Thanks for any advice !

-Marty S.

 

Please keep continuations of a topic as a single thread. Otherwise it is impossible for anyone to keep track of what was already done, what wasn't, and pretty much everything else. No harm no foul. Also moved to S car section as it should have been here in the first place but that's my bad for not noticing

 

i believe that on the 93, all the injectors fire at once, so i wonder if all 4 could go bad at the same time?

have you changed the crankshaft position sensor? there is a magnet in there that can lose it's magnetism resulting in a weak signal to the ignition module.

i just picked up a couple of PCM's for 38 bucks each, just match the p/n on yours to something on evilbay. they are pretty robust units, dipped in sealant, the soldering is great and the circuit board material is top notch, so a used one should be fine. just spray the plugs with DeOxit, wait for it to dry for a while before plugging back in. I bought PCM's for a manual shift and a DOHC, so those two conditions must be met during replacement. the VIN # and miles will be different but who cares. be sure to put the car through the "learning process" after PCM replacement, the procedure is probably in a book or online somewhere or maybe a forum member can spell it out.

you can measure the output of the crank sensor by pulling the harness and getting an AC millivolts meter on the two pins. my 92 uses pins 1 and 2 of the 5 pin jack, yours might be different. mine measured 55 millivolts during cranking, i can't wait to see what the new one reads,

 

The injectors do not activate all at the same time.
Each cylinder receives a spark whatever one hits TDC or whatever advanced timing it's at. Hence the term waste spark ignition system.

 

Hey Marty,

Any progress to report?

 

i know that the injectors on my 1992 SL all fire at the same time. this is called bank firing and is very common on cars from that era.

if you open up the PCM, you will see that pins J1D13,14,15,16 are all connected together by a common PC board trace,

From there they go to the Drain of an International Rectifier 9191 N Channel Hex MOSFET. When the fet gate is made positive, it decreases the Drain to Source resistance and all four injectors fire.

To see if this is the case for the 93, simple set a DMM to Continuity Check and listen for the beep as you go from pin 16 to 15, 14 and 13.
Or you could simply check for continuity between all 4 green wires on the injector harness.

No, the IR 9191 is not a standard p/n. Probably a private label done for Saturn.

If you want pics of the PCM internals in question, let me know and i will post them.

 

Hey,

I had always assumed that one of the reasons MPFI, such as that on the DOHCs, was desirable was because each injector fired separately to suit the position of the intake valves.

However, this batch firing is actually used in most cases, apparently including the 1.9 SOHC and DOHC. If the injectors were firing at different times, I assume they would have referred to it as SFI not MPFI.

Only other difference is that an SL in the early days used TBI for the SOHC. The DOHC used MPFI. Eventually SOHC switched over to MPFI as well.

Thank you for teaching me something today!

PS: where does your semiconductor background come from?

 

Thanks Derf!

I took 3 years of electronics at Homestead High School. We had this old retired Navy guy named John McCollum as a teacher. He was very strict but very good. Jobs and Wozniac were in the class also. TV repair out of High School then 50 more years in the Bay Area tech scene, now I fix guitar amps for a music shop just for kicks.

I was very surprised by the bank firing. Good thing I did not send my injectors out for precision matching. I did build a cleaner from a 555 timer chip that allows me to vary the frequency of the pulse and also the duration. Made it out of an old fuel rail. Did you know that there is a non serviceable O ring in the fuel rail? It is swedged in there. That's why you can rotate the fuel inlet if you use a big wrench
I was always worried about the loose fitting. Chopped up a rail from the wreckers for research . Bad news if it fails.

I have the complete GM factory service manuals for my Saturn and they do not mention the bank firing thing. I guess they did not want to advertise it.

I miss the Saturnfans site and oldnuc.
I wish there was a way to retrieve all that data.

 

Note: since all the injectors are tied together, a shorted injector will shut down the whole show.

To see if you have a shorted injector simply pull one injector wiring harness at a time until the car starts.