Testing the 4.9 ESC module. Any ideas?
 

Is there a way to test the electronic spark module on the 4.9 turbo cars? Mine crapped out last year & I had to take the jumper wire approach so it would run again. I always run 91 or better octane & the car is only driven around town & sparingly. In the meantime, I have been watching for a replacement module & I found one that has been in storage for many years & I was told it came from a low mileage car when it was a year or two old. I realize first & foremost the car needs to start & run with the replacement module plugged in to verify its not dead, but is there a test to see if it is actually working? Maybe a pulsed ground input from the knock sensor wire & a timing light?

Does the knock sensor provide a steady ground, or maybe a pulsed ground with each ping it detects? I have never studied how the system works, I have only researched how to bypass a failed unit ;)

Thanks, 68RT

probably get better info over at 301 garage for 301t stuff like this.

I haven't been on the site in several years & outfoxed myself on the username & password.
I tried to reset my password via registered email address & it said it sent an email, but I never received it. unless that takes some time.

I will work on that.


Thanks!

should be able to get signed back in or just set up a new user name.

a member there that runs tta performance should be able to help out on how to test the box. or maybe the GM service manual has a testing procedure. luckily my 81 301t doesnt have any ESC issues.

ive sold quite a few used ESC boxes & they all worked when pulled from higher mile parts cars, should be a good chance a used one on ebay or wherever should work.

I figured out my old user name & reset my account. I have not been on that site in many many years. Where does the time go.......

I did get my replacement ESC module, plugged it in & the car started right up. Still not sure if its working as it should be, but its not a dead duck like my original was, so thats a good beginning.
I will lurk around on the 301 site & see if I can find any topics about testing the knock sensor & control system in general.

Thanks!

Solved !
 

So thought I would follow up with some interesting developments.

Its been 2 years since I installed the new ESC box & I just now finally got the car out for a wash, light detail & some cruise miles. Its running great, but I am just now realizing something I never knew.

For so many years I always heard comments about the 4.9 turbos being complete dogs & powerless. I never really compeltely agreed with that. No, they are no W72 car, but I felt it pulled pretty decent & spirited when the turbo spooled up. Would almost always squeek the tires on the 1-2 shift. It has been that way since I bought it 23 ish years ago. The only thing I did notice negatively was a little detonation when the engine was hot. nothing terrible, & not all that often & usually fresh gas premium fuel kept it away as far as I could tell.

So fast forward to today with the new ESC box installed & the car has officially transformed to what so many others have described as a non performer. Clearly my orignal esc box had never worked correctly:D

If it wasn't for the sound of the turbo, and the lights on the hood, I would question if the turbo is even doing anything. I am guessing the new ESC is pulling timing as designed & maybe even too much. Its ok, & I am not complaining. I drive it to enjoy the 1980 experience & its never been about performance, but I just think its funny that I was getting more out of it all these years with a bad ESC box & I didn't even know it. now its fairly anemic. 1-2 shifts are now stiff, but no way its able to break the tires at all. :p

hey, good to hear its running ok. well so much for 301g, it vanished! :( Reading back through this im surprised i didnt ask where you got the new ESC box, usually rebuilds require the PROM chip to be swapped as it has info specific to each car. or was it a original or rebuilt from a 1980 turbo 301? Some of the testing you asked about is in the GM service manual, do you have one? Makes working on these turbo cars much easier.

These cars did get a bad rep back in the day, and yes they are not "fast" compared to earlier bigger cube engines, they were never intended to be in 80-81. but they were the best performance for the price you could get in an american car at the time. When set to the designed 9psi boost on premium fuel these were almost as fast as the 78-79 400s, many werent at that psi when new or got messed with by guys that didnt know turbos or computer control on the 81's.

Stock times are in the low to mid 16's, compared to mid to high 15's for the 78 400 ta, my 81 is 99% stock original 28k mile engine, with the cat removed & no mufflers it runs mid to upper 14's, has a little detonation at WOT also so was only about 3/4-7/8 throttle past about half track, and being its a lower mile pace car, i was taking it easy compared to all out max effort. With very minor changes these cars can run into the mid 14's pretty easy... from a 30mph roll or on the highway, the 81 tta is about as fast as a mild cam w72 ta.

Check the box/PROM is correct for your car, then do some basic checks like timing, check boost psi, be sure carb is working right with choke pulling off, distributor/coil, etc etc. Kill the cat, get some straight through mufflers or remove them to run straight pipe, the turbo/wastegate muffles the sound very well... then you really hear the turbo whine. If its all original, keep as much of the exhaust as you want but the cat is a major restriction. It should do some weak power breaking or spin the tires off the line some when running right, mine with full dynomax turbo type mufflers will still power break easily & chirp 2nd gear pretty good with brand new 255/60 BFG tires.