BUILD THREAD 84 Hurst Olds - TechG8

[rfpowerdude]

You could buy my scanner that will allow you to monitor each sensor real time like the ECM sees and be able to tell if any of them are bad... 😀

OTC Monitor 2000 scanner (old school OBD 1 ECM scanner) - GBodyForum - '78-'88 General Motors A/G-Body Community

Thought I posted this here before, but I cannot find it now. Up for sale is my OTC Monitor2000 scanner. I used to use it on the '83 H/O since that was all original. Asking $100+shipping (OBO). Anyone with an original G-body that still has the ECM (or putting one back together) can use this for...

gbodyforum.com

 

[69hurstolds]

My personal experience showed me that Bosch O2 sensor = problems

I tried a Bosch one time because that's all the local parts store had in stock when I accidently broke a wire off the sensor on my old 87 many years ago. That was one PITA. Had me cycling on station because I couldn't figure out why the car was running like crap with a new O2 sensor. Nothing else had changed, thinking I got a bad sensor. They wouldn't take it back because it was "electrical" so I bought yet another one thinking I had a bad egg. STILL had an issue with the new one. Choked back the tears and surrendered my wallet to the local dealership and they said it was the O2 sensor. They put in a Delco and the problems INSTANTLY went away. I learned something that day...and it cost me about 90 bucks at the dealership plus the cost of two crappy Bosch O2 sensors that ended up in the trash.

I cannot say this is your actual problem. But with sensors and gage parts, etc., I stick with ACDelco stuff if I can get it. Preferably the older ACDelco stuff. I've got about 7 or 8 M/C solenoids, a big handful of TPS's, and several intake manifold temp sensors and pressure gage sensors, and about 10 O2 sensors. All of it the older stuff. I'm probably set for life.

 

[techg8]

well its an easy swap. I got an AFS21 coming fast via Prime so I'll try that first. Thanks for the info

I had blinked the codes previously and it indicated an O2 sensor problem. I forget the exact code, should have wrote it down.

That OTC scanner is really cool. I love all the old retro tools and diagnostics, manuals etc etc. I think I have an Auto Xray around here that could scan the ecm.

 

[techg8]

New AC O2 sensor installed.

i cleared codes and ran it again til codes popped.

I had a code 13 and 21

checked out the throttle position sensor, and its resistance was far too high.

Swapped a new TPS in there, and now it runs without throwing codes.


It still runs pretty rich, and dwell "appears" stuck at about 40 now. When I jumper the test terminal to ground and dwell goes to 30 it idles great.

I do not see a discernable difference in dwell from cold running to hot running Fiddling with the choke, air bleed, or mix screws does not change the dwell reading when hot.

I decided to start from the beginning, and took a look at my timing. Here something is awry. Grounding the test terminal, checking timing I see 57degrees. I was going to twist the dist back to 20 or so degrees, but its frozen in the block. Also, I highly doubt that I have 57 degrees initial timing. it starts and runs too well . perhaps the balancer has slipped?

Giving it a rest for now. Theres going to have to be some diagnostics performed.

 

[69hurstolds]

I think it's a 1" square if memory serves on the distributor housing right above the base. I could be wrong about the size. You may can get the distributor to turn with a big azz wrench. Maybe. If not, don't force the wrench. I have seen busted distributor housings due to the frozen housings. I've had them stuck so bad I had to take the pan off and drive that sucker out from the bottom.

It certainly does sound like there's some slippage on the balancer ring. 57 degrees with the test lead grounded is way way to much.

If you can get the distributor loose, find TDC and paint a mark at zero on that balancer and at least get the timing down until you can get it replaced if it is found to have slipped. Of course, if it's slipping all over the place, may want to fix that first.

 

[TURNA]

 

[techg8]

So I investigated a bit more.

The engine is running pretty well but the Dwell at idle is stuck about 32....not too bad. It varies with throttle position input. However it is not responding to the 02 sensor.

I ran the diagnostic chart for stuck dwell between 10 and 50, and everything looks to be operating properly EXCEPT the ECM. According to the chart its either the connection to the ECM or its the ECM itself.

will advise...

 

[olds307 and 403]

That might explain the timing advance being so far out to lunch.

 

[Canon_Mutant]

Yeah, 57 is almost in lean burn mode in 4th and lock up. Mine will go low 60s then. 22 initial with 30s once she warms up and leans out a bit. The O2 sensor is either not functioning, the connection to the ECM is missing which should latch a code, or that circuitry in the ECM is toast. I seem to recall lean O2 signal to the ECM when cold and idle through light throttle will even latch a code.

 

[techg8]

Got a reman ecm on Amazon for $15!!!

Installed it, no change. It held at 32 dwell at warmed idle, no codes. Dwell would drop if I floored it into the secondaries in P, then return to steady 32. No dwell response to idle screws or air bleed, though the engine responded properly.

I ran it 5 miles around town and rechecked hot idle. Dwell now stuck at 44 with same responses as above. No codes.

Hmmmm