After searching and reading, I am unable to find others with a similar problem and am looking for a reason and/or fix:

91 RS 305 stock rebuilt engine is getting tons of knock (over 1000 knocks in one cell on one occasion). The knock seems to be cumulative- It will increase continually for a period of time and then drop off to nothing, then start all over again. WinALDL log attached: change extension to .txt.

I have never gotten a SES light for this (it is funcational).
I have read about the forced knock, but why don't I get a SES light?
I cannot feel any timing being removed while driving.
Car runs good except for limited stumble at low RPM under acceleration.


I have Checked:
Knock module: 100Kohms
Knock sensor lead wire: 10v KOEOff, 11.8v KOErunning
Proper configuration of spark plug wires
esc module (DS firewall)
Timing-set to 0*
bin and computer: stock 8746 AXKW

Anyone with any ideas or a similar situation?
Any inputs appreciated- I am not sure what to do next.

Thanks,
S-D

 

Am I doomed? If the answer is comically simple, please let me know, make a joke at my expense and we're done with it.
I cannot figure this out, particularly the lack of codes.

If any other info is needed, just let me know-
Any help appreciated-

I am considering RBob's patch to eliminate the spark knock test and see if the run-away knock stops.

Thanks,
S-D

 

I'm no expert, but here's what I know:

1.) Mechanical Gear timing set instead of a chain can cause excessive knock.

2.) I BELIEVE when no knock is occurring, the knock sensor outputs a +8 to +10 VDC signal and this drops to zero during knock. What I do to probe lines is I soldered a sewing needle onto the end of a length of wire and then push the needle through the insulation. I'd recommend checking the voltage between the ground @ the battery (specifically) and at the ESC module. Someone let me know if I have my voltages backward for the knock.

3.) Check the resistance between the ESC module ground wire and the battery negative.

4.) Check the resistance of the ESC RETARD line between the ESC module and the ECM. According to this schematic:

http://www.chevythunder.com/1228746_ecm_198992_tbi.htm

it's pin B7. If the resistance is more than a few ohms (probably 100, but I haven't worked out the math), try to find out why.

On a side note, I'm currently experiencing a new knock problem myself. Just started for the first time since I've had the car. I replaced the sensor and it went away until the first heavy rain. I'm going to track down what I believe is a corroded connector somewhere. When I first got the car, it almost didn't run, but in the end it was all ECM issues which I've tracked down one by one. During this time, I temporarily fixed a sensor ground problem by running a 16 gauge wire from a ground point near the steering column to the ECM. I cut back the insulation on all ground wires (A11, A12, D1, D2) and soldered them together.

 

not to high jack the thread, but how come i get a knock on decell(or reving down)? timing is set to 0*, its a rebuilt motor, i only got one code and it hasnt reappeared(aside from the rich O2). any hints would be very much liked

 

Do you actually hear any knocking? If not my first guess would be that your KS connections/wire/circuit is picking something up inductively, any chance that it runs along the plug wires for a while?

 

I was able to eliminate the problem by modifying KS-related parameters in the bin. At least, the knock is no longer showing up in the cumulative area in WinALDL.
I will check for inductive interference as I am still unlcear as to the source of the knock (real or not).
S-D

 

Did you use RBob's patch? Just as something simple to check, you might want to make sure the KS is not torqued down too much, that would give false knock easily.

 

No, I did not use RBob's patch, but did vastly increase my knowledge of the inner workings of ecms in the process (granted, I was starting near zero). RBob was was laying stuff down two years ago that I have a hard time learning today.
Learning it is one thing, producing it from imagination is something all together different. That was some dry reading, though. I tend to like books with lots of pictures and very few equations. I'm just a Luddite, I guess.

I took it very easy torquing the sensor in. I forget the spec, but it is very low- 14 ft-lbs or similar. Essentially just tight enought to keep it from leaking.

-
S-D

 

How's that T5 holding up? If it's bolted to the engine it's a suspect. If the exhaust is hitting anything it too can trigger false knock counts. I'd get a ccc application knock module from a junkyard and try it out. Then I'd fix the sad T5.

 

JP-
The T-5 has the requisite rash from running the 350 in the past. I am about to rectify that with the T56. I was actually recording knock just while sitting in the driveway- tried clutch in, clutch out etc.... nothing would stop the knocking, but I see your point. I clearanced the stock cross-over pipe (it was close to the starter)- to no avail. It is strange.

Never searched for the ccc knock module idea. After doing so, I see some people having success with that idea.

S-D

 

The speed has to be above 10mph before the knock actually starts retarding the timing. You say a slight stumble in acceleration... why not retard the timing. The balancer can and does slip on older originals. Worth a try, take out 4 degrees and see if it's any better.
I trust balancers for setting timing but it can be even better if you mark the distributor's location with a scratch on the collar and the intake manifold. Since TBI is 0 degrees this makes it simple to revert back to 0 base when no timing light is avail.

 

No, didn't hear audible knocking. I checked on the KS being too close to the other wires etc... I was not able to find anything that look suspect.

The 305/T5 is coming out and a 383T56 going in within the next two weeks or so, depending on work schedule.
I am right in the middle of dropping the gas tank to install a higher capacity fuel pump right now. Sweet mother of jesus, getting that gas tank out was a terror. Almost enough to make me understand why people install a trap door. Almost.

JP- I will take a close look at the HB to see if it slipped- it is fully possible. I like the idea about scratching the dist. base for a sure mark.
S-D

 

Hey S-D, I thought you had a Vortec 350 in there before? What happened to that, or am I just remembering wrong?

 

Nothing wrong with your memory- I pulled the 350 and put in the re-built stock 305 so I had something to drive while assembling the 383.
Also, one thing I did not do prior to exchanging the 305 for the 350 was to datalog how the 305 ran, its parameters etc...

I realized only after the 350 was in how dumb it was to go into tuning a fairly modded 350 with no real baseline (and no prior experience). Now that is in hand, the new setup is bolted together and I'm about ready to exchange again.


S-D

 

Alright, thought so. Sounds like a good setup you got going there. Are you keeping the TBI on this new 383?

Also, have you checked out the Chicago regional board? We're renting out a dragstrip on June 11th. You should try to make it out.

 

Damn straight.
I am using the GMPP vortec-tbi intake- It is bored out to 2" and I have a matching 2" TBI with 65#/hr injectors.
I just put on an AFPR after I replaced my old fuel pump with a Walbro. My fuel pressure shot up from 12 to 21psi, so I thought it might be good to have a little control over that. I ran the 350 vortec at the stock 12 psi with the 65#/hr injectors and it did good (with much chip tuning).

This will allow me to finally get my moneys worth out of the Prominator.

I will check out the boards for the track rental, but can't make any promises on attending. This will take some time as I have to fabricate a trans cross member and get the Dakota Digital speedo installed as well. All right, that is a bunch of bs. The real reason is new chick and new house- those take up way more time than I had counted on.

S-D

edit: After checking the track rental, I likely will not be going. I like to head north to Union Grove, WI. Home of the oldest operating drag strip in the country. A dubious honor.
S-D

 

Hey, that's cool. I'm waiting to get my moneys worth out of my Prominator too, good luck with it and keep us updated. I think we'll see some solid times out of that combo.

 

I got a couple of suggestions, though probably obvious.

You say you had a 350, then put the 305 back in. What exactly were you using for knock sensors? You technically should have had two different knock sensors and two different knock modules, since the bore size is different.

maybe mis-matching the components is doing something?

other than that, maybe check for loose accessory brackets? you should have serpentine belts, but I had a funny rattle that turned out to be a loose power steering bracket on an '87.

also, maybe bad alternator bearings?

 

jwscab-
Yes- I have the appropriate knock sensors and modules for each engine.
The 305 is out of the car now and after inspecting, I find all brackets tight and in place.
It is funny you mention the altenator- Just prior to installing the vortec 350, I bought an altenator from NAPA auto parts and had to use my old pulley. I did not have the nut on the pulley tight enough and it chucked out the center of my pulley. $90 down the drain- it trashed the pulley and the alt. shaft. But I did catch it before it went flying off at high RPM. I found it no so much by the noise, but I noticed the inside of the pulley was getting really rusty. Live and learn.
But, the 305 knocking is resolved and is a moot point now, since the 305 is out and the 383 is ready to go in. I finished installing a new fuel pump, and am in the middle of installing the new hydraulic clutch assembly. Next comes the installation of the Dakota Digital speedo calibrator and the UPS site says the Sphon t56 x-member and TA will be here by 6-2-05. Also have a Nippendenso-style stagger-mount starter coming soon- damn, that was pricey.
I plan to begin re-paving the road in front of my house with tire rubber by the begining of July (will be driving by mid June, but must allow for tuning and break in of new engine/clutch, etc...)! The neighbors are gonna love this!
S-D

 

https://www.thirdgen.org/techbb2/sho...starter+offset

I am glad I read the above thread before installing the motor. I thought I had found the miracle starter- offset starter for 153 tooth flywheel. Wrong. That is on its way back to the manufacturer, whose eBay ad read wrong (see ebay item #7976783724). They indicate their offset pattern starter will work on both 153 and 168.
Ah well, could have been worse.
Looks like I have some drilling and tapping to do. Unfortunately, I have already bolted the trans and engine together. That has to come apart and engine goes back onthe stand for drilling and tapping.
Damn-it Jim!
S-D