My friend just got his 91 RS back on the road after an engine rebuilt. His old 305 got renewed after 170,000+ miles. As far as I know it got these major mods in the rebuild:
.30 over (Flat top pistons I think), Edelbrock TBI performer intake, GM performance roller cam, Double roller timing chain, Ebelbrock water pump.
Mods before build: Hypertech thermomaster chip, 160 stat, fan switch, open element air cleaner, MSD blaster.

The car runs great for a while, lots more power than before. It will then start to stumble an little. Then it starts to be down on power and the SES light on. We checked the code and got 43. Since I had this several yearts ago, I thought easy fix: Knock sensor.
We installed a new knock sensor and cleared ECM. Go for a drive and same thing. Short runs are ok. The longer runs are when it goes south.
Anybody have any ideas? We are getting too close to G8 and need to get 400 more miles on break-in. Must get this car right to go to G8. May end up taking mine which is currently an eye sore due to previous owner not caring ( in the works$$$)!

 

code 43 is talking about your ESC module. Many times these are replaced, and people do not out the grease on the bottom of them. This code says that there is low voltage detected at the ESC. Replace it, and make sure you put the grease on the bottom.
Keep us posted

 

Code 43 also occures when the car fails a forced knock test, and if the cam is much bigger then stock (lower cylinder pressure do to overlap)I would bet that is what is happening. After I put a ZZ4 cam in my LO3 I couldn't make my car Knock if I tried, so I got that code all the time till I dissabled the forced knock test in the chip. After the car warms up the ECM does a test where it tries to force the motor to knock so it can see if the sensor and ESC are working. If it cant hear a knock it assumes the system is malfuntioning and backs the timing way off to protect the motor. Thats where the poor performence comes in. If you shut the car off and turn it right back on it is reset and in a normal timing mode till it tries the forced knock test again in a few minutes.

 

Man I've been having the same problem with my car for the past 4 months. I've tried so much to get it to stop. I'm almost to the point of having the test written out on the next chip I buy.

 

I bet it would fix the problem of throwing code 43 and the poor performence that it causes. The knock senser would still be in opperation but it wouldn't self diagnose.

 

Wow joker, hi had no idea about that. All I ever learned about was from Mitchell1 (So much for them). So what is the primary cause you think? the overlap, the duration, or the lift? Maybe all of the above?
So I guess when I am ready to do the cam and prom, I'm going to have that excluded from the chip too

 

We have now noticed that this is happening when the car gets hot. If sitting still like at a long red light or in traffic, the temperature guage goes past 220 before the fan kicks on. (Thanks to a poor working HYPERTECH fan switch that is suppose to kick the fans on at 176).
I know that the car must be kept "cold" with a Thermomaster chip to prevent detonation. This did not happen before the rebuild when the car would get hot. This does not seem to happen before the car gets hot.
Could the knock sensor be picking up detonation with the chip and cam combination because the switch is not kicking on the fan?

 

I had it happen after a cam change. The neighbor had it happen on a stock LO3. He replaced everything and it still did it. That was about the same time that I figured out what was going on with mine(with the help of this board). I think in my case the overlap lowered the cylinder pressure enough that the computer couldn't get a good knock out of it. The forced knock test happens after the car has ran awhile and is warmed up (like maybe 10 min.) Warm temperatures aggrevated my neighbers cars condition. I burned a chip for him to shut the test off and it has never happened again.

fireball451, what are the specs of the cam you put in?

 

It is not my car, but my friends car. All I can tell you right now , is that the cam is a GM cam found in a 350 tpi police Caprice. My friend shouild be able to get me the specs. He can drive the car around for a long while without the SES light coming on.Once he has to sit still like at a long red light or in a drive-thru line, The engine will surge a little while idling. When he starts back down the road, the car fall on its face and the light comes on.
I have been talking to about five mechanics that I know. They all have different thoughts on the cause..... broken wire, bad ESC, bad ECM, etc. An auto electrical specialist that I know says that code 43 is a pain to diagnose, but the first question he asked was if the distributor had been apart. I told him that the engine builder went throught the distrubutor and throttlebody as part of the motor built. (excellent engine builder, would not trust my car with anyone else!, just limited when it comes down to electronics diagnosis). Anyway, he said that the control module may not have enough di-electric grease on it. And he rarely sees ESC's bad.
Most all the mec's say that there maybe a stressed wire or a ground that got missed or is not suficiently grounded.
We have faced the truth: this car will NOT make G8. Will be taking mine that was very neglected by previous owner and will hopefully see paint this summer.

 

Man it makes me feel better to see others having the same problem as me. I just went through a head and valve job a few months back and I got the ol' code 43. I've about had it with this, so I'm going to have it written out of the chip I'm getting made. Enough is enough. Away with knock sensors!

 

I was going to replace my knock sensor to see if it fixes the problem. Are you guys saying that by doing this it won't fix the problem??

 

Try that first, I'd say. After that, if you're still getting the code after you clear them, (disconnect battery for a few minutes) then go into the knock. The sputtering and all might be from the ESC.
I forgot, does this car have a 350 in it now? If so, then get the ESC for a 350. I was told to change that and the knock sensor from the 305, to the 350 when I did my swap.

 

Yea I bought a new knock sensor, that didnt help anything. The one thing that I have done to kind of bandage the problem is I am using a 160 Tstat ( not emissions legal ) and I have the timing advanced a little farther than I normally would. With the 160 Tstat my engine takes a lot longer to get to the temp that the test usually takes place at, and when it fails my timing falls off but I hardly notice due to that I have it advanced a little more.

 

Thanks Guys (and Gals?) for all of the info. I guess since this is my car we are talking about I should add to this post my self. Fireball451 and I have really tried to get this thing going but everytime we think we are getting ahead, we get knocked back a few spots! We have checked as many "grounds" as we can find, all seem good. We have replaced the knock sensor, same problem. We have replaced the Control Module in the distributor (and yes, we did use the grease), same problem. I put back the "stock" ECM PROM to see if the problem might be related to the Hypertech Chip, NOPE, same problem. I have adjusted my timing (0* BTDC right now), same problem. I am thinking of burning my own chip but need to do some research about this before I try. The setup I have is this, 5.0 (LO3) bored .030, GM performane roller cam (271*/280* duration, .410"/.427" lift), double roller timing chain, flat top pistons & edelbrock performer TBI & victor jr. water pump. I have not replced the ESC module on the firewall but I'm getting into some $$$ buying and replacing everything on the repair tree and still not have any luck. Anyone else have more? Thanks in advance!!!

 

With that much cam duration I still think you are failing the forced knock test. If that is the case the only way I know to fix it is to dissable the test in the chip.

 

There maybe a topic elsewhere on this but what do you use (equipment, software, etc.) to write/burn you own chips (i.e. to remove the knock test)? I also do not think the "off the shelf" Hypertech chip is helping me now with the new motor. I would like to be able to customize a PROM for my ECM that would give me the most support for my new engine. Should I replace the ESC on the firewall or start with a new PROM? LMK

 

You might try advancing your timing around 12 to 15 degs base and see if that will cause some knock. If not advance it a little more or run some cheap gas in it.

Steve

 

With that much duration it would run better with a good deal more advance.

 

Is this a new problem since you changed motors? Some motor specs would help.

Yes you deffinantly need to learn how to burn your own chips to make your perform correctly. Today I knocked .7 seconds off my 0-60 time just correcting 1 table in the chip. (I burned 4 chips to get there). Check out the DYI PROM board at this site.

 

I'll jump back in here!

The problem was not present before the rebuilt and has only surfaced since the rebuild.

 

lmao....gezz l hada set up a acount because of this silly post...

Knock sensor errors can be caused by timeing gears..espeasialy a mechanical gear where a chain isnt used,,weak chains will also set of error messages,,hope this solves yer probs.....most of these probs are popin up after modifictions...cahnge your cam what do ya do..you change timeing gears to !!!!!! hint

 

Hey CanCritter welcome to the boards. Sorry you wasted your time registering though. The problem is that he is not getting any knock counts, not even when the ecm does a forced knock test. If it was a problem with too much knock then you would have a good suggestion. We're all guilty of not reading thru the whole thread before we give advice so join the crowd.

Steve

 

np....have found a wealth of knowalge here and some very well informed and talented folks here....at least l have a direction to head in now...just have to fine tune mah wish list now and proceed...wish l had done this years ago but alas life sidetracked me somewhat.....anyway guess l'll start with the heads there PN.14101083 194 exaust and 150 if lm right......are these heads worth the time to mod a tad? if so will port and polish and change the stock springs to a heaver spring...seems from what lve read re the 4500-5000 deadend may be partialy responceible to springs that are done at 5000 rpm...am l partialy right here? and runners,,,,what diffrence do they make..ie longer or shorter runners..better top end or low end?