I finally upgraded to a 7427 pcm, have some comments and questions

[pmkls1]

I've used the Moates.net G1 memory adapter with a ZIF socket http://www.moates.net/gp1-package-gm...h-2-chips.html to make chip swapping easy. I've even swapped chips out and into the ZIF socket when the was battery connected, with the ignition switch off! I can't recommend swapping chips with the battery connected, so maybe I've been lucky a few dozen times.

I've also seen bogus knock counts after swapping to a '427 PCM. I think the knock module in the Memcal could be the problem? In a couple instances, I've swapped Memcals and the bogus knock counts were cured. In a couple instances, I simply disabled the knock sensor in the PROM programming.

dave w

Regarding the G1 adapter and ZIF sockets, I do have that exact adapter as I stated in my earlier reply. I have always used ZIF sockets for chipping ecms with the exception of the modified memcal I made for this project and buy all of my hardware from moates.net (product plug ! lol).

I also have disabled the knock sensor flag in this pcm once as I didn't get the correct knock sensor until a day after the install and the pcm didn't like the 100k ohm knock sensor already in the car. I also backed the pin out of the pcm connector until I installed the correct sensor. What I did find odd was that the pcm would still register knock counts with the 100k ohm sensor plugged in even with the knock sensor code set (I always forget if it's 42 or 43 because the other code is the est/bypass code that sets when setting distributor timing). My concern with disabling the ks is detonation that I cannot hear as the combination of the very open intake and accompanying noise and the exhaust make it hard to hear any pinging at wot. I may disable the ks for now and back off of the timing a little until I find a solution.

[pmkls1]

Another issue that I have noticed is that I cannot get the pcm to operate the ccp solenoid for some reason and I thought that I had checked and set all of the ccp parameters in the bin. I have already verified the circuit integrity and solenoid operation. The old ecm quit commanding the solenoid when it started taking a dump so I temporarily wired the solenoid so that it activated with the ignition on and it was working when I did the swap. I had seen somewhere in either this or another forum a few posts regarding the ccp operation when installing a 427 pcm, but forget the details. I am going to double check everything before I burn my next chip and see if I can find the cause.

[JeepsAndGuns]

Another issue that I have noticed is that I cannot get the pcm to operate the ccp solenoid for some reason and I thought that I had checked and set all of the ccp parameters in the bin. I have already verified the circuit integrity and solenoid operation. The old ecm quit commanding the solenoid when it started taking a dump so I temporarily wired the solenoid so that it activated with the ignition on and it was working when I did the swap. I had seen somewhere in either this or another forum a few posts regarding the ccp operation when installing a 427 pcm, but forget the details. I am going to double check everything before I burn my next chip and see if I can find the cause.

What bin are you running? Most bins I looked at did not have ccp selected, and most of the parameters looked ok, but a few were either maxed out, or set to min, so I doubt just selecting the flag to turn it on will make it work. I am getting ready to install a ccp solenoid and controll it with the pcm (I am also running a 7427) When I got me a ccp solenoid from the junkyard, I got it from a 95 surburban, witch by chance, still had the pcm in it, so I grabbed that too. The bcc is BJYK, I checked it and ccp was active in it, so I opened two instances of tuner pro and copied every single parameter for ccp from BJYK and put them into my bin. BUT, I have not actually had a chance to install the solenoid yet and hook it up. I am hoping to have some time this weekend, so it hasnt been tested yet. I think BJYK is in the $0D thread, if not, let me know and I can post it up.

But back to your originial question, I really cant help you, as mentioned above, I am also running a 7427, however mine is a conversion (jeep 401 V8) I too get thousands and thousands of knock counts. I was unable to get it to work correctly, so I have simply disabled knock retard and have tuned by ear.

[dave w]

I wonder what would happen if knock sensor input was connected to a 4K ohm resistor? Connect one side of the resistor to B15 and have the other side of the resistor connected to battery negative? In my thinking, a constant 4K input should eliminate knock counts, figuring everything inside the Memcal / PCM are working correctly?

dave w

[pmkls1]

I'm Short on time so I'll make this response quick. I'm running an $OD mask and the bin is based off of a BJYL bin. . I have been logging since the install but have only had time to glance at the logs thus far but looked closer this morning and had a major breakthrough regarding issues that date back to the install of the L31 vortec long block. I noticed while watching a pull at wot up to 5k rpms that the engine speed was fluctuating a lot and got worse as the rpms got higher. The problem is that the engine speed want actually fluctuating during that run so I watched the rest of the drive and verified that the fluctuation shows up under normal conditions as well. Sooooooo, "houston, we have a problem". Only this time I know exactly where to look. The problem could be inside the dizzy OR the wiring as I did have the dizzy apart during the engine install to replace the gear and also remove the rust where the rotor installs because it was getting to be near impossible to remove/install the rotor. Either way, I'm going to just replace the 220k mile dizzy as well as go over the wiring since the harness could easily have gotten pinched during install as itt runs right across the top of the trans bellhousing. I am positive that this condition is the cause of most of my problems and that it only occurred after the engine swap and have not been able to identify it until now because the fluctuation does not register on the tach which is most likely buffered and the 8746 data stream is so slow that it would most likely not show up on a datalog. I have had the same issue before when a map sensor went bad. The car would lunge and nearly stall when pulling out from a stop but I could not figure out why because the sensor would still read sort of correctly but it was very slow to respond to changes in vacuum so by the time the data would update on the screen the map readings looked fine. Anyway, I gotta run. Hopefully I will have a new dizzy I installed and the wiring checked and/or fixed tonight. I will post as soon as I have verified that the issue has been corrected.

[EagleMark]

That is also a cause of EFI wires to close to high voltage spark.

[pmkls1]

Good point, but I'm tired of having to stay late at work to fix it so I'm going to go ahead and replace the dizzy and inspect the harness along with the plug wire repairs/rerouting that I had planned just to eliminate most of the probable causes. I am also going to double check the pins at the pcm connectors for proper pin tension and repair as needed.

[EagleMark]

As far as chip swapping goes, I had trouble with the 8746 and also a nissan 240sx that I used to own if I changed chips without removing battery power. In both it seemed that I could get away with 1 or 2 swaps and then they would exhibit some very bizarre behavior.

This could be from the BLM learn and you changed fuel VE tables?

My very first thought upon reading that was DUH !

I hate when that happens!

Before I ask a question I will describe my problem and then attempt a solution for the drive home and post the results. I installed the correct 4k knock sensor for the application. I went by the gm parts catalog for a 95 c/k 1500 5.7 vin k with auto trans and used a brand new delco sensor. My problem is that I am getting tons of bogus knock counts beginning right when I crank the engine. I bypassed the esc module by butting the black and white wires together near the module. I have used 2 different pcms and memcals with absolutely no difference. It will register between 200-500 knock counts while cranking to start. From there it will randomly register 25,50,100, or more counts at a time. I know the counts are bogus most of the time because of the counts it registers during startup and it will also register counts while idling. One possible cause I am considering and am going to eliminate is that the sensor wiring runs through the harness across the rear of the engine very close to the distributor and plug wires. I am using universal cut to fit accel spiral core wires and believe that I have some arcing at the cap due to the stainless conductor being pulled through the boots during assembly. My theory is that the wiring is picking up rfi and the pcm is interpreting that as a knock signal. I have a spare set of terminals and boots that I am going to install along with a new cap and rotor, but not tonight as I don't have time. But, I am going to fix the sensor wiring so that it runs straight through the main harness to the pcm and eliminating the loop that passes by the distributor. I was planning on doing that anyway, but was in a hurry to get the car running when I did the swap.

Running a EFI harness to close to distributor or spark plug wires in a conversion has caused many issues with RFI noise so this is always a possibility. But you keep saying how load this car is with headers and exhaust! Known issue! Some camaros will get knock counts and retard from rear axle control arm bushings, so anything that makes noise even that far away can cause knock counts. De sensitizing the Knock Sensor has worked, first step would be several wraps of teflon tape and since you know better not to over tourqe the knock sensor, second step would be a brass fitting or elbow is sometimes needed. Of course any rattle during cranking or running will set it off too.

You didn't mention the mask but I am assuming $0D, there is a catagory with some paremeters that may help "Knock Retard Paremeters" to disable knock. Turning off the Code 43 will only turn off the CEL, not the circut. Also is there Spark Retard happeneing when getting these knock counts?