Greg,
I am going to copy and paste my long saga below. It's something I wrote a while back. It might give you some clues of other things to check, but at a minimum, it will make you feel better about your own problems.
--- Ken
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I installed the VEC2 when my car was NA car some time ago. As part of the install, I added supplemental grounds at the battery temp sensor, TPS and MAP sensor to the chassis. The car seemed to have some issues whenever I used the VEC2 to try to trim A/F or advance timing. It would stumble badly at times and seemed temperature dependent. Warm 80+ days were the worst. Running the VEC2 with the stock settings and the car ran fine no matter what the temp. I did a lot of troubleshooting with Sean including running the timing and injector circuits half with theVEC2 and half with the stock PCM, but could not get it totally figured out. I was also one of the first to install a VEC2 on a NA car, so some figuring out was expected. Since my plan was to install the SC, I figured I would just wait until the SC was installed and then go from there.
The SC was installed at a local Dodge dealer last spring. They had it dyno tuned by a 3rd party. This tuner had tuned 3 Roe SC’s before. A 5lb system making 530RWHP, an 8lb w/ H2O injection making 650RWHP and a head/cam/10lb system making 670RWHP, so the tuner seemed to be reasonably knowledgeable on the Roe SC system.
When I picked the car up at the Dodge dealer, I was given a dyno sheet showing 480RWHP. When I asked where the missing 100HP was, I was told that I would need to deal directly with the 3rd party tuner. To say I wasn’t thrilled would be an understatement. With my setup (6.5lb w/ water injection, headers, HF cats and catback), I expected to see something in the 575-590RWHP range on 92 octane fuel. I am running 3:55 gears, so maybe at least something over 560 at an absolute minimum. The dyno is a Dyno Dynamics system. From the above numbers and the fact that minor modified Gen IIIs have shown around 450RWHP, I think the dyno puts out similar numbers as a DynoJet, so the low HP isn’t just a dyno thing.
On the way home, the car ran crappy even though it had supposedly run smoothly when it was picked up from the tuner. It would cut out / stumble severely when I gave it any gas. I tried putting Sean’s standard program for my setup in and the car ran even worse and would barely even idle. It seemed to me there was an issue with the car and the car was essentially detuned to try to compensate for it, hence the low HP.
I took the car back down to the dyno and worked with the tuner. The water injection tubing fell out on the drive over to the dyno and watered down the engine. Got that fixed. While trying to tune the car, things kept changing on us. For instance, we would reduce the fuel and the A/F would get richer. Then we seemed to get things running fairly smoothly by dialing it in on the road and resetting the PCM. Once we strapped it back down on the dyno, it started crapping out again. Things just didn’t make sense. After 6 hours we finally just gave up.
While out test-driving it, it set check engine lights for misfire codes. I ordered and installed a ’96 PCM from Sean and that seemed to take care of the misfire codes and the car ran OK for a while.
I also installed an oil catch can in-line with the factory valve cover breather system to prevent too much oil from getting into the intake.
While talking to the Viper tech about my problems, he mentioned that the other recent Roe SC install had a 2nd box in the wiring harness while mine only had one, but he wasn’t sure what it was for. I did some investigation and found out that the 2nd box is used to adapt low impedance injectors to the high impedance drivers on the VEC2. I measured my injectors and they were low impedance (3 ohms). I checked with Sean and he confirmed I had a mismatch in the injector drivers and sent out the 2nd box to correct that problem. This issue occurred because I already had the VEC2 installed rather than getting it with the SC kit.
At this point, I am pretty happy since having a mismatch on the injector driver could seemingly account for the A/F and drivability problems that I have been having as well as the missing HP. Sean’s standard program now seemed to run pretty well in the car whereas it would barely run on it before.
I once again go down to the dyno and we start dialing it in. Once again, the car does not seem to be behaving properly. The A/F is still not responding to VEC2 programming changes as we expect. We finally just do a number of runs without changing anything and we see that the A/F is changing from 10.2 on one run to 13.0 on another for no apparent reason. We checked fuel pressure and it registered a good 55PSI throughout the RPM range, but something just isn’t right with this thing. We hook up a DRB scan tool and start poking around. We finally notice that the car is not going into open loop mode when we go WOT. Seems to make some sense that if the car is staying in closed loop mode, it will continue to try to adjust A/F using the O2 sensors when it shouldn’t be and perhaps cause the problem that we are seeing. Further diagnostic work shows that the TPS sensor is reading about 3.4V at WOT which is on the low side. 3.5V seems to be the minimum acceptable. To test if this is the root of our problem, we disconnect the O2 sensors to force the car to go into open loop. We do a quick pull and the car runs cleaner and the HP comes up to around 530 on a partial pull and the A/F looks more stable. Still low, but better than the 480hp we got before. With the problem ID’d once again, I pack up and go home after 5 hours on the dyno to figure out how to fix it.
At home I pull the intakes off and find that the throttle plates are not opening fully and hence the low TPS voltage. On Sean’s recommendation, I redrill the throttle cable mounting bracket to move it back towards the fire wall. Now the throttle plates open more fully and the TPS voltage has gone up to around 3.9V at WOT which seems reasonable. I take the car down to the Dodge dealer and have them plug in a DRB while we do some WOT runs and the car now seems to be going into open loop mode as it should. Great! Once again I am ready to get this thing tuned in. I also plug in a laptop and do a few runs on the open road and the A/F looks to be fairly stable from run to run, though not optimized which gives me further confidence that this thing has been put to bed.
Then my WBO started swinging wildly, so I stopped in at the Dodge dealer. O2 sensors were shot and I had to have them replaced. Possibly caused by driving the car for a short while with the front O2’s disconnected from power which I later learned can kill them.
I decide to drive the car for a couple of weeks and make sure that it is fully sorted out before I put it back on the dyno for the 4th time. It seemed to run fine, so I made an appointment at the dyno. The day before, the weather got hot (high 90’s), so I decided to take it out and test it in the hot weather one last time. The car ran like crap again! Basically cuts out or something under heavy throttle. Doesn’t sound like pinging or knock, but almost like a stuttering feel and sound and loss of power like a heavy miss or something.
The dealer did not install the better MSD fuel injector connectors and so a loose connection here could be a source of A/F stability problems, so I got the connectors and spent 6 hours tearing the inlet tubes and fuel rails off the car to get to the fuel injector harness so that I could change the connectors. This went smoothly, but wasn’t a simple task. I also ground down the stops on the throttle body actuator to try to get the throttle bodies to open a little further. Now the linkage hits the SC snorkel, but the TBs are opening 100% or at least pretty close to it.
Once again I drive the car and it seems to be driving OK, then it starts to act up again. I do notice some oddities like the injectors going to 100% at times when the car is not running well, but it seems to be a little unclear if this is a direct cause or not. I also have a problem with Cylinder #10 fouling out from running too rich even when I take about 1mSec of injector pulse width out of that cylinder.
I insert a 4.7K resistor in-line with the AIT to give a lower temperature reading and perhaps avoid the 100% duty cycle on the injectors as recommended by someone. The problem seemed worse and Sean said that the resistor trick only works on the 2000-2002 PCMs and makes matters worse on the ’96 that I have installed, so I removed the resistor.
Roe released new VEC2 firmware that he thinks will help my situation. He sends me a beta version to try before he releases it to everyone. I install the firmware (and new VEC2 software for the PC which has filtering on the fuel injector signals). Running the same VEC2 program as before, the car now throws lean bank 1 and bank 2 codes in about a 20-mile drive. Apparently the VEC2 firmware change has caused my car to run way leaner for some reason.
I ordered the EASE software from Roe and checked my adaptives which are pegged at +32. Sean decided that I should try to tune my car from scratch as he had run across one or two that were different than every other car out there. We programmed everything out of the VEC2 and started with just the adaptives. I adjusted the injector % to bring the adaptives close to zero at idle. Then the left and right banks were trimmed to bring them to the same level and the rear cylinders were leaned out using the individual injector offset controls. The injector % ended up being 74%, which is way different than what they should be - Typically in the 57% to 59% range. Also I had to run the right bank richer than the left bank which is the opposite of what Sean says he typically sees.
The car now starts to run pretty good, but is running lean during closed loop operation (16:1 - 18:1). Found out that the problem went away when I moved the O2 sensors back up to the header tubes instead of being in the collectors. Car now runs at 14:1 - 15:1 in closed loop as it should.
Final numbers came in at 571RWHP and 565RWTQ which I am happy with, though the torque seems a little low to me. This is also with me doing the tuning. I bought a WBO and laptop and do all my own tuning on the car now and just put it on the dyno for the numbers. The only outstanding issue for me is the huge drift on the tune that I get with temperature. A VEC3 upgrade is in my future since it should take care of this last problem.
.........................
..... and then prepare for the ground to come up REAL fast on ya when he responds.
