427 engine (part 2) - RHS block

[Rich Z]

Originally Posted by schpenxel

When the pellet on mine had issues it would stall as soon as I started moving.. I don't see how that would cause your issues but what do I know

Yeah, I'm just winging this too. Thankfully this isn't all done by magic, so there WILL be something causing it that can be fixed or replaced.

[Rich Z]

I replaced the TAC module in the car today, so I guess the only thing I can do is just wait it out to see if the intermittent start up problem goes away or not. I sprayed the male and female pins in the two connectors and sockets with contact cleaner too. Wasn't too tough of a job. The single retaining screw on the back end is a little challenging to get to, though.

Here's some pics I took in case some of you aren't really sure what the TAC module is or located...











Basically the TAC module takes the signals from the sensor in the gas pedal and relays that to the throttle body plate position motor. Feedback from the throttle plate sensor is compared with what the TAC/PCM believes the throttle plate should be. A mismatch in the PCM tables between this feedback and the relevant table can trigger the REDUCED ENGINE POWER fault, because the PCM then believes that the throttle body has failed and in order to prevent an engine runaway condition, shuts it down to limp mode. Of course, this is just a vague description of the process as I'm still a bit hazy on the exact steps that take place. I believe there is some sort of throttle plate movement test done at engine startup, and possibly the PCM is not happy with the results of this test, giving me the problem I have been having.

One thing I made note of is that the part numbers are different on the two TAC modules. The one that just came out of my car is to the left. There seem to be a lot of part numbers for this module, but trying to figure out if one is more correct to use than the others has proven to be a challenge. So I just don't know. I guess all I can do is drive the car and wait and see....

FYI, the TAC module shown to the left is not the original one that came on my car. Back when Aaron Scott was working on the car, he suspected a bad TAC module. Unfortunately at that time, the TAC modules were on back order from GM, with no predicted delivery date. So I had to buy a used one. I do not recall whether the replacement corrected the problem Aaron was trying to fix or not, and I did not get my original one back when I picked up my car.

Anyway, if the problem still persists, then the gas pedal sensor would be the next thing I'll try. But thinking about it, perhaps it is unlikely that this could be causing the problem. Since this only happens at startup, does the gas pedal sensor even have anything to do with the test being done then? Again....

So, fingers are crossed....

[Rich Z]

You know, looking at this latest pictures, I sure hope I never have to replace that PCM. That STS pipe underneath it makes it look like it will be a real challenge getting that sucker out of there. But yet, Aaron Scott removed the PCM each and every time his tuner modified a new tune for the car, so perhaps it is easier to do than it looks. Jim Smith did all his PCM flashes with the PCM sitting on a work table rather than through the ODB II slot like most other people do it.

Of course, Aaron Scott DID break a couple of mounting tabs on the front fender in the process, so maybe that helped make it easier to get the PCM out.

[Rich Z]

Took the car out today for a ride and stopped in at both of our post office boxes. So that was four start-ups today, and at least two after I installed the spare TAC module. Not much of a sampling, but the problem hasn't shown up yet, at least. Just have my fingers crossed.

[Rich Z]

So far so good..... Made quite a few startups since I replaced the TAC module, and so far no problems noted.

Maybe that problem is fixed. (if the doesn't invoke Murphy's Law, then nothing will)

Still hearing a drivetrain noise every now and again when the clutch takes up the load from a dead stop. Little bit irritating, but nothing worth tearing apart the drivetrain over. If something is going to break, let it break, THEN I'll fix it.

[schpenxel]

Originally Posted by Rich Z

So far so good..... Made quite a few startups since I replaced the TAC module, and so far no problems noted.

Maybe that problem is fixed. (if the doesn't invoke Murphy's Law, then nothing will)

Still hearing a drivetrain noise every now and again when the clutch takes up the load from a dead stop. Little bit irritating, but nothing worth tearing apart the drivetrain over. If something is going to break, let it break, THEN I'll fix it.

Good deal!

Kind of a side note.. sold the BMW and bought a 2005 Corvette last weekend. I'm going to pick it up this weekend!

Black/black coupe. Has a ding on the passenger side rocker panel, which is going to fun fixing, but it's priced right so I'll figure that out

Excited to get back into one. Hopefully I can actually drive this car without worrying about it constantly

[Rich Z]

Originally Posted by schpenxel

Good deal!

Kind of a side note.. sold the BMW and bought a 2005 Corvette last weekend. I'm going to pick it up this weekend!

Black/black coupe. Has a ding on the passenger side rocker panel, which is going to fun fixing, but it's priced right so I'll figure that out

Excited to get back into one. Hopefully I can actually drive this car without worrying about it constantly

Good deal!

Hope you don't have any problems with it, but heck, remember you are talking about a car that is now 9 years old. Pick up a set of service manuals, just in case.

[schpenxel]

Originally Posted by Rich Z

Good deal!

Hope you don't have any problems with it, but heck, remember you are talking about a car that is now 9 years old. Pick up a set of service manuals, just in case.

Will do, any suggestions on where to get them?

The last one ('99) I drove until somewhere around 200K miles before I sold it.. as far as I know it's still on the road. It only needed a clutch and torque tube bearing in the 70K miles I drove it.

Hopefully this one will be as reliable. It has about 100K miles on it, but for some reason miles don't really bother me. It needs some TLC, you can tell the previous owner wasn't quite as detailed as I would have liked (stuff like he had an amp/speakers in the back at one point and did a crappy job putting the carpet back in after taking the wiring out). Easy enough to fix, just needs some love

[Rich Z]

Originally Posted by schpenxel

Will do, any suggestions on where to get them?

The last one ('99) I drove until somewhere around 200K miles before I sold it.. as far as I know it's still on the road. It only needed a clutch and torque tube bearing in the 70K miles I drove it.

Hopefully this one will be as reliable. It has about 100K miles on it, but for some reason miles don't really bother me. It needs some TLC, you can tell the previous owner wasn't quite as detailed as I would have liked (stuff like he had an amp/speakers in the back at one point and did a crappy job putting the carpet back in after taking the wiring out). Easy enough to fix, just needs some love

Off hand I don't know of anyplace cheaper than any other for the manuals. You might be able to luck out with a set from Ebay, or perhaps on the larger Corvette forums' classifieds. Matter of fact I need to get a set for my 2009 one of these days.

Yeah, I guess this thread is pretty much living proof that anything can be fixed on these cars no matter how badly someone else has screwed it up.

Good luck with your new ride. Don't forget pics when you get a chance.

[schpenxel]

Attached are a couple of pictures of it. There is some damage (can't see it in the pictures) right where the rocker panel/front fender meet that I'm going to have to fix. I think I'm going to try doing some of it myself, but we'll see how it looks after I get it apart. Actually, I think these pictures were from before the damage. You should be able to see it in at least one of them