so we had a 4-5 period of nonstop rain recently, and i had to go get some errands done, so the vette had to go out. while i was out, i noticed a fluctuating idle sitting at a light, i thought i might be low on gas, causing some oddities, so i filled up, and it seemed fine. get home, park for a bit, go to start it, and immediately a get a REP, drive around the block vert roughly, and park it. let it sit for a week or so to dry, clean the headlight grounds, no improvement. let it sit to dry another week, pull the intake from the tb, pull the tps sensor plug, and the sensor on the other side of the tb, let them dry, blow them out with electrical cleaner, and still nothing.

about 2 months ago the car did take some water in and fried the bcm, some water did make it into the motor, but it had been driven for over a month after the new bcm with no headaches.

doing some research it sounds like it is either, the tps, tac or the actual tb motor. with the key in the on position, but motor off, i had an assistant tap the gas, an the throttle plate did not move. i was able to move it by hand, and it did not seem especially sticky or notchy. i did not see any visible corrosion on the connectors.

the codes were

p1120
p1220
p1516

what i should do for my next step would be appreciated.

 

P1516 is giving you reduced power,Has something to do with the TAC module.First I would pull the pcm and check for water where the 2 plugs plug into the pcm.Any mods to the car? What year?.........Paul

 

99 vette

heads, cam, bbk tb, ls6 intake mani, halltech intake, long tubes, returnless fuel, descreened maf.


i can reach the tac from the wheel well access panel, or do i have to pull the fender off?

 

I have a '99 FRC. You can reach it by pulling the inner fender well out, and through the brake vent if necessary. It's a PIA, but possible.

Something else to chech are the grounding points. There are several of them through the car on the frame. The 2 major ones though are junctions for multiple grounds to one harness. There is one on each frame rail, under the hood, behind the headlights. They are easy to access. I would check for any corrosion in them by separating the junction. These have been known to corrode, and cause your issue; along with corrosion in the TAC harness.

Good luck with the search

 

This sounds exactly like what happened to me when I washed my car about a month ago. I popped the hood and could see traces of water on top of my battery. I ended up pulling the passenger front wheel and getting to the TAC module. As soon as I unplugged it, I could feel water in the plug. I removed the tac module and dried it out along with drying out the connector. I put dielectric grease around the connector seal and at the base of the wiring harness (being careful not to get it on the pins). Plugged everything back in and it was good to go, no trouble since then. I had the exact same codes as well, I would give your tac module connector a good look. Seems like GM didnt seal the connection very well and didn't install a long enough wire to create a drip loop on the harness.

 

so still trouble shooting. popped the fender access panel off to clean the tac module. i was able to do this with the wheel on fwiw. i removed the plugs, sprayed them clean and applied dielectric grease around the weather pak seals, not the conductors. i didn't see any sign of corrosion or water contamination on the connectors themselves.

codes now are
p1221
p1515

when the car is on, engine not running, and i clear the codes, the 1221 immediately returns.

car on, engine on, throttle response is rough, idle high and uneven. if i reset the codes while running, the idle momentarily drops, then returns to a high uneven idle. i'm thinking a new TPS is the next step