1998 C5, Relevant mods?= CAI, C5 Z06 TI exhaust.

So, I haven't driven my Corvette very much in the last few months, the winter being what it's been. I had been taking it out in the dry for some spins around the block to keep it fresh once or twice a week. I'd also run idled it for about 15 minutes in the garage about 4 times too.

Then a problem: While visiting my dad for his birthday: Check Engine, Reduced Engine Power, Service Traction Control.

It threw these codes:

P1120 HC
P1221 HC

And a TCS code that I suspect is the result, but not the cause of teh trouble:

C1278 H

It was a little rainy but not much else in terms of weather. I turned the car off and parked it in the driveway and spent the night as it was already late, determined to take it to some local place in the morning. In the morning, I started it up and ran it. No codes. Drove it around for 20 minutes, no codes. So I headed home. On the way back, the weather got messy, but still no issues until I was about 5 minutes from home (I'd gone over 50 miles at this point), it suddenly came back on, and with it, a rough idle that worried me a lot. I turned the car off, let it sit, and cleared the codes while I pondered my next move. Called my mechanic, etc. Started it back up, ran again, so I got it home.

All was fine for several days. Ran it up to 6K RPM drove like always. Idle flat as a pancake. Then today, it's on again, rough idle again, the whole bit. Let it sit for a while, start it, sometimes it's fine and drives fine for as long as I want, sometimes it isn't.

My reading on the forum indicates that it may be either a dirty ground, or the throttle position sensor, or the throttle body. Do any of those things explain the rough idle?

Also, my grounds are insanely dirty, have probably never been cleaned (car came from Florida). Is there any trick to getting those gray connectors apart? I tried pushing the clasps in gently but firmly with a punch, prying at it with a dull butterknife, that sucker is really on there. I'm worried about breaking it trying to separate the two halves.

Advice would be great, as always.

 

TPS errors (Current), check cable/connector 1st.

 

Sorry for my ignorance, but where's the TPS connector on the LS1?

 

For cleaning your ground connections, refer to this thread: http://forums.corvetteforum.com/c5-t...tion-long.html. It has GREAT info on all kinds of electrical stuff.

It may also be helpful to check your battery and/or alternator. Many problems originate from an under-charged battery.

 

On the side of the Throttle Body, GOOGLE stop working?

 

As far as getting your ground connector off try getting some electrical contact cleaner and spray it and soak it down. That could remove some grit and lubricate the connector, try to remove it before it all evaporates. Just don't pull on the wires. I don't like removing electrical connectors in the cold, plastic is real brittle and tends to break. If it is really cold, try using a hair dryer to heat it up.

You can get the cleaner from most auto stores or Radio Shack and probably Lowe's, etc.

 

Well, I'm not an electrical magician by any chance, but the same problem came up on my DIC readout as well. For my car, and all C5's are different, I had the rear part of the switch replaced after during a lot of research. Many of the internal brass connections were burnt down and was causing essentially a short circuit. IMO, there is a lot of current that is being bypassed through the switch which will cause the brass pins to errode over time and improper passing of current causing issues such as this. What took the icing from the cake was this; I'm out driving and all of a sudden the car goes from 30mph to a max of 5mph and I barely crawl home and up the driveway.

 

Pull your MAF sensor and double check that its clean, if its not it can put you into reduced power mode. Electrical contact cleaner will do the trick if its dirty.