Kaleb_C5

First off I want to say thank you to the forum and you members for providing wonderful information on these cars. I'm not very active here but I have used the forum several times to help me fix and work on my car. I have used it a lot for this current problem as well, however still am having issues and am hoping you guys can provide more information or ideas.
Just a heads up, this will probably be a very long post. Thank you in advance if you read all the way through.

So I currently own a 1998 Base Corvette with the 6-speed manual. I bought it 2.5 years ago with 95k miles on it, and it currently has 103k miles. In March of this year, I began to get some engine knock. It was diagnosed to be a bad cam bearing. I used a mechanic that had a good reputation overall but was a little cheaper, and he was also supposed to be a master LS mechanic. I went ahead and forked over the money to have the engine completely rebuilt. Before the rebuild my mods were just an air intake and long tube headers that went through a straight pipe exhaust. I didnt have any major electrical problems before the rebuild. So he rebuilds the engine and we go ahead and add some performance parts from Texas Speed including the Cleetus McFarland Bald Eagle Cam. Although he took forever, I dont at all question his mechanic skills on the engine build, as it came together very well and runs good overall. The problem I'm having is this...Ever since the engine was rebuilt and the car put back together, I've had an incredible amount of electrical issues. The car will randomly start idling terribly, jumping from 900 rpm to 3,500 rpm and back and eventually die. When it dies, it's very hard and takes awhile to get it restarted. It will run super rough then eventually calm back down and be completely perfect. This seems to happen at random. Then sometimes I'll be driving along and the car is running normally, then all of a sudden begins to stutter like its misfiring, and also the throttle seems to engage itself, not at full throttle, but just enough that even with my foot off the gas it will hold speed or slowly accelerate on its own. I continue to recieve check engine lights, the service ride control light, and used to get the engine reduced power warning but not lately. Also the gauges all work perfectly except for the water temp will randomly peg out in either direction, and the DIC controls no longer respond to inputs. One time while driving at night I went over a couple speed bumps slowly, and on each bump when I hit them all the interior lights (maps lights, footwell lights, etc) all flashed on for a second then back off. At this point the mechanic who I dont really trust anymore anyways, has moved away and cant help me. My thoughts, and everyone else I have talked to including other mechanics, believe it would be some sort of electrical issue. We would think its likely a grounding issue. So heres the troubling part that is stumping me. I used the Bill Curlee thread and cleaned all of my chassis grounds. The mechanic cleaned all the grounds on the engine and even added some extra. My battery is in good shape and holds good charge. I recently learned that supposedly the previous owner of this car traded it in because of an electrical problem, and the shop he went to told him it needed a whole new under dash harness. Well when I bought the car it didnt have issues. Nevertheless I have gone and checked all the connections and wires under the dashboard and I cant find anything that looks bad. So I can't figure out what would possibly be causing the entire car from engine to interior and dash to randomly go absolutely haywire and then the next minute be completely fine. Is my BCM going bad? My ECU? Should I go ahead and burn the car to hell? You're help is much appreciated, thanks.

J. Chris Davis

Grounds, connections and ECU would be my first thoughts as well. I hope someone has some help for you here. I'll be watching incase I have this problem in my future.

C5 Diag

Sorry to hear of your dilemma my friend
Look like some throttle system issues there and maybe some other driveability ones too with the rough idle....what DTC's do you have if you have a CEL ??...that may give you some "direction" !!...I would look at the TPS connections, APP sensor connections, TAC motor connections and TAC module itself that is attached to the PCM...oh, the TAC module ground number and location escapes me...maybe someone can chime in with that one but I can look at Service Info for your '98 later !!

Kaleb_C5

Anyone else got any ideas?

Kaleb_C5

I'll post them up in the morning. I really don't see how they would be involved though as these problems existed from day one that I got the car back, and the CELs came later. From last time I checked the codes it was something about the TPS sensor, which I since then replaced.

runner140*

Please....someone post up instructions on how to pull the DIC codes. AND why.

oelarse

Have you checked these door connectors ? Sometimes the wires inside get worn in this area and the serial wire can get grounding issues causing alarms and other problems .
I would checked these areas in both doors

Kaleb_C5

Thanks I'll check that out

tblu92

We need trouble codes !! You can go to Autozone or O Riellys and they normally will read them for FREE Then post them here ALL OF THEM even if repeats
The 97-98 C5 had electrical gremlins ------- 97 and 98 cars have a LS1A ECM and 99 to 04 uses a LS1B ECM--- 05 uses an E40 ECM 06 to 13 uuss an E38 ECM 14 and newer cars use an E92 ECM
Most common issues with the LS1A ECM's
Bad ignition switch
Faulty column lock
Poor grounds
Bad BCM
Old worn out KEY yes these keys have an OHM pill in them and they wear out
anti theft system failures ( most often caused from)
aftermarket alarm system
aftermarket stereo
Blue tooth phone
Remote start sytems

pewter99

bad/loose ground somewhere especially after you say it was rebuilt...check the one on the back of the engine block.....passenger side, reach back there when its cold and see if its loose...BTDT...I would check them all since you said it runs fine then its not...something is loose somewhere.

Kaleb_C5

I'll check that again but the mechanic cleaned the grounds up on the block and also added extra grounds so I doubt he forgot but you never know...

C5 Diag

We need DTC’s (codes) or your are just GUESSING towards a diagnosis !!

02general

Did you have the car tuned after up-grading the cam? All the funny idling issues and stalling could be a tuning issue.

Kaleb_C5

Yes it was tuned. And I see where you're coming from, but if that were the case it would do it all the time right? Cause my issue is intermittent. Plus all the other issues have nothing to do with tuning.

Also I may have forgot to mention earlier, but I cant read the codes off the DIC because the buttons are no longer working, yet another symptom. Dont feel comfortable driving it right now either with these problems so as of right now, driving to autozone is kinda out of the question. But previously the only CEL code was for the TPS sensor, which it has since been replaced.

neaz

I think they will rent you that code reader

vetteLT193

It could be the car had an intermittent problem already and the lopey cam is making it worse / exposing it more. C5's are an electrical dumpster fire. You are going to have to check everything twice. I'd also consider pulling some fuses to non essential items like the power seats to see if that changes anything.

Bill Curlee

Yes,,, Please read and post the DTCs. That will get us on to the correct path for repair.

PM SENT

Bill