Wildvettes

Hi,

I just picked up a 99 30th with 173k miles. She has had a rough life and is making some top end noise.

The previous owner said she broke a rocker and bent a lifter and that is why it is noisy. The rocker was repaired. I have not pulled the valve covers yet. The car does drive and seems to have OK power.

The car has a cracked clear aftermarket lid I am working on replacing with stock. I just need to replace the two lines coming off the stock box.

The car has long tubes and has had a shift light installed inside so I know she was beat on. No clue what the tune looks like if it has ever even had one.




The car drives and shifts like normal but when you rev the motor above 4k and shift the car will lose total ignition and shifting back and forth between gears does nothing to fix the problem. If you give the car gas the bog will get louder but you can tell there is no ignition there. Once the car is below 25 mph it will kick the ignition back on and continue driving as normal.


I have quite a few Vettes and it almost feels like reduced power mode but I don't know if 99 T/As displayed a DIC message for Reduced power. I doubt it since everything is light related on the speedo.

The car is reading low oil pressure and the change oil and check gauges lights are coming on and oil level is good. I figured it was probably a bad sensor but figured I would include the info.

I am trying to determine if the problem is mechanical, electrical, fuel, air, or tune related. I don't know whether the PCM might be bad or if it is killing power because it is picking up on something bad like detonation.

Thoughts on where to start?

Thanks in advance.

Old Geezer

iTrader: (3)

Take a look at the tune and do a data log.....or 2.

danieloneil01

Bent lifter? I would pull the heads before romping on it anymore. But I would sell it before having to work on that engine in that tight space.

MontecarloDrag

iTrader: (3)

LS1 Camaros/Transams are drive by cable so they don't go to reduced power.

The way you describe the problem it sounds like an electrical issue. I would start by tightening battery cables and securing the battery in it's place. I have seen quite a few cars with loose battery losing all power under heavy acceleration. Cleaning and tightening the wires and securing the battery solved the problem.

If this doesn't help, clean and tighten all grounds. There are several and some of them are not easy to reach, but cleaning and tightening them gets rid of most electrical gremlins. 50% of all cars I have had in my shop with electrical problems were fixed this way.

If the problem isn't fixed doing this then you need to troubleshoot a little deeply.

rpturbo

iTrader: (47)

It could be a lot of things. Like was said, check tune, and log. The cracked lid could spike IAT's, pulling a ton of timing. There is no location on your post to know where your at, but it's hot here.

Wildvettes

I am in SoCal and temps have been insane. I don't have any software that will look at the tune.

I was kind of thinking it could have been a bad ground. This is a very common problem on C5 Corvettes and it causes all sorts of electrical gremlins. I haven't heard of ignition issues from it, but it makes sense it could cause a problem.

I will check that first. As for the bent pushrod I am hesitant to put any work into rebuilding this engine with this kind of mileage. I MIGHT pull the heads and replace the whole top end but I would prefer to pull the whole thing and do it all at once.

I have four Corvettes and will admit working on them is way easier. I got this car for a couple reasons. I had a 98 firebird at 18 right out of high school and wanted to get something to take me back. I always wanted a WS6 and to this day they look bad ***. They are going to be a timeless design. Plastic crap everywhere and all.

I got it because it was cheap and at the bottom of its depreciation cycle and because it is a rare options W54/BBS 30th coupe. Some day this car will have a good resale.

In the meantime it will be a long road to restore a car this year because they aren't collectible so aftermarket repro is light and because it is just old enough for GM to have nothing for them any more.

Used parts have been a challenge so far but I am optimistic.

First step is to fix the stupid stuff. The A/C compressor was out and the previous owner didn't know anything about newer cars. $40 later and a safe to run 25+ psi of refrigerant and the A/C is back on.

I know that cracked intake is a major problem too so it is on my next list. I am having a hard time locating the two factory lines coming off it though. I may hit up pick a part and see if they have any of these things laying around.

I am really thinking for the interior I am going to find a nice cheap 99 V6 and swap everything. Then dump it.

I can get a whole car for $3000 when some parts are $500 lol.

Thanks for the replies so far.

Wildvettes

A couple new developments.

I ran a data log and I am new to that. It isn't showing any misfires under cylinders but it counted 15 misfires under primary and secondary. I am not sure if this means it was actually misfiring since all the cylinders showed zero.

I found out the whole driving part didn't matter. If it is idling and you slowly push the gas pedal it will rev all the way to redline. If you floor the pedal it will start to rev and then dies. It then backfires all the way down.

It also is shooting pieces of the old cat out the tail pipes(a big chunk hit my Corvette right in the front bumper). I am almost wondering if the exhaust is getting plugged? Seems weird it would only do it at WOT if it was plugged I would think it wouldn't rev period.

It was also showing a P0336 pending code. I have to look into what kinds of problems could cause that. Maybe the crank sensor going bad.

I think the oil pressure is a sensor issue since voltage didn't change and was flat across the board. I would think it would change at least somewhat.

Seems like every day it has a new problem lol. I got the intake swapped to stock and it did zero help.

Old Geezer

iTrader: (3)

"It also is shooting pieces of the old cat out the tail pipes(a big chunk hit my Corvette right in the front bumper). I am almost wondering if the exhaust is getting plugged? Seems weird it would only do it at WOT if it was plugged I would think it wouldn't rev period."

Fix that before you start chasing other items.

jimmyblue

iTrader: (11)

What does IGN power look like, before/after an event?

Just replaced my alternator, far from home, after some
highway romping it dropped out. Not sure why, but it seems
to be not-uncommon.

Might check tightness of alt power output, and the motor
ground straps.