Nvrfastenough87

99 C5 LS1, headers, intake, exhaust, ECS tune.

Hi everyone

For awhile I started to notice I had a rough idle at stop lights and if I just touched the gas and raised the idle up 50 -100 rpms it smooth out. It was dropping to about 500, I believe c5 AT's are supposed to idle at 550?

So I changed plugs and wires and sent my pcm away to ECS to be tuned. Had them raise my idle to 650 and it helped a lot but I could still feel the idle wanting to drop when I came to a stop.

And I also fixed afew air leaks I found prior to that. One was pretty major and it didn't help... at all.

After the tune everything was great, I'd punch it at about 25 30 and spin the tires shifting at 60. Just did afew test runs when I first got the PCM and then went back to my daily routine of driving to work no WOT or anything over 3500rpms at all for about a month.

Now its back to stumbling and really wanting to drop down.

Also about a week ago I had to gas it to avoid a red light ticket and noticed it would only rev to 5400 maybe even 5300 and shift roughly. Tried again on the way home and sure enough it wont rev past 5400 and I have a VERY noticeable power loss, its very slow to rev also.

I've gotten afew suggestions for the shifting problem. Tune or Fuel delivery problems

As far as the idle goes I'm stumped and about to take it to a mechanic. It also smokes alittle in the morning for afew mins.. thin white smoke.

I know its a lot. I really appreciate any suggestions. I plan on taking it to a guy and just having him make a list for me.... Just have to save up and I'd like to fix anything I can.

poltergeist 02

iTrader: (65)

If you have access to a scanner, look at your iac, tps, maf, and O2 sensors just to rule that out.

ls1 1990 VN

You may have a valve spring issue in that it won't rev past 5400, is that also causing your idling problem...could be.

Nvrfastenough87

Wouldn't the check anything light be on if any of those things were malfunctioning? Autozone or discount does that for free right?

Nvrfastenough87

Would that explain the thin white smoke too?

After all the air leaks I fixed and new plugs wires, new intake, maf clean, TB clean... It does seem like it could be something more serious like that.

What about a head gasket leak? I had a little oil on my plugs but I read somewhere else that it was normal?

I've only got 58k on it

Exidous

iTrader: (11)

Burnt crispy oil or wet oil? You should not have any on the plugs. If you do the rings are bad or your valve stem seals need replacing. Do a wet compression test on all the cylinders.

White smoke is usually coolant from the head gasket.

spy2520

iTrader: (3)

If they are malfunctioning yes, but if something else is causing them to make the wrong corrections, not necessarily.

Nvrfastenough87

White smoke is usually coolant from the head gasket.[/QUOTE]


I guess after 14 and years and almost 60k miles i'm not surprised if the valve seals and head gaskets leak. They're plastic/rubber right?
makes perfect sense.

Hopefully its not the rings with such low mileage.

No one has any ideas about the early shifting besides a broken spring? I've got no ticking what so ever. I started getting a ride to work from my buddy just incase though.

Ok thanks guys

JakeFusion

iTrader: (7)

It definitely seems valvetrain related. Broken valvespring could possibly damage a seal. I think it's time to pull the valve covers and take a look.

poltergeist 02

iTrader: (65)

Do you have cats on your car?

Nvrfastenough87

Ok, I'll do it this weekend.

Nvrfastenough87

Yes I do actually. Factory. That would be great if that's the problem. I'm in FL so I can go get them replaced with straight pipe and disconnect that annoying air pump that whines for 20 mins on start up.

That could cause a bad idle, i know, but could it have anything do with the early shifting?