This really sounds like knock due to carbon buildup. I suppose it could be a valve seat, but then why would a PCM reset make the problem worse for an hour? That sounds to me like the PCM had to relearn to pull out timing. How many miles are on the vehicle? Its probably been ran on bad gas and/or is an oil ingester. The suggestion for seafoam or the GM Top End cleaner is the first thing I would try. If its carboned up that bad it may need multiple treatments. If this is the problem and you get it cleared up, definitely get a PCV catch can installed and run it on good gas.

 

maybe your knock sensors are dead. The low octane maps are pretty damn well weak.. It looks like you could run 89 on that beotch and not have a problem. If you aren't wanking the motor (ie cruise control) the car probably wont ping as much, if your car pings on cruise control you got serious issues.

Do you have efilive or a friend with it around you? log the HIGH/LOW octane MAP PID and see where you stand, and look for the KR on the logs. If you're pegging out the low octane PID at 0 and still getting KR/PINGING you got some serious problems.

gm built the motors so that a dumb lady buying crap gas wouldn't destroy the motor under warranty. The knock system is pretty decent, unless someone has gone in and given it a soup up poorly (hpp3 comes to mind).

 

99C5JA, I never pumped anything less then 92. I have never noticed oil consumption, but I have not been tracking it lately, I will check. The car has 50k miles on it.

I had engine/fuel system cleaned by dealership ("EngineVac"), it helped "a little" for about a day. Come to think of it, in the next few days after that, the problem started getting worse and worse. Maybe I could get some GM cleaner and do it myself, should not be that complicated. Can I buy this stuff only from dealer? Do autoparts stores carry this? I would need to do it ASAP, since I am leaving on sunday..

In fact, I think I am going to hook up a ghetto version of a catch can tomorrow and then run GM cleaner through it.

 

and if that does not help, I will check octane maps and see if switching to crappy gas helps...

 

yea in that case best thing would be to take it to a shop. now if the car is pinging under partial trotle and at a certain rpm, and if it is burning a some oil then there is a good chance thta it could be the seats but there is no way to tell for sure. hell it could just as easyli be a timing issue check your chain and see how it feels.

 

Your car sounds exactly like mine. I read that it is caused by "Consertive Defaults" in the timing settings of a stock motor. Although your on the other side of the country, a good dynotune by somebody who knows what there doing, such as Jeremy at www.fasterproms.com should be able to fix you right up. Get you some more horsepower and fix it so it doesn't run at 210 all the time.

 

UPDATE:

I put in the fan switch(really cheapo way, don't ask me where I put the switch itself ).

Get this: running the fans on "high" makes NO DIFFERENCE on the temp gauge with outside temp at 55F! It still shows just a hair under 210 - same as with fans off. I doubt the gauge is broken: when the engine goes cold->hot, it climbs up pretty smoothly, same when it goes from hot to cold. But when the fans are turned on it doesn't move at all.

What the hell is going on?

 

The dynotune can reprogran your computer so your fans kick in at a lower temp., but, what you need is a lower temperture thermostat. I've seen them for Sale for Camaros and Thunderbirds and they were way too expensive for what they are so I'm just waiting fpor my mods to be installed and see how it behaves. I don't think your problem is related to temperture as I have exactly the same behavior in Florida. I think its all in the tune. Any mod will affect the tune.

 

well you know the temp gauge is bollock on 99+ cars. You can be at 160F and read 210F lol.

Use a logger to see the true temps.

And if your thermostat isn't 160 or 180, but stock 210, don't expect much if any.

i'd go for the 160 and then adjust the fans seasonally.

set then to low 183+ on winter and 163+ on summer.

This gives you some flexilbility you dont want to really run in 160-180F temps. 185 is probably a good ideal range to get a complete combust (while being slightly cooler).

If you drop to 160F at highway speeds in the cool, that might not be so hot if theres any cold start enrichment.

 

I don't get it - the gauge shows the temperature correctly when it is going up but it shows it 40 degrees higher when it is stabilized? It shows temp going down when the engine is shut off but it does not show it going down when I cool the radiator? What kind of gauge is that?

I'll see if I can find someone with the scanner...

 

It's not really a guage, more of a "dummy light".

 

It should have been marked

Cold (lay off the gas)... Hot(time to get on it)...Oh **** you're overheating.

 

The temp gauge is controlled by the computer. If the computer receives a signal in what it considers the "good" range it will display 210 and never move from it. That means you could be at 190deg or 220deg and it will show 210. Second by just turning the fans on earlier will not cool the radiator. You need a 160 or 180 deg thermostat in addition to the fan switch or reprogramming the fans turn on temp. You can get one at Napa for $20 unlike some of the sponsers here.

Being that you are local you should come over to the Northwest section and put a call into Ellis. He is the local guru that we all rely on when the chips are down. He even has a shop close to you in Kirkland.

 

Ellis looked at the car twice, in person, and could not find a problem. He changed spark plugs and fuel filter. He suggested to change o2 sensors but I am reluctant to do it since I am not sure it will fix my problem (he did not seem to be sure of that himself) and o2s are pretty expensive. In no way I am trying to badmouth Ellis or Kirk. Trans. - it just seems to be a problem above their level of expertise - can't fix em all i guess.

 

You just have to keep working.You'll find the problem eventually.

 

I pulled PCV valve - the valve and the housing were literally soaked with oil and black sludge . Also, I tried blowing into the valve from both ends (it tastes HORRIBLE ) and it lets the air pass both ways! what kind of a valve is that?

I replaced the valve with a similar one I got from NAPA (it did not fit into the housing very well so i wrapped some electircal tape around it) and put 2 fuel filters in-line. Also I put in some tubing so the valve stands vertical. Hopefully this will stop the oil flowing through it...


Aftwewards, I put 2 cans of seafoam (fuel/oil/vac. hose on TB). Boy did I get a heart attack when I tried to start the car afterwards....

Anyway, I am idling much smoother now and it SEEMS that the ping/rattle is less frequent. I am going to drive it around some more and put in syn. oil on monday...

Well, if you don't hear from me by next sunday, it will mean I'm stranded somewhere between Seattle and LA...

 

What's the story now?

 

Ping was tuned out by making it run richer and the car was sold 2 days after that. I never really found what was causing it w/ factory tune.

 

I was going to say that you should just get a tune. It was definatly running lean if the plugs were white.

 

Agreed on that one, I read through all of the posts and was waiting for somebody to say he was running lean w/ the white plugs. And it looks like you seafoamed, which I'm a supporter of. (Never personally used it, but watched my dad use it on a friends POS truck)

I think if you do that PVC mod, seafoam the top end, (make sure to change your oil if you decide to put it in there), change O2's, and I really think your ping will be a thing of the past.

Or, just get a tune like 777 said