Has anyone experienced any "occasional" lifter noise and only at part (50%) throttle? It does not happen all of the time. I haven't been able to figure out if it is a temp sensitive issue. I use Chevron 91 octane, I recently used a can of the GM Top End Cleaner. I switched to NGK TR6 plugs.

Could I have a piece of crap floating in my oil that starves a lifter once in a while? A partially clogged fuel filter. Would some seafoam in the fuel tank help? An O2 sensor that is going out to lunch?

I am running out of ideas. Any nuggets of wisdom would really be appreciated.

Has anyone else ran into this?

 

Anyone.

 

Find someone in you area with scanning software and log a 15-20 minute run. From the log it should identify is it detonation, fueling, advance, etc. Other wise you will chase shadows with various fixes until it goes away.

 

Bluefire, your post said pinging, which I associate with detonation/pre-ignition/bad gas, not a mechanical lifter sound. Which do you think it is?
Mine "pings" or detonates slightly at part throttle in the low (1500) rpm range. Only thing that totally eliminated it was to lower the water temp with a 160 thermostat and lower fan settings.
But, I don't have the stock tune, and it's cam'ed.
Ha, it's just my motor's way of telling me to drive it, not lug it!

If it's truly an intermittant lifter "peck" I don't have a good suggestion; I can't think of a scenario where light throttle would cause a quiet valve train to make noise. Maybe an exhaust leak?

DG

 

DG,

Thank you for the response.

To be completely honest because it is so infrequent I can't be 100% sure if it is ping (pre-detonation) and not lifter noise. Six months ago I had a tune (FYI, he is an excellent tuner in the Pac/Northwest). We couldn't finish it because at that time I was getting knock retard. The HP curve just nosed over at ~5500 rpm's. Just for a quick test, he disabled my knock sensors and the HP dip was still there. He felt it was carbon build-up. He suggested (and I did) use the GM Top End Cleaner, changed to TR6 plugs, installed a 160 stat, and he lowered the fan settings. I don't think it is going into knock retard anymore. I no longer feel the timing being pulled at the upper rpm range. This current "noise" started after I did all of the above. It happens, as you said, from ~1500 - 2500 rpms. Just to throw in another variable, about a month ago I decided to try a different Chevron station. This has signifcantly reduce the frequency of this noise happening.

I will probably have my tuner check the wide-band numbers on it again. If I was getting bad gas (maybe some water in it) how long does it take to clear it out? Is it possible that after I cleaned out the carbon I just coincidently started getting bad gas too?

Thanks for the listen. Any feedback will be greatly appreciated.



Randy

 

Randy, that's pretty interesting.
We have a few parallels here.
1. If the noise stops instantly when you back off the throttle, it's ping, not lifter noise.
2. Back in the day, when my 2000 was new, I attended several dyno days. My car, and several others, fell off 10-15 HP at exactly 5500, accompanied by a puff of black smoke. Then they recovered and pulled fine to 6000.
I never found a good explanation for this here on the forum - most thought it was valve float. My car only had 3k miles when it did it, so carbon is not the likely suspect. About a year later I dyno'd again and had no 5500 issue.
3. I have a mild cam, and it's been tuned by 20th Century here in Dallas, one of the very best shops in the country. I noticed the part-throttle ping last year, and took it back to have it checked. They backed off the timing just a bit, and all was good - until really hot weather this summer. I installed a 160 thermo, and all was good.
But recently, it's pinging a bit again, in much cooler weather.

I am beginning to suspect, that when we go into spring and fall, the gasoline formulations change. During this time, we get winter formula while it's still hot, and vice-versa. And with all the gasoline issues and hurricanes, we may not be getting the best gas.
several of my friends have complained their cars are not running quite as well lately. If you suspect bad gas, you might add a bottle of Chevron Techron, to pull any water out of the system, and clean the injectors up. And try a different brand of gas.

DG

 

DG,

Sorry for the late response. Work lately has been hectic. My noise did stop when I lifted my foot off of the gas pedal. I am starting to think my issue was bad gas. I have changed Chevron stations and have ran ~3 tankfulls through now. I no longer hear any pinging under acceleration.

Do people normally use two different tunes (one winter, one summer)?

Regards,

Randy

 

Randy, a 1:40 AM post - you are working too long.
After being retired 2 years, it's just a dull memory for me!!!

No, I haven't heard of actually retuning the computer for seasonal changes. However, it's been pretty well documented that the gasolines we buy are slightly reformulated for seasonal changes.
So, in the fall and spring, you might get fuels with slightly different volatility, and you computer would take a little while to adjust and self-tune.
I really believe I can tell a difference in the driveability of my cars at this time of year, especially my old Mercedes, with it's archaic injection system.

Having said that, a couple of weeks ago I went out to play with the Vette, which had a tank of gas that was several weeks old. I noticed a touch of clatter at 4-5k. Checking with the scanner, I was indeed getting 3 degrees retard.
Then the gas guage went to zero - the dreaded fuel sender deposits!
It came and went for about a week.
I ran the tank down to almost empty, Bought a $7 can of the Chevron techron+, and put in 10 gallons of fresh gas. Voila: gas gauge works, and the retard is gone!

Here's another weird one for you; last summer I was getting the little part-throttle ping as we discussed. I had a 185 thermo, but of course the temp would often go up to 200 (my fan setting) when driving around town. I put in a 160 thermo, and with a lower temp, the ping stopped. But..........even when I would sit at lights and get the temp to 200, the ping was still gone! Go figure.

DG