valve clatter at part throttle

[Bad99Ram]

I just got a '99 with a 5.2 in it. The issue I'm having is valve clatter at part throttle. I thought it might have been bad gas at first but it's persisted for a couple of tanks now. It's not there at light throttle. Just at low to mid throttle. Once you push it to half throttle it goes away again. The engine runs strong and smooth with no other issues. Any suggestions on what to check? Thanks in advance for your help.

 

[Redtruck-VA]

I believe partial throttle valve noise may not be correct. I would think fuel knock and would check the distributor and determine what the timing curve looks like. Good luck..

 

[Okiespaniel]

I believe partial throttle valve noise may not be correct. I would think fuel knock and would check the distributor and determine what the timing curve looks like. Good luck..

Sadly...the distributor on a 2nd gen has nothing in it to affect timing as far as an ignition advance curve.
It has the cam sensor in it....and you don't want to move the distributor because it will mess up your fuel sync. Unless you have the proper tool to check that, and it's not a Wal Mart scanner!

Suggestions more in line might be a check of the plenum to see if has pooled oil in it. This suggests a blown plenum gasket, which will cause pinging. Other symptoms are slight oil loss and poor mileage.

Could be sludge buildup in oil passages causing the lifters to not pump up, but in such cases it'd be prevelant throughout the run cycle

Perhaps dribbling some seafoam through the throttle boy to clean the valves and running some Chevron techron fuel system cleaner through the tank might help.

 

[talon6]

okie you are just to fast.lol

I would check the plenum gasket.

 

[Redtruck-VA]

Sadly...the distributor on a 2nd gen has nothing in it to affect timing as far as an ignition advance curve.
It has the cam sensor in it....and you don't want to move the distributor because it will mess up your fuel sync. Unless you have the proper tool to check that, and it's not a Wal Mart scanner!

Suggestions more in line might be a check of the plenum to see if has pooled oil in it. This suggests a blown plenum gasket, which will cause pinging. Other symptoms are slight oil loss and poor mileage.

Could be sludge buildup in oil passages causing the lifters to not pump up, but in such cases it'd be prevelant throughout the run cycle

Perhaps dribbling some seafoam through the throttle boy to clean the valves and running some Chevron techron fuel system cleaner through the tank might help.

Al, thanks for the information, clearly I don't know 2g trucks. Just felt partial throttle valve clatter unlikely and was reaching for something that might provide fuel knock. thx

 

[talon6]

Al always does a good job of explaining things a little too. a lot better than me.

 

[Okiespaniel]

Well... it was purely by accident when I discovered this...by pulling up the cam sensor. Nothing under there but a funky looking curved piece of heavy sheet metal. All is done in the ECM which is a ****** shame! I used to love setting Mopar advance curves on a Sun machine back in the day.

 

[Bad99Ram]

Thanks for the suggestions. I have someplace to start now. Excuse my ignorance with this question but I'm used to working my old hotrods with carburetors. Can you detect a plenum gasket leak with a vacuum guage or by spraying starting fluid around it to get an rpm increase if there is a leak?

 

[Okiespaniel]

Funny you should mention testing the plenum with a vacum guage. The factory developed just such a test...

TSB 09-05-00

Miight want to save this site to your favorites. Covers a lot of 2nd gen stuff that is longer availible.

http://www.dodgeram.org/

 

[Bad99Ram]

Thanks for the link. That website looks to have a lot of good info. My gut tells me it's a vacuum leak. I had to replace the thermostat that was stuck open and when I removed the housing a chunk of the intake around the thermostat that was corroded broke off. Since I have to replace the intake manifold anyway I'll see if that fixes it.

 

[Bad99Ram]

Well I replaced the intake manifold and the chatter is still there. I have another idea of what it could be. Let me know what you think.

When I got the truck the thermostat was stuck open and never got above 135 degrees. Who knows how long it was driven that way. Is it possible that because of the low running temp that deposits could have built up on the valves and pistons? I'm going to Seafoam it this weekend to see if it helps. Other than the valve chatter the engine is runs strong and smooth. It's not that high of a mileage engine either with only 71k on it.

Any more suggestions would be appreciated.

 

[Okiespaniel]

Are you sure it's valve train noise or injectors. Usually valve train noise occurs in the lower or upper rpms. Noisy injectors can occur anytime.

 

[Bad99Ram]

Are you sure it's valve train noise or injectors. Usually valve train noise occurs in the lower or upper rpms. Noisy injectors can occur anytime.

I've never heard of injectors making noise before. What would they sound like?


One thing I've noticed is when I get near half throttle is that the A/C goes from blowing through the dash vents to coming out at the floor. If this is vacuum operated could there be a vacuum leak in the dash somewhere causing this?

 

[Bad99Ram]

Just found out about this "wild vents" issue in these trucks that I'm having. Could the vacuum leak causing that issue be leaning out the engine causing the spark knock?

 

[Okiespaniel]

^^^^^ Yeah it could...

 

[wingnut]

Did you check the "knock-sensor"? This is a device that feeds-back to the computer to retard the timing if detonation is occurring? Just saying......

 

[Okiespaniel]

Our Dodges don't have knock sensors.