Another daily driver q. My 85 Caprice's PCV is still creating a good vacuum. It makes that nice "snap" sound when you put your finger over it, and the suction is strong. But the finger over the PCV does absolutely NOTHING to the idle quality or idle speed. Exactly the same with finger on or off. This is a high mileage engine, by the way. I read in my Chilton's that the idle should change (go up or down, cant remember which) when you put your finger over the PCV.

Should I spray carb cleaner into the pcv with engine running, and hopefully clean out a partial clog? Will all the gunk going into the engine cause some problem ???


BTW, the car is idling normally (I had to turn up the idle a while ago) and runs just fine, except for a slight knock when hot and low rpm under load. I assume, though, that I am accumulating more blowby contaminants than I have to, if the PCV is underfunctioning.

Thanks

 

I think the PCV is just fine. I wouldn't change a thing.



ODB

------------------
*I do custom performance mods on Edlebrock Performer carburetors (dualplane intake mods in the works),
White 1986 Irocz, 305 with iron #416 heads,
383 with aluminum TFS heads,
Edlebrock Performer-RPM intake and Performer #1407 carburetor, +110hp shot of crack, 700R-4 tranny, Vigilante 2400 lockup converter, 3.25:1 Ford 9" rear, Mcreary Road-Stars, SLP-stainless 1.75" shortie headers & Y-pipe, single 3" Borla exhaust, Linginfelter-TPI camshaft part number 74216 pulls 17" vacuum solid. Cam specs 213/219 @.050 114-LSA, sometimes advertised at 216/219 @.050 112-LSA .462/.470 lift @1.5:1 ratio. Using Harland Sharp 1.65:1 roller rockers. MSD-6AL, billet distributor, multi-retard, blaster-3 coil, and RPM switch. SouthSide machine subframe connectors, SSM lift-bars, Moroso 4" underdrive crank pulley.

N/A runs 10.9 @124,
Crack-runs 10.3 @135
haven't run at track since Oct-99

[This message has been edited by The ODB (edited February 09, 2001).]

 

Well you have vacuum, so thats ok. With the engine off, shake the PCV, it should rattle. If it does, its fine. Dont worry about the idle change thing if there is vacuum and the PCV rattles.

 

The slight "knock" you are hearing is actually called pinging. You're getting detonation. You should get that fixed because it can cause damage. First make sure the timing is set right. If it is then the EGR valve may not be working.

------------------
'89 Formula 383 TPI

 

Cool. I'll leave the PCV alone. Thanks for the replies.

About the knocking or pinging , Greg : My timing is correct ( 6 deg BTDC). The egr works, since forcing it open by hand makes the idle change. I even checked the vacuum at the egr by attaching a long tube and snaking it into the passnger window, and feeling for suction while driving. There was suction at low rpm, just as you would think, but it was quite weak suction.

I am still fairly stumped about the knock/ping. It sounds like it is coming from only one cylinder, by the way. Only shows up when engine is hot. It was even worse before I put in a new radiator, then went away completely for about 6 months, now is creeping back.

John

 

Try running some carb cleaner or GM top engine cleaner (water mist, crushed walnut shells, or your favorite choice) through the engine, it may have some carbon buildup that is causing the knock problem.

[This message has been edited by madmax (edited February 10, 2001).]

 

GTA,

You have teh 305 and E4ME Rochester, don't you? Check the idle mixture control solenoid, TPS voltage, and clean the PCV valve and hose.

If you are getting localized detonation, you might have excessive carbon buildup in one cylinder, a hot plug in that cylinder, a leaking intake gasket at that cylinder, or deposits on the back faces of the intake valve(s). For the cost of some GM Top Engine Cleaner, I'd get a little bit and try cleaning the chambers/valves, then change the plugs.

------------------
Later,
Vader
------------------
"No matter how hard you try you can't stop us now..."
Adobe Acrobat Reader 4.0

 

Yes, it is a Rochester E4ME. Did the GM top end cleaner. Didn't help. Also did the spray mist while engine running. Didn't help. Maybe it is the intake manifold. I do have a coolant leak from the back of the intake manifold gasket, so perhaps other areas of the gasket are going also.

At one point I had a sort of combo miss / knock going on in the same cylinder. Compression check showed one low cylinder. I ran a couple bottles of Techron through, which brought the compression back up in the low cyl (dirty valve, I guess) , and got rid of the miss.

The only thing that helped was putting in a brand new radiator. I had been running hot with the old one. The new rad almost removed the knock completely.


At one point I had a sort of combo miss / knock going on in the same cylinder. Compression check showed one low cylinder. I ran a couple bottles of Techron through, which brought the compression back up in the low cyl (dirty valve, I guess) , and got rid of the miss.

Maybe I am building up some more carbon on the valves in that cyl. Maybe time for another bottle of Techron. If that doesn't work, then I'll try carb adjustment, check TPS voltage, mixture solenoid, etc. I'll also check the spark plug in the "low" cyl for carbon.

Thanks,
GTA

 

That Techron cleaner is awesome stuff! It really works unlike the other cleaners. It sounds like the pinging is being caused by heat. Are you sure the engine is not running too hot? Maybe there is partial blockage in the coolant passages around that cylinder which is causing it to run hotter there. Get some radiator flush and flush it out real good and replace the coolant when your done with a 50/50 mix.

------------------
'89 Formula 383 TPI

 

Greg,

I have wondered too if there might be a "hot spot" in the engine. I already did the chemical flush. Didn't help. I wonder if there is some way to snake a flexible steel cleaning tube through the coolant passages just to make sure they are all open and clean. Maybe have to take off the water pump.
There are just soooo many things that could becausing the knock. The knock comes and goes, even after the car is hot. Only happens in first and second gear. Highway driving in o/d is fine, usually. My mech says to just live with it, or just try a different brand of gas. Exxon regular seems to reduce it a little. High octane reduces it a little bit more. Maybe it's a combination of carbon buildup, hot spoot, carb mixture, intake manifold leak, valve deposits, the list is endless. I used Bars Leak a few years ago, during the winter and the following summer the knocking started. Maybe the BarsLeak started the whole thing !!

John

 

I've heard to never use stop leak additives in the cooling system because it can block the passages. That could be the problem. You could try and flush the system again and run some Techron through it again to possibly remove more deposits. Make sure it is not running too lean also. This will cause it to run hotter. The intake leak should be fixed too. Other than that I would leave it alone considering the age and mileage.

------------------
'89 Formula 383 TPI