Truck HELP,Running rough(again) PCV valve???

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LandfillLumber

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warren, michigan, USA.
Hello, well my old tired truck is acting up again it just started running really rough like it was running on 7 cylinders or it is running out of gas.It ran fina all day then I went to drive a mile down the road and it did it right from the start of the engine.I thought it was a little cold at first but that was not the issue.I noticed I had a couple spark plug wires laying on the engine that had melted so i replaced them and it did nothing for the rough idling.I also noticed a PCV valve missing on the passengers side of the engine that appears to feed into the air cleaner??This is my biggest question is would the PCV valve missing cause this and does it go into the air cleaner( I can't see any other place it would go).Thanks for the help in advance,Victor
 
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Could be dirty plugs, a cracked spark plug wire, distributor cap dirty, cracked or worn out (if it has one). Timing belt could have slipped. Pull out the plugs and replace or clean them, also check the spark plug wires for cracks since they could be arcing on the block DAMHIKT but these are what I would check first.
Jerry
 
That hose may go to the air filter but it isn't a PCV hose. It goes to a small filter clipped to the filter housing. A PCV valve normally goes into a valve cover & if taken out =, the vacuum loss will normally kill an engine. 2 plug wires grounded out may have caused the plugs to carbon up on those cylinders from not firing, especially if it burns some oil. First, check for a vacuum leak. Next try a cylinder balance test. Loosen the wires in the distributor then let idle. Pull one wire from distributor at a time around the firing order. The one that doesn't drop the RPM's is the problem. On the older Chevy's a small vac. leak will kill # 5 & 8 cylinders. I've seen Fords that a small leak will kill 4 cylinders. Normally 1-4 6-7.. Talk about running rough. You can do the balance test on plug end of wire but that may give you a headache. Not so much the getting bit--but from smacking your head under the hood from jumping outta there.
 
My plugs look like heck so I will replace them all.I'm interested to see if the wires that had burned through are the ones that are most carboned up.Fouling of plugs has always been an issue for the truck in the past but not like the one plug I pulled this time.

Okay next ?
What is the hole in the head cover on the passenger side of the engine?Its about 5/8" round and the new PCV valve I bought fits right into it?I have a PCV valve on the drivers side also,do trucks only have one or two PCV valves????

Thanks everyone for all the help its much appreciated.This is why I'm on a new truck mission this month.Victor
 
Heck, i'm not a mechanic, but the PCV valve is important, and it's only 3 or 4 dollars, usually...cheaper than spark plugs! Check your oil - might be that the oil is getting burned in the cylinders, because of the missing PCV causing a vacuum....is your oil low? Are you noticing black smoke? !

Change the usual subjects - air, oil, fuel filter recently?

On my old 8 cylinder truck, the culprit turned out to be the fuel pump...it was pumping fuel, but not enough - so it ran like crap...fixed a lot of things first - took five mechanics to figure that one out!

Not the best advice, as I just know the problems I had in my truck and know very little about engines - but it's a start! Andrew
 
Okay I have replaced the PCV valve/Plugs and its still rough.I turned the idle up and it runs well?It was only running bad when idling so could turning up the idle be the problem(I don't think so but not sure).Thank,Victor
 
The hole in the valve cover is just for blow by. Yes you should have a PCV valve in the hole and a hose running to air filter box. The hose is just so the engine will burn up the blow by rather then blowing it all over the engine compartment. I would not run the idle higher then 1500 RPMs, could be vert hard and a automatic trans.
 
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Make sure you got the wires in the right firing order. You could of got the 2 that were burnt in half backwards.
 
Are you talking about it missing while under a load [driving] or when only on an idle. To slow an idle can cause it to 'loap'. Standard shift should be about 500-550 RPM. Auto. trans is about 600 in drive gear. I've never seen a vehicle with 2 PCV valves. The older models had a valve cover filter that pushed into a hole similar to the PCV hole. A PCV valve has to have vacuum to it. Try the cylinder balance test. Now- if it's idle only problem, set the idle at a norm. idle--not so slow it wants to quit. In front & at the base of the carb. there are 2 springloaded screws. SLOWLY turn each one in--it will idle rougher. then crew it outward. you'll notice a place that it idles best. Do each one, one at a time. Those are your idle/air adj. screws. Shouldn't be more that 1 turn either way.
 
what type of truck are we talking about here? if it's a ford, feel free to PM me with any questions.

IF it's a an older ford, a rough idle is very often a dirty IAC which can be cleaned. lemme know and I'll explain how.
 
Victor. I don't know where Warren, Mich. is, but here in GA, the quality of gas has gone WAY down. I was having similar problems with my "work" truck (1988 Chevy C 1500). I tried every thing you tried.

Finally, what made a REAL difference was adding STA-BIL ethanol fuel conditioner each time I gassed up. It's been fine ever since. This truck doesn't get driven very much, just to the garbage dump, to haul wood, tow a boat etc.

Normally, I think "additives" are a hoax, but the ethanol treatment worked for me. It's cheap, try it.
 
It sounds like you should check all of the vacuum lines. If the truck is that old and you haven't replaced any of the vacuum lines then you may have hoses that look good, but have small micro cracks or be so hard at the attachment site that they are allowing air leaks. I would also check the fuel pump pressure.
 
Worn valves can allow a vacuum leak through the breather hose. Whether it's connected or not...

What kinds of numbers did you get last time you did a compression check?
 
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