Shoorty911

i was at in the garage today trying to figure out the low idle (200-300rpms) and rough shaking at idle. Ive recently changed the spark plugs and wires with NKGs, rotor, cap and pcv valve. I pulled the number 6 wire off the cap and no change in idle or shakiness whatsoever so i guess that is it.....when i would hold the end of the wire close to it's socket on the cap it would spark so i know there isnt a problem there or with the wire because obviously it is grounding. The fuel injector on the cylinder has to be working too since the exhaust smells of fresh fuel. When i changed the spark plugs all of them except had the normal tan ashy stuff on them but cylinder 6's plug....it had black soot on it.....ive also checked all of the vacuum lines and had no apparent disconnections or leaks.....ANYTHING ELSE I CAN LOOK FOR???? because the shaking is really annoying and it's drinking gas like a bitch....7.5mpg!!!

Shoorty

Shoorty911

bump....

4Paws

run a compression test on that cylinder and also on the one adjacent to it.
Badly worn rings or head gasket.

okidoc

My #6 went bad last week. Truck is in the shop now. The plug was wet and black mostly. I also had a slow coolant leak that I couldn't find until now. The idle went really rough too.

I would run a leak down and a compression check, however both of these were done prior to the bad miss and both were negative. #6 I think is the weak cylinder.

On the bright side if the HG is the problem at least you'll know what it is and how to fix it. Good luck

Shoorty911

my plug wasnt wet just kinda sooty looking.....how much money does a leak test and compression check usually run??

shoorty

Firefyter-Emt

$25 bucks and do it your self.. on #6, I will take a guess on a burnt valve. But a compression tester, You should be at least 150psi with less that 10psi drop on any cyl. If you have a very low#6 drop in about a tea-spoon of oil and retest. If it goes up, it is your rings, if not your valves.. It could be a HG, but with out any other sings of a HG failure I say it is in the heads.. The tester is about $25 and it screws in like the spark plugs.. Pull all the plugs and install one at a time and crank the motot 4 or 5 turns (oh, yea.. unplug the coil) and write down the reading.. Very easy, as easy as changing your plugs..

okidoc

Also run a vacuum gauge test. Very easy and about $10. The fluctuation in the needle on the gauge will point you to low idle setting, burnt/stuck valves, bad timing, worn rings etc. Very useful to get moving in the right direction but not a definitive test.

Astralplane

I did a compression test after I noticed I was losing coolant and the truck would idle real rough at start-up and then run fine after that.
I also replaced plug wires, cap/rotor, and even the ignition coil (waste of money, the manual said it was out of spec but the new ohm'd out the same).
I was shocked when the compression test was great.
I then had my exhaust analyzed and it came back positive for coolant.
I then had dealership scope #6 with a fish eye camera and of course it showed a blown head gasket. I had them look at #6 because that spark plug looked completely different than the others.
I had the HG repair done during recall in March 1998 with around 44,000 miles.
This one cost $1732 which included new belts. The truck has 132,000 miles now.
One wierd note:
I did use about a quart of oil every 1000-1500 miles, especially during highway speeds. Since the repair two months ago the oil level has stayed rock soild. I've driven about 2,000 miles. I did fix oil cooler gasket leak and valve cover leak just before repair, but I don't think that's where the oil was going.
I'm also 500 miles into first AUTO-RX treatment.

Shoorty911

What exactly did the #6 plug look like when you pulled it? Mine had some black soot on it whereas the others only had the normal tan ashy stuff. I am also using about 2qts of oil between every change which is about 4000 miles, but it it leaking from somewhere though....i think from the valve cover gaskets since there is an awful lot of sludge up there.

shoorty

Astralplane

5 of plugs had a build up of white ash caused by feeding it too much fuel injector cleaner. I thought it would help the rough start-up idle.
#6 plug had no ash and was very clean.
Plugs only had about 10,000 miles on them before my HG problem.
Also, when it cold out my truck would not idle high when first started.
It would just stumble and chug for about 2 to 5 minutes.
I've had the truck since it was brand new and I've never felt the engine chug & stumble like that before.
Have you checked the inside of your oil filler cap?
Mine kept filling with an off white/lt.brown gel.

Sbrut95

Maybe a stupid question but I dont know...

which plug for which cylinder? if youre in front of the car what order does it go in. Thanks

Astralplane

I don't have my manual at work but I'm pretty sure it goes like this.
Passenger Side: 1,3,5 (1 closest to the radiator)
Driver Side: 2,4,6 (2 is closest to the radiator)

Shoorty911

Cylinder #6 Plug...here is a quick diagram

----Firewall-----
5 6
3 4
1 2
----Radiator----

shoorty

Sbrut95

Thanks guys,

So if I was having a HG problem, one of the plugs would be noticeably different looking than the others right? Ive actually noticed coolant loss from the resevoir. But not from the actual radiator itself. Very small amount though.

Shoorty911

Have you looked at your oil-fill cap? If there is a milky substance like mayonaise under it then more than likely your head gasket is blown. I dont have that so i dont think my head gasket is blown. The HG recall was done on my car in december of 97.

shoorty

Astralplane

HG problems are not the same for everybody and hopefully you don't have a HG problem. This was just my experience and my symptoms for a blown HG were pretty standard.
The dealership did say everything else about the engine looked great.
I also asked about valve adjustment.
They said they don't do it and it's not needed, hopefully they know what they are talking about.

Firefyter-Emt

Some times a valve adjustment can make a workd of change.. Like on mine, I could go from 40ish psi to 150psi !! But after 3k the valve would warp again.. They are just too lazy and may not stock the huge assortment of shims needed to do the job.. At the very least, they should tear down the intakes and measure the valve clearance. There is no adjustment on the heads for the valves. You get new adjustments by removing a wafer shim and installing a thinner or thicker one. All that you need to do the check the clearance is to check the gap in the correct order. They are giving you lip service because they do not want to do the job.. It is a flat rate nightmare and their tech's don't like to do them because they can not take the 8hr job and do it in 4hrs like most other flat rate jobs..

Shoorty911

Ok ive been adjusting the idling screw for the past week now but whenever i unscrew it to make it idle where it is supposed to, the vacuum sucks on it and screws it back in to where it makes it idle at like 100 rpms....can i use teflon tape on it to stop it from screwing back in or is there somthing else i can do?

shoorty

MTL_4runner

You can use some Loctite on it but you need to adjust it fast and let it set overnight.
I know it is not ideal but it will work.