missing on idle

Getafix · tinkerer Joined: 16 Jan 2002 Posts: 146

ok, Im running a TF, stock, granny spec to the max (down to the AM radio! im gonna start modifying it soon)1.6l, when im sitting at the lights, revs are low, it'll miss, im pretty sure on #3 cyclinder. When i pull the plug out its covered in crap, burnt oil type crap. other plugs are beautiful, replaced the leads and plugs not long ago so their fine. I was thinking it could be the valve guides in the head? Should i get it reconditioned or is there a better idea? I havnt checked compression, im hoping its not the rings, but i assume its the head cos the oil has to drip in from somewhere. Doesnt burn a lot of oil and engine has done few k's.
Also if i go for a reco, is there anything i should ask for/you guys recommend? hardened valve seats to run ULP?

thanks

rob_w · tinkerer Joined: 19 Feb 2002 Posts: 395

check for air leaks in your inlet manifold/gaskets, check your point gaps, dizzy condition,coil,fuel filter,float level,and then if that doesnt help,do a compression test, and see if the engine blows smoke under heavy acceleration. if it blows smoke when you floor it, it's fucked valve stem seals. if it doesnt, its probably a rooted head gasket or at worst, fucked rings/hole in piston.{does it have oil build-up in the air-cleaner? if it has bad blow-back, the sump is pressurising.ie fucked piston.}. i had the same problem,and sorted it by a process of elimination.[fucked rings.]if the engine has a hole ie the piston, go and get a checked replacement....mine cost $270, which was cheaper than the quoted price for pistons.the black shit on your plugs is the plug not working.
hope this helps.....i know the feeling.
rob.

Gold TX Sleeper · backyard mechanic Joined: 05 Feb 2002 Posts: 509

With oil on the spark plug, it's either gonna be the rings on that No. 3 piston, or like you said the valve stem seal. Lift the tappet/rocker cover off and have a squizz. Gaskets are only around 5 bucks. Then get hold of a comression tester from someone if you dont own one, and test all cylinders for a comparison.
Was the miss still there after you replaced all the said parts ? If it is, then do the points as well and see what happens. While your there, check the condition of your dizzy cap and rotor button.
as Rob said, if it has bad oil blow back through the PCV, then it's a good chance your rings are rooted.
Hope you find the problem easily and it's cheap to repair,
Jasyn...

Getafix · tinkerer Joined: 16 Jan 2002 Posts: 146

well thanks to both of you for the tips, im still at work but ill check it once i get home, It used to miss before i replaced plugs etc .. the dizzy cap is fairly new (when it first happened i let it go so far that the cylinder wasnt firing at all, i had to drive home 40k's hitting on 3, wasnt a happy chappy as i had nfi what the hell was going on and i didnt wqant to stop just in case it wouldnt start again) .. ill tends to blow a bit of smoke on hard pumping of gas (only noticed when i was in driveway and was in neutral), but it aint a blue smoke, so i dunno. if compression is down on the no 3, that means rings dont it? hrm... anyway ill give it a burl. the thing runs fine if i take the plug out and clean it (for a couple of months).

thanks again..

Nick_H · tinkerer Joined: 12 Oct 2001 Posts: 76

i have the same problem right now.....but this is my new rebuilt motor that has done 370 km (Not Happy) the last one did the same (mine is turboed) mine was a broken ring landing in both motors(the metal between the compression rings) so i loose compression on idle till about 1000 rpm then is goes away.. thats because the piston is moving fast enough to have enough compression to fire. thay were also cracked through to the inside of the piston so a small amount of oil could get through which makes the plug black and a little puffs of smoke from the engine. mime was caused by to much advanced timming and leaning out up top whiched caused the motor to PING..yours may not be the same but now you have a better idea if the head is ok.

Nick

Gene FJ20DET · Posted: Thu Jun 05, 2003 1:11 pm Post subject: Re: missing on idle

fix it yet?
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Gene FJ20DET · Posted: Thu Jun 05, 2003 1:11 pm Post subject: Re: missing on idle

fix it yet?
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Gene FJ20DET · Posted: Thu Jun 05, 2003 1:11 pm Post subject: Re: missing on idle

fix it yet?
_________________

Gene FJ20DET · Posted: Thu Jun 05, 2003 1:11 pm Post subject: Re: missing on idle

fix it yet?
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Gene FJ20DET · Posted: Thu Jun 05, 2003 1:11 pm Post subject: Re: missing on idle

fix it yet?
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Gene FJ20DET · Posted: Thu Jun 05, 2003 1:12 pm Post subject: Re: missing on idle

fix it yet?
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