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Hi, happy to be in the ETCG garage. Been trying to diagnose this problem at ToyotaNation for a while, so I thought I’d try my luck here. I love my 98 Camry V6, it’s always been reliable and I try to do all the work to it myself. Recently it has developed its first engine performance issue (at 207K), which is a rough idle/engine lope that occurs only when the engine is cold. If I let it warm up 10 minutes it is fine, although I think I feel some slight jerking when I hit the gas sometimes as well.
I’ve replaced the air filter and a very old PCV valve as attempts at an easy fix, but to no avail. I’ve done due diligence reading everything I can find, so I know there are LOTS of potential causes of a rough idle :(, but the thing I don’t see very much is common causes of a rough idle that ONLY occurs while the engine is cold. In fact the loping is noticeably worse when the outside temperature is very cold. This is the only real clue I have, but I’m not sure where it should point me to.
For reference, the engine starts cold at around 1800 RPM. After 5-10 minutes it drops to about 800 and then all is well. If I put it in gear cold it goes to about 1000 and lopes hard. It only lopes in park/neutral if it is very cold out. After I drive the car a good bit, even if I let it sit for a while afterward, it starts at only 1200RPM and then I can put it in gear right away and all is well.
Vacuum leak is next on my mind, but I find it a hard test to do, so many places to look. And of course the question that keeps bothering me – why would a vacuum leak (or any problem) only cause an issue while the engine is cold? What do you think, these conditions point to anything in your mind?
Thanks all
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If you do not do the rear bank you are only doing half a check… If you would confirm a problem cylinder with a power balance test, then maybe..
A proper compression test is done with a warm engine, ALL spark plugs removed and the throttle at WOT…
Now you will still get some data if you do it the way you plan…
Had you gotten a relative compression test prior to all of this you would have saved weeks of your time.
Yea, you need to remove all the plugs. Thanks Toyota. I usually lift the intake up to get to the rear plugs. I would think you can actually leave it that way to do the test and you won’t have to worry about holding the throttle open.
I only want to compare the bad cylinder to the other two on the front, so I was just going to pull the front sparks, but I do want a look at the rear plugs anyway to see what shape they are in.
When you say “lift the intake”, do you mean removing it? Or is there a way to shift it up a bit to make the plugs more accessible?
Edit: Oh, got it: http://www.youtube.com/watch?v=0IcfeyA3L3E
Got to be your best video ending Eric. Thanks as always. But I really wish I had the weather in that video right about now.
Actually, the rear bracket bolts on my plenum weren’t put back in by a dealership years back, I guess this is one time to be thankful! I did finally just get the bolts though…
Ok, update. I did the screwdriver-listen test to the injectors, they all seem the same.
Put a can of Seafoam in half a tank and gunned it.
Car drives beautifully, but…still misfires/wheezes/shakes/rough idles or whatever it is, but only when I start it cold.
I got impatient with the weather so I took it to a garage to do the compression test. Went to my favorite mechanic with 20+ years of experience, has always done well with my car. He test drove the car (after it was warm of course) and said there was no way in the world the cylinder had lost significant compression from mechanical damage. Said he’d just be stealing my money to even test it. I expected as much, you’d really think the same if you felt how well it drives. (He also said he hadn’t seen a spark break like mine in over 10 years. Lucky me. Of course, if it really did no damage I guess I am lucky.)
He recommended changing the rear plugs first before bothering with anything else, and of course I need to do that anyway, so that’s next when I get a decent day. Got new wires too (all NGK).
New thought: what vacuum leak could the electrode have created on its way out to electrode heaven?
I want to do a piston soak on that cylinder once I pick up something to suction out the gunk, though I can’t imagine how carbon gunk would be causing the issue either.
I’d entertain the idea that the bad spark plug and the rough cold idle are unrelated, but it’s just not possible. I first felt the car jolt just a few minutes before I heard the electrode break off and bounce around the engine, and it was the very next morning that the rough cold idle started, and hasn’t stopped since. There’s just no denying the correlation.
One caveat – it may be my imagination, but it does seem that the loping/misfiring/whatever has decreased since I put in the new plugs. Where the lope used to occur almost rhythmically it now is more sporadic. Once every 5-10 seconds instead of once every 2 seconds or something like that. Don’t know what it means. The Hornet just likes to play games with me.
Interested in everyone thoughts.
Thanks ECTG and friends.
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