Yes I noticed the spark escaping right under the intake near the coil. Only noticable at night. After replacing the coil it seemed to help at idle but not at start up or 50+mph. So what your saying is my sparkplug could be shot ? The misfire has been happening since previous owner. I owned the car for two months.
***misfire help***
- Thread starter RJLeagles2010
- Start date
Yes I noticed the spark escaping right under the intake near the coil. Only noticable at night. After replacing the coil it seemed to help at idle but not at start up or 50+mph. So what your saying is my sparkplug could be shot ? The misfire has been happening since previous owner. I owned the car for two months.
yes, the plug could be shot.
grab some of the uber cheap autolites from the parts store for $1.60 each and see if it goes away.
or swap that plug with a different cylinder and see if the code jumps to the other cylinder if there's not visual damage to the porcelain on the plug, etc.
grab some of the uber cheap autolites from the parts store for $1.60 each and see if it goes away.
or swap that plug with a different cylinder and see if the code jumps to the other cylinder if there's not visual damage to the porcelain on the plug, etc.
LittleCaesar
New member
My bad Doc, I thought the OP had posted a P300 code, not 304 as for a specific cylinder. I had a T100 whose upstream 02 sensor bought the farm and it was throwing a P300 constant plus random cylinders.
Did you perform a leak down test as well?
Yes I noticed the spark escaping right under the intake near the coil. Only noticable at night. After replacing the coil it seemed to help at idle but not at start up or 50+mph. So what your saying is my sparkplug could be shot ? The misfire has been happening since previous owner. I owned the car for two months.
Doc2012 said:
I would not worry about the cylinder #4 issue right now what with the compression as good as it is.
your issue is in cylinder #3 with the 105psi. if you have an air compressor, go rent a leak down tester...or just buy one from harbor freight. lots of tutorials on youtube.
first order of business. are your plugs wet? if so, pull all of them out and un hook the coils from their plugs and crank it over real quick to see if any water shoots out the hole. telltale of a cracked head.
I do my leakdown tests the quick way now days. I dont even hook the gauge up anymore. I just put the adapter down the hole after I bring it up TDC and then hook it to an air compressor around 40psi. if you crack the throttle body open and feel air, its your intake valves.
if you go to the exhaust tailpipe and feel air, its your exhaust valves. If you pop off the oil dipstick and feel air, its your rings. if you pop off the radiator cap and you see bubbles, its the head gasket/cracked head...or both lol.
if its the valves it "could" be a dropped valve, a bent valve, a burned valve, valve guide, etc...unless you got trash in the engine I'm not going to go with a bent valve. I've got a 5vz-fe head setup that I've had the intake/exhaust cam out 180* and rotated it and the valves never got close to contacting.
considering you have low pressure in all three centering on #3 I'm going to guess either cracked head or head gasket is on its way out.
did you have the engine open before this issue occurred? if so I'd rotate the engine to TDC at the crank pulley until you also get the cams lined up TDC, pop the valve cover and check the timing dots on the intake/exhaust cam to make sure both single dots line up. you can also keep rotating the engine after you verify this and look manually for a bent valve after the lobes are off the cam buckets. shouldnt be any space compared to the others on the other cylinders.
but I'm really leaning to a head gasket/cracked head issue with those compression results.
I had this exact thing happen to me recently. Cylinder 4. Replaced the sparks, and then the coil pack (twice) but it was still happening. I then had the compression checked, which was fine so i ran a couple bottles of injector cleaner through which didn't help. I then replaced the injector & seals exc. Problem solved for me. Originally the problem was intermittent, and only when the truck was hot so I assume it was an electronic issue with the injector.
First post on here, and I am by no means an expert but I hope this helps.
First post on here, and I am by no means an expert but I hope this helps.
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RJLeagles2010
New member
this is exactly what mine is doing! i noticed it was off and on and then it quit for about a few weeks and now its back and it misfires all the time. it is the worst when just at a steady speed
Ok I'm back, after long day at work I got new sparkplugs but only replaced cylinder #3 as that's the one that threw the code for misfire. So after replacing one plug it started up like a baby. No more misfire. Idles good, at 50mph and more no more jerking. I couldn't be happier. Here's a picture of the old sparkplug. I will replace all plugs though when it's lighter outside.
Tell me about it. People should also make sure when they replacing the plugs or have misfire to really really examine the parts carefully and if they can match it to the other part that's new.
normally when the coil breaks down and gives you the misfire under load...and then scores the porcelain, its on the upper section of porcelain on the outside (it'll look like a deep burn mark down the side and into the porcelain). you can see though on that piece in the inside middle where it was grounding out though with the deep scorching focused right there.
Is it because it's a old plug ? A new one shouldn't get the same way ? After I put the new one in it ran like a champ.
no, it can happen to a new plug as well. the outer case is porcelain, its tough but it can only take so much of a beating. the coil breaking down can release none of its capacity or all of it, or the regular amount or any in between as its lost its ability to regulate itself. thats also the reason you saw blue sparking on the outside of it. it wasnt always finding ground at the plug itself, it was finding ground on its own casing (there's a magnet the surrounds the coil itself inside the plastic housing) as well as finding ground on the coil bolt, etc. just is what it is.
I got new wires, new coil on cylinder #3, and new sparkplugs. I should be safe right? It's not misfiring anymore.
Doc2012
Senior Member
Thanks for the info man. That helps a lot.
I did have the engine open before this happened. I had a blown HG, and did the TB, WP, all that shit. I had the heads cleaned and pressure checked, and they checked out just fine.
At this point I'm leaning toward either a faulty HG, valves, or somethis other with the head.
I really need some money so I can swap in a damn V8........
Bumper2Bumper Auto
New member
Also be sure to remove the EFI fuse. This will prevent the injectors from firing fuel into the cylinders. Part of standard procedure for compression checking.
Doc2012 said:
A little extra bit of information about engines and misfires:
Every engine has what is called a companion cylinder. That is the cylinder that is on the EXACT opposite cycle as it is on. So if one cylinder is TDC of it's compression stroke, it's companion cylinder is on TDC of it's exhaust stroke. How do you find the companion cylinder? On a V-configured engine you stack the firing order. So for the 3.4 the firing order is, interestingly enough, 1,2,3,4,5,6. So now you stack that.
1 2 3
4 5 6
So 1 and 4 are companions, 2 and 5, and 3 and 6. This is also obvious when you look at how the coils and coil wires are routed. This helps in misfire diagnosis because it is not uncommon that a misfire code sets for a specific cylinder, but the culprit is a part on the companion cylinder. I just wanted to add this information for those who are chasing a misfire and can't seem to find the failure.
As for your engine Doc, you obviously can see the low compression on 3. Did you run a wet compression test to pinpoint the loss of compression? If you haven't, then I suggest you do it so that you can save some time. If you do not know how to run a wet compression test it is identical to a regular compression test. Before doing a wet test, retest a dry one. Pay attention on EACH stroke how quickly the compression builds. You need 5 good "puffs" per cylinder to get an accurate reading. To do a wet test, remove the compression gauge and squirt in about a teaspoon of engine oil into the cylinder. Make sure it goes into the cylinder, and not get stuck up where the plug screws in. Immediately run a compression test on that cylinder. Does the compression build up faster, then flatten at at the same pressure, or does it build up faster and go higher? Does it not change at all?
If the compression builds up higher, then you have faulty rings on the piston, or a worn cylinder. If the compression does not change at all, then you have a valve train problem, or a head gasket/cylinder head issue.
I hope this helps someone out.
And by the way, Doc...Semper Fi Marine!
Doc2012
Senior Member
I did do a wet compression check, and the pressire jumped up 15PSI, but no more than that. I let it crank for a good 5-6 tries.
When I did the HG, #3 looked to be a little scored. HOWEVER, I never had this problem before I did the HG. Now, I can't get it to go away.
If I HAVE to, I can pull the heads again, but I'd really rather not do so, until I have a for sure answer as to what the problem might be.
I guess I need to get a leak down test in order to R/O some shit.....
you probably did the same stupid thing I did when I replaced the cracked head on the 97 3.4 I just got finished working on. I had the intake cam installed 180* compared to the exhaust cam which was installed correctly.
you're actually getting 3x better compression than I was lol. my compression was 20psi @ #5, 30psi @ #3, and 60psi @ #1. oh and to give you an idea. mine did run when setup like crap and would either run like crap or sound completely normal. it would just belch gas smoke and it would rattle like a son of a if you revved. thought I had bent valves too. but I confirmed on the old head that the valves will never contact. It also tossed P0300, P0301, P0303, P0305 codes at me too.
heck, just read through my thread if you dont believe me. I was scratching my head for days thinking it was an ignition problem until I finally did the leak down test, then pulled the valve cover and slapped myself in the head:
http://www.toyota-4runner.org/3rd-gen-t4rs/151575-need-help-weird-engine-issue.html
did you put the bolt in the exhaust cam before you pulled it out as well?? if not that'll toss it off a tooth as well. you just toss the exhaust cam in a vice wrapped in a towel and get in it with a small flatblade to move it back into position. I held it together with a pair of vice grips while I put the lock bolt in.
anyway, if you pull the valve cover and rotate the cams, the double dots should line up and then the single dots will obviously line up. anything else and you have them screwed up.
Just lock out the exhaust cam (if possible as you may need to do as I stated above), pull out the exhaust cam, rotate the intake cam so the double dots are pointing at the exhaust cam and then install the exhaust cam with double dots facing the intake cam.
I just snugged it down with the two cam caps surrounding the gear to check the alignment. you will not get full rotation of the cams until you pull the lock bolt out. and yes, the intake pulley will be pointing 180* when you install it all due to toyota for some ungodly reason putting the lock bolt hole on the side of the exhaust cam they did.
I re-aligned everything correctly, set the timing back up, and did a compression test before putting the engine back together and got 175+psi on all cylinders.
cliffs: pull valve cover and turn engine over until double dots on the backsides of both cams line up. if they dont, you have an issue. if they do, see if you can get the lockout bolt in the exhaust cam gear. If you cant, then it is still not setup properly.
I still have the old head sitting on my garage floor setup and I can take a pic of how it should look if you need it.
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