I just had the same problem, except it was cylinder #6. I did a compression test, checked out 190 psi, I also could smell gas when I hit the pressure release valve. I put a screw driver on the injector to see if I could hear the pulse from the electric current. I also changed the spark plug. It turned out to be a bad spark plug wire. The worst part about it was I had the wires changed just last year. Try switching one of the wires around to see if you get a different cylinder misfire.
Dec 30, 2008 Rating
99 4runner 3.4 by: Anonymous
I did a compression test today on cylinders 2,4,6. Cylinder 2 was 60 psi, cylinder 4 was 70psi, Cylinder 6 was 75psi. I noticed oil coming out under valve cover by # 2 cylinder. The odd numbered cylinders are 190 psi - 200 psi. Is it a blown valve? head gasket?
I still have the same po302 code. Thanks for all your help. If it's a blown valve gasket or head gasket I am willing to tackle the challenge. Would one of these cause the misfire for a single cylinder? Thanks again.
Steve Says
This sounds more like it might be a timing problem. It would be rare that a blown head gasket would cause all of those three cylinders to be low on compression. If it were a blown valve all of the cylinders would have to have blown valves to have compression that low. It might be an intake manifold leak, but then you should have oil and coolant leaking into your cylinders. You might want to check your oil level and coolant level to be sure that they are correct and are not low.
The reason I think it might be a timing problem is that you have three cylinders that are low on compression while the three on the other side are fine. Cylinder #2 is the lowest on compression and that might be why it is showing the misfire. These engines have been known to shear off the locating pin for the camshaft pulley. This makes it so the marks still line up but since the pin has sheared the cam timing is actually off. It could also be a slipped timing belt so you should check the timing marks first, if they are right on then you should take the camshaft pulley off and see if the pin is there or if it is bent or sheared off. It might even be that the hole is wallowed out. Good luck!
Dec 27, 2008 Rating
Thanks by: Anonymous
Thanks for the quick answer. I've read a lot of posts and usually if the coil pack is not bad the injector is to blame. I plan to do an ohms test, lots of people have said that the test will not prove anything. If its out of spec. it will prove a lot to me and add to things I can cross off the list. I plan to check primary and secondary resistance on the coil. I don't think its the coil because the code did not follow the coil pack switch. Could be the #2 wire. I'm not sure because I switched back to original OEM wires unless both new and old wires are bad. Any other advice would be greatly appreciated. I've been told that I should take it in, but I'm pretty good with a wrench, I just don't have as much equipment and resources as I'd like. I do have an Innova 1303 scan tool. I'm not really sure how to interpret what it's saying. If needed I can post the freeze frame data and live data? Again thanks for your help. mark usmc
Steve Says
The injector is definitely something I would suspect, but there are other things as well. The ohms test for the injector will tell you if it is really bad, but won't tell you if it is marginal or intermittent. It also won't tell you if the computer is telling it to fire. BUT it will tell you if it is really bad, and since it is an easy test you should definitely do it. If you go buy a "noid light" (available at most auto parts stores) you can plug that into the harness in place of the injector and it will tell you whether the computer is trying to fire the injector.
It is very unlikely that the coil is bad because, like you said, the problem did not follow the switch.
Freeze frame data will probably not be much help in this instance. I think you can find the problem by performing the tests that I told you about.
The tests that you are doing are the tests that a mechanic would do at his shop, so until you do all of these simple tests I don't think you should take it anywhere. If you do all of them and still do not know what is wrong then you should consider taking it to a repair shop.
