turtle79

So, I have a 2000 3.4 and am experiencing some misfiring. Engine light is on and code reads as a misfire in cyliders 3 and 4. I replaced the plugs, wires, and the coil pack for the 3rd cylinder. The original boot on the 3rd also looked like it had been hot (it was not as black as the other ones). The plugs looked old, but not otherwise bad or faulty. I've also run Lucas through the tank once, and am currently running some Sea Foam through the tank. My concern is that it is one of the injectors failing, but I don't really want to go to the trouble of pulling the intake plenum off and the fuel rail if there may be some other more easily accessed solution that I haven't thought of. A vaccum leak, or some other electrical element that I'm not thinking of?

Symptoms that cause the misfire are kind of strange too. On a cold start it runs fine, to and from work, even drove it up to tennesse (about an hour and change) this past weekend. No problems. The misfire starts fairly reliably if I run it for a short period of time. Turn it off for a short period of time. And then start it again. For example, drive home from work (15 minutes) no problem. Drive from work to the store (a short drive) spend a little time inside and come back out it almost always misfires on the rest of the drive home. Seems to be starting the engine and shutting it off a lot that starts the misfiring.

So am I into doing the injectors or does someone else have a more clever idea?

paxam

check the IAC valve in the throttle body. I had idling issues in the past and after I cleaned it all was well. I also had a code and 2 bad coil packs, it may be more than 1 pack bad .
I had fouled plugs and O2 sensor issues after I ran seafoam through I will not do that again.
check for wires rubbing on the engine or someplace that may cause a short.
if you have a way of checking fuel pressure that would be good.

turtle79

I did clean the IAC valve while I had the intake hose off. Just seemed like par for the course. Did you run the sea foam through the tank or through the vac system? I do have another set of plugs to use, but was trying to narrow down other problems. I had to gap the ones that are in there myself. The next set is a factory gapped set. I was careful about placing the plug wires when replacing them. They're as good as i can make them I guess. The injectors seem the next logical place to go to for me, but I guess it could be another coil pack. Do you know how the computer generates codes? Since both 3 and 4 coded, I wasn't sure how that translated. 3 and 4 aren't "partners" so I was wondering if the computer code drew a line across the engine in pairs coding for both 3 and 4 when it may just be the 3rd misfiring, or if a code for 4 meant that it's companion cylinder's coil pack (i.e. 1) might be bad as well? I replaced the 3rd cylinder's coil pack mostly based upon the appearance of the boot, thinking that was the best indication as to which one was bad, if any of them were. Thanks for the response. This truck is new to me and has me wondering if I should've just stuck with my 22RE......

j2the-e

How many miles? Have you done a compression test? Same codes after doing plugs, wires, etc? Always cylinder 3 and 4? Pretty rare for these injectors to fail, but it does happen. I wouldn't ever run a fuel tank additive. Its all snake oil. However, if you find a shop that does a fuel injector cleaner, that may actually help if you determine that injectors are your issue. You disable the fuel pump and plug an adapter directly into the fuel rail. Toyota actually makes their own 3 part kit and I think its really good stuff. Kinda pricey though to have it done

akaphilly

i had the same problem years back. which i istill have. i want to get my injectors sent out and cleaned. but to pass inspection i would use seafoam. throught the pcv valve. NOT the tank. that dosent do anything. u gota do it through the intake. theres many many threads on yotatech explaining it

turtle79

139K and change. I haven't done a compression test. I've never done one, though I think I understand the basic concept. I'll search for that here and elswhere, though if anyone has some knowledge based tips on making that go smoother, I'm all ears.

turtle79

Since this engine doesn't have a distributor where do I disconnect the ignition system? Do I have to do this or can I just test with the gas pedal down?
Geez I hope it's not the rings or head gasket. That will suck.

rworegon

Going through the PCV valve will have ZERO impact on the injectors. There might be some cleaning action of the injectors via addition to the gas tank.

j2the-e

With an intermittent mis-fire, it's probably not a compression issue, but I believe in doing your basic tests first to be sure. To dis-able the ignition when doing the compression test, pull the efi fuse under the hood. This will also clear any check engine light, so if you want to check for codes, do it first.

akaphilly

false. first statement. it sucks the other way into the intake. not into the engine

https://www.yotatech.com/forums/f2/y...n-port-230029/