Fuel injector?

When engine is started hot, truck runs badly, like on 3 of the 4 cyl. Code reads random misfire cyl 3. changed spark plugs, fuel filter (not easy) and ran sea foam through at last fill up.

While engine running badly (after starting with engine hot), I disconnected Fuel Inj’s #1 & #2 (one at a time)and the engine died down to almost a complete stall. When I disconnected #3 there was no change in the way the engine ran.

After checking most sensors, etc. Did listen to injectors test with a screwdrive on the injectors and the other end in my ear while having condition. Still have the screw driver stuck in my ear, but that’s another story for another day.Nice clicking sound in #1 and #2, forget #4 (can’t even see it let alone reach it). But #3 has more of woosh sound than a click sound.

Put Noid light on connectors while engine running badly, #1 & #2 light bright and on / off. # 3 flashing on and off but much dimmer than the others. Let’s again not talk about #4.

So, my question: Is this an electrical problem or is it the injector? I do a lot of short trip driving and the engine is started hot very often. If it is an electrical problem, is dynamite the only answer?

It sounds like it is time to see the mechanic (I recommend a local INDEPENDENT mechanic - No chains or dealer unless it is nuder new car warranty.)

It would be helpful if you told us what year and how many miles that Tacoma has. Are you up to day for ALL the maintenance items listed in the owner’s manual?

Run a compression test using a mechanical gauge. If that checks out good, especially on #3, check the spark on all the plugs with a test plug. If you have spark and compression, change the injector. Sometimes you can find sets of injectors on eBay…Or, depending on where you live, at a salvage yard…

No dynamite needed. It sounds to me like you just need to follow the wiring & test to find the power problem.

thanks for the replies. I ran another test with an ohmeter and dc voltmeter.
With the engine cold, the injector resistance readings were 16 -17 ohms. With the engine hot and malfunctioning, Injectors 1 & 2 read 17.2 ohms and #3 read 45!!
I then put a voltmeter on the electrical connectors for the injectors. 1 , & 3 all read between 2.1 and 0.6 volts as they pulsed. No significant difference between any of them.
Engine compression is also ok in cylinder 3 as the engine runs fine after starting cold.
New spark plugs, that’s the first thing I changed.
Oh, it’s an 2002 tacoma with 80,000 miles.
I think the signal is ok, I guess I’ll be changing a fuel injector. What do you think?

I think you’ve got it, but if you really want to be sure before buying the new injector, swap the #1 and #3 injectors. If the problem goes to the #1 cylinder it’s the injector, if the problem stays at #3 then it’s a wiring problem you missed.

IT’s not going to be easy getting to the fuel rail and getting them out. I like your idea.

You have to pull the rail to swap the injectors anyway - and it is a bit of a PITA. I’d probably just have the new injector on hand. The high resistance on that injector pretty much says it all.

Left work at lunch today to do this. Well, got the rail out no problem. took about an hour.
then went to my favorite auto parts store, only to find out, no in stock. Got the same answer at every auto store withing a 15 mile radius (visits, then came home and started calling), not even the three closest toyota dealerships stock this injector.
Lesson: don’t assume that a part you are going to need is in stock, check before dissambley.

A used injector from an auto recycler / junkyard is another alternative. If you know what a new one costs, it may help you determine a fair price. Injector failure is rare, so a used one is probably just fine.

Have you tried tapping on #3 with, like, a screwdriver handle? I was about to buy a new injector for my Honda and someone at the parts place (where they did not stock the item, probably because of very low demand) said he tried this on his Chevy pickup and the injector sprang back to life. I did the same and had the same results. Unplugging it and then cleaning the contacts may have also helped. Your ohmmeter readings may indeed indicate an internal electrical fault, but don’t give up on simpler/cheaper solutions.

Lesson: don’t assume that a part you are going to need is in stock, check before dissambley.

Been there, done that, got the T-shirt. Now, I always get the parts I need to do a job before I start. It’s a hard lesson to learn.

lesson learned. this is the first time working on engine parts for a vehicle this young.