Are my fuel injectors worn out?

121k miles. Besides inexplicable mpg decline and an otherwise well running machine (doesn’t burn a drop of oil 20 years later), there’s a loader “rumbling” noise at idle. Done the usual good upkeep. When did anyone finally decide their fuel injectors needed changing. Backfires CEL’s or other obvious signs. A “rumbling” idle is supposedly one sign, with no other obvious signs besides less mpg.

 

Got any OBD codes for injector banks?

I check them by removing the injectors one by one with the lines connected (replace the rubber gaskets while you're in there.) Turn the key on which should fire up the fuel pump and pressurize the system. There should be no drip from the injectors. If they're dripping it's time to go. Disconnect the plug wires so it doesn't start, put a can under the injector and crank it over a couple times, see if you have an even atomized spray. I know this is a basic test which really doesn't spell "bad injector" but if it's dripping under pressure or you get a weird spray, it's probably time to get new ones.

edit: Sorry, corrected as below, these don't pressurize with key on (which I'm surprised to hear.) In this case check for drips after cranking it over a few times and checking the spray, the idea is pressurize the system, see if they leak.

 

Someone more knowledgeable than me should chime in but I don't think that the fuel pump on these trucks do any priming until you start to crank. That's why you don't hear it prime when you insert the key before cranking over.

 

Correct.

 

You could be correct, it's just how I've always done it. Now I have to go check LOL.

 

How many miles on the plugs? Has the valve cover gasket ever been replaced? When the truck is idling does the tachometer needle bounce a little bit or is it steady?

 

About 19 months on Toyota brand gapped plugs. Fuel injectors professionally cleaned about the same time. Haven’t paid to have the coils checked. I’m losing about $20 per filllup of now summer blend. That’s around $80 or more per month. I hate it when a system hint is poor fuel economy. It seems that’s a symptom of about 5 different things. Maybe EGR valve or O2 sensor? MAF sensor clean. I put in 2 cans of Berryman’s “Total Fuel System Cleanup.” Tires inflated, stuff like that. No other obvious symptoms to report.

 

Get a cheap blue tooth or wifi OBD-2 adapter and choose a budget friendly phone app (torq, in-car-doctor) and you can see a bit more involving fuel trims and rent a compression tester for free from any parts store that loans out tools for free and do a compression test.

 

Check for vacuum leaks, split hoses etc. Maybe run a scangauge to check fuel trims. I don't think injectors wear out... I changed mine out of boredom around 350,000 miles since I was doing valve covers and had the top off.