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Can Fuel Injectors Test For Normal Ohms But Still Be Bad?
I drove my car not too long ago and I've been have sporadic idle and stalling issues. I just had a theory. Can fuel injectors test for normal or great Ohms but perhaps be falling some other way (such as either poor flow or leaking)?
I know even when warm all 8 injectors test perfectly for 16 Ohms. I'm going to throw my fuel pressure gauge on the car tomorrow and tape it to the windshield and go for a short drive. I'm wondering if they either have poor flow or they are perhaps leaking (which may explain the burning smells). Last night, after my car sat for 6+ hours, I smelt fuel on the driver's side.
Fuel Pump, Fuel Sending unit and fuel pressure regular have all been replaced. Charcoal canister was rebuilt with the inline valve and hose replaced. I feel like I am getting close to solving this mystery.
Re: Can Fuel Injectors Test For Normal Ohms But Still Be Bad?
they can leak and they can clog.. in addition if injectors are dirty they will not low within spec. So the answer to your question is that injectors can have other issues besides a bad coil
Re: Can Fuel Injectors Test For Normal Ohms But Still Be Bad?
...Or streaming, or dribbling, and still pass a flow test. Or stuck, clogged, rusted, and not flow anything. All while checking out just fine for resistance.
An injector power balance test is pretty tough to fool, however.
Re: Can Fuel Injectors Test For Normal Ohms But Still Be Bad?
I posted this on the other thread:Updates. So I did a fuel pressure test. Good news, I was able to test at idle with no problem. Bad news, my fuel pressure gauge isn't long enough to reach my windshield...
Anyway, with the car set to run the fuel pressure climbs to just under 50 psi and hovers around 47 or so. After 10 minutes it's around 45. With the car running. When started it drops to 40 even and after about 2 to 3 minutes, it drops to 37-38 psi. It remained there for 15 minutes until I shut off the car. I let the car sit for 10 minutes and fired it up the second time. The car did the sporadic idle thing. I ran to go look at the gauge. It only moved slightly with the rev jumps. Basically jumping between 33 psi and 40 psi. After the car settled it hit 38ish and remained there.
Injectors again tested at 16.5 ohms.
I'm guessing it has something to do with the 02 sensor then. That's my only remaining guess. Any thoughts?
Re: Can Fuel Injectors Test For Normal Ohms But Still Be Bad?
Start the engine, let it run for a minute, shut it off, see what the fuel pressure gauge does. It should stay steady for quite sometime. If it is slowly dropping you have a leak, it can be an injector(s) or anywhere along the high pressure side of the fuel system.
Re: Can Fuel Injectors Test For Normal Ohms But Still Be Bad?
Originally Posted by Michael Beck
Start the engine, let it run for a minute, shut it off, see what the fuel pressure gauge does. It should stay steady for quite sometime. If it is slowly dropping you have a leak, it can be an injector(s) or anywhere along the high pressure side of the fuel system.
I did that. After I shut off the car, the fuel pressure shot up to 45 psi. After 10 minutes it was still at 45 psi. After 30 minutes it dropped to 38 psi. After an hour it dropped to around 30 PSI.
I'm assuming that means the fuel pressure is normal? Injectors still at 16.5 Ohms.
Re: Can Fuel Injectors Test For Normal Ohms But Still Be Bad?
Ok, then you don't have leaking injectors, that is normal for the pressure to drop over time.
Now you'll need to do a cylinder balance test or pull the injectors and get them flowed to see if one of more isn't flowing enough.
You can run some injectors cleaner through them first, or get the can that GM sells (or used to) that you put right on the fuel rail and unplugged the power for the fuel pump and let the engine run off that can cleaning the injectors.
Re: Can Fuel Injectors Test For Normal Ohms But Still Be Bad?
Originally Posted by m4bgringo
Ok, then you don't have leaking injectors, that is normal for the pressure to drop over time.
Now you'll need to do a cylinder balance test or pull the injectors and get them flowed to see if one of more isn't flowing enough.
You can run some injectors cleaner through them first, or get the can that GM sells (or used to) that you put right on the fuel rail and unplugged the power for the fuel pump and let the engine run off that can cleaning the injectors.
I'll try injector cleaner first. Do you have a link for that GM injector cleaner? I usually use Technron clear about twice a year.
Before I pull the injectors, I'm going to take my car to an exhaust shop and have them look at that missing 02 sensor. At this point I'm convinced it's that. Most of the evidence is pointing that way.
Awesome. I'm going to order at the end of the week. I'm guessing I putting on right where the fuel pressure gauge attaches? I pull my fuel pump fuse to deactivate that?
Re: Can Fuel Injectors Test For Normal Ohms But Still Be Bad?
If you want to see if you have a leaky injector pull the plugs after you run it...if you have any wet cylinders then you have a leaky injector. Be careful with injector cleaners. Depending on the condition of the injectors and your fuel system if any debris gets dislodged it can go right into the injector
Re: Can Fuel Injectors Test For Normal Ohms But Still Be Bad?
I must have missed that you have a missing O2 sensor?
Stop right there and get that fixed.
Those cars would never run right without the O2 being present.
Re: Can Fuel Injectors Test For Normal Ohms But Still Be Bad?
Originally Posted by m4bgringo
I must have missed that you have a missing O2 sensor?
Stop right there and get that fixed.
Those cars would never run right without the O2 being present.
I have had a few threads going. Basically three months ago, I took my car to a tire shop since my front driver's side tire was flat. My car has been running poorly with the symptoms on my first post. I've been starting threads and trying to chase down the problem. A few weeks ago a few Chevy Truck forums someone posted that the RPM surge is a common symptom of a bad 02 Sensor. So I try looking for it. Can't even find a trace of it. I post another thread asking about that. People tell me it has to be there and to follow the wire. I can't find a wire.
I ask for pictures of what the pigtail looks like instead everyone just post pics of the 02 sensor itself not where it runs too... Awhile people keep insisting my 02 sensor has to be there, I'm just not looking hard enough.
Eventually I find a long pigtail near the brake booster. Someone confirms it is the 02 pigtail. So I get an 02 sensor, I find a bung on the driver's side near the header. It's plugged up with some sort of metal. Nothing can go in and I can't get the metal out... Some have suggested maybe my old 02 sensor snapped off and if that is the case it's the cleanest break of all time.
Nothing on the threads and the pigtail is intact.
So it's been crazy trying to simply trying to find out this problem. Likely next week I'm going to take my car to an exhaust shop since they have to clean out that bung and possible cut out part of the pipe.
However narrowband can still be useful diagnostic tools, it is worth learning how it works. Engine need to run 14.7 to 16.5:1 air fuel ratio to avoid fouling the spark plugs for idle and cruise conditions. For example I always keep 15.2 to 15.8:1 air fuel ratio using wideband sensor, is keeping plugs to last the longest, cleanest plug possible.
The narrowband can only sense 14.7:1 average air fuel across some bank of cylinders. What they call stoichiometric mass to mass air and fuel ratio is purely theoretical, nothing ever can combust using perfectly matched mass ratios using a single sensor because all cylinders are averaged together on that bank and every cylinder is off slightly from perfect. And even if you had one per cylinder the reported ratio is temperature dependent, higher temperatures will report richer air fuel ratios in general. At some high temperature T the wideband will fail altogether and simply report rich no matter what, they are often installed at some minimum distance from the turbine or engine, unlike narrowbands which tend to be very close to the engine and partially rely on engine exhaust heating to perform faster or better. They often won't work well when cold and you should be aware of any cold-temperature situations such as sitting at a stoplight or idling in neutral after a cold start, the narrowband will not function properly. It may take 15minutes to warm well enough or not even warm up enough at all until you drive it around to put some heat into the narrowband sensors.
If you can understand narrowband and wideband output, it will help you diagnose all engines, they only need 3 things spark fuel air and the wideband/narrowband looks at 2 of those. You can usually look at a wideband gauge and know immediately if there is some issue with fuel combustion quality, it is a handy gauge to have on an engine.
Narrowband switching action is meant to be digital in nature. Either *ON* or *OFF*. 0 or 1 volt, 995mV to .005Volts for example is a typical range. It can of course .028v and .112v or similar, doesn't need to be zero exact, that is the point of digital anything even close to zero assumes a zero by the ECU
03-29-2022, 05:23 PM
