Fuel Fuel Injector replacement

gearhead77

Active Member
Mar 13, 2019
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Pittsburgh PA
My 89 5.0 has a stumble at part throttle and idle. I have replaced most everything ignition related except the distributor itself. I'm fairly certain I have a bad injector or two, the car sat for a long time (10 years). I have run all methods of injector cleaner through it (including at the rail) and it improved a little bit , but now its worse, leading me to believe an injector is bad. No codes from the EEC. Car is stock and I plan on keeping it like that or maybe some very minor mods.

- What brand injectors should I get?
- Tips or tricks to getting the top of the intake apart?
-Do new injectors come with all necessary parts or do I need to buy O-rings and such too?

Of course, I have some other seepage at the valve cover gaskets. Should I do those while the intake is apart? Anything else on the top of the engine to deal with while the intake is off?

Any suggestions are welcome, this is my first project car and I'm trying to keep it as it was in 1989 when it left the factory but upgrade when I can.

Thanks.
 
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An option is to send you injectors in for professional rebuild. I did this with the 30's on my LX. They work great and came back with a flow chart showing the recorded performance of each injector. It's also cheaper than buying new ones.

 
Sorry guys, I realize the post is a bit vague and I haven't been able to get here (or to the car) like I've wanted to. Anyway..

89 GT convertible. Stock 69k miles. 5 speed. Largely original.

Starts can be kind of rough, but it will start and remain running on the second try without giving it gas. Mostly.
Idles, but the whole idle is kind of "shaky". The engine is not running that smoothly at idle.
At idle, you can hear a bit of "stumble" in the right side exhaust, but the left bank sounds fine

Low rpm, high load, like right after 1-2 shift at light throttle, there's stumbling, surging and what sounds like backfiring but maybe through the intake? It will improve as revs rise and it will run hard, but it seems like it's struggling to rev.

( This is my first project and while I'm mechanically inclined, its not my job and only recently a hobby!)

Gas mileage is awful, 14 highway at most.

The car sat for a long time (10 years) and was only started and moved minimally during that time.

What I've done so far:
- New radiator, thermostat, hoses, belts, fan and fan clutch (the radiator was bad when I bought it, so I figured I might as well replace stuff while it was all apart)
- New plugs, wires, cap and rotor, all Motorcraft. New coil is coming soon
-New fuel filter. I've also run every manner of fuel system cleaner through it, including at the rail
-Replaced the missing PCV valve and filter
-Cleaned IAC and EGR valves
-New Air Filter. The MAF sensor is cracked at the top to housing of the sensor itself. No codes either KOER or KOEO for anything.
- I can't find any vacuum leaks at this point.

The reason I *think* its injection is that it started running better as I ran it and ran fuel system cleaner through it, but the last time I ran it, it seemed worse.

Thanks in advance, mods if you want to move this some place else that's OK.
 
Car car sitting for 10 years cannot be fixed by running cleaner through it. Good job on the cooling system rebuild, now it's time to do the fuel system. Drop and inspect the tank, new pump, any hoses, new filter. Blow the crap out of the fuel lines.
Now about the computer not giving any codes, if you get no codes, nothing, na-da, something is amiss.
 
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Car car sitting for 10 years cannot be fixed by running cleaner through it. Good job on the cooling system rebuild, now it's time to do the fuel system. Drop and inspect the tank, new pump, any hoses, new filter. Blow the crap out of the fuel lines.
Now about the computer not giving any codes, if you get no codes, nothing, na-da, something is amiss.

Thanks for the fuel system tips. I have one of those EEC computer testers and it just gives me the "Everything is OK!" codes. I've done both KOEO and KOER tests multiple times and I can hear the car cycling through the various tests.
 
Run the cylinder balance test process at the end of the code running procedure. When the final KOER codes are done spitting out, give the throttle a 50% blip and release. This will trigger the CBT in which the ECU will disable the injectors one at a time and check the o2 sensors to see how they respond. If one cylinder is not contributing properly, it will spit out a number 10-80 for the corresponding cylinder (20 is cyl 2 for example) or a 90 meaning all cylinders are equal.

If one cylinder comes up bad, swap the injector with another cylinder and rerun the CBT. See if the code follows the cylinder. If not., it could be compression that is the cause.

You can also take a multimeter and test the injectors. They should measure 14.4 ohms if good.

Then you can take a 9V batter with connector and leads and touch to the power leads of each injector. The injector should click. If you have a FP guage, cycle the key to build pressure and turn off. WHen FP is stable, activate the injector with 9V and see if the FP drops slightly.
 
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Run the cylinder balance test process at the end of the code running procedure. When the final KOER codes are done spitting out, give the throttle a 50% blip and release. This will trigger the CBT in which the ECU will disable the injectors one at a time and check the o2 sensors to see how they respond. If one cylinder is not contributing properly, it will spit out a number 10-80 for the corresponding cylinder (20 is cyl 2 for example) or a 90 meaning all cylinders are equal.

If one cylinder comes up bad, swap the injector with another cylinder and rerun the CBT. See if the code follows the cylinder. If not., it could be compression that is the cause.

You can also take a multimeter and test the injectors. They should measure 14.4 ohms if good.

Then you can take a 9V batter with connector and leads and touch to the power leads of each injector. The injector should click. If you have a FP guage, cycle the key to build pressure and turn off. WHen FP is stable, activate the injector with 9V and see if the FP drops slightly.

Awesome!! Thank you so much for this write up!
 
I'm not sure in my 25+ years in this hobby, I've ever seen a stock 19lb injector fail.
I've also found that almost all stumbling is ignition related, I can't see a reason at part throttle an injector wouldn't work and at full throttle it would...
Pip, distributer, and worst off all the TFI are usually the issue.
 
I had one fail.

Car had a stumble and vibration at 3k rpm. Did the CBT and it pointed to a cylinder. I tested the ohms and it was open. Replaced the injector and cylinder was alive again.
 
I'm not sure in my 25+ years in this hobby, I've ever seen a stock 19lb injector fail.
I've also found that almost all stumbling is ignition related, I can't see a reason at part throttle an injector wouldn't work and at full throttle it would...
Pip, distributer, and worst off all the TFI are usually the issue.

What is the PIP? I'm aware that the other parts mentioned could be suspect too. I was going with easy/cheap first. Most of my wrenching on cars is of the plug and play variety, so I took care of the easiest items first just to get it on the road to see what else I had going on.

I know it's probably rare for stock injectors to fail, even after 30+ years, my concern is that since I didn't bring this car back to life the right way ( drain gas tank, etc.) that some crud could have clogged an injector. I read somewhere else that they can get gummed up, especially from sitting and that the injector might be too gummed up to function right.
 
PIP = Profile Ignition Pickup


Thank you! I see where it lives. Seems like a bit of a PITA to deal with.
 
Run the cylinder balance test process at the end of the code running procedure. When the final KOER codes are done spitting out, give the throttle a 50% blip and release. This will trigger the CBT in which the ECU will disable the injectors one at a time and check the o2 sensors to see how they respond. If one cylinder is not contributing properly, it will spit out a number 10-80 for the corresponding cylinder (20 is cyl 2 for example) or a 90 meaning all cylinders are equal.

If one cylinder comes up bad, swap the injector with another cylinder and rerun the CBT. See if the code follows the cylinder. If not., it could be compression that is the cause.

You can also take a multimeter and test the injectors. They should measure 14.4 ohms if good.

Then you can take a 9V batter with connector and leads and touch to the power leads of each injector. The injector should click. If you have a FP guage, cycle the key to build pressure and turn off. WHen FP is stable, activate the injector with 9V and see if the FP drops slightly.

Finally got around to running cylinder balance test. #8 is apparently not playing with the other 7 cylinders. 91 KOER code tells me it’s running lean, so I suspect the injector is bad. No other codes or issues, no CEL. I’ll try some of the other tests 5L5 mentioned above to narrow down.

Should I have to replace the injectors, besides injectors and o-rings, what else do I need to purchase? What other items should I replace with the upper intake manifold off the car? Finally, should I drop the tank at all?
 
Since it sat for 10 years I would drop the tank and clean it real good, if you have a helper it is not too hard of a job. Why take the chance of clogging a new injector. Also may want to replace the rubber on the filler neck while its out, they tear easy as they get old. Also if the valve covers are leaking I would replace them when you pull the upper intake it is a lot easier to pull the covers with the top of the intake off. Pulling the top of the intake is not that hard either. Be prepared to replace a few vacuum lines if they are old and hard.
 
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I would start at one end, being the fuel tank, drop it, inspect and replace pump, filter and any associated rubber parts, blow out the lines including the fuel rail, done. Then move on to the vacuum lines.
Once and done.
I can't tell you how many times someone comes in here and posts problems that would not be if they would have done this when dealing with a car that has sat for many years.
 
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I recently got a set of injectors cleaned from an online outfit for 100$. This service included new o rings and caps too. You could replaced that one injector.. or just have them all cleaned. Probably not a bad idea considering the age of them anyway. JMO.
 
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