Fuel Fuel Injector replacement

Interesting plot twist: I checked the spark plug for condition for the #8 cylinder. I had just replaced them last year, one of the first things I did when I got the car. It was wet, like running rich. I decided to pull #5, which was the easiest one to reach on the same bank. Looked normal. Swapped the plugs (8 to 5, etc.). Started car and let it run. Seemed smoother.

Ran KOER (no codes)and cylinder balance test after car warmed up. Showed number 5 as being the one with the problem! Went and bought one new plug, installed it and drove car around to warm it up. Smoothest it’s ever been, but still a misfire here and there, not like before though. Ran cylinder balance test and it was 90 90 80. So I suspect #8 injector is still bad, but I would have never thought a brand new plug would be bad. (And yes, I had checked and checked again to make sure connections were tight, etc.).

General karthief said:

Change the #8 plug wire

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Yeah, pretty dumb of me not to go down that road! Cheapest to most expensive and complex things right? Thanks.

Learnin’ all the time with this project. So I tried karthiefs suggestion.

Out of all the chain parts stores (except NAPA, I didn't try them) , only Autozone will sell you one plug wire. Kind of a tricky thing to navigate on their site, you need to know the length (28DQ for the number 8 cylinder on a stock car!) but can be done. Even the clerk there was like “well, we don’t sell many of these single wires.”. But for chasing down a problem for cheap ($2) I was glad for the option. The guy was like " This was a headscratcher as I tried to fill your order ( I did "Pick up in store) because we don't sell many of these single wires."

The issue is not resolved though. I just ran it about 70 miles, mostly highway and it's still not 100%. But the misfire happens much less often now and the idle is much smoother. Last cylinder balance test was all 90's, but I think the issue is more intermittent than it was previous. I'm considering replacing all the plug wires with a new set, even though the set I have is a year old (Motorcraft).

I might just end up re-doing the fuel system anyway. The sending unit appears to have stopped working because the gauge never leaves full now. It wasn't accurate before, it certainly isn't now. If I have to drop the tank for that, might as well do other stuff.

91GT, no smoke on start, but the start can be a bit rough. It starts, but not always smoothly when cold. Hot starts, no problem.

Fuel pressure is around 35 psi at the rail, I'm not sure the accuracy of the Harbor Freight fuel pressure tester. Max is 39 I believe I read in the service manual.

Thanks for all the help so far.

Monkeybutt2000 said:

I bought an 87 LX back in 97". Car had a funky idle I could never figure out. Well, bit the bullet and bought new injectors, they were like $200 back then! After replacement,the car ran like new,huge difference.

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Yeah, I’m fairly certain it needs done. The car sat for 10 years and noob that I am, I figured just running the bad gas out of it would be enough. I was just trying to exhaust all cheap and easy options before tearing the upper intake off.

Reman 19 lb injectors are about $35 (Rock Auto price). Might go with the Accels or the AFIS ones Summit has.

So, if anyone finds this thread or any of the other three, I did pull my upper intake off, remove my injectors and drop the tank. Tank is being refurbished by a local shop and I've got a new pump, sending unit and fuel filter all ready to go. The tank wasn't terribly bad, but if you haven't stumbled on my other thread, it was something I didn't feel I could do a decent job with.

My injectors are on their way back to me. It'll be one week since I mailed them out Friday last week, so I expect them Monday. The following is from email sent by the shop that did the flow and cleaning (www.injectorrepair.com).

The email from the shop:

Your set of eight OEM Ford injectors flow tested bad right out of
the box (after an initial exterior cleaning / de-greasing). During the
initial flow test; one of the injectors was significantly clogged. It
was not the injector that you had labeled #8. Good news was that they
all held pressure (no leaks).

The engine would not have been able to run well with these
injectors.

I see this all the time esp. with engines that have sat for a
long time unused, or were run with E85. After an extra long session in
the cleaning tank and back-flushing, I was able to get the injectors to
like new function (good spray pattern and flow rates).

An Injector Flow Balance of under 5 % is considered necessary for
proper engine performance. When I sell refurbished sets, I try to get
them flow matched at one to three percent flow balance.

The closer the flow rates of the injectors are to each other, the
better the engine will run, and the engine will run smoother and get
better miles per gallon.

The microfilters were clean. After removing the microfilters, the
injectors were clean on the inside. No noticeable debris came out of the
injectors when I back-flushed two of the injectors. The discharge tips
were clean for a used set of injectors.

Attached are pictures of some of the multiple flow tests I ran on
your set of injectors. Picture # 1269 is of the initial dynamic flow
test (before cleaning). Picture # 1273 is of the final flow test after
the ultrasonic cleaning sessions. I ran all tests multiple times.

Your injectors final flow tests improved, and were great !! The
dynamic flow test ( 12 ms pulse width / 2400 rpm / 25 seconds ) had flow
rates of 48 to 49 cc.s across the board. The injector flow balance is
now very close to
2 %. Good to go.

They all performed flawless in all the tests.

All of your injectors held pressures over 80 psi without leaking
a drop, and their spray patterns were good.

They are 100% ready to be put into service.

If you have any questions, give me a call or email anytime.

Take care, Jim
Injector Repair LLC

I'm sure I could have gotten OK results cleaning them myself, but probably not as good as this place did and not with the technical background/equipment. It was worth it to hear how these injectors were from someone who deals with these things all the time. Can't wait to get it all back together and running! This place is up near Schenectady NY for the east coast folks.