Performed cylinder balance test....results.

[Mustang5L5]

Fixed a few sensors today and got my car running better....code 11s across the board finally. So I ran a cylinder balance test.


I ran it three times and got results pointing to an issue with cylinder 4 all three times.

I had felt the car was down on power a bit and had an odd shake up to 1500 rpm.

I ran some test on the wires and pulled the spark plug to inspect and all checked out...then I realized I did cylinder 8


Anyway, I guesSs first thing to do tomorrow is check for spark and inspect the plug on cyl 4 which is rear pass side correct?

Assuming all is fine, what next? Injector? Compression test?

Pretty sure I got a spare 19# er sitting around somewhere.

I just hope it's not mechanical. I should prob do a compression test first to confirm it's not mechanical before swapping injector.

 

[jrichker]

Do a compression test on all the cylinders
Take special note of any cylinder that shows up as weak in the cylinder
balance test. Low compression on one of these cylinders rules out the
injectors as being the most likely cause of the problem. Look at cylinders
that fail the cylinder balance test but have good compression. These
cylinders either have a bad injector, bad spark plug or spark plug wire.
Move the wire and then the spark plug to another cylinder and run the
cylinder balance test again. If it follows the moved wire or spark plug,
you have found the problem. If the same cylinder fails the test again,
the injector is bad. If different cylinders fail the cylinder balance test,
you have ignition problems or wiring problems in the 10 pin black &
white electrical connectors located by the EGR.

 

[Mustang5L5]

Okay, did some diagnostic work today. I figure i just document what I did for future reference if someone does a search. Keep in mind, i did the cylinder balance test just to try it out...i wasn't looking for anything specific. I had fixed a couple codes i was having and saw it mentioned in my code readers manual and gave it a shot. I was surprised when it came back with a prob on cyl 4.



Anyway, started with ignition. Hooked a timing light up to the wire and confirmed spark. Swaped a spare wire on and no change. Finally i pulled the spark plug. Looked like it had never seen a drop of fuel in it's short 600-mile life. See where i'm going with this? I swapped the plug around so the "new" plug was on a different cylinder now.

(it looks oil coated but it's not)

Anyway, i had my IR thermometer so i shot all 8 headers and found the other 7 were within 50 degrees or so of each other while the "bad" cylinder was prob half the temp of the other 7. Okay, def have a dead cylinder here now.

Since i didn't have the equipment to do a compression test, i jumped over to the injector. Pulled the plug and confirmed i do have an injector pulse by measuring voltage.

Next, i checked resistance of the injector...and got nothing. Checked some of the other ones, got 13.5-14.5 ohms of resistance, but Open Line on the offending injector. BINGO! In all fairness, i prob could have told it was bad by visual. The other 7 injectors were semi-clean and dry...the bad one was dirty and wet looking.

So, basically i've been running on 7 cylinders for at least a year since i put the car together and over 600 miles. Only clue was the fact that engine had a minor shake from idle to 1500RPM but i thought it could have something to do with the fact i did a t-5 swap and something could have been out of balance? It's possible this prob started when the car was an AOD and i was driving around before like this...6 years ago!


Anyway, not fo find a good used 19#er and get some Horsepower back. I think I have a few spares and even think I have some explorer 19s from an intake I picked up over the winter. Believe it or not, the car ran fine and was decently quick. Since i don't race, i guess i never realized how much power i was losing by having a dead cylinder. Thank god i did the cylinder balance test!!

 

[BlackGT89]

Wow, interesting results and great documentation ! I've got a little engine shake too and it seems to run out of breath easily, but I've got a high mileage engine. Still after seeing this I think I'll investigate further, starting with the infrared themometer test on the headers !

 

[Mustang5L5]

Do it whe yup first start the engine before everything heat soaks. Was pretty easy to see the one cylinder was not firing. 7 cylinders would be 300 degrees and climbing while #4 was about 150 degrees or so (from heating up fro the rest of engine). After the engine gets warm and toasty, everything was pretty much the same temp.

 

[tmoss]

Use the Explorer injectors.........

 

[CDQICKGT]

Hmmm I will be checking as well. My engine has some shake to, I just figured it was from harlem....(lame i know).

 

[Mustang5L5]

Use the Explorer injectors.........

I want to...but unfortunately I only have 6 of them.


Don't really want to mix and match pintle style with disk style.

 

[will1992]

why not i have replaced a bad stock injector with a disc style and it runs great

 

[Mustang5L5]

Well, I just looked them over. One is damaged and unusable and all of them need new pintle caps and o rings. I'll need to pick up three and I'll swap them all in.

In the meantime, I have one clean good newish stock injector ready to go. I would just rather swap it in, get the car running 100% and then take my time getting the other exploder injectors. I kinda want to replace all 8 as the resistance values of the coils on the seven good ones were not consistent. They varied from 12.0 - 16.5 ohms. The explorer ones are new and all at 14.3-14.8 ohms. Just rather have the new stuff now.

 

[will1992]

i just noticed my 92 mustang gt motor shakes i think it has another bad injector i replaced one and it ran good for a while, but after i had it rebuilt it shakes slightly from idle to 1500 rpm. i dont know whats wrong with it i did a cylinder balance test and got a 9 that means its running like it should. my oil smells like gas , and ive already changed the oil once since it was rebuilt and it still smells of gas. i am frustrated and dont know where to look since i got a code 9 however, it runs/ sounds good, but the engine shakes intermittently. could it be an injector is stuck open?

 

[Shaolin Crane]

Mike dont you have a Cobra intake, and some GT40's waiting to go on? Might as well just to 24lb injectors and a new MAF

 

[Mustang5L5]

Mike dont you have a Cobra intake, and some GT40's waiting to go on? Might as well just to 24lb injectors and a new MAF

I do, but I want to drive the car....not turn right now.

Cobra intake is already on.....I have 40ps, cobra roller rockers and a TFS cam waiting.

 

[Mustang5L5]

i just noticed my 92 mustang gt motor shakes i think it has another bad injector i replaced one and it ran good for a while, but after i had it rebuilt it shakes slightly from idle to 1500 rpm. i dont know whats wrong with it i did a cylinder balance test and got a 9 that means its running like it should. my oil smells like gas , and ive already changed the oil once since it was rebuilt and it still smells of gas. i am frustrated and dont know where to look since i got a code 9 however, it runs/ sounds good, but the engine shakes intermittently. could it be an injector is stuck open?

Could be because I just think then balance test turns off the injectors. Put a piece of hhose on the body ofnthe injector and to your ear and listen for the clicking of the injector opening and closing.

 

[will1992]

thanks i never thought of this before, how do i reach the injectors under the intake?

 

[Mustang5L5]

thanks i never thought of this before, how do i reach the injectors under the intake?

Small baby

Good question. Would be hard to get to those. How bout just pulling the plugs to see if any look fuel soaked?

 

[tmoss]

use an automotive stethascope..........

 

[skunk21]

Mike if you are in need of some #19 injectors for now I know I have some good ones around. let me know.

 

[Mustang5L5]

Thanks Chris. I have a single good used injector here. Just gonna toss it in and get the car running 100%. Got the upper intake off, just need to swap it out now.


Funny thing is...i've gotten TWO inspection stickers with the car running on 7. No emissions in MA so it was never sniff tested...but passed visual perfectly fine. Hell, i never even noticed.

 

[HISSIN50]

The CBT looks for a drop in RPM as each cylinder is deactivated. If that contribution is not there, it notices. If the car passes the CBT, the cylinder is making a contribution.