So I just ran a balance test for the first time. First run flashed 8 then 9. Second run flashed 9 then 9. Third run flashed 7 then 6 and flashed that twice. Should I just go straight to compression testing from here or what would you suggest?Cylinder balance test:
Warm the car's engine up to normal operating temperature. Use a
jumper wire or paper clip to put the computer into test mode. Start
the engine and let it go through the normal diagnostic tests, then
quickly press the throttle to the floor. The engine RPM should exceed
2500 RPM's for a brief second. The engine RPM's will increase to about
1450-1600 RPM and hold steady. The engine will shut off power to each
injector, one at a time. When it has sequenced through all 8 injectors,
it will flash 9 for everything OK, or the number of the failing cylinder
such as 2 for cylinder #2. Quickly pressing the throttle again up to
2500 RPM’s will cause the test to re-run with smaller qualifying figures.
Do it a third time, and if the same cylinder shows up, the cylinder is
weak and isn’t putting out power like it should. See the Chilton’s Shop
manual for the complete test procedure
Here's the link to dump the computer codes with only a jumper wire
or paper clip and the check engine light, or test light or voltmeter.
I’ve used it for years, and it works great.
IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.
For those who are intimidated by all the wires & connections,
see http://www.actron.com/product_detail.php?pid=16153 for what a
typical hand scanner looks like. Normal retail price is about $30 or so
Or for a nicer scanner see http://www.midwayautosupply.com/detailedproductdescription.asp?3829 – It has a 3 digit LCD display so that you don’t have to count flashes
or beeps.. Cost is $33.
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.
How to do a compression test:
Only use a compression tester with a screw in adapter for the spark
plug hole. The other type leaks too much to get an accurate reading.
Your local auto parts store may have a compression tester to rent.
If you do mechanic work on your own car on a regular basis, it would
be a good tool to add to your collection.
With the engine warmed up, remove all spark plugs and prop the
throttle wide open, crank the engine until it the gage reading stops
increasing. On a cold engine, it will be hard to tell what's good &
what's not. Some of the recent posts have numbers ranging from
140-170 psi. If the compression is low, squirt some oil in the cylinder
and do it again – if it comes up, the rings are worn. There should be
no more than 10% difference between cylinders. Use a blow down
leak test (puts compressed air inside cylinders) on cylinders that
have more than 10% difference.
See the link to my site for details on how to build your own blow
down type compression tester.
So I just ran a balance test for the first time. First run flashed 8 then 9. Second run flashed 9 then 9. Third run flashed 7 then 6 and flashed that twice. Should I just go straight to compression testing from here or what would you suggest?
koer I got a 41 and 91 then ran the balance test. I also have no idle problems at all. I'm thinking of replacing both o2 sensors and the wiring harness cause it looks like someone hacked into it and wired it all themselves down there.What did you get for the code dumps? Trying to to a cylinder balance with active fault codes is a guaranteed way to get bad results. Fix the fault codes BEFORE running a cylinder balance test.
if the engine will not idle at 650-725 under computer control, the cylinder balance will fail with random results. You cannot just screw the throttle stop in or out to get the engine in the desired RPM range. Fix any idle related problems before trying to run the cylinder balance test.
You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. It includes how to dump the computer codes quickly and simply as one of the first steps. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix.
It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 250,000 hits, which indicates it does help fix idle problems quickly and inexpensively.
Code 41 or 91. Or 43 Three digit code 172 or 176 - O2 sensor indicates system lean. Look for a vacuum leak or failing O2 sensor.koer I got a 41 and 91 then ran the balance test. I also have no idle problems at all. I'm thinking of replacing both o2 sensors and the wiring harness cause it looks like someone hacked into it and wired it all themselves down there.
That won't do anything to fix the 91 code, so the problem needs you to do the testing as it is written ...This was incredibly insightful. Thank you! So instead of going through the trouble of removing the thermacter crossover tubing could I do a test of that by just bypassing the air pump or temporarily plugging the tubing to the H pipe or both?
Understood. Thanks again man!!
So I've dug a bit deeper. I tested fuel pressure and it was 33-34 with vacuum connected and stuck solid at 41 with vacuum off and plugged. I found where that orange wire connects to and it's incredibly caked in dirt as well as you can visibly see it's loose. I can only imagine that's the problem. Anyway, it's pretty difficult to get back there without removing the entire upper manifold. Is there any way I can just cut that, solder in a new ring terminal and ground it some place else? The body?That won't do anything to fix the 91 code, so the problem needs you to do the testing as it is written ...
Yeah, I figured that's what I was going to hear haha. I'm just being impatient and want to actually know if that's what's wrong. I guess I'll be pulling the intake next week. I'll let you know how it goes. Thanks for every one's help!!That wire needs to be grounded to the block.
Pulling the upper intake is a piece of cake, and if affords the opportunity to inspect and replace any vacuum lines as needed, and clean the crap off the lower too.