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1995 Mustang V6 - Cyl #3 Misfire - Help!

  • Thread starter Thread starter JasonBlue
  • Start date Start date Aug 30, 2023
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JasonBlue

Member
Aug 30, 2023
16
3
13
South Alabama
Aug 30, 2023
#1
  • Aug 30, 2023
  • #1
Hello Everyone-
I have searched around and have been unable to find possible solutions to my problem.
To start off, I acquired the car about a year ago, with about 60k miles. It sat for an extended length of time before I acquired it. When I first got it, I was told it had an oil leak. After inspection, it did have a bad oil leak, as the oil sending unit was broken and oil pouring out. I repaired this, and drove the car roughly 1k miles with absolutely no issues at all.
Then, on my way back from a trip, the car overheated. The needle never got to the red, but it did get close, and as I was in a very bad location, I had to continue driving a short distance, after turning the heater on (which I believe kept it from getting into the red), before I could pull over.
As I was slowing down to pull over, the car died. At this point, I knew I was screwed.
Skipping ahead, I took both heads to the machine shop, and they did shave a small amount off of them (I can't remember exactly how much they said). There was no coolant in the oil, and there was no oil in the coolant, but I had very low compression on multiple cylinders. Also, I had to replace the cooling fan, as low speed was gone.
I cleaned up the rest of the parts, and not familiar at the time with the head gasket issues plaguing these engines at the time, I replaced the gaskets, and put it all back together. Filled back up with antifreeze/water, got all the air out, car would run. But initially, it ran really good. Soon, it developed a small skip/misfire, which over the period of a couple weeks, progressively got worse. Temperature stayed normal during all this time.
I ordered better head gaskets, the 3 layer gaskets for the 99 V6, and tore it all back down and installed new gaskets again, from the heads up.
The skip/misfire is still here, and the DTC is still saying Cyl #3.
I put a small amount of oil in Cyl #3, tested compression, and the compression was a small amount higher, but not by much. So at this point, I'm not certain, but I am thinking my rings are alright.
Also, while cleaning and putting it all back together, I did lap all valves, and they all appeared to be in great condition (visually).
I have ruled out fuel injectors (swapping #3 and #4 injectors), checked 3+ times visually and with starting fluid for vacuum leaks, finding none. Ruled out spark plug wire by replacing with new ones. Ruled out spark plug on Cyl #3 (even though I did put new ones in), I swapped #3 with #4 anyway just to make sure.
What are my chances of a cracked/warped lower intake?
Any other ideas or suggestions?

Thanks in advance!
 

General karthief

wonder how much it would cost to ship you a pair
20+ Year Stangneter
Aug 25, 2016
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polk county florida
Aug 30, 2023
#2
  • Aug 30, 2023
  • #2
Compression on #3 cylinder is what compared to the others?
 
J

JasonBlue

Member
Aug 30, 2023
16
3
13
South Alabama
Aug 30, 2023
#3
  • Aug 30, 2023
  • #3
It's very low I am sure, based on my compression tests after the first head gasket change.
But, I am currently at work, and when I get off, I will test all cylinders again and post the results.
Should be in about 2 hours, considering the rain holds off long enough.
 
Reactions: General karthief

General karthief

wonder how much it would cost to ship you a pair
20+ Year Stangneter
Aug 25, 2016
27,935
10,575
203
polk county florida
Aug 30, 2023
#4
  • Aug 30, 2023
  • #4
No hurry
I'm here all week
 
J

JasonBlue

Member
Aug 30, 2023
16
3
13
South Alabama
Aug 30, 2023
#5
  • Aug 30, 2023
  • #5
Alright, compression test results as follows, and they aren't so great:
Cyl 1 - 185
Cyl 2 - 155
Cyl 3 - 90
Cyl 4 - 95
Cyl 5 - 140
Cyl 6 - 190

I did fail to mention that I do refer to the FSM for torque specs and I do properly torque each and every bolt per spec.
 

General karthief

wonder how much it would cost to ship you a pair
20+ Year Stangneter
Aug 25, 2016
27,935
10,575
203
polk county florida
Aug 31, 2023
#6
  • Aug 31, 2023
  • #6
Numbers 3 and 4 are not good but not likely to cause a skip, can you do a leak down test on those two?
 
J

JasonBlue

Member
Aug 30, 2023
16
3
13
South Alabama
Aug 31, 2023
#7
  • Aug 31, 2023
  • #7
Yes, it will be tomorrow, as I will have to pick up a tester after work.
I will post back with the results.
 
J

JasonBlue

Member
Aug 30, 2023
16
3
13
South Alabama
Sep 2, 2023
#8
  • Sep 2, 2023
  • #8
Leak down results are as follows:
Cyl 1 - 20%
Cyl 2 - 76%
Cyl 3 - 92%
Cyl 4 - 92%
Cyl 5 - 70%
Cyl 6 - 28%

It was difficult to hear where all the air was going, but in all cylinders except #3, the air was escaping through the valve cover, where I took of the oil filter cap. I could clearly feel the air blowing out here.
Cylinder 3, most of the air is escaping through the intake manifold out the air intake, in which I could clearly feel it escaping here.
I'm not an experienced mechanic, I am learning a lot as I go through all this. But how is this car running so well? It has a bad skip especially at lower rpms, and backfires through the intake some. At higher rpms (2500-400) it's fairly smooth and has a good bit of power.
 

General karthief

wonder how much it would cost to ship you a pair
20+ Year Stangneter
Aug 25, 2016
27,935
10,575
203
polk county florida
Sep 2, 2023
#9
  • Sep 2, 2023
  • #9
Things happen faster at higher RPMs (duh) so the miss/skip is not noticeable,
Swap the #3 plug with another and check if a code follows
 
J

JasonBlue

Member
Aug 30, 2023
16
3
13
South Alabama
Sep 2, 2023
#10
  • Sep 2, 2023
  • #10
I did. Actually twice. Code stays with cylinder 3.
 

General karthief

wonder how much it would cost to ship you a pair
20+ Year Stangneter
Aug 25, 2016
27,935
10,575
203
polk county florida
Sep 2, 2023
#11
  • Sep 2, 2023
  • #11
Swap plug wires?
 
J

JasonBlue

Member
Aug 30, 2023
16
3
13
South Alabama
Sep 2, 2023
#12
  • Sep 2, 2023
  • #12
The set I had on only had about 2k miles on them, but to rule them out, I did replace the whole set. Made no difference.
 

General karthief

wonder how much it would cost to ship you a pair
20+ Year Stangneter
Aug 25, 2016
27,935
10,575
203
polk county florida
Sep 2, 2023
#13
  • Sep 2, 2023
  • #13
Cap?
 
J

JasonBlue

Member
Aug 30, 2023
16
3
13
South Alabama
Sep 2, 2023
#14
  • Sep 2, 2023
  • #14
Cap? what cap?
 

General karthief

wonder how much it would cost to ship you a pair
20+ Year Stangneter
Aug 25, 2016
27,935
10,575
203
polk county florida
Sep 2, 2023
#15
  • Sep 2, 2023
  • #15
Individual coils?
Shows what I know about these cars.
Swap coils?
 
J

JasonBlue

Member
Aug 30, 2023
16
3
13
South Alabama
Sep 2, 2023
#16
  • Sep 2, 2023
  • #16
One coil pack.
Brand new, it was one of the first things I replaced trying to find the problem.
 

General karthief

wonder how much it would cost to ship you a pair
20+ Year Stangneter
Aug 25, 2016
27,935
10,575
203
polk county florida
Sep 2, 2023
#17
  • Sep 2, 2023
  • #17
We are missing something
Can you start the car and let it idle, turn out the lights and look for a spark jumping across coil or wires?
 
J

JasonBlue

Member
Aug 30, 2023
16
3
13
South Alabama
Sep 2, 2023
#18
  • Sep 2, 2023
  • #18
Not seeing anything. Even checked again making sure they are snug fitting on each end and followed them end to end.
 

General karthief

wonder how much it would cost to ship you a pair
20+ Year Stangneter
Aug 25, 2016
27,935
10,575
203
polk county florida
Sep 2, 2023
#19
  • Sep 2, 2023
  • #19
Got me now, let me look around see if I can find anything similar.
Sorry I'm not much help.
 
D

dcm0123

5 Year Member
Mar 11, 2017
94
30
28
Sep 4, 2023
#20
  • Sep 4, 2023
  • #20
Possibly cam lobe is bad?
Never heard of this happening on a car with roller lifters but not much left to check.

Did you replace the O-rings on the fuel injectors?
You may also want to try replacing the connector on the #3 fuel injector.

You may have a vacuum leak off the engine which leans it out causing a misfire which only shows up on #3. Check hoses going to the fuel tank vent and canister. Check to see if purge valve is stuck open.
 

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