Replaced Heads And Cam, Now Cylinders 5, 6, And 7 Aren't Firing

  • Sponsors (?)


Could you describe what all-thread is? I've never heard of it before
Threaded rod, great for making low strength fasteners of odd lengths.

Before going to the trouble of taking the intake off, do a compression test. If the rocker arms are too tight, the affected cylinders won't run.

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 with a plastic screwdriver handle between the throttle butterfly and the throttle housing. 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.

I generally use a big screwdriver handle stuck in the TB between the butterfly and the TB to prop the throttle open. The plastic is soft enough that it won't damage anything and won't get sucked down the intake either.

A battery charger (not the trickle type) is a good thing to have if you haven't driven the car lately or if you have any doubts about the battery's health. Connect it up while you are cranking the engine and it will help keep the starter cranking at a consistent speed from the first cylinder tested to the last cylinder.



If you do have to remove and replace the manifold gasket, here's a very useful tip.

My favorite trick that saves time and effort is the stay in place gasket. Be sure that you scrape (don't use a wire brush) all the old gasket material off, then clean all the surfaces with acetone or MEK.

When the surfaces are clean, use weather strip adhesive on the head to manifold surface. Also use the weather strip adhesive on the side of the gasket that mates to the head. When you are done, the head surface and the gasket surface that mate together will have weather strip adhesive on them. Follow the instructions on the tube or can and when it gets tacky, press the gasket down on the head.

Clean the area where the rubber rails mount to the block in front and in the rear with more acetone or MEK and do the same trick with the weather strip adhesive that you did to the heads.

Coat the rubber seals and the gasket area around the water passages with lots of Blue Silicone gasket sealer and put it together. Bingo! no leaks, and no gaskets that shifted out of place.


Ask Nicoleb3x3 about the intake gasket that slipped out of place and caused idle and vacuum leak problems that could not be seen or found by external examination. Spay everything with anything you have, and you won't find the leak...
photodisplay.php
 
  • Like
Reactions: 1 user
Answer these questions and let's see how far down the rabbit hole you are going

thread sealer on the lower intake bolts?
Did you use new head bolts or reuse the old ones?
What sequence did you tighten the head bolts and in what order?
What head gaskets and did you install them with the front towards the fron and with the word FRONT up?
since you didnt measure pushrod lenghth, did you at least measure for proper preload and how many turns past zero lash did you go before getting the proper torque on the rockers?
How did you align the timing chain and gears
what intake gaskets did you use and did you use the cork end gaskets
Did you put RTV around any of the head ports
Did you install the intake gasket dry or use some permatex like product to keep it in place
what order did you tighten the intake bolts and in how many sequences.
Did you get the motor to TDC prior to installing the distributor
Do you have spark on those 3 dead cylinders
Are the spark plugs fouled, wet

At the minimum you have a bad vacuum leak, most likely due to your intake. The fact you have 3 dead cylinder and gas in the oil is because you are not firing on 3 cylinders and washing down them which can wipe out your bottom end quickly. Assembling an engine without a manual or experience to know how to do it right is asking for trouble. This could be a very costly learning experience.
 
  • Like
Reactions: 1 users
Answer these questions and let's see how far down the rabbit hole you are going

thread sealer on the lower intake bolts?
Did you use new head bolts or reuse the old ones?
What sequence did you tighten the head bolts and in what order?
What head gaskets and did you install them with the front towards the fron and with the word FRONT up?
since you didnt measure pushrod lenghth, did you at least measure for proper preload and how many turns past zero lash did you go before getting the proper torque on the rockers?
How did you align the timing chain and gears
what intake gaskets did you use and did you use the cork end gaskets
Did you put RTV around any of the head ports
Did you install the intake gasket dry or use some permatex like product to keep it in place
what order did you tighten the intake bolts and in how many sequences.
Did you get the motor to TDC prior to installing the distributor
Do you have spark on those 3 dead cylinders
Are the spark plugs fouled, wet

At the minimum you have a bad vacuum leak, most likely due to your intake. The fact you have 3 dead cylinder and gas in the oil is because you are not firing on 3 cylinders and washing down them which can wipe out your bottom end quickly. Assembling an engine without a manual or experience to know how to do it right is asking for trouble. This could be a very costly learning experience.
I'm fairly certain it's a vacuum leak from the intake manifold, I sprayed carb cleaner on the intake manifold on the side where the three cylinders aren't firing and rpms jumped instantly. I'm going to take the intake manifold off and put rtv on both sides of the gasket and see if that fixes it. Thanks for all the help
 
I'm fairly certain it's a vacuum leak from the intake manifold, I sprayed carb cleaner on the intake manifold on the side where the three cylinders aren't firing and rpms jumped instantly. I'm going to take the intake manifold off and put rtv on both sides of the gasket and see if that fixes it. Thanks for all the help
It seem that you didn't see the stay in place gasket tip in my post. That is the best bet to get the gasket to stay in place.
 
  • Like
Reactions: 1 users
I'm fairly certain it's a vacuum leak from the intake manifold, I sprayed carb cleaner on the intake manifold on the side where the three cylinders aren't firing and rpms jumped instantly. I'm going to take the intake manifold off and put rtv on both sides of the gasket and see if that fixes it. Thanks for all the help

Ok. since you dont want to answer any of my questions, I'm outta here. I will leave you with this final thought.Putting RTV on both sides of an intake gasket is the best way to distort it and cause a gasket leak. They go on dry with some permatex to hold them in place. Good luck with your build.
 
Answer these questions and let's see how far down the rabbit hole you are going

thread sealer on the lower intake bolts?
Did you use new head bolts or reuse the old ones?
What sequence did you tighten the head bolts and in what order?
What head gaskets and did you install them with the front towards the fron and with the word FRONT up?
since you didnt measure pushrod lenghth, did you at least measure for proper preload and how many turns past zero lash did you go before getting the proper torque on the rockers?
How did you align the timing chain and gears
what intake gaskets did you use and did you use the cork end gaskets
Did you put RTV around any of the head ports
Did you install the intake gasket dry or use some permatex like product to keep it in place
what order did you tighten the intake bolts and in how many sequences.
Did you get the motor to TDC prior to installing the distributor
Do you have spark on those 3 dead cylinders
Are the spark plugs fouled, wet

At the minimum you have a bad vacuum leak, most likely due to your intake. The fact you have 3 dead cylinder and gas in the oil is because you are not firing on 3 cylinders and washing down them which can wipe out your bottom end quickly. Assembling an engine without a manual or experience to know how to do it right is asking for trouble. This could be a very costly learning experience.

No thread sealer
Old head bolts
Tightened head bolts from center, then the bolts just to the right, then to the left, then outer right, then outer left. Started from a low torque all the way up to 72 pounds.
Fel pro head gaskets with front up and forwards.
Measured proper preload.
Timing chain was aligned dot to dot cam at 6 and crank at 12 did not use cork end intake gaskets.
Intake bolts tightened from inside to outside, just like heads in three sequences.
Motor at tdc with distributor installed with pointer facing number one spark plug wire.
Three dead cylinders do have spark and compression, plugs are wet when I pull them out.

I didn't know you meant answer them on the post, thought you meant answer to myself
 
Threaded rod, great for making low strength fasteners of odd lengths.

Before going to the trouble of taking the intake off, do a compression test. If the rocker arms are too tight, the affected cylinders won't run.

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 with a plastic screwdriver handle between the throttle butterfly and the throttle housing. 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.

I generally use a big screwdriver handle stuck in the TB between the butterfly and the TB to prop the throttle open. The plastic is soft enough that it won't damage anything and won't get sucked down the intake either.

A battery charger (not the trickle type) is a good thing to have if you haven't driven the car lately or if you have any doubts about the battery's health. Connect it up while you are cranking the engine and it will help keep the starter cranking at a consistent speed from the first cylinder tested to the last cylinder.



If you do have to remove and replace the manifold gasket, here's a very useful tip.

My favorite trick that saves time and effort is the stay in place gasket. Be sure that you scrape (don't use a wire brush) all the old gasket material off, then clean all the surfaces with acetone or MEK.

When the surfaces are clean, use weather strip adhesive on the head to manifold surface. Also use the weather strip adhesive on the side of the gasket that mates to the head. When you are done, the head surface and the gasket surface that mate together will have weather strip adhesive on them. Follow the instructions on the tube or can and when it gets tacky, press the gasket down on the head.

Clean the area where the rubber rails mount to the block in front and in the rear with more acetone or MEK and do the same trick with the weather strip adhesive that you did to the heads.

Coat the rubber seals and the gasket area around the water passages with lots of Blue Silicone gasket sealer and put it together. Bingo! no leaks, and no gaskets that shifted out of place.


Ask Nicoleb3x3 about the intake gasket that slipped out of place and caused idle and vacuum leak problems that could not be seen or found by external examination. Spay everything with anything you have, and you won't find the leak...
photodisplay.php
I was following up until the point where you said clean the area where the rubber rails mount to the block in front, what rubber rails?
 
I was following up until the point where you said clean the area where the rubber rails mount to the block in front, what rubber rails?
Most gasket kits include a rubber rail for the front and rear of the intake manifold where the manifold mates up against the engine block
 
We are all very knowledgeable. Each one of us could probably walk you through an entire engine teardown and rebuild.

We try not to give any advice unless we have a decisive answer.

You messed up on the intake.
-remove the intake
-Clean surfaces
Go buy 5/16 all-thread at the hardware store, cut them longer than the bolts for the intake.
-Install the gaskets with a smear of rtv around the water jackets, then screw the all thread into the bolt holes. (No need to do every one of them 4 will do)
Slide the intake over the all-thread this will ensure that everything lines up correctly.
-install the intake bolts then removing the all-thread and replace it with the correct bolts.
-re-torque intake and install plenum ect ect.




Good luck

Could you describe what all-thread is? I've never heard of it before

You can also get an intake manifold stud kit. Not as cheap as all-thread, but a lot less work. Cheapest would be from Speedmaster on Ebay.

Most gasket kits include a rubber rail for the front and rear of the intake manifold where the manifold mates up against the engine block

I (and a lot of other technicians I know) throw those rubber pieces of crap away and put a bead of RTV in their place at the ends of the intake. Not saying that's what happened here, but it's as good an idea as any.

I'm going to take the intake manifold off and put rtv on both sides of the gasket and see if that fixes it. Thanks for all the help

RTV on your intake gaskets anywhere but the cooling passages isn't a good idea. Gasoline eats it over time, you'll be buying yourself more trouble for later. If you want to put a sealant on the gasket surfaces themselves (and a lot of people will argue it's not necessary, but I do it on older engines when I work on them), use Indian Head Shellac (it's usually on the bottom shelf of the chemical aisle below the RTV in most parts stores in little brown bottles).

If @jrichker comes across as a know-it-all, it's because he pretty much is. I work on cars for a living, have for years, but if I'm dealing with an old 5.0/302 and something's eluding me, I look through his posts and find the answer.
 
  • Like
Reactions: 1 users
You would have oil leaks there, not a misfire.
So like I said before, I sprayed carb cleaner on the intake manifold on the driver said and the rpms shot up. So now I'm trying to chase down an intake manifold leak. I'm going to take the intake mani back off and spray some permatex on the gaskets. I took the intake off last night just for giggles to see if the gasket had fell down when it was put on before, and it didn't look like that was the case. I put it back on and made sure the gasket stayed in place, but still had the same problem, and same results with carb cleaner. Do you think I'm on the right track? I've been working on cars for a few years now and never had anything like this happen, it's stumping me
 
I would not reuse the intake gaskets, what intake gasket are you using? New heads? Are your head bolts torque to yield?
Get a spec sheet showing torque patterns for head and intake bolts. Use the all thread to keep gasket in place.
I've never bought intake gaskets that didn't include the end rail pieces, try to get the blue end rail gaskets, they have tabs that keep them in place, use a skim coat of silicon to help seal, if you don't get the blue ones just run a line of blue rtv about 1/4" thick on the rails, make sure everything is clean and dry
 
So I just finished putting the intake back on and cranked it back up.. it's firing on all 8 now it seems, however it won't stay running with the intake on which is the same issue I was having before, it chokes out when I put the intake on. Any ideas for this? It has a good air filter on it
 
I would not reuse the intake gaskets, what intake gasket are you using? New heads? Are your head bolts torque to yield?
Get a spec sheet showing torque patterns for head and intake bolts. Use the all thread to keep gasket in place.
I've never bought intake gaskets that didn't include the end rail pieces, try to get the blue end rail gaskets, they have tabs that keep them in place, use a skim coat of silicon to help seal, if you don't get the blue ones just run a line of blue rtv about 1/4" thick on the rails, make sure everything is clean and dry
The heads are new, and I'm using felpro gaskets. The head bolts are torqued to the proper specs and torqued in the proper pattern and sequence
 
Dump codes sticky

Look at the top of the 5.0 Tech forum where the sticky threads are posted. One of them is how to dump the computer codes. Codes may be present even if the CEL (Check Engine Light) isn’t on. You don’t need a code reader or scanner – all you need is a paper clip, or if your lady friend has a hair pin, that will do the job.
I highly suggest that you read it and follow the instructions to dump the codes. http://www.stangnet.com/mustang-forums/threads/how-to-pull-codes-from-eec4.889006/
 
Pictures. Plz
pictures of the heads?

Dump codes sticky

Look at the top of the 5.0 Tech forum where the sticky threads are posted. One of them is how to dump the computer codes. Codes may be present even if the CEL (Check Engine Light) isn’t on. You don’t need a code reader or scanner – all you need is a paper clip, or if your lady friend has a hair pin, that will do the job.
I highly suggest that you read it and follow the instructions to dump the codes. http://www.stangnet.com/mustang-forums/threads/how-to-pull-codes-from-eec4.889006/
Ill do that, I hadn't done it yet because I figured it would be throwing so many codes I wouldn't be able to figure out what was actually causing it. On top of the fact that it wont run with the intake on, its backfiring through the intake as well, I can hear it popping.
 
The engine does not need to be running to dump the codes.



Backfiring out the intake is either a valve stuck open or a lean mixture or spark plug wire(s) connected to the wrong cylinder(s). Check compression on all cylinders and then look for vacuum hoses loose, cracked, or misconnected. Check the line for the vapor recirculation system – it is easy to knock loose and not see it when you connect the air pump plumbing. If the vacuum line for the EGR valve and the air pump are cross connected, some very strange things can happen. Check the mass air flow electrical connection and see that it is tight, the same goes for the fuel injection wiring harness connectors up on top of the manifold near the firewall.

Sticking valves: If a intake valve is bent, has a bad spring or is misadjusted, the engine will sometimes backfire through the intake. Use a vacuum gauge connected to any convenient spot on the intake manifold. Run the engine at 1000 RPM & look for 18-21 inches of vacuum with a steady needle. A problem intake valve will make the vacuum gauge needle sweep 5-10 inches.

Lean fuel mixture breaks out into several sub categories:
A.). Vacuum leaks
B.) Air entering the intake without passing through the MAF on Mass Air cars (89-95 models).
C.) Failure of the MAF, BAP/MAP (Baro or Manifold Air Pressure, same sensor, different name), ACT (air charge temp), or ECT (engine coolant temp). These should set a code in the computer.
D.) O2 sensor problems: one or both O2 sensors with low output or bad O2 sensor heater ground. This should set codes 41/91. The O2 sensor heater ground is an Orange wire in the engine mounted fuel injector harness. Ground it to the back of the head or intake manifold.
E.) Leaking exhaust gases from EGR valve at WOT or EGR opening when it should not be open.
F.) Poor fuel delivery due to bad fuel pump, clogged filter or bad fuel pump wiring. Look for low pressure or fluctuating pressure. Standard injector pressure is 39 PSI at idle, with the vacuum line disconnected from the regulator and capped.
G.) Clogged fuel injectors.- see the cylinder balance test below
H.) Fuel injector wiring problems causing injector not to deliver rated flow (dirty or stuck shut injectors).
I.) Computer problems: (computer problems are not common like sensor problems)
J.). ROM has bad data in fuel or timing table. This should also set a code in the computer.
K.) Failure of one or more of the computer's driver transistors for the fuel injectors. No code set on this one. Use a noid test light to test the injector wiring & injector drivers,
L.) MAF calibration off or mismatched to injectors.
M.) ACT or ECT bad. Sometimes the sensors will be off calibration, but not bad enough to set a code. If they falsely read too high a temp, the engine will back off fuel delivery.

The HO firing order is 1-3-7-2-6-5-4-8.
Non HO firing order is 1-5-4-2-6-3-7-8

attachment.php?attachmentid=51122&d=1183977187.gif



Vacuum leak due to slipped lower intake manifold gasket...

Ask Nicoleb3x3 about the intake gasket that slipped out of place and caused idle and vacuum leak problems that could not be seen or found by external examination. I don't care what you spray with, you won't find the leak when it is sucking air from the lifter valley. It simply isn't possible to spray anything in there with the lower manifold bolted in place.

photodisplay.php




Cylinder balance test:
See the procedure below to dump the codes and place the computer into diagnostic mode.

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

Dump the codes: Codes may be present even if the Check Engine Light (CEL) isn't on.

Dumping the computer diagnostic codes on 86-95 Mustangs

Revised 26-July-2011. Added need to make sure the clutch is pressed when dumping codes.

Codes may be present even if the check engine light hasn’t come on, so be sure to check for them.

Here's the way 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. You watch the flashing test lamp or Check Engine Light and count the flashes.

Post the codes you get and I will post 86-93 model 5.0 Mustang specific code definitions and fixes. I do not have a complete listing for 94-95 model 5.0 Mustangs at this time.

Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. On a manual transmission car, be sure to press the clutch to the floor.
Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.

Underhoodpictures007-01.jpg


Underhoodpictures010.jpg


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.

attachment.php


The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

attachment.php


The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.


WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems. This is crucial: the same wire that provides the ground to dump the codes provides signal ground for the TPS, EGR, ACT and Map/Baro sensors. If it fails, you will have poor performance, economy and driveablity problems

Some codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off, and clutch (if present) is pressed to the floor, and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see Equus - Digital Ford Code Reader (3145) – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.