1973 Grande Build

[cjstaci]

The vacuum reading is low and the needle is bouncing and the exhaust sounds rough. I would make sure the EGR isn’t stuck open. I would check each cylinder for spark. If you find the spark is good but you find a cylinder is not producing power, then check it for fuel. If it has fuel then do a compression check and leak down check. You can also remove a valve cover and observe rocker arm and pushrod movement.

 

[Steve McMahan]

I’m going in a slightly different sequence; here are the 8 plugs organized by cylinder, upper left starts 1-4, bottom row 5-8. All look fuel fouled and smell like unburned fuel 15 hours after I turned the engine off:


Next 4 pics are cyl 1-2, 3-4, etc





I’m going to do the static compression test, will post those results.

BTW, I did test the EGR valve, it holds vacuum, and I did ca a leak test around the valve stem to stem interface and it was a tight seal. The low vacuum I’m worried is compression related, so I’ll know very soon.

 

[Steve McMahan]

Ok, so static compression test results are, from 1 to 8:

130, 140, 130, 130, 140, 115, 135, 110

So, cylinders 6 and 8 are lower than the average, with 8 the lowest. But, enough to account for the very low vacuum?

Since I have the gt-40 intake, pulling the valve covers is a much bigger job.

And just to make sure I’ve said this, I’ve done a very complete smoke test and have no visible leaks AND have verified the integrity of all vacuum devices.

What causing my low vacuum? If one of both O2 sensors were sending wrong or none data, could that produce these conditions; very rich mixture combined with low vacuum?

 

[Sheriff41]

Check to make sure you don't have a couple plug wires crossed. Cheap and easy to check off the list.

 

[73MustangCoupe]

Those plugs look like what I pulled when the Rickster was running really rich. In my case, it was a very small leak in the exhaust about 6 inches behind the O2 sensor. I had to run smoke up the tailpipe to finally find it. What a PITA. In your case, it may not be a leak, but a bad O2 sensor, but don't rule it out completely, just yet. Cleaning the plugs will definitely help with it starting and running more smoothly. As I said before, I'm not an expert, but have fought these issues in the recent past, and finally got them sorted, so I hope my suggestions help.

 

[Steve McMahan]

Yes, it seems, whatever the problem is, the plugs tell the story that it’s affecting all of the cylinders, not one or two. So, O2 sensor fault fits the narrative. But, and I’m hoping some of the more experienced engine folks read this over; does that add up to a low vacuum reading? I mean the smell test says it’s running rich, all 8 plugs say it running rich, but I’ve had that before and had above average vacuum. Thinking how the EEC-IV system responds to a high Ox signal, it adds fuel, but does it do anything, like retard timing, or increase air via the idle speed solenoid? I’m don't know, but I suspect someone does.

 

[Cleveland Crush]

Ok, so static compression test results are, from 1 to 8:

130, 140, 130, 130, 140, 115, 135, 110

So, cylinders 6 and 8 are lower than the average, with 8 the lowest. But, enough to account for the very low vacuum?

Since I have the gt-40 intake, pulling the valve covers is a much bigger job.

And just to make sure I’ve said this, I’ve done a very complete smoke test and have no visible leaks AND have verified the integrity of all vacuum devices.

What causing my low vacuum? If one of both O2 sensors were sending wrong or none data, could that produce these conditions; very rich mixture combined with low vacuum?

Looking at those plugs I imagine the O2 sensor is probably coated just as bad. No way the O2 sensor will give anything close to an accurate reading. Also, are you running the correct plug heat range?

 

[boilermaster]

Steve,
Suggest after cleaning or those nasty spark plugs that you simply unplug both oxygen sensors to keep you in open loop.
EEC1V can and will foul o2 sensors with no codes stored.
Usually a giveaway is that the system goes into closed loop way too fast.
When I worked at the dealership, I had made a set of o2 jumpers to measure live o2 voltage.
each and every time that I ever saw spark plugs that bad with both o2 sensors bad, there was also a fuel issue, dirty fuel injectors with Teflon contamination in the fuel rails.
I see that you have had issues with injector seals, have you flushed the fuel rail and cleaned all 8 injectors ?.
There are ways to reverse flush ford injectors to remove Teflon from the injectors and their screens.
A typical injector cleaning will NOT remove Teflon from an injectors screen.
If you find Teflon in your fuel rail, be sure to replace the Teflon o rings on both quick connectors.
Boilermaster

 

[Steve McMahan]

The spark plugs are NGK TR55-1GP. Those spec out to be a standard replacement for the 87 TBird 5.0 Sport. On the injectors, I did a complete rail and injector cleaning when I first tested the new fuel system and found a leak at one of the injectors. I removed the rails and steel lines down to the connectors, at the bottom of the engine. I replaced the inlet filters on each injector (I didn't see anything in any of them), and replaced both of the “O Rings” at the connection points. I flushed the rails and tubes with a whole can of brake cleaner. Nothing came out of them when I did that.

Just for info, the cars been running like this since I first started it. It didn’t have a solid idle, etc and had the strong fuel smell from the start. I suspect what’s wrong was wrong before I dropped it into the 73. And, for some reason, I cannot get my OBD-1 tester to work. I’m going to try and see if I can borrow or rent one that’s know good. Or, break out the old VOM with a sweeping needle to do the testing the old fashion way.

New Bosch O2 sensors arrive on Tuesday.

 

[cjstaci]

Those plugs aren’t gonna fire, clean them or replace them. As Cleveland Crush said the o2 sensors are most likely fouled. How’s the spark? Possible weak coil or ignition module? Is the fuel fresh?
If it’s computer related, maybe mass airflow sensor, fuel pressure regulator, o2 sensors.
When you cold start does it run okay in open loop? If so, that might indicate a sensor issue when in closed loop.
I am sure you will figure it out, it’s just a matter of how much hair you have to pull out.

 

[Steve McMahan]

Great questions: I’ve got great spark, I replaced the thin film ignition item on the distributor before I started this process, as I understood it would reduce the hair pulling later. I have a Speed Density system, not MAF. I did replace the Manifold pressure sensor because the original unit has a slight leak in its ability to hold vacuum. My fuel is 100 percent new. My pressure regulator seems to be working, have checked it twice at 38 psi.

I‘m not sure about the open/closed loop several of you have mentioned. I think you mean, open as in running from the presets of the computer, and closed, using the various sensor inputs to adjust idle, AFR, etc. Since I cannot get my OBD-1 tester to function, I’m kinda flying blind. If I cannot find one to rent, I’m gonna have to bite the bullet and buy one.

I‘m not sure if this helps, but from cold start, I turn the key, let the fuel pump bring the system to pressure, turn the key, starts instantly, then rough idle, bit of a lope, but steady at 750, and 12” of vacuum. So, maybe that answers the open loop question?

One question I did have, is the intake suppose to get hot at idle? I have the get-40 intake, and yesterday when I put my hand on the top, it was hot to the touch. I have no idea if that’s normal, just another observation.

 

[cjstaci]

Try a fresh set of spark plugs (basic autolite), start it up, see how it runs, shut it off before it warms up (avoid closed loop) and pull the plugs for inspection. My guess is the plugs won’t be wet fouled. Reinstall them, run the engine to normal temp and see what happens. If the plugs wet foul again, then I think vacuum leak. If the O2 sensor sees too much oxygen then the computer will compensate with more fuel.
I know you did a smoke test, but were you only checking for external leaks? Smoke in the crankcase??? Possible lower intake manifold leak???

 

[Steve McMahan]

Today I did more smoke testing. I tested both sides of the dual exhaust and found one leak at the passenger shorty header to down pipe. That leak was before the O2 sensor, so I hope tightening that and eliminating the leak will help. No leaks on the drivers side. I guess it’s possible to have a lower intake leak, as I never removed that in the engine swap.

 

[AcesArneson]

Hmm, cold would indicate to me that either your spark timing is mixed up on two cylinders on that side or your fuel pulses are not getting the injectors to open up properly or could be mixed up too, easy thing to do when the wiring has been pulled and re-installed in another car. Listening to the videos there is way more pressure coming out of the hot pipe. Does your EFI use wasted spark ignition? Maybe it has a failed coil? Have you verified spark on every cylinder? In aby event, before you start that car again I would change the oil, running rich passes fuel into the oil system and your engine will wear prematurely. Do you have lean/rich indication gauges? You could always just swap the injectors on the drivers side for the ones on the passenger side to verify the injectors are not the problem.

Is there a check-valve between your recovery cannister and the valve cover to prevent a loss of vacuum at idle? I seem to recall some mention of this for idle when using an EFI system. Your old cannister may not have the required equipment for blocking this line when the engine is cold and the Tbird cannister might be required. The valve might not be a check valve and could be a vacuum activated or ECM actuated valve either on the cannister or the valve cover manifold. You could test it by blocking in the recovery line when you first start up on cold idle. If your problem goes away, that's where your leak is.

Another thing you may want to look at is the difference between alternators. The first Gen alternator in the 73 required an external voltage regulator on the dash for your cluster and if you are using the Tbird alternator you likely have a gen 3 alternator which means you will need to upgrade your main voltage generator as well, they are not the same so hopefully you used the one from the Tbird. You can tell it is not gen 1 or 2 by simply looking at the alternator to see if the cooling fan blades are external. Pretty sure from Gen 3 on they are internal. If you have a gen3 you might want to ensure you don't have too much voltage on your cluster. Check to see if your ammeter gauge, that was stock on the 73, works. This is a common failure point in the gen 1 Stangs and can cause a dash fire because this gauge is wired to your dummy gauge on the cluster and requires the resistance from that gauge light to work properly. Do a google search on 'gen 1 to gen 3 alternator conversion for 73 Mustangs' and you will likely find some articles on the change over for full details. You get a lot more current when you need it which can be used for upgraded EFI components eg fuel pump etc... but depending on your configuration you may need to rewire some of the feeds to and from the alternator as well as running a 4 gauge wire to ground to the chassis and engine/tranny ground.

 

[Steve McMahan]

Lots to consider. I have a bone stock, 1987 Ford Speed Density EFI system. The complete drive train from tje donor 87 TBird was installed in the 73. I don’t believe it has any special waste spark system, although I don’t know what that is. I’ll do a cylinder by cylinder test to ensure I have spark. When I tested the stock 87 coil, it produced a very healthy spark. A long time ago I realized the purge valve activation might be a cause of the vacuum leak and I’ve temporary disconnected it, and yes, my vacuum canister has a check valve that works.

I have a Gen 2 Alt which is working great (has built in Reg). All of my dash lights and warnings seepms to be working as required.

I’m not convinced I have a one or two cylinder issue because all the plugs look exactly the same. You would expect good cylinders to look different from those causing the issue, if that was the causal factor. I agree with you that something that effects all the cylinders is the likely issue, like a bad O2 sensor(s) or the ECU isn’t working, or it’s in limp mode. I’m unable to make that simple determination because I either have a from the factory defective OBD1 tester or I’m too stupid to understand how it works. I follow the directions to the letter and the results of pressing the test button is no results.

I’ve posted a message on StangNet, hoping someone with OBD1 experience can help me. I understand this is the 71-73 forum, so not as much experience in testing these older Ford EFI systems.

I‘m gonna replace both the O2 sensors next week after doing the cylinder spark test. If that fails, I will likely purchase a new OBD1 tester and go from there. Thank you for your help.

 

[AcesArneson]

If the sensors are new it is likely not the sensors. Do your sensors have 3 or 4 pins? If they have 4 pins they are grounded to the ECU. If they have 3 pins they are grounded to the tailpipe which would likely be your problem. 3 pin sensors need a solid ground on the tailpipe to ensure good communication with the ECU that is where I would start.
As I understand it you have placed your battery in the trunk. Do you have solid 4 or 6 guage ground wire attached to the chassis and the engine/transmission? Ground loops will form all over your electrical system if there is insufficient grounding to the battery. I would run a temporary ground wire directly from the battery and attach it as close as possible to the O2 sensors then fire up the car. If this solves your problem you need better grounding.
Where did you attach your chassis ground and your engine/transmission ground? This is the first thing a tuner will look for if your car runs rich
The O2 sensors need heat to switch back and forth from lean to rich. If you are trying to diagnose these issues at idle you won’t produce enough heat to activate them. Get the hot and see what happens.
I was very serious about the rich fuel affecting your oil in my previous post. Pull your dipstick and smell the oil, if it smells like gas get rid of it before you cause irreparable harm to your cylinders.

 

[Steve McMahan]

Ok, great questions. I have three wire O2 sensors. The ones I currently have are the ones that came with the car, in unknown condition. On the TBird ECU harness, they had their own separate ground attachment point of the back of the block, one for each side.

Regarding grounds, I have one at the battery, connected to the rear frame rails, a dedicated #2 wire going to the engine compartment which connects to the block and the drivers apron, to mimic the wiring from the TBird. My ground from the block to the frame is part of the drivers side ground; an integrated wiring that came from the TBird harness. Also, the ECU has two separate grounds, one to the frame, and one to the engine block, per the way it was wired from the TBird.

I pickup the oil yesterday to change it. While the engine is not new, I don’t want to add to my issues. Thank you so much for the questions. My new O2 sensors arrive next Tuesday; got a great deal from Rockauto with a close out on two Boush direct replacements.

 

[AcesArneson]

Ok, great questions. I have three wire O2 sensors. The ones I currently have are the ones that came with the car, in unknown condition. On the TBird ECU harness, they had their own separate ground attachment point of the back of the block, one for each side.

Regarding grounds, I have one at the battery, connected to the rear frame rails, a dedicated #2 wire going to the engine compartment which connects to the block and the drivers apron, to mimic the wiring from the TBird. My ground from the block to the frame is part of the drivers side ground; an integrated wiring that came from the TBird harness. Also, the ECU has two separate grounds, one to the frame, and one to the engine block, per the way it was wired from the TBird.

I pickup the oil yesterday to change it. While the engine is not new, I don’t want to add to my issues. Thank you so much for the questions. My new O2 sensors arrive next Tuesday; got a great deal from Rockauto with a close out on two Boush direct replacements.

I looked up your HEGO and it is 3 pin. If your O2 sensors are not new and you have good grounding then it is likely your sensors are gone and your new ones will do the job. If you warm up the engine on new oil and don't see a performance change just try to run an extra ground wire from the ECU grounding points on the engine to the tail pipe. I think I recall your tailpipe was welded on the sections close to the engine so grounding should be good but you never know until you try.
The stock hp of those 5.0's in 87 was listed at 150hp. If you ever decide to rebuild the engine there is a ton of potential there. If you stick with your original heads make sure you get them ported and the valves ground. Likely will need a cam and a bit more lift to get more air in there. I imagine this is all already covered under stage 2 or 3 of your plan. Those GT40 intakes are so cool, I tried to get one fit on my Cleveland when I could not find a standard intake for my rebuild during Covid. There is a couple companies that sell adapter plates to get the 302 intake on a Cleveland. I found a company in the US that specializes in porting those GT40 style intakes so that you don't choke off the potential of the reworked heads and a new cam. Their name is Bigdogs Porting and they are only on Facebook. They take a while to complete the work because they are so busy but the savings you get from them is worth the wait. Plus their experience is in doing these intakes, so they are the ones you want to do it.

 

[AcesArneson]

Since you already have the wiring all hooked up you could also consider an newer ECU with more speed if you ever do rebuild that motor. You will be getting into the world of tuning so cost is going to go up unless you have a tuner friend. The EEC-V from a 2003/4 Crown Vic or Lincoln Town car is about the fastest available that is easily self-tunable (you will need a Moates Quarterhorse). I am pretty sure the pinout changes but you only need the one device, the EEC-V is also the ECU which is a change from the EEC-IV. The integrated circuitry and faster clock speed give you instantaneous control of your fuel. Plus the ability to tune your transmission shifts on an electric transmission like a 4R70W is pretty cool too. If you go looking for a 4R70W make sure you get one with the Essex bellhouse pattern (costly mistake I made), they were on the 2003/4 V6 Mustangs. Mine even has a slot for the cabled speedo so I can keep all the original dash gauges. If you want more info on tuning capabilities checkout EFIDynoTuning. The guys name is Cypher and he can guide you on your journey.

 

[Steve McMahan]

Thanks guys for the great advice. Tomorrow, I’m going to try and remove one of the last potential source for a vacuum leak, the PVC valve. I’ve already isolated every other connected source with no change. I didn’t see anything in the compression check that would lead me to think the motor cannot create at least 17” of vacuum. After several discussion with others on other forums, I’m beginning to believe my problem with low vacuum is mechanical in nature. If it turns out to be the PVC, and it’s a new one with a new rubber insert, what would you do next?

If isolating the PVC doesn’t improve the idle vacuum, the only other known vacuum leak source is the idle air control valve. There is no easy way to isolate that, as far as I know. The other sources of leak are the manifold. I’m trying so hard not to do that, for now.