Extremely Low Mpg...why???

[rideapony]

Now, I have removed all the smog system long time ago, removed the rear crossover pipe from the heads and plugged the holes on the heads with a couple of setscrews, do hot air still coming out from the center of the head to the intakes? If so how to plug those holes? My lower intake gaskets have no holes.

Please advice. Thank you all!!!

 

[rideapony]

Well I found answer to my inquire. Fel-Pro has an article that says, "No need to modify the 1250S3 gaskets to install the plugs, the gaskets will do the job and survive the crossover function"
.
I found out some interesting thing that obviously I'm guilty of. With the new set of 1250S3 gaskets I put them over the intake mating surface and to my surprise and embarrassment I installed the old one WRONG!!!

The old set looks like they shifted under torque but they didn't. I installed them up side down. I put some weatherstrip glue any ways just to prevent possible sliding. at back and rear I put a Ultra black silicon strip, I just snug the nuts and will let it set about 12 hrs before doing final torque to specs.

I really don't think there was a vac leak but itf it was it should be corrected . Will see what it does after everything is together and fired up.

Usually I take problematic matters very seriously, and this is not the exception. I learn and fix the problems.

Thank you all

 

[Noobz347]

Let us know how it turns out drives. It should be a different animal.

 

[General karthief]

Well I found answer to my inquire. Fel-Pro has an article that says, "No need to modify the 1250S3 gaskets to install the plugs, the gaskets will do the job and survive the crossover function"
.
I found out some interesting thing that obviously I'm guilty of. With the new set of 1250S3 gaskets I put them over the intake mating surface and to my surprise and embarrassment I installed the old one WRONG!!!

The old set looks like they shifted under torque but they didn't. I installed them up side down. I put some weatherstrip glue any ways just to prevent possible sliding. at back and rear I put a Ultra black silicon strip, I just snug the nuts and will let it set about 12 hrs before doing final torque to specs.

I really don't think there was a vac leak but itf it was it should be corrected . Will see what it does after everything is together and fired up.

Usually I take problematic matters very seriously, and this is not the exception. I learn and fix the problems.

Thank you all

Why wait 12 hrs before torquing the manifold?

 

[Noobz347]

Why wait 12 hrs before torquing the manifold?

Read above

 

[rideapony]

you're right Noobz347, it better be a different animal or else!

I've been reading articles left and right, I follow the things that make sense and ignore the ones that don't.

I will allow the Ultra Black RTV to set before doing the final torque. Right now the silicon is already sandwiched and only applied about three pounds of torque evenly. If I do final torque before the silicon sets I will squeeze it out of the mating surfaces.

Will see how it works out

 

[rideapony]

Udate:
Up and running and it seem to be doing the same, vacuum is 9 in and have a hunting idle.

So I adjusted timing to 12* and speed up the idle to 850 - 900 rpm. I see about 12 in of vacuum.
I did this with the IAC unplugged and at normal temperature, TPS is at 0.985 Volts.

Disconnected the negative terminal at the battery to reset the computer and still doing the same hanging .

One weird thing I noticed is that even with the IAC disconnected and while doing the throttle stop adjustments and I stab the throttle the revs go up and stay there for a few seconds and then drops to the set idle speed, why is it doing that? is this considered "Hanging"??? Why is hanging without the IAC? Could I have a bad PCM???

I also tried to set the base idle using the 0.010" filler gauge but once I reset the computer and connect the IAC it just idles way too low, and hangs up high while shifting dropping to idle until get to full stop.

please I want to hear your opinion about this.

Thank you all!!!.

 

[General karthief]

What computer do you have in the car

 

[rideapony]

I have A9L

 

[Mustang5L5]

Why are you blocking the center ports to the intake that feed the EGR? The EGR does contribute to cruising fuel economy somewhat, so blocking this ports in essence eliminates the EGR and will results in a slight worsening of fuel economy.

Since that seems to the be the main intent of this thread, it makes no sense to do this.

 

[rideapony]

Well following chronology steps, there was a massive vacuum leak at the EGR valve. Thinking that that was the problem of my low vacuum which also contributes to low fuel economy, I removed the EGR valve and replaced the spacer with a thinner plate. Since my low vacuum problems persisted I went and removed the lower intake and as I was ready to re-assembly I found out that the Fel Pro 1250S3 gaskets don't have a cutout for the EGR passage from the head, and since the valve was not there already left it blocked. And the results as updated, were that low vacuum numbers still the same.

That's the latest situation, I must say that I still think there is a vacuum leak but, where???

Today I intend to run a compression test on a cold engine and see what numbers I get. Would that give a possible internal vacuum leak indication?

At this point I rule out a leak under the low intake because I followed every suggestion at installation meticulously.

Even though it is quite of work I really don't mind to remove the LIM again if I have to re install the EGR but I would like to focus on this potentiallly mysterious vacuum leak.

Please comments and or suggest.

Thank you all!

 

[rideapony]

I just ran a compression test. I warmed up the engine for about 15 minutes, removed all the plugs, and unplugged the coil and fuel pump relay, and then proceeded with the test. The results are NOT good

Compression test results:
# 1.- 120 Dry
# 1.- 148 Wet
# 2.- 135
# 3.- 135
# 4.- 130
# 5.- 110 Dry
# 5.- 140 Wet
# 6.- 138
# 7.- 135
# 8.- 135

Cylinder # 1 is borderline good but # 5 is definitely out of specs. What do you guys think?

A few days ago I ran a cylinder balance test and it was good.

So where should I go from here???

Please advise or suggest. Thank you

 

[rideapony]

Sorry I ran out of the initial topic, unfortunately here is where the whole thing took me. Now with this new issue I might have to put new rings and do all the bearings to freshen it up.

Thank you all