88 Mustang Gt No Power, Sputters Etc.

bhoove40 · Jul 12, 2017

Hello all, I've read through this website for a long time now but have never posted anything. I recently did a motor swap on my 88 Mustang because it was not running right by any means. The new motor was free from a family friend and was taken from a crate. After installation and a few thousand in extra new parts, the car is still running like it did before.

I've done the timing at 10 btdc and slowly adjusted it about 30 times with multiple people (with knowledge) and it still doesn't want to run.

We can get the car to idle well at 900 RPMS and when we rev it without a load it revs up nicely (not going over 2500 for sake of the flat tap cam..). However, when we drive it down the street it can't get out of its own way. Letting the clutch out and coasting is fine but when you hit the gas it jumps forward slightly and backfires, has no power, and won't even gain RPM. Instantly assume it's out of time but that just can't be it .

I took out the plugs the other day and their all black, I'm not sure if their from setting the timing or not but I cleaned them and replaced them...

FOR NEW PARTS :
new distributor, fuel pump, fuel filter, new coil pack, plugs (.52), ford racing wires, maybe some other things I'm forgetting...

IN THE MOTOR:
mild cam, different lifters , overall a mild build by a professional who built motors for my step father for 35 years .regardless of that, it is running exactly like it did before I changed the motor.. This is a Speed density car , not MAF.

Any help is appreciated I think I have tried everything in my knowledge , anything you can help me with help a ton! Thank you

SOLVED: Fuel pump was only putting out 18 lbs of PSI thank you for the info guys!

-Blake

General karthief · Jul 12, 2017

A little more info.
Stock intake
What firing order is the cam, note: I realize this likely has nothing to do with the problem(s) but you need to know it.
Have you looked for codes
Did the car run good and then started going down hill or did you get it running bad
Is it originally a V8 car
Does it have the same type of trans it originally came with
There are other factors in play but this is a start.

bhoove40 · Jul 12, 2017

karthief said:
A little more info.
Stock intake
What firing order is the cam, note: I realize this likely has nothing to do with the problem(s) but you need to know it.
Have you looked for codes
Did the car run good and then started going down hill or did you get it running bad
Is it originally a V8 car
Does it have the same type of trans it originally came with
There are other factors in play but this is a start.

The car has always been a V8. It was running exactly like it is now BEFORE i changed the motor. However, from what i can remember the car ran decent when i bought it and progressively got worse over the next year until i let it sit and hardly played with it for 2 years. I then decided to take my family friend up on this offer on the new motor. having these problems with old motor and now new motor. But, i can now rule out the old motor being junk, i still can't find my problem.
It has a cold air intake (The intake manifolds are both stock)
the cam firing order is 1-3-7-2-6-5-4-8.
I have looked for codes, sadly i do not have a scanner. I did this before i let it sit and all the codes where miscellaneous and to my knowledge had nothing to do with the car running. ( i can take it somewhere possibly).
Same trans that was in the car and it is the T5 manual trans.
--
After some more research i'm leaning towards the fuel injection system. I checked my fuel pressure 2 years back and it was 38 pounds... ( i replaced the fuel pump and filter back then because i thought that was the issue). However, i have never checked the injectors. I emptied the gas via the fuel pump from the bleeder on the fuel rail yesterday and replaced it with fresh.

General karthief · Jul 12, 2017

First order of business is to make sure all the grounds are in place and have good connections, there are four under the hood and one in the passenger kick panel where the computer lives. There is a surging idle checklist Jrichker and a few others that contributed put together that can help you narrow down your problem, it will tell you about cleaning connections and checking sensors. It's in the tech/how to section, click on the tech/how to and scroll down to the checklist.

jrichker · Jul 12, 2017

Speed density and a 347 stroker do not play well together. Here's why...

Speed Density uses Manifold vacuum (MAP), Throttle position (TPS) and RPM, & Air Temperature (ACT) to guess how much air the engine is pulling in. Then it uses all of them plus the O2 and ECT sensors to calculate the air/fuel mixture. It is dependent on steady manifold vacuum and minimal changes in airflow from the stock engine configuration to maintain the proper air/fuel ratio. Change the airflow or vacuum too much and the computer can't compensate for the changes, and does not run well. Forget about putting a supercharger, turbocharger or monster stroker crank in a Speed Density engine, because the stock computer tune won’t handle it. Every time you seriously change the airflow through the engine, you need a new custom burned chip to make the engine run at peak performance.

Mass Air uses a Mass Air Flow meter (MAF) to actually measure how much air is being pulled into the engine. The computer uses this information and inputs from the O2, TPS, ACT, ECT, RPM and Barometric Pressure (Baro) sensors to calculate the proper air/fuel ratio. It is very tolerant of changes in airflow and vacuum and tolerates wild cams, high flowing heads, and changes in displacement with minimal difficulties. Larger injectors can be used with an aftermarket calibrated MAF or a custom dyno tune. This makes it possible to use the stock computer with engine displacements from 302-408 cu in, and make many modifications without a custom dyno tune chip. Put a new intake manifold on your 331 stroker and the computer figures out how much more fuel to deliver without having to have a new chip burned to accommodate the extra airflow.

First step BEFORE you turn any wrenches. Find and fix any code related items that the computer has found. That way you have fixed everything computer related before you make any changes. That eliminates trying to figure out if the problem was already there or was a result of the modifications you made.

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/

When, and only when, you have all of the sensor and wiring problems fixed, then do a Mass Air conversion.

You will need a 76 MM or 80 MM PMASS air meter calibrated for the injectors, a 70 MM throttle body, Trick Flow Track Heat or Edelbrock Performer intake manifold, 30 lb. injectors, 155 LPH fuel pump to match the capacity of the 347 stroker you say that you have.

MASS air conversion instructions from http://www.stangnet.com/tech/maf/massairconversion.html FREE

Revised 2 Aug 2014 to add new links to conversion harness suppliers, diagram for repining computer wiring connector and YouTube video

A9L (5 Speed) computer from junkyard $100-$150
A3M (5 Speed) computer from junkyard $100-$150
A9P (Auto or in a pinch, it will work in a 5 Speed car) computer from junkyard $100-$150
70MM MAF from 94-95 Mustang GT - $40-$70
MASS Air wiring harness kit $30-$85

The whole thing is probably less than $300 using junkyard parts.

A9L computers are 5 speed only
A9P computers are automatic, but will work with a 5 speed.

The conversion harness seems to work well for most folks. It avoids the compatibility problems in using a harness from the junkyard. Simple and cheap, actually less work that swapping the wiring harness.
Conversion Harness kits & parts
http://www.mass-air.com/
http://www.latemodelrestoration.com...ustang-50L-Mass-Air-Conversion-Wiring-Harness

Youtube video how to do a Mass Air conversion using a conversion harness kit (somewhat long but useful)

View: http://www.youtube.com/watch?v=mnnTgXkHU9Q

Wire side 60 pin computer wiring harness connector

Computer side 60 pin computer wiring harness connector

If the idea of moving & soldering wires scares you, here's a list of compatible Mass Air wiring harnesses.

Copied from bbunt302
Just for reference, here's a list of all the compatible years:

89 harness should work for 86-89 as long as you're using mass air.
90 harness will only work in a 90. (because of air bags and dual dash connectors)
91 through early 92 harnesses should be compatible (single dash connector, fuel pump relay under driver's seat)

Copied from the FORD RACING PERFORMANCE PARTS catalog:

PROPERLY SIZING FUEL SYSTEM COMPONENTS

Fuel Pumps
The following information is presented assuming the above information has been taken into consideration regarding BSFC, fuel pressure and specific gravity of the fuel being used. Most fuel pumps for electronic fuel injection are rated for flow at 12 volts @ 40 PSI. Most vehicle charging systems operate anywhere from 13.2v to 14.4v. The more voltage you feed a pump, the faster it spins which, obviously, will put out more fuel. Rating a fuel pump at 12 volts then, should offer a fairly conservative fuel flow rating allowing you to safely determine the pump’s ability to supply an adequate amount of fuel for a particular application.

As previously mentioned, engines actually require a certain WEIGHT of fuel, NOT a certain VOLUME of fuel per horsepower. This can offer a bit of confusion since most fuel pumps are rated by volume, and not by weight. To determine the proper fuel pump required, a few mathematical conversions will need to be performed using the following information. There are 3.785 liters in 1 US Gallon. 1 gallon of gasoline (.72 specific gravity @ 65° F) weighs 6.009 LBS.

To be certain that the fuel pump is not run to its very limit, which could potentially be dangerous to the engine, multiply the final output of the fuel pump by 0.9 to determine the capacity of the fuel pump at 90% output. This should offer plenty of ‘cushion’ as to the overall “horsepower capacity” of the fuel pump.

To determine the overall capacity of a fuel pump rated in liters, use the additional following conversions:
(Liters per Hour) / 3.785 = Gallons
Multiply by 6.009 = LBS/HR
Multiply by 0.9 = Capacity at 90%
Divide by BSFC = Horsepower Capacity
So for a 110 LPH fuel pump:
110 / 3.785 = 29.06 Gallons
29.06 x 6.009 = 174.62 LBS/HR
174.62 x 0.9 = 157 LBS/HR @ 90% Capacity
157 / 0.5 = 314 HP safe naturally aspirated “Horsepower Capacity”

Safe “Horsepower Capacity” @ 40 PSI with 12 Volts
60 Liter Pump = 95 LB/HR X .9 = 86 LB/HR, Safe for 170 naturally aspirated Horsepower
88 Liter Pump = 140 LB/HR X .9 = 126 LB/HR, Safe for 250 naturally aspirated Horsepower
110 Liter Pump = 175 LB/HR X .9 = 157 LB/HR, Safe for 315 naturally aspirated Horsepower
155 Liter Pump = 246 LB/HR X .9 = 221 LB/HR, Safe for 440 naturally aspirated Horsepower
190 Liter Pump = 302 LB/HR X .9 = 271 LB/HR, Safe for 540 naturally aspirated Horsepower
255 Liter Pump = 405 LB/HR X .9 = 364 LB/HR, Safe for 700 naturally aspirated Horsepower

Note: For forced induction engines, the above power levels will be reduced because as the pressure required by the pump increases, the flow decreases. In order to do proper fuel pump sizing, a fuel pump map is required, which shows flow rate versus delivery pressure.

That is, a 255 liter per hour pump at 40 PSI may only supply 200 liters per hour at 58 PSI (40 PSI plus 18 lbs of boost). Additionally, if you use a fuel line that is not large enough, this can result in decreased fuel volume due to the pressure drop across the fuel feed line: 255 LPH at the pump may only result in 225 LPH at the fuel rail.

My Comments:

A lot of people oversize the fuel pump by buying a 255LPH pump thinking that the fuel pump regulator will just pass the excess gas back to the tank. It does, but… Did you ever consider that circulating the fuel around as a 255 LPH pump does will cause the gas to pickup engine heat? What happens to hot gasoline? It boils off or pressurizes the fuel tank! With most of the 5.0 Mustangs having the carbon canister removed or disabled, the car stinks like gas, and the gas mileage drops since the hot fuel evaporates away into the air.

Fuel injector sizing & injector photos

Revised 26-Dec-2014 to add statement about figures are for flywheel HP and not rear wheel HP

Injector HP ratings: this flywheel HP, not rear wheel HP.
Divide flow rating by.5 and multiply the result by the number of injectors. This uses a 100% duty cycle. These ratings are for naturally aspirated engines at the flywheel.

Example:
19/.5 = 38, 38 x 8 = 304 HP
24/.5 = 48, 48 x 8 = 384 HP
30/.5 = 60, 60 x 8 = 480 HP
36/.5 = 72, 72 x 8 = 576 HP
42/.5 = 84, 84 x 8 = 672 HP

The preferred duty cycle is about 85% maximum, so for a safety factor multiply the final figure times .85.

19/.5 = 38, 38 x 8 = 304 HP x .85 = 258 HP
24/.5 = 48, 48 x 8 = 384 HP x .85 = 326 HP
30/.5 = 60, 60 x 8 = 480 HP x .85 = 408 HP
36/.5 = 72, 72 x 8 = 576 HP x .85 = 490 HP
42/.5 = 84, 84 x 8 = 672 HP x .85 = 571 HP

Remember that the above ratings are at 39 PSI. Increasing the pressure will effectively increase the flow rating. Example: a 19 lb injector will flow 24 lbs at 63 PSI, and a 24 lb injector will flow 30 lbs at 63 PSI.

See http://users.erols.com/srweiss/calcpchg.htm to get the calculators used in these examples.

Here's the duty cycle explanation. Duty cycle is how much of the time the intake is open the injectors are turned on. The 85% figure means that for 85% of the time the intake valve is open, the injectors are spraying. The idea is that you want some percentage of the duty cycle left over so that you have some room to grow the process.

If you are at 100% and you need more fuel, all you can do is turn up the fuel pressure. That means the whole fuel curve from idle to WOT is affected. Maybe you are already too rich at idle, and turning up the fuel pressure makes it worse. If you had some injector duty cycle left to play with, a custom tune could use that where it is needed. That would not over richen the whole range from idle to WOT.

If you did turn up the fuel pressure, you might be able to change the injector duty cycle to get the air/fuel mixture ratio you want since the injectors will have extra fuel delivery capability.

With larger than stock injectors or higher that stock fuel pressure, you will need an aftermarket MAF that matches the injector size. The MAF “lies” to the computer to get a fuel delivery schedule that meets the engine’s needs and isn’t too rich or too lean. The best strategy is an aftermarket MAF and a custom tune to insure the best air/fuel ratio over all the RPM range.

Don't forget to increase the fuel pump size when you increase injector size or significantly increase the fuel pressure

Diagram courtesy of Tmoss & Stang&2birds

88 Mustang Gt No Power, Sputters Etc.

bhoove40

New Member

General karthief

wonder how much it would cost to ship you a pair

bhoove40

New Member

General karthief

wonder how much it would cost to ship you a pair

jrichker

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88 Mustang Gt No Power, Sputters Etc.

bhoove40

New Member

General karthief

wonder how much it would cost to ship you a pair

bhoove40

New Member

General karthief

wonder how much it would cost to ship you a pair

jrichker

StangNet's favorite TOOL

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