Engine 1988 CA mass air GT hesitation 3000rpm and higher

Png1978 · May 10, 2018

Have a slight hesitation/miss when at WOT after about 3k Rpms.
Last until car shifts. Regular driveing seems to be fine although sometimes it seems to do it intermittently at part throttle. I also noticed the car was pinging in &7 and 89 octane but not 91. Timing is at 10.

Plugs are new autolite 25s gapped to 50 it did it on old plugs gapped lower to.
Accelerate coil is new
Wires are new
Mass air has been cleaned
Fuel filter is new

Fuel pump is new although it's a crappy auto part store one that puts out significant less lPH than even a stock pump. I think it's like 78 or something. Was in a pinch to get. Car going. I Have a walboro 155 going in this Weekend.

Car has shorty headers
Blue ford KnN filter with no silencer
Flow master turn downs
Pulleys.

Any thoughts on what this might be? It does it hold and cold so I don't think it's TFI. I do know the stock h pipe pre cat was rattling pretty bad a few months ago. So I'm thinkingit might be fuel pump or the stock cat could be clogged. I did pull codes the other day and it was 41 and 91. Found a vacuum leak fixed it. Still problem there. I was going to pull codes again tonight and also test with the old stock coil since it started a few months after it has well.

Any thoughts or info will help. my money is on the crappy auto parts fuel pump.

General karthief · May 10, 2018

The fuel pump change would be a good idea. Clear the computer, pull the negative battery clamp off while you change the fuel pump and that will clear any codes in the computer then drive it around for an hour or so and then check for codes again. Let us know what you find, for information on checking for codes look in the 5.0 technical/how to threads. There could be codes without the check engine light on.

Png1978 · May 10, 2018

General karthief said:
The fuel pump change would be a good idea. Clear the computer, pull the negative battery clamp off while you change the fuel pump and that will clear any codes in the computer then drive it around for an hour or so and then check for codes again. Let us know what you find, for information on checking for codes look in the 5.0 technical/how to threads. There could be codes without the check engine light on.

cool thanks will do

Png1978 · May 10, 2018

I actually have that exact little code reader in the sticky.

Png1978 · May 11, 2018

Ran codes last night. Engine off None in memory. Will try a engine on test today.

jrichker · May 11, 2018

High speed miss on a warm engine

Revised 7 Nov-2016 to add PIP sensor as possible problem and dumping the codes to help determine if it is the TFI or PIP.

The TFI module mounted on the distributor is one of the culprits for a high speed miss on a warm engine. The other suspect is the PIP sensor inside the distributor. If the problem does not occur when the engine is cold, the TFI module or PIP is definitely suspect. Dumping the codes may help determine which one it is. You may need a special socket to remove the TFI module, but most auto parts stores will have one for $5-$7.

Be sure to use plenty of the heat sink grease on the new TFI and clean the old grease off the distributor.

See Automotive Tools Specialty | Auto Mechanic & Technician Diagnostic, Testing Equipment | Thexton

diagram courtesy of Tmoss & Stang&2Birds

Blown88GT · May 11, 2018

The 70mm maf you got from the junkyard (from a 1992 Lincoln) will not work with California 1988 Mustang EEC-IV

Png1978 · May 11, 2018

Everything I had read said these sensors will work. Is it because it's a CA car?

Png1978 · May 11, 2018

That Theread in the pic on 70mm Mass are said that sensor came on all those cars and will work. I found the same sensor on a 94 3.8 mustang. Are you just saying it won't work on my specific computer?

jrichker · May 11, 2018

Blown88GT said:
The 70mm maf you got from the junkyard (from a 1992 Lincoln) will not work with California 1988 Mustang EEC-IV

Why? what proof do you have that it won't work correctly?

Blown88GT · May 12, 2018

jrichker said:
Why? what proof do you have that it won't work correctly?

1992 Lincoln did not have 19lb injectors.

Png1978 · May 12, 2018

Blown88GT said:
1992 Lincoln did not have 19lb injectors.

The same sensor was in a v6 mustang I looked at. Same number. So is it the sensor or the housing that's calibrated for 19 pounds

jrichker · May 12, 2018

Blown88GT said:
1992 Lincoln did not have 19lb injectors.

You missed that one...

The OEM Ford MAFs are not calibrated to injector size. The injector sizing is done in the computer’s internal programming. Aftermarket MAF’s “lie” to the computer in an attempt to fool the computer into changing the injector pulse on timing to match the increased airflow.

The exception to the above statements is if you have an aftermarket tuner system such as Moates Quarterhorse, Tweecer, or similar device. Then you can alter the computer's MAF transfer function table to match whatever MAF housing and sensor you have. The tuner device works in conjunction with a high quality Air/Fuel ratio meter so that you can tell what sort of air/fuel mixture you have a any given time.

The transfer function curve for the MAFs below is almost identical to the 89-93 55MM MAF.

The The 94-95 Mustang 5.0 MAF & sensor is also found on:
1995-94 Mustang 3.8L F2VF-12B579-A2A,
1994-92 Crown Victoria 4.6L F2VF-12B579-A2A,
1995-94 Mustang, Mustang Cobra 5.0L F2VF-12B579-A2A,
1994-92 Town Car 4.6L F2VF-12B579-A2A,
1994-92 Grand Marquis 4.6L F2VF-12B579-A2A,
Evidently the –A1A, -A2A, AA, etc. on the end of the part number is a minor variant that did not change the operating specs. You should be able to ignore it and have everything work good.

Png1978 · May 12, 2018

jrichker said:
You missed that one...

The OEM Ford MAFs are not calibrated to injector size. The injector sizing is done in the computer’s internal programming. Aftermarket MAF’s “lie” to the computer in an attempt to fool the computer into changing the injector pulse on timing to match the increased airflow.

The exception to the above statements is if you have an aftermarket tuner system such as Moates Quarterhorse, Tweecer, or similar device. Then you can alter the computer's MAF transfer function table to match whatever MAF housing and sensor you have. The tuner device works in conjunction with a high quality Air/Fuel ratio meter so that you can tell what sort of air/fuel mixture you have a any given time.

The transfer function curve for the MAFs below is almost identical to the 89-93 55MM MAF.

The The 94-95 Mustang 5.0 MAF & sensor is also found on:
1995-94 Mustang 3.8L F2VF-12B579-A2A,
1994-92 Crown Victoria 4.6L F2VF-12B579-A2A,
1995-94 Mustang, Mustang Cobra 5.0L F2VF-12B579-A2A,
1994-92 Town Car 4.6L F2VF-12B579-A2A,
1994-92 Grand Marquis 4.6L F2VF-12B579-A2A,
Evidently the –A1A, -A2A, AA, etc. on the end of the part number is a minor variant that did not change the operating specs. You should be able to ignore it and have everything work good.

That's good to know. I figured it was like that since I found the same sensor on many cars. Once I fix the high end miss I will try one of these out. Anyone seen any real world results swapping one with a stock foxbody maf?

Mustang5L5 · May 12, 2018

Png1978 said:
So is it the sensor or the housing that's calibrated for 19 pounds

Sensors aren't calibrated. That's strictly and aftermarket thing. The sensor outputs a specific value for a know flow through it. The ECU then takes this signal and operates the injectors based of that flow. Each ECU is tailored for the injectors on the car, so basically if input signal from the MAF is x, then output to injectors is Y.

Aftermarket mAFs being calibrated basically output different values than the oem MAF. By telling the ECU a different value, it "tricks" the ECU isn't adding less fuel due to the larger injector.

Oem systems are grouped in families of compatibility. What those families are is still up for debate.

Png1978 · May 12, 2018

General karthief said:
The fuel pump change would be a good idea. Clear the computer, pull the negative battery clamp off while you change the fuel pump and that will clear any codes in the computer then drive it around for an hour or so and then check for codes again. Let us know what you find, for information on checking for codes look in the 5.0 technical/how to threads. There could be codes without the check engine light on.

New walboro 155 in. miss still there and no codes. Going to try my stock coil and see if it's the accel coil I put in a few months ago.

General karthief · May 12, 2018

When you say no codes, are you getting an 11 koeo and are you letting it go through the koer codes?

Png1978 · May 12, 2018

I was only able to do the engine off test and it gave me 11. I fix to run the engine on and balance test.

General karthief · May 12, 2018

Ok, I just realized you have two threads going, not a good idea to add stuff to a car that already has a problem, makes it hard to fix

Png1978 · May 12, 2018

Yea I did not add anything to the car. Other then a new fuel pump and a tune up. Filter, cap and rotor, plugs. Problem was before and after all that.

I wa just asking a question about the maf because when ever I get the miss fixed I want to upgrade the maf meter.

Engine 1988 CA mass air GT hesitation 3000rpm and higher

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