Need Help With Getting My 89 Mustang Lx Running Right

tony_jr_50

New Member
Jul 21, 2016
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Just picked up an 89 LX Vert and it runs horribly, Im new to mustangs.

It has a ford explorer intake manifold, GT40 Heads, e303 cam, msd distributor, 30LB injectors, and a 190LPH fuel pump. I know its probably going to need to be Re-timed but from other experiences what do you guys find to get the mustang running right? and i'm also probably gonna revert the injectors and fuel pump back to factory ones
 
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Two areas that I see from your description that need further investigation:


30LB injectors - way too much injector for your setup. You need 19 LB injectors.

MAF is it stock or aftermarket? The 55MM stock MAF will not work well with anything but 19 LB injectors unless you have an external chip to modify the computer program.


Swapping the MAF sensors between different MAFs is a big no no. The MAF body and sensor are designed to match each other. Therefore you can't swap sensors between different part number MAF bodies and maintain proper calibration. The assembly is designed to match the computer’s internal program, and swapping a different MAF can upset the computer's calibration.

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 only other MAF that is a one for one swap for a 93 and earlier 5.0 Mustang is the 94-95 Mustang MAF.

94-95 Mustang GT MAF - $40-$100. It is 70 MM instead of the stock 55 MM on regular stangs built prior to 94. It uses a slip on duct on the side that goes to the throttle body and a 4 bolt flange on the other. You need a flange adapter to fit the stock slip on air ducting that goes to the air box. Wiring plugs right in with no changes. *1 *2

Once your replacement 70MM MAF is in place, disconnect the battery for about 10 minutes. When you reconnect the battery and start the engine, the computer will relearn the settings for the new MAF.

*1.) Metal flange adapter http://www.kustomz.com/cat3.html Buy the TR70 for $44.95. Or spend some time on eBay looking for one that may fit.

*2.) MAF & sensor interchange
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.
 
When you get time, post some pictures of you mustang. I'd like to see what it looks like.

jrichker will get you going, listen to what he's telling you. You'll be cruising around smoothly in no time.
 
Two areas that I see from your description that need further investigation:


30LB injectors - way too much injector for your setup. You need 19 LB injectors.

MAF is it stock or aftermarket? The 55MM stock MAF will not work well with anything but 19 LB injectors unless you have an external chip to modify the computer program.


Swapping the MAF sensors between different MAFs is a big no no. The MAF body and sensor are designed to match each other. Therefore you can't swap sensors between different part number MAF bodies and maintain proper calibration. The assembly is designed to match the computer’s internal program, and swapping a different MAF can upset the computer's calibration.

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 only other MAF that is a one for one swap for a 93 and earlier 5.0 Mustang is the 94-95 Mustang MAF.

94-95 Mustang GT MAF - $40-$100. It is 70 MM instead of the stock 55 MM on regular stangs built prior to 94. It uses a slip on duct on the side that goes to the throttle body and a 4 bolt flange on the other. You need a flange adapter to fit the stock slip on air ducting that goes to the air box. Wiring plugs right in with no changes. *1 *2

Once your replacement 70MM MAF is in place, disconnect the battery for about 10 minutes. When you reconnect the battery and start the engine, the computer will relearn the settings for the new MAF.

*1.) Metal flange adapter http://www.kustomz.com/cat3.html Buy the TR70 for $44.95. Or spend some time on eBay looking for one that may fit.

*2.) MAF & sensor interchange
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.
Thanks!! sorry i work during the day and don't have too much access to a computer but when i get a chance i'll update the thread with pictures, the mustang was a steal though i paid only 1,450 for it.

When you get time, post some pictures of you mustang. I'd like to see what it looks like.

jrichker will get you going, listen to what he's telling you. You'll be cruising around smoothly in no time.
will do i'm heading out soon to go snap some pics
 
Welcome and congrats on the purchase.

As mentioned,
  • 30# injectors are way too much for that combo. 19's are fine.
  • MSD distributors are junk- find a Cardone rebuilt
  • I never understand why people with mild builds run E cams- they have an SLA that causes low vacuum and idle problems and they don't make power until 3000 rpm. You are much better off with a stock cam or an Anderson N41 which is designed to go with GT40 heads.
  • With the MAF- get a 94-95 mustang GT 70MM MAF and it will work well with the stock injectors and is a nice cheap pickup in hp over the stock 55MM MAF
Your timng should be anywhere from the factory 10 BTDC to 14 depending on the gas you run and each car's resistance to detonation.