Mass air conversion woes.

[Saber123316]

So I did a mass air conversion to my car.

Car starts fine however it does not run right or idle correctly.

It runs really rich and eventually stalls out when trying to idle.

Back when it was Speed density when cold the car would start hard and die if I didnt keep the gas in and revving while idling. and once it had been running for awhile all was good. NOW could it be because the current electrical system does not have enough charge (spark) at the lower RPM to keep this car running. so once it starts to idle lower it fights to stay alive.

Sadly I cannot list my MODS as I have no idea what is in the motor.. its a 88 mustang with a 5.0 conversion that was running speed density now I switched it to mass air. (It had a mass air harness but no meter or computer)

Now it just surges at idle and dies and it will only let me rev it up to 3500 and it won't rev any higher and it bounces around the computer I put in is a A9P

The injectors I have say ford on em and are yellow. 19 lbs is my guess.

also the kid had the timing advanced so could to much timing be the problem? cause I know the A9P has a more aggressive timing curve.

Also another note is when Speed density the TPS was unplugged when I found that I plugged it in and the car would surge like it does now and eventually stall. (bad TPS)?

 

[jrichker]

Recheck all your Mass Air conversion wiring.
MASS air conversion instructions from MAF - Mustang Mass Air Conversion - StangNet - The Mustang Network FREE
A9L (5 Speed) computer from junkyard $100-$150
A9P (Auto or in a pinch, 5 Speed) 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.

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, it is actually less work that swapping the wiring harness. I have pulled the stock harness out of a wrecked car and it was like wrestling a big python.

Conversion Harness kits & parts
Interactive Systems & Technologies Mass Air Home Page
Ford Fuel Injection EFI Harness Pigtails

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. (B/c 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)
Late 92 through 93 harnesses should be compatible (single dash connector, fuel pump relay under the hood)

Larger MAF to go with Mass Air conversion:
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

*1.) Metal flange adapter Kurtz Kustomz Motorsports, Inc. KKM Buy the TR70 for $44.95. Or spend some time on eBay looking for one that may fit.
Try AutoZone and ask for 81413 - Spectre / 3 in. Aluminum Intake Mass Air Flow Sensor Adapter at $12.00. You may have to order it online.

*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.

A Also see Ford Fuel Injection for help with the harness parts RJM Injection Tech EFI Harness Pigtails:, and connector pins, RJM Injection Tech Ford Terminals:

First rules of basic troubleshooting
You should have fixed the idle problem before converting it to Mass Air. Now you have 2 separate problem areas to try and troubleshoot. Fix one thing at a time. Once the first problem has been resolved, then attempt something else.

Dump the codes and see what the computer says is wrong…Codes may be present in the computer even if the Check Engine light isn’t on.

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

See Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical

If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.


There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see EQUUS DIGITAL FORD CODE READER (3145) – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

 

[noslow1986]

i had the same problem. i took mine for a tune and the idle is a little rough during start up but after it warms ups it fine. the guy that did my tune had a iac program to fix my idle problem its a little rough but it never dies first start dies but second start is fine. will idle low but wont die. try turning ur iac motor upside down its wierd but it runs better like that on my car at least

 

[jrichker]

I will be repetitive, with good reason...

First rules of basic troubleshooting
You should have fixed the idle problem before converting it to Mass Air. Now you have 2 separate problem areas to try and troubleshoot. Fix one thing at a time. Recheck you Mass Air conversion wiring, make sure all the pins are in the correct location AND completely seated in their respective connectors. Then once the first problem has been resolved, attempt to fix the idle problem.

Dump the codes and see what the computer says is wrong…Codes may be present in the computer even if the Check Engine light isn’t on.

If you fix the codes and still have idle problems, See the "Surging Idle Checklist for help with all your idle/stall problems. Everything you need to find and fix idle problems is in there.

The first two posts contain all the updates to the fixes. At last count there were 24 possible causes and fixes for surging idle/stall problems. I continue to update it as more people post fixes or ask questions.