mikestang63
SN Certified Technician
Disconneting your coolant lines will have no impact on the TPS. I've had mine disconnected on several cars with no adverse impact.
Vacum Line Diagram For Later Explorer Intake On A 5.0 Foxbody
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Okay, that sounds good. After the GT40 upper/lower install, I replaced all vacuum lines under the upper intake because the old ones were starting to harden and dry-rot. I checked for vacuum leaks and don't have any as far as I know. I installed a new TPS, a new IAC, a new 70mm TB and my idle still surges up and down until the engine stalls. After I installed the TPS, I set it at.97 volts. I also did the base idle reset, and still no luck. I have a new H-pipe with new o2 sensors and seems the fuel is burning rich. The car starts just fine, but you have to feather the gas to keep it from stalling. Once it warms up, it idles somewhat better, but still surges. I can't seem to think of any other reason why it would surge. Yesterday I installed a new fram fuel filter, as the old one was looking bad. My fuel pump seems to be fine as it was working perfectly before I removed the stock HO upper \lower intake to change over the the GT40. I have the EGR disconnected and and the 2-coolant lines blocked off and capped. I am at a dead street with this! What is the next step? Thank you
I believe it did surge when the IAC was disconnected, including the spout. It's funny because there are times it will have a smooth idle, and other times it will surge up and down til the engine wants to stall.
I redid the base idle reset and it wasn't the new IAC or ECM, what I found was the small vacuum line that runs from the FPR to a vacuum tee, so I replaced that vacuum line with a new line. With the engine idling at operating temperature (190-210 degrees), the idle is smooth and the tach on the dash doesn't fluctuate during idle. During idle in park, my tach reads between 850-900 rpms. I'll let the motor cool down a bit, then go back out and start it again to see if the idle stays smooth or surges. The only mods I have on the motor are a new 70mm TB, BBK CAI (no MAF), the Explorer GT40 upper/lower intake, AC and smog pump delete pulleys. The 302 I believe was rebuilt at some point. The roller cam sounds like it's possibly 1 step up from stock, like a RV cam. The water pump, IAC, TPS, TB, vacuum lines, 8mm Taylor wires, cap and rotor, motorcraft spark plugs, serpentine belt and tensioner, BBK shorty headers, 2 1/2 Pacesetter H-pipe and o2 sensors are all new. The TPS is currently set at 1.000 I may have to drop it down to .98 Base idle reset is done. I hope this resolves the problem.
I checked all other connections and everything seems to be hooked correctly. I tapped and drilled the hole for the ACT sensor in the cold air intake tube since the GT40 lower intake had no boss for the sensor. It still surges no matter how many times I reset the TPS or base idle. IAC and TPS are new.In case you haven't seen this before...
You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix.
It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 134,000 hits, which indicates it does help fix idle problems quickly and inexpensively.
The fact that you are running Speed Density on an engine that has increased airflow from stock may be the source of your problem.
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 hot cam, 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.
If the engine idles OK with the IAC & SPOUT disconnected, it is time to consider a MAF conversion.
If it still surges and misbehaves you have a mechanical problem. The lower intake manifold gasket may have slipped out of place during installation.
Vacuum leak due to slipped lower intake manifold gasket...
Ask Nicoleb3x3 about the intake gasket that slipped out of place and caused idle and vacuum leak problems that could not be seen or found by external examination. I don't care what you spray with, you won't find the leak when it is sucking air from the lifter valley. It simply isn't possible to spray anything in there with the lower manifold bolted in place.
MASS air conversion instructions from http://www.stangnet.com/tech/maf/massairconversion.html FREE
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/
See 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 helpful)
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. (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 may be compatible (single dash connector, fuel pump relay under the hood). You may end up running some extra wire for the fuel pump relay. Comments and input from someone who has actually used the 92-93 EFI harness would be nice.
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 http://www.kustomz.com/cat3.html Buy the TR70 for $40-$45 depending on if it’s on sale or not. 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.
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 hot cam, 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.
If the engine idles OK with the IAC & SPOUT disconnected, it is time to consider a MAF conversion.
If it still surges and misbehaves you have a mechanical problem. The lower intake manifold gasket may have slipped out of place during installation.
Vacuum leak due to slipped lower intake manifold gasket...
Ask Nicoleb3x3 about the intake gasket that slipped out of place and caused idle and vacuum leak problems that could not be seen or found by external examination. I don't care what you spray with, you won't find the leak when it is sucking air from the lifter valley. It simply isn't possible to spray anything in there with the lower manifold bolted in place.
MASS air conversion instructions from http://www.stangnet.com/tech/maf/massairconversion.html FREE
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/
See 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 helpful)
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. (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 may be compatible (single dash connector, fuel pump relay under the hood). You may end up running some extra wire for the fuel pump relay. Comments and input from someone who has actually used the 92-93 EFI harness would be nice.
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 http://www.kustomz.com/cat3.html Buy the TR70 for $40-$45 depending on if it’s on sale or not. 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.
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