Engine 1993 doesnt want to idle

May 29, 2017
45
2
18
48
west liberty ky
#1
i have a 1993 mustang v-1 supercharger gt-40x heads Anderson b21 cam trick flow track heat intake 60lb injectors its been tuned but I still have a idle problem I have it set to idle at 1100 rmps right now and it will idle 2-3 minutes and then it just dies its got a new mass air meter everything is new on it and it runs great but at slow speeds it does have alittle surge and the car is an aod with a non lock up stall
 
  • Sponsors (?)

John Dirks Jr

5 Year Member
Jun 28, 2013
2,173
807
174
54
Maryland
#3
Does it have a pcv valve system? It should, and the vent should be connected to the air breather box up stream of the MAF a manner that lets the MAF measure the air being drawn by the PCV system. In some super charged installs I've seen the pcv vent omitted and a valve cover breather being used instead. This can cause idle problems because the MAF is not measuring the air used by the pcv in that case.

Post some detailed pictures of your engine showing how things are hooked up. Many times, pictures will show us what could be wrong.
 

jrichker

StangNet's favorite TOOL
SN Certified Technician
Mar 10, 2000
26,591
2,381
224
73
Dublin GA
#4
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. It includes how to dump the computer codes quickly and simply as one of the first steps. 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. :D

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 250,000 hits, which indicates it does help fix idle problems quickly and inexpensively.
 

mikestang63

SN Certified Technician
Aug 27, 2012
9,729
6,453
204
In the garage
#8
bring oit back to the tuner and have him fix the tune. You don't know what he did to the timing and fuel tables. Chance are if you need to have it at 1100 just to idle that is masking something off in the tune.
 
Jun 28, 2013
2,173
807
174
54
Maryland
#14
I’ll try to explain how it works and differences in hose routing between natural aspiration(non boosted) and boosted applications.

The Pcv valve is a check valve that gets plugged into a hole in the rear center of the lower intake. A hose should be connected to it that goes to the upper intake where it gets its vacuum source. The vacuum from the upper intake pulls crankcase fumes back into the engine to be burned during the normal combustion cycle. This part of the pcv system can be the same for either application. The reason is, the pcv valve , being a check valve should only allow air to flow in one direction which is from the crankcase and to the intake. When the intake is under pressure from boost, the pcv valve blocks air movement from the intake and prevents the boost pressure from getting into the crankcase. So you don’t need to change that part of the pcv system on a boosted application. It just stays the same as stock.

Under vacuum, the air being sucked out of the crankcase through the pcv valve needs to be replaced by air coming into the crankcase at some other location. In stock form on these typical 5.0 Foxbody engines, there’s a hose/pipe that goes from the passenger side valve cover to the side of the throttle body. The drivers side valve cover is sealed and has no vent. This way, all air sucked out of the back of the lower intake through the pcv valve gets replaced by air coming from the intake track prior to the throttle blade but after the MAF. This setup is important because it draws clean air through the filter and also draws this air through the MAF which includes that air in the measurement sent to the computer for A/F adjustment made by the computer. So for non boosted application , that’s it.

On a boosted application , there’s a bit of a problem with this crankcase “supply” hose that is normally connected to the throttle body. Under boost, the entire throttle body internal is under pressure. If the supply hose for the pcv is connected here, boost pressure will be shot down into the crankcase. In addition to loosing boost pressure and less performance, it can also blow out oil seals in the engine.

So, on boosted applications we need to find an air source for the pcv system that is not subjected to boost, but is still filtered and entered through the MAF.

There may be other examples and I hope others can chime in with them. However, on my setup I just followed the lead in the Vortech inst. They provide an inline filter for the inlet hose and a fitting to connect it to the air box upstream of the MAF.

Here is the connection at the passenger valve cover

77FB4760-F3B2-480F-8899-63B8A729C0E5.jpeg


Here is the inline air filter

646CED93-6939-4232-B61E-F7DB318A895B.jpeg



Here is the connection at the air box upstream of the maf allowing pcv air to be metered an included in data sent to computer

F8371B4D-B1D5-42F9-9309-A7717BE5D59D.jpeg


F5EBE51F-3CA4-44CF-BE69-2B59CDD61AA9.jpeg
 
Jun 28, 2013
2,173
807
174
54
Maryland
#15
Oh, one more pic. Here is the stock connection point for pcv air supply hose at the throttle body. I pulled the angle pipe out and plugged it with a bolt and sealer on the threads.

DB7D99F0-E35C-4211-BB03-CCA061A0995C.jpeg
 
May 29, 2017
45
2
18
48
west liberty ky
#16
ill do that in a couple of days when I get a minute the only issue I have is the idle when I start it the cold idle kicks in and it will idle like it should but when it starts to come down the idle just keeps dropping until it dies I set the idle up to 1100 rpms and rest the tps and stared the car back up same thing again plus its got alittle surging but i'll try about anything and out driving the car it runs great but pull up to a stop and if I have to sit there more than 30 sec. there the idle goes again keeps dropping till it dies. P.S thanks for the reply
 
Mar 11, 2019
15
14
13
45
Milton, Ontario
#17
Oh, one more pic. Here is the stock connection point for pcv air supply hose at the throttle body. I pulled the angle pipe out and plugged it with a bolt and sealer on the threads.

View attachment 622719
Excellent explanation. What is the best way to replace the pcv and filter from behind the intake?
 
Jun 28, 2013
2,173
807
174
54
Maryland
#18
On a stock setup there is no pcv filter to change. The stock setup uses air pulled through the regular air intake filter.

To replace the pcv valve, you pull it and the hose it’s connected to out from the back of the intake. Remove the valve from the hose, put a new one in the end of the hose and insert it back in to the intake.

Sometimes the pcv valve is just gummed up with crankcase sludge. Sometimes a you can clean it by spraying carb cleaner or similar into it. If it’s clean and functional, you should be able to blow through in one direction, but not the other.

Check the hose too. If it’s hard, brittle or cracked, toss it and replace with a new one.
 

Similar threads