Vaccuum routing on a MAF-upgraded '86

95Convert · 03-05-2001, 07:38 PM

I have a 1986 GT. I recently purchased a mass air conversion kit and ported upper and lower from a 90 GT. The mass air kit went in no prob and works fine. However, I have a question. The vaccuum lines to the '86 intake are not the same as the '90. What is the proper routing of these lines with the new intake versus the original. Anybody done the swap before?? Any help would be appreciated.

Capri306 · 03-05-2001, 08:49 PM

I did the MAF conversion on my '87. The only thing different I remember doing is having to plug the MAP sensor port, easily done with a vacuum plug. Other than that, you have the canister purge port, the EGR/Thermactor port, the vacuum tree port, the PCV port, and the fuel pressure regulator port. Hope this helps.

------------------
Capri306, Moderator, The Mustang Works Online
1979 Mercury Capri, 5.0L -- C4 -- 2.73
1987 Mustang LX Notch

95Convert · 03-05-2001, 09:47 PM

Like I said the conversion is done. What I need to know is why the '90 intake is different. The '86 only has one large vaccuum line and a smaller tree, the '90 has TWO large vaccuum lines and the same smaller tree, on the intake itself. Also, it does not have and of the original air pump equipment on it. How should I run the lines to ensure I do not have a vaccuum leak. Right now, the vaccuum fluctuates at idle, as opposed to my '95 which remains steady at idle.

Capri306 · 03-06-2001, 12:06 AM

Remember it's all manifold vacuum, so the number of ports are dictated by requirements of the vacuum accessories on the car. As long as everything's hooked up and nothing's left open, don't worry about it. The fluctuating idle could be several things. First make sure the idle air bypass is clean and I mean CLEAN. Same deal with the EGR valve. Next you need to reset the idle parameters. Click here to find out how to reset the idle correctly. Good luck.

------------------
Capri306, Moderator, The Mustang Works Online
1979 Mercury Capri, 5.0L -- C4 -- 2.73
1987 Mustang LX Notch

moosejaw · 03-07-2001, 04:14 AM

One large connection went to the PCV. The to the vacuum tree on the fire wall.

Make sure you are metering the air from the PCV. Ensure the valve cover fitting has the hose hooked the T-body (unless your blown then its different). If this isn't hooked up the PCV acts like a large vacuum leak. On the speed density programming this didn't matter, on the mass air it matters a bunch!!

Other than that I defer to Capri306's statment. Plug those lines!!

Mike

------------------
Live near St.Louis?
Check out Mustang Muscle and Dyno in High Ridge, MO
Check out my ride.

gray87GT · 03-07-2001, 10:29 AM

I have a question. I installed a mass air system in my 87, and it has a very bad surging idle with the oil fill tube to T-body PCV hose hooked up. When I unhook it it idles perfect. Could it be that since I do not have an EGR system there is too much gas in the crankcase, which in turn would cause the idle to surge if that gas is going directly into my T-body? IF I leave that hose off, could that hurt anything even though it idles perfect??? Thanks

withamc · 03-07-2001, 01:01 PM

MOOSEJAW - what do you mean by "metering" the PCV? I did the mass air conversion on my 86 and din't do anything like this. What do I need to do?

------------------
86 GT, GT40P heads, Crane 2031, 1.7 RR's, Cobra intake, 65mm TB, 73mm Vortech, 24# injectors, MAC GT40P headers, 2-1/2" BBK H-pipe (w/cats), Flowmasters, 3.55s, Groundpounder subs and lower control arms.

moosejaw · 03-08-2001, 02:03 AM

All air that goes into the motor should be measured by the air meter. To follow the air flow path for the PCV it goes:

1. From intake to PCV valve.
2. From PCV valve to crank case (now this air has to come from somewhere So..)
3. From fill tube fitting to T-Body connection, then..
4. to air meter.

At low total air flow #'s (ie. idling) the ratio of air let in by the PCV to the air coming in through the normal route is very close. Lets say 1:1. If you don't have the PCV air "measured" you would be missing half the air going in the motor. Therefore your motor would run lean or stumble or surge at idle.

At high load the amount coming in through the PCV becomes insignificant because the ratio becomes very lopsided.

So if the PCV air is not measured it acts just like a big vacuum leak at idle. Vacuum #'s won't change but it will affect mixture calculations like a vacuum leak does.

Gray87GT I would hook up the hose again and then reset all idle parameters. ( I believe there are other posts in the archive that can describe the proper idle set better than I can.) This should help the idle air valve get into its proper control band to stop closing all the way and making a surge with the tube hooked up.

Mike
------------------
Live near St.Louis?
Check out Mustang Muscle and Dyno in High Ridge, MO
Check out my ride.

[This message has been edited by moosejaw (edited 03-08-2001).]

03-05-2001, 07:38 PM	#1
95Convert Registered Member Join Date: Oct 1999 Location: Murfreesboro, TN Posts: 123	Vaccuum routing on a MAF-upgraded '86 I have a 1986 GT. I recently purchased a mass air conversion kit and ported upper and lower from a 90 GT. The mass air kit went in no prob and works fine. However, I have a question. The vaccuum lines to the '86 intake are not the same as the '90. What is the proper routing of these lines with the new intake versus the original. Anybody done the swap before?? Any help would be appreciated.

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03-05-2001, 08:49 PM	#2
Capri306 Moderator Join Date: Sep 1998 Location: Grand Rapids, Michigan, USA Posts: 1,001	I did the MAF conversion on my '87. The only thing different I remember doing is having to plug the MAP sensor port, easily done with a vacuum plug. Other than that, you have the canister purge port, the EGR/Thermactor port, the vacuum tree port, the PCV port, and the fuel pressure regulator port. Hope this helps. ------------------ Capri306, Moderator, The Mustang Works Online 1979 Mercury Capri, 5.0L -- C4 -- 2.73 1987 Mustang LX Notch

03-05-2001, 09:47 PM	#3
95Convert Registered Member Join Date: Oct 1999 Location: Murfreesboro, TN Posts: 123	Like I said the conversion is done. What I need to know is why the '90 intake is different. The '86 only has one large vaccuum line and a smaller tree, the '90 has TWO large vaccuum lines and the same smaller tree, on the intake itself. Also, it does not have and of the original air pump equipment on it. How should I run the lines to ensure I do not have a vaccuum leak. Right now, the vaccuum fluctuates at idle, as opposed to my '95 which remains steady at idle.

03-06-2001, 12:06 AM	#4
Capri306 Moderator Join Date: Sep 1998 Location: Grand Rapids, Michigan, USA Posts: 1,001	Remember it's all manifold vacuum, so the number of ports are dictated by requirements of the vacuum accessories on the car. As long as everything's hooked up and nothing's left open, don't worry about it. The fluctuating idle could be several things. First make sure the idle air bypass is clean and I mean CLEAN. Same deal with the EGR valve. Next you need to reset the idle parameters. Click here to find out how to reset the idle correctly. Good luck. ------------------ Capri306, Moderator, The Mustang Works Online 1979 Mercury Capri, 5.0L -- C4 -- 2.73 1987 Mustang LX Notch

03-07-2001, 04:14 AM	#5
moosejaw Registered Member Join Date: Apr 1999 Location: St.Louis,MO Posts: 274	One large connection went to the PCV. The to the vacuum tree on the fire wall. Make sure you are metering the air from the PCV. Ensure the valve cover fitting has the hose hooked the T-body (unless your blown then its different). If this isn't hooked up the PCV acts like a large vacuum leak. On the speed density programming this didn't matter, on the mass air it matters a bunch!! Other than that I defer to Capri306's statment. Plug those lines!! Mike ------------------ Live near St.Louis? Check out Mustang Muscle and Dyno in High Ridge, MO Check out my ride.

03-07-2001, 10:29 AM	#6
gray87GT Registered Member Join Date: Jan 2001 Location: Minnesota Posts: 177	I have a question. I installed a mass air system in my 87, and it has a very bad surging idle with the oil fill tube to T-body PCV hose hooked up. When I unhook it it idles perfect. Could it be that since I do not have an EGR system there is too much gas in the crankcase, which in turn would cause the idle to surge if that gas is going directly into my T-body? IF I leave that hose off, could that hurt anything even though it idles perfect??? Thanks

03-07-2001, 01:01 PM	#7
withamc Registered Member Join Date: Aug 2000 Location: Thousand Oaks, CA Posts: 396	MOOSEJAW - what do you mean by "metering" the PCV? I did the mass air conversion on my 86 and din't do anything like this. What do I need to do? ------------------ 86 GT, GT40P heads, Crane 2031, 1.7 RR's, Cobra intake, 65mm TB, 73mm Vortech, 24# injectors, MAC GT40P headers, 2-1/2" BBK H-pipe (w/cats), Flowmasters, 3.55s, Groundpounder subs and lower control arms.

03-08-2001, 02:03 AM	#8
moosejaw Registered Member Join Date: Apr 1999 Location: St.Louis,MO Posts: 274	All air that goes into the motor should be measured by the air meter. To follow the air flow path for the PCV it goes: 1. From intake to PCV valve. 2. From PCV valve to crank case (now this air has to come from somewhere So..) 3. From fill tube fitting to T-Body connection, then.. 4. to air meter. At low total air flow #'s (ie. idling) the ratio of air let in by the PCV to the air coming in through the normal route is very close. Lets say 1:1. If you don't have the PCV air "measured" you would be missing half the air going in the motor. Therefore your motor would run lean or stumble or surge at idle. At high load the amount coming in through the PCV becomes insignificant because the ratio becomes very lopsided. So if the PCV air is not measured it acts just like a big vacuum leak at idle. Vacuum #'s won't change but it will affect mixture calculations like a vacuum leak does. Gray87GT I would hook up the hose again and then reset all idle parameters. ( I believe there are other posts in the archive that can describe the proper idle set better than I can.) This should help the idle air valve get into its proper control band to stop closing all the way and making a surge with the tube hooked up. Mike ------------------ Live near St.Louis? Check out Mustang Muscle and Dyno in High Ridge, MO Check out my ride. [This message has been edited by moosejaw (edited 03-08-2001).]