Starts, idles itself high, bogs to stall...

E.Morel · 10-06-2009, 01:27 AM

Ok, Ive searched and read through my Haynes manual and can't seem to pinpoint a solution here...

I have a 1989 2.8 TBI that I just came into possession of last week. I've never seen these engines before then. The truck has been idling really high when in neutral lately, so I figured some basic tuning up was necessary, maybe some adjustments and new vacuum hoses or something.

Well tonight I went to change the air filter only to find that the P.O. had for some reason used a silicone sealant to close the air cover onto the air box... so I had to remove the whole box from the TBI unit... In doing so, I unplugged the green plug on the drivers side, removed the aluminum flex hose, and removed the hose from the drivers side valve cover to the airbox (preheater?). I replaced all of these while reinstalling the box.

Upon returning the box to the TBI unit I realized theres a small hose with a spark plug like 90° boot on the end coming from the front side of the TBI unit and I have no idea where it plugs into. Also, there are two small boots on the rear of the airbox (toward the cab) that look like they're related to the PCV in the airbox? One has a hose going to the sensor in the air ducting tube, the other is just a boot with nothing coming out of it. There is also a hose coming from the passenger side valve cover going to nothing?

So, thinking these are all just misc. hoses that don't necessarily NEED to be connected i went to start the truck. Fired right up, sounded much better with a smoother idle for about 10 seconds, then it revved up to about 1500, then bogged down and stalled. It filled the garage with the smell of gas, which leads me to believe something I left unplugged is responsible for air/fuel mixture...but I don't know what.

Sorry for the long post, I'm just trying to be as descriptive as possible. Again, I'm new to these older motors, coming from a 2.0 4cyl Zetec in a focus, these are a bit more complicated to me so far in my limited experience. I can get pics tomorrow afternoon of the hoses in question if that helps.

Any help is appreciated folks!

-Evan

Jaxom · 10-06-2009, 01:46 AM

I have the year before... Make sure you check the map sensor on the side of the cleaner box, there's an electrical connector and vac tube that run to it, if either are disconnected makes my engine run just as you described.

Jax

E.Morel · 10-06-2009, 02:00 AM

Hmm.. That would be the green connector on the drivers side? I definitely plugged that electrical connector back in, but that MAY be the stray booted hose that comes from TBI unit? Ill have to check that out in the AM. Thanks man!

Jaxom · 10-06-2009, 02:15 AM

Yeah, the vac hose I'm speaking of goes to the "front" side of the TBI, this connects to the same bracket as the map sensor connector does. And then as you said there's 3 vac lines off the firewall side of the tbi, I'd make sure all are connected properly as well.

phaderus · 10-06-2009, 08:40 AM

IIRC there is larger plug on the back passenger side of the throttle body that goes to the PVC valve in the passenger side. There is a tube about 1/2 wide off of the air breather that goes to drive side for blow-by gasses. If you have the Hayes manual there is an image of the PVC system on page 6-18.

One line goes to the egr controller and a line from that goes to the EGR valve.

As Jaxom said the front plug goes to the MAP sensor.

One vacuum plug will go to a vacuum line that comes from the firewall. It controls which vents the air from HVAC comes from.

then you have lines for vacuum canister, possible 4x4 actuator, and one if you cruise control. That is all I can think of the top of my head.

E.Morel · 10-06-2009, 11:05 PM

The map vacuum line did the trick. That was the hose that was not connected...

However my original issue remains... the truck idles WAY high.

chaospartners · 10-07-2009, 11:50 PM

thats a 2.8 for ya!

10-06-2009, 01:27 AM	#1
E.Morel Doin' Work Age: 22 Join Date: Aug 2009 Posts: 39 Location: User is: OffLine	Starts, idles itself high, bogs to stall... Ok, Ive searched and read through my Haynes manual and can't seem to pinpoint a solution here... I have a 1989 2.8 TBI that I just came into possession of last week. I've never seen these engines before then. The truck has been idling really high when in neutral lately, so I figured some basic tuning up was necessary, maybe some adjustments and new vacuum hoses or something. Well tonight I went to change the air filter only to find that the P.O. had for some reason used a silicone sealant to close the air cover onto the air box... so I had to remove the whole box from the TBI unit... In doing so, I unplugged the green plug on the drivers side, removed the aluminum flex hose, and removed the hose from the drivers side valve cover to the airbox (preheater?). I replaced all of these while reinstalling the box. Upon returning the box to the TBI unit I realized theres a small hose with a spark plug like 90° boot on the end coming from the front side of the TBI unit and I have no idea where it plugs into. Also, there are two small boots on the rear of the airbox (toward the cab) that look like they're related to the PCV in the airbox? One has a hose going to the sensor in the air ducting tube, the other is just a boot with nothing coming out of it. There is also a hose coming from the passenger side valve cover going to nothing? So, thinking these are all just misc. hoses that don't necessarily NEED to be connected i went to start the truck. Fired right up, sounded much better with a smoother idle for about 10 seconds, then it revved up to about 1500, then bogged down and stalled. It filled the garage with the smell of gas, which leads me to believe something I left unplugged is responsible for air/fuel mixture...but I don't know what. Sorry for the long post, I'm just trying to be as descriptive as possible. Again, I'm new to these older motors, coming from a 2.0 4cyl Zetec in a focus, these are a bit more complicated to me so far in my limited experience. I can get pics tomorrow afternoon of the hoses in question if that helps. Any help is appreciated folks! -Evan Last edited by E.Morel : 10-06-2009 at 01:28 AM.
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10-06-2009, 01:46 AM	#2
Jaxom Registered User Age: 44 Join Date: Feb 2008 Posts: 191 Location: User is: OffLine	Re: Starts, idles itself high, bogs to stall... I have the year before... Make sure you check the map sensor on the side of the cleaner box, there's an electrical connector and vac tube that run to it, if either are disconnected makes my engine run just as you described. Jax
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10-06-2009, 02:00 AM	#3
E.Morel Doin' Work Age: 22 Join Date: Aug 2009 Posts: 39 Location: User is: OffLine	Re: Starts, idles itself high, bogs to stall... Hmm.. That would be the green connector on the drivers side? I definitely plugged that electrical connector back in, but that MAY be the stray booted hose that comes from TBI unit? Ill have to check that out in the AM. Thanks man!
	[Reply w/Quote]

10-06-2009, 02:15 AM	#4
Jaxom Registered User Age: 44 Join Date: Feb 2008 Posts: 191 Location: User is: OffLine	Re: Starts, idles itself high, bogs to stall... Yeah, the vac hose I'm speaking of goes to the "front" side of the TBI, this connects to the same bracket as the map sensor connector does. And then as you said there's 3 vac lines off the firewall side of the tbi, I'd make sure all are connected properly as well.
	[Reply w/Quote]

10-06-2009, 08:40 AM	#5
phaderus Registered User Join Date: Aug 2008 Posts: 27 Location: User is: OffLine	Re: Starts, idles itself high, bogs to stall... IIRC there is larger plug on the back passenger side of the throttle body that goes to the PVC valve in the passenger side. There is a tube about 1/2 wide off of the air breather that goes to drive side for blow-by gasses. If you have the Hayes manual there is an image of the PVC system on page 6-18. One line goes to the egr controller and a line from that goes to the EGR valve. As Jaxom said the front plug goes to the MAP sensor. One vacuum plug will go to a vacuum line that comes from the firewall. It controls which vents the air from HVAC comes from. then you have lines for vacuum canister, possible 4x4 actuator, and one if you cruise control. That is all I can think of the top of my head.
	[Reply w/Quote]

10-06-2009, 11:05 PM	#6
E.Morel Doin' Work Age: 22 Join Date: Aug 2009 Posts: 39 Location: User is: OffLine	Re: Starts, idles itself high, bogs to stall... The map vacuum line did the trick. That was the hose that was not connected... However my original issue remains... the truck idles WAY high.
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10-07-2009, 11:50 PM	#7
chaospartners Registered User Join Date: May 2007 Posts: 1,164 Location: Somewhere in Ohio User is: OffLine	Re: Starts, idles itself high, bogs to stall... thats a 2.8 for ya!
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