3.8 Running Bad

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3.8 Running Bad

December 11, 2012, 07:06:16 PM

Let my mom take the bird out because i needed her Jeep she came back saying the car died on her a few times, I started it up it's idling real rough, bogging down on more than half throttle, feels really sluggish I had an extra fuel filter so I popped that in got a bit better but still is annoying, looked in the engine bay and the vacuum plug was missing? Could this cause it to have bad idle, bogging? Where does it go? I found the end that plugs in but I don't know where it goes.

3.8 Running Bad

Reply #1 – December 12, 2012, 12:34:31 AM

This is the HVAC vacuum check valve. The hose to the vacuum storage tank is off the nipple. This vacuum leak will cause poor idle.

3.8 Running Bad

Reply #2 – December 12, 2012, 12:34:40 AM

Do you have any unplugged vacuum lines in the area?

3.8 Running Bad

Reply #3 – December 12, 2012, 01:05:23 AM

the horizontal section is the source from the vac tree.
the sectioin that penetrates the fire wall is the vac source for all things considered for hvac especially for manual heat/cooling controls.

the third is missing but you will find it penetrating the pass fender well. this line leads to a vac storage round looking bomb looking thingy,

since you have no more stored vac pres, you would experience these symptoms.
search for a vac line near this area or a line that is going into the pass fender well.

also, follow your vac diagrams, they are accurate and you will see this T check valve on the diagram.

3.8 Running Bad

Reply #4 – December 12, 2012, 01:11:51 AM

Thanks I have the section that plugs into the tree, I just didn't know where it goes, I'll look inside the fender.

3.8 Running Bad

Reply #5 – December 12, 2012, 01:22:52 AM

the missing vac line "could have" pulled through the pass fender. thats what plugs into the missing point on the check valve.

3.8 Running Bad

Reply #6 – December 12, 2012, 02:06:32 AM

That's probably what happened, I'll have to look tomorrow.

3.8 Running Bad

Reply #7 – December 18, 2012, 05:35:10 PM

So i found the bomb thing and fixed up the vac line, it's a bit better but still bogs and wants to/does stall out when slowing down, I'm thinking maybe its clogged cats, ughh I just want to rip this pos out and throw it half way across my yard.

3.8 Running Bad

Reply #8 – December 18, 2012, 10:11:25 PM

if this is an 87,, i highly suggest you vist my diy link and dig into the area where i describe the gold fitting on the rear drivers side. its the section that talks about removing the carbon build up under the egr plate ect.

and also,, if you have a half second delay or maybe a second when hitting the gas, peek at the area discussing pulling the injector screens.

Also, a 5.0CFI finally matches the intake holes to the CFI tunnels.... more air. those 3.8CFI's had small air ports and did not match the intake at all.

you also have a factory equipped adjustable fuel pres regualtor and you prob didnt know it. the oem ones have a freeze plut in the top you drill / pop out using a punch which will reveal an allen head adjustment screw.
too much stuff to list but the CFI 3.8 is about as simple as it gets in the world of fuel injection,,, although the 2.5GM made it much simpler.

3.8 Running Bad

Reply #9 – December 29, 2012, 10:13:36 PM

okay so, I got a 5.0 cfi and swapped it on, got it all buttoned up but now the car idles at like 2-3k if you give it some gas it goes up and then drops to 1-1.5k and then quickly goes back to 2-3k. Also if I put it into drive it'll either idle at 1k or stall out.

3.8 Running Bad

Reply #10 – January 19, 2013, 02:44:16 AM

so this is my dilemma

3.8 Running Bad

Reply #11 – January 19, 2013, 12:05:22 PM

you must put the original green top injectors on the 5.0cfi. the 5.0 injectors have different resistance and different flow.
your going to dump too much fuel into the six cyl and fill up your oil pan!

now pay attention because i thought we solved this high rpm thing.
go down behind the coolant fill tank and locate the vac solenoid bank, there are a buch of vac driven solenoids there.
there is a main vac line feeder which is red. at the very bottom of the vac bank this main vac splits in two and there are plastic fittings which one of these may have broken. also pull off the red vac line on the round thingy and go to the intake and pull that off as well. plug off the end at the intake, suck on the other end and see if its holding vac. wash rense and repeat for the green, white, black and tan.

if your speaking to just the cfi and you did not lift off or remove the egr spacer block, then when you took presure off the four mounting bolts, the egr gasket may have cracked. this is a minor issue and just make your own gasket to resolve. if you choose to not have the egr but want to keep it in place for inspections, then make your "intake to egr spacer" gasket such that it blocks off the EGR ports. I have an etch and sketch of it.

sounds like your leaking or suckin air along the cfi base or egr base or another vac line somewhere

i did not know the 3.8L had buttstuffog guages,,?

3.8 Running Bad

Reply #12 – January 19, 2013, 02:09:22 PM

Yeah i thought the vac pressure bomb thing would be it and after patching up the line it started and drove fine. I'll try and do as you say and check all the vac libes. I installed the buttstuffog gaige from a turbocoupe.

3.8 Running Bad

Reply #13 – February 11, 2013, 09:30:50 PM

So i checked all the vacuum hoses again, found 2 others that were broken and patched them. I also changed the tps which helped, and it will actually stay running 2-3 minutes. Now though my alternator keeps on draining my battery. So I'm guessing the alternator is bad or the voltage regulator is bad. Which makes me think that the alternator is not providing enough current for the coil and gas floods the engine causing it to stall. Could i be on the right track?