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I just put my 1987 944 T all back together after changing the vacuum lines and deleting the ICV and Venturi. The car will start for a second or two but then dies. If I keep my foot on the gas at higher RPM the car stays alive but as soon as I let go it dies. I replaced the spark plugs and wires and the DME temp sensor. The car also has the lindsay racing MBC. Im thinking maybe I have the vacuum hoses connected wrong or there is a leak? Venturi delete done wrong? The car was running fine a month ago. All that I changed was vaccum lines but maybe something else got damaged in the process?
How did you delete the ICV? Did you bypass it or did you block off the lines? If you bypassed that will cause running issues. Also curious why you deleted it as you will have to now manually regulate the throttle to keep it idling when the engine is cold. Venturi delete is quite straightforward but if you think you may have done it incorrectly or inadvertently caused a leak, tee in a vacuum gauge and check the system works.
I didn’t delete the ISV but the ICV. I have a vacuum gauge installed, what should is a healthy reading? I didn’t buy a Venturi delete kit, instead I used Hester hose to make a make-shift version. I’ll check to make sure everything is connected right.
I didn’t delete the ISV but the ICV. I have a vacuum gauge installed, what should is a healthy reading? I didn’t buy a Venturi delete kit, instead I used Hester hose to make a make-shift version. I’ll check to make sure everything is connected right.
I meant ICV, corrected my post. I only ask because it’s an unusual thing to do for no reason and if you simply bypassed it by connecting the hoses then you will have issues with unmetered air.
Search is your friend about using a vacuum gauge to diagnose problems and leaks.
Well two of the hoses were already disconnected from the ICV for my boost controller and I read that the other one isn’t needed so I plugged the hole on the j boot. I don’t think it’s the idle screw, how can I check to see that the fuel regulator is working properly? I was doing some tests today and when I was reving aound 2500rpm the engine cut out. Also the vac gauge said 10psi so that’s a place to start.
Well two of the hoses were already disconnected from the ICV for my boost controller and I read that the other one isn’t needed so I plugged the hole on the j boot. I don’t think it’s the idle screw, how can I check to see that the fuel regulator is working properly? I was doing some tests today and when I was reving aound 2500rpm the engine cut out. Also the vac gauge said 10psi so that’s a place to start.
Sounds like you re-connected vacuum hoses incorrectly. One common mistake is to mix up the AOS hose and the ISV hose. At idle, you want 17-18Hg of vacuum, but since your car is not idling at the moment, I'm not sure your reading is all that useful. To be clear, are you saying you still have the idle stabilizer but bypassed the cycling valve in favor of a manual boost controller?
Sounds like you re-connected vacuum hoses incorrectly. One common mistake is to mix up the AOS hose and the ISV hose. At idle, you want 17-18Hg of vacuum, but since your car is not idling at the moment, I'm not sure your reading is all that useful. To be clear, are you saying you still have the idle stabilizer but bypassed the cycling valve in favor of a manual boost controller?
Yes I still have the Idle stabilizer and removed the cycling valve. I pretty sure I have the ISV/venturi delete hoses connected correctly. I kept the three piece metal tube to connect the AOS to the J-boot. Would having the small vacuum lines connected in the wrong way cause issues? If they all have a vacuum it should work right? Anyways i'll check to make sure they match the diagram.
Yes I still have the Idle stabilizer and removed the cycling valve. I pretty sure I have the ISV/venturi delete hoses connected correctly. I kept the three piece metal tube to connect the AOS to the J-boot. Would having the small vacuum lines connected in the wrong way cause issues? If they all have a vacuum it should work right? Anyways i'll check to make sure they match the diagram.
The 3 piece metal tube only uses the center tube. And all the other hoses connecting to it and the cycling valve get removed. Plug the line going to the j boot with a big bolt and hose clamp. The Venturi hose goes from the j boot to the isv to the manifold. Take some pictures of your vac lines, we can probably tell you what's wrong from that.
The 3 piece metal tube only uses the center tube. And all the other hoses connecting to it and the cycling valve get removed. Plug the line going to the j boot with a big bolt and hose clamp. The Venturi hose goes from the j boot to the isv to the manifold. Take some pictures of your vac lines, we can probably tell you what's wrong from that.
Yes I cut off the other lines on the tube so its just the big one, also the j-boot is plugged. Doesn't the Venturi go from the hardpipe-isv-manifold? I still haven't taken the manifold off due to school so i'll get to it tommorow and send pictures.
Yes I cut off the other lines on the tube so its just the big one, also the j-boot is plugged. Doesn't the Venturi go from the hardpipe-isv-manifold? I still haven't taken the manifold off due to school so i'll get to it tommorow and send pictures.
Yes the hard pipe, sorry typo.
My setup is similar to this, but I simplified mine a bit more, by removing the vac line starting under the throttle body and it's connecting systems. The charcoal canister system was removed.
So like this:
You'll have to plug the nipple under the throttle body and connect the the blue and black plastic one way valve to the vac line at the fuel pressure regulator. I remember there being another vac line that ran to the j boot near the turbos auxillary water pump that gets removed and there's a long one that runs back to the fuel tank that gets removed. You cut it off near the tank above the passenger CV axle, some people install a filter on there or just leave it open. It just vents excess pressure in the tank. You also remove the charcoal canister hiding behind the driver side fender plastic trim.
Last edited by mahoney944; 01-18-2019 at 12:48 PM.
My setup is similar to this, but I simplified mine a bit more, by removing the vac line starting under the throttle body and it's connecting systems. The charcoal canister system was removed.
So like this:
You'll have to plug the nipple under the throttle body and connect the the blue and black plastic one way valve to the vac line at the fuel pressure regulator. I remember there being another vac line that ran to the j boot near the turbos auxillary water pump that gets removed and there's a long one that runs back to the fuel tank that gets removed. You cut it off near the tank above the passenger CV axle, some people install a filter on there or just leave it open. It just vents excess pressure in the tank. You also remove the charcoal canister hiding behind the driver side fender plastic trim.
Is there any benefit to removing all that stuff? Or just to simplify? Also which way should the arrow be pointing on the ISV?
Is there any benefit to removing all that stuff? Or just to simplify? Also which way should the arrow be pointing on the ISV?
It reduces many vacuum lines that could cause leaks, weight reduction with the canister removed, and just overall makes the engine bay more tidy. The vac lines being as simple as possible makes checking all your vac line a 2 second process without hurting normal operation. I prefer it that way. I think about as a simple vac loop that connects the fpr to the dampener then you "T" to the manifold for a vacuum source, "T" to the bypass valve, "T" to the blue/ black one way valve. Simple as that.
The isv arrow points towards the manifold.
The vac lines that are not on the picture but worth checking are the ones on the car side of the blue/ black valve. There should be a line running to the canister beside the battery from the blue/black valve with a line "T" ing off that goes to the nipple on the heater core on the firewall, the other nipple there runs to the plastic heater valve between the back of the head and firewall.
Well I took off the manifold this morning and can't find anything wrong with the vacuum lines or venturi hoses, seems to match the diagrams. Here's a picture.
01-14-2019, 10:48 PM
944 T Starts then dies without throttle
