Starting Problems, Starting with Throttle but Won't Idle Options

[nmkimosabe]

My 1974 1.8 with fuel injection will only start by manually opening the throttle but I can't get it idle and thus run properly. I recently had the AFM rebuilt and replaced the points, plugs, condenser and replaced the CHT sensor but the problem continues as it did before. I've looked for vacuum leaks to no avail with starter fluid. I now seek the expertise of the members of this forum for additional suggestions.

[TRP]

Congratulations on getting it to start and idle. The struggle with 1.8 and vacuum leaks can be a pain. a 60.00 smoke machine is completely worth the investment.

I'm trying to figure out how you found leaks down at the valve covers!!?

One area that plagued me for a bit was that my Auxiliary Air Valve wasn't sealing all the way once the car was warmed up, causing the idle to hang a bit. My deceleration valve was also not fully closing causing extra air to get pulled back into the system... and again... high idle. Those two items are the opposite of what you are getting.

Keep after it! it sounds like you are close.

Ted

[nmkimosabe]

Congratulations on getting it to start and idle. The struggle with 1.8 and vacuum leaks can be a pain. a 60.00 smoke machine is completely worth the investment.

I'm trying to figure out how you found leaks down at the valve covers!!?

One area that plagued me for a bit was that my Auxiliary Air Valve wasn't sealing all the way once the car was warmed up, causing the idle to hang a bit. My deceleration valve was also not fully closing causing extra air to get pulled back into the system... and again... high idle. Those two items are the opposite of what you are getting.

Keep after it! it sounds like you are close.

Ted

Here is my understanding of leaks at the valve covers: Because the engine's crankcase is connected to the intake manifold via the crankcase breather hose, smoke fills the entire vacuum and crankcase system simultaneously. Since the pushrod tubes create an open tunnel between the engine crankcase and the valve rocker boxes, any gap in the valve cover gaskets becomes an instant exit point for the smoke. I'm hoping the new oil filler cap seals and valve cover gaskets will help smooth out the idle. Stay tuned and thanks for your response.
Gary

[wonkipop]

Congratulations on getting it to start and idle. The struggle with 1.8 and vacuum leaks can be a pain. a 60.00 smoke machine is completely worth the investment.

I'm trying to figure out how you found leaks down at the valve covers!!?

One area that plagued me for a bit was that my Auxiliary Air Valve wasn't sealing all the way once the car was warmed up, causing the idle to hang a bit. My deceleration valve was also not fully closing causing extra air to get pulled back into the system... and again... high idle. Those two items are the opposite of what you are getting.

Keep after it! it sounds like you are close.

Ted

Here is my understanding of leaks at the valve covers: Because the engine's crankcase is connected to the intake manifold via the crankcase breather hose, smoke fills the entire vacuum and crankcase system simultaneously. Since the pushrod tubes create an open tunnel between the engine crankcase and the valve rocker boxes, any gap in the valve cover gaskets becomes an instant exit point for the smoke. I'm hoping the new oil filler cap seals and valve cover gaskets will help smooth out the idle. Stay tuned and thanks for your response.
Gary

good stuff.

the curious thing about the 1.8 L jets is the oil cap itself is also the pcv valve.
its all built into the cap (the bit that screws off), quite unlike the D jets.

there is a vacuum operated membrane built into the very top of the cap.

the membrane and therefore the entire cap can fail, (at this point in time after half a century) - not just the seal which is a giant o-ring on top of the thread.
the EC engines in the VW 412 just had the top portion of the oil filler cap as the pcv valve - those engines had a separate oil filler cap and tube that came out in the body work on the inners after you lifted the engine lid.

so if new cap o-ring does not do the trick, investigate the cap itself further.
if the membrane (diaphram) has failed smoke will blow through the tiny hole in the centre of the top of the cap. if the o-ring has failed smoke will trail out around the edges of the cap.

[nmkimosabe]

Congratulations on getting it to start and idle. The struggle with 1.8 and vacuum leaks can be a pain. a 60.00 smoke machine is completely worth the investment.

I'm trying to figure out how you found leaks down at the valve covers!!?

One area that plagued me for a bit was that my Auxiliary Air Valve wasn't sealing all the way once the car was warmed up, causing the idle to hang a bit. My deceleration valve was also not fully closing causing extra air to get pulled back into the system... and again... high idle. Those two items are the opposite of what you are getting.

Keep after it! it sounds like you are close.

Ted

Here is my understanding of leaks at the valve covers: Because the engine's crankcase is connected to the intake manifold via the crankcase breather hose, smoke fills the entire vacuum and crankcase system simultaneously. Since the pushrod tubes create an open tunnel between the engine crankcase and the valve rocker boxes, any gap in the valve cover gaskets becomes an instant exit point for the smoke. I'm hoping the new oil filler cap seals and valve cover gaskets will help smooth out the idle. Stay tuned and thanks for your response.
Gary

good stuff.

the curious thing about the 1.8 L jets is the oil cap itself is also the pcv valve.
its all built into the cap (the bit that screws off), quite unlike the D jets.

there is a vacuum operated membrane built into the very top of the cap.

the membrane and therefore the entire cap can fail, (at this point in time after half a century) - not just the seal which is a giant o-ring on top of the thread.
the EC engines in the VW 412 just had the top portion of the oil filler cap as the pcv valve - those engines had a separate oil filler cap and tube that came out in the body work on the inners after you lifted the engine lid.

so if new cap o-ring does not do the trick, investigate the cap itself further.
if the membrane (diaphram) has failed smoke will blow through the tiny hole in the centre of the top of the cap. if the o-ring has failed smoke will trail out around the edges of the cap.

Thanks for the info. I also have a new oil cap coming just as backup in case the new O-ring & gasket don't help.
Gary

[wonkipop]

Congratulations on getting it to start and idle. The struggle with 1.8 and vacuum leaks can be a pain. a 60.00 smoke machine is completely worth the investment.

I'm trying to figure out how you found leaks down at the valve covers!!?

One area that plagued me for a bit was that my Auxiliary Air Valve wasn't sealing all the way once the car was warmed up, causing the idle to hang a bit. My deceleration valve was also not fully closing causing extra air to get pulled back into the system... and again... high idle. Those two items are the opposite of what you are getting.

Keep after it! it sounds like you are close.

Ted

Here is my understanding of leaks at the valve covers: Because the engine's crankcase is connected to the intake manifold via the crankcase breather hose, smoke fills the entire vacuum and crankcase system simultaneously. Since the pushrod tubes create an open tunnel between the engine crankcase and the valve rocker boxes, any gap in the valve cover gaskets becomes an instant exit point for the smoke. I'm hoping the new oil filler cap seals and valve cover gaskets will help smooth out the idle. Stay tuned and thanks for your response.
Gary

good stuff.

the curious thing about the 1.8 L jets is the oil cap itself is also the pcv valve.
its all built into the cap (the bit that screws off), quite unlike the D jets.

there is a vacuum operated membrane built into the very top of the cap.

the membrane and therefore the entire cap can fail, (at this point in time after half a century) - not just the seal which is a giant o-ring on top of the thread.
the EC engines in the VW 412 just had the top portion of the oil filler cap as the pcv valve - those engines had a separate oil filler cap and tube that came out in the body work on the inners after you lifted the engine lid.

so if new cap o-ring does not do the trick, investigate the cap itself further.
if the membrane (diaphram) has failed smoke will blow through the tiny hole in the centre of the top of the cap. if the o-ring has failed smoke will trail out around the edges of the cap.

Thanks for the info. I also have a new oil cap coming just as backup in case the new O-ring & gasket don't help.
Gary

another gasket that can go is the throttle body to intake plenum gasket.
mine went hard and no longer seated properly - caused me similar issues to what you have experienced.
about 5-6 years ago after i had recommissioned it from 16 years of storage. (IMG:style_emoticons/default/sad.gif)
got a replacement repro gasket. problem solved.
but i think your smoke test would have picked up that one if it was a problem.

[nmkimosabe]

Congratulations on getting it to start and idle. The struggle with 1.8 and vacuum leaks can be a pain. a 60.00 smoke machine is completely worth the investment.

I'm trying to figure out how you found leaks down at the valve covers!!?

One area that plagued me for a bit was that my Auxiliary Air Valve wasn't sealing all the way once the car was warmed up, causing the idle to hang a bit. My deceleration valve was also not fully closing causing extra air to get pulled back into the system... and again... high idle. Those two items are the opposite of what you are getting.

Keep after it! it sounds like you are close.

Ted

Here is my understanding of leaks at the valve covers: Because the engine's crankcase is connected to the intake manifold via the crankcase breather hose, smoke fills the entire vacuum and crankcase system simultaneously. Since the pushrod tubes create an open tunnel between the engine crankcase and the valve rocker boxes, any gap in the valve cover gaskets becomes an instant exit point for the smoke. I'm hoping the new oil filler cap seals and valve cover gaskets will help smooth out the idle. Stay tuned and thanks for your response.
Gary

good stuff.

the curious thing about the 1.8 L jets is the oil cap itself is also the pcv valve.
its all built into the cap (the bit that screws off), quite unlike the D jets.

there is a vacuum operated membrane built into the very top of the cap.

the membrane and therefore the entire cap can fail, (at this point in time after half a century) - not just the seal which is a giant o-ring on top of the thread.
the EC engines in the VW 412 just had the top portion of the oil filler cap as the pcv valve - those engines had a separate oil filler cap and tube that came out in the body work on the inners after you lifted the engine lid.

so if new cap o-ring does not do the trick, investigate the cap itself further.
if the membrane (diaphram) has failed smoke will blow through the tiny hole in the centre of the top of the cap. if the o-ring has failed smoke will trail out around the edges of the cap.

Thanks for the info. I also have a new oil cap coming just as backup in case the new O-ring & gasket don't help.
Gary

another gasket that can go is the throttle body to intake plenum gasket.
mine went hard and no longer seated properly - caused me similar issues to what you have experienced.
about 5-6 years ago after i had recommissioned it from 16 years of storage. (IMG:style_emoticons/default/sad.gif)
got a replacement repro gasket. problem solved.
but i think your smoke test would have picked up that one if it was a problem.

UPDATE: Well, the car finally was running better in the shop but then died when the car was taken for a test drive. During this test drive the ECU was fried. The mechanic is in the process of replacing the ignition components including the points, rotor, cap, wires and possibly the coil as he thinks somewhere here is the issue that fried the ECU. He feels confident the wiring harness is in good shape. I wish I had better news and if any of you reading this has any further suggestions, they would be much appreciated. As an owner of many vintage Porsche's going back to 1966, I've never had such frustration especially with an engine that should be so simple.

[Artfrombama]

I too have a 74 1.8 with FI
I was having a similar problem but in addition to idle problems, was way down on power. Found the pipe from the air flow meter to the throttle body was cracked and was leaking a substantial amount of vacuum. Sourced a good replacement from the classified section and was amazed how much better the car runs.
Not saying this is your problem but is easy to check.