1985.5 Porsche 944 Engine Hesitation
#31
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Feeling a bit disheartened...
Still haven't been able to identify the root cause of the hesitation/sputter...
Over the Holiday's I had time to do the following:
Still haven't been able to identify the root cause of the hesitation/sputter...
Over the Holiday's I had time to do the following:
- Replaced engine mounts
- Replaced intermediate steering shaft
- Replaced brake booster
- Replaced brake master cylinder
- Tested AFM and re-positioned wiper arm
- Tested AFM relay
- Water temp gauge fluctuates. Had thermostat replaced in August (rated for 80°C/176°F). At times it'll hit 100°C...
- Cam tower gasket oil leak
- Incorrect adjustment after installing TPS sensor?
- Incorrect idle speed adjustment tuning? (referred to Clarks-garage. Adjusted idle after running the engine for 10 minutes...)
- O2 sensor out of spec?
- Possible intake and exhaust manifold leaks?
#32
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#33
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I spent some time on the 944 this morning hoping to pinpoint the issue...I checked the gap of the spark plugs and re-gapped them to 0.029". I did notice the terminal threaded tops were loose so I carefully tightened them with some pliers. The plugs I installed are Bosch WR8DS and the wires were replace as well(Beru)...
I also cleaned the throttle body; which had a good amount of oil buildup, the throttle position sensor, and replaced the fuel filter, yet, there is still a hesitation at idle and "popping" from the exhaust... Attached is a picture of an old plug (all having the same wear) and the throttle body before I cleaned it...maybe they'll help diagnosis the issue.
Is there a vacuum line diagram available for the 944 8v? Maybe there's a hose/line that I was unable to catch...and speaking of vacuum lines/hoses, what's their purpose? I'm hoping the injectors haven't failed because they are quite expensive..Lastly, are there detrimental effects to the engine if I drive the car while I'm self-diagnosing it? At the moment it's my daily driver...
I also cleaned the throttle body; which had a good amount of oil buildup, the throttle position sensor, and replaced the fuel filter, yet, there is still a hesitation at idle and "popping" from the exhaust... Attached is a picture of an old plug (all having the same wear) and the throttle body before I cleaned it...maybe they'll help diagnosis the issue.
Is there a vacuum line diagram available for the 944 8v? Maybe there's a hose/line that I was unable to catch...and speaking of vacuum lines/hoses, what's their purpose? I'm hoping the injectors haven't failed because they are quite expensive..Lastly, are there detrimental effects to the engine if I drive the car while I'm self-diagnosing it? At the moment it's my daily driver...
What is the source of oil? It is probably the engine crank case. What parts attach to the crank case? Is one of those parts letting excessive oil vapor into the intake because the internals of the part failed. Maybe a source of unmeterrd combustion air. Popping at exhaust indicated a lean mixture.
#34
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@T&T Racing Thanks for your input! Could you go more into detail about connection(s) "upstream" of the throttle body? What areas could let excessive oil vapor into the intake?
Also, I just realized my car was built for CA emissions. Are there specific settings/adjustments for these cars; for instance, idle speed adjustment? The car could be receiving too much air, creating a lean mixture, since I tinkered with the idle speed valve (on the throttle body) and installed a throttle response cam...
Thoughts?
Also, I just realized my car was built for CA emissions. Are there specific settings/adjustments for these cars; for instance, idle speed adjustment? The car could be receiving too much air, creating a lean mixture, since I tinkered with the idle speed valve (on the throttle body) and installed a throttle response cam...
Thoughts?
#35
Drifting
He's referring to the connections before the throttle body (other than crankcase venting via air/oil separator, air is flowing from air cleaner to throttle body, therefore before TB equals "upstream"
From my reading of the procedures in the workshop manuals, there is no difference between California cars and the rest of North America
From my reading of the procedures in the workshop manuals, there is no difference between California cars and the rest of North America
#36
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He's referring to the connections before the throttle body (other than crankcase venting via air/oil separator, air is flowing from air cleaner to throttle body, therefore before TB equals "upstream"
From my reading of the procedures in the workshop manuals, there is no difference between California cars and the rest of North America
From my reading of the procedures in the workshop manuals, there is no difference between California cars and the rest of North America
#38
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@Swenny I will have to make a note to replace the AOS seals as preventative maintenance. Thankfully, the air filter compartment/housing was very clean and dry. Nothing like the picture you posted...
@T&T Racing What could cause a lean mixture? Just today, I disconnected the o2 sensor (at the back of the engine) to see if there were any changes in the behavior of the car. At first, I thought I may have found the issue, but the popping/sputtering at the exhaust reappeared...several things I noticed during this test:
@T&T Racing What could cause a lean mixture? Just today, I disconnected the o2 sensor (at the back of the engine) to see if there were any changes in the behavior of the car. At first, I thought I may have found the issue, but the popping/sputtering at the exhaust reappeared...several things I noticed during this test:
- Lots of smoke from the exhaust (white/gray)
- The engine hesitation/exhaust sputter started to happen more frequently as the engine was heating up
#39
Racer
My guess with the white/grey smoke and the popping from the exhaust is that you need a head job and/or rings. The AOS is the easiest thing to check first,the seals slowly fail until one day you're putting the petal down and then poof! Oil throughout the intake.You've checked that so a valve,ring job or even the worst case- worn out cylinders. A compression test and a leak down test could confirm that.
#40
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Originally Posted by pointFive;15557109.
[utag=110213
[utag=110213
T&T Racing[/utag] What could cause a lean mixture? Just today, I disconnected the o2 sensor (at the back of the engine) to see if there were any changes in the behavior of the car. At first, I thought I may have found the issue, but the popping/sputtering at the exhaust reappeared...several things I noticed during this test:
- Lots of smoke from the exhaust (white/gray)
- The engine hesitation/exhaust sputter started to happen more frequently as the engine was heating up
#41
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Update: 3/14/2019 (updated running list)
Replaced the O2 sensor - no change
I did, however, notice an additional bung next to the O2 sensor as I was under the car. I traced the metal pipe, coming from the additional bung, and it seems to have been plugged by the previous owner at some time in time...
The last things I plan on doing before taking it to the shop:
Is this a common issue among Porsche 944's?
Replaced the O2 sensor - no change
I did, however, notice an additional bung next to the O2 sensor as I was under the car. I traced the metal pipe, coming from the additional bung, and it seems to have been plugged by the previous owner at some time in time...
The last things I plan on doing before taking it to the shop:
- Replace AOS seals
- Replace intake manifold gaskets
- Check various hoses underneath intake manifold
Is this a common issue among Porsche 944's?
#42
Drifting
Update: 3/14/2019 (updated running list)
Replaced the O2 sensor - no change
I did, however, notice an additional bung next to the O2 sensor as I was under the car. I traced the metal pipe, coming from the additional bung, and it seems to have been plugged by the previous owner at some time in time...
The last things I plan on doing before taking it to the shop:
Is this a common issue among Porsche 944's?
Replaced the O2 sensor - no change
I did, however, notice an additional bung next to the O2 sensor as I was under the car. I traced the metal pipe, coming from the additional bung, and it seems to have been plugged by the previous owner at some time in time...
The last things I plan on doing before taking it to the shop:
- Replace AOS seals
- Replace intake manifold gaskets
- Check various hoses underneath intake manifold
Is this a common issue among Porsche 944's?
#43
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Did you ever check that the fuel pressure regulator is working correctly? With exception of the grey sooty spark plug -- your symptoms mirrored ones I had with my 86. It turned out to be a failed diaphragm in the fuel pressure regulator. The vac system was sucking fuel past the failed diaphragm causing a rich condition that mimics your videos. Only diff was my plugs were dirty and wet. Try putting vac on the output vac line on the FPR and if you see fuel -- it has failed.
Just a thought.
Dan C.
Just a thought.
Dan C.