Rough Idle when Engine Reaches Operating Temperature

[Rick L]

This isn't my BMW E34 but another car that I have. It is 1984 Maserati BiTurbo (carbureted). Recently, I took the intake manifold off to get to the starter to fix loose connection and clean connector contact but after putting the manifold back and everything else, I noticed a rough idle (same thing with giving gas) when the engine reaches operating temperature. :( This ONLY happens when the engine is hot. When cold or during warm up, engine idles and runs very smooth but once it reaches operating temperature it does this. Click the link below to see what I mean. Any idea why this is? Sorry, took the video with my phone so video quality isn't that good. Anyway, thanks in advance for any comment or suggestions.

http://www.youtube.com/watch?v=AF_5TM20t-A

http://www.youtube.com/watch?v=BnOE5a3E48c

[h2oyo]

This isn't my BMW E34 but another car that I have. It is 1984 Maserati BiTurbo (carbureted). Recently, I took the intake manifold off to get to the starter to fix loose connection and clean connector contact but after putting the manifold back and everything else, I noticed a rough idle (same thing with giving gas) when the engine reaches operating temperature. :( This ONLY happens when the engine is hot. When cold or during warm up, engine idles and runs very smooth but once it reaches operating temperature it does this. Click the link below to see what I mean. Any idea why this is? Sorry, took the video with my phone so video quality isn't that good. Anyway, thanks in advance for any comment or suggestions.

http://www.youtube.com/watch?v=AF_5TM20t-A

http://www.youtube.com/watch?v=BnOE5a3E48c

I dont claim to know Maserati's but I had a 70 Porsche 991T that had the triple webers on it. I did pretty much the same thing you did to do a repair. I had to use a gasket sealer to seal up the vacuum leak. It did the exactly the same and had absolutely no rime or reason but that is what I had to do. Hope you figure it out soon that is a beautiful car.
Johan

[bimmo_2007]

I don't know much about Maserati, but as you said you took off the intake manifold and insalled it back, and the symptoms shows only at operating temprature I'd suspect that you forgot plugging a connector, sensor,...etc.

[Rick L]

Thanks for the info. I’m very thorough but I could have missed something (either forgotten a vacuum line or something). Looks like I would need to take this apart again to check and see since everything is so cramped in the engine bay.

Actually, I have few questions if anyone knows from this forum. I did not change the intake manifold gasket since they looked almost new (it’s the metal kind with rubber o-ring – see pictures below). If not changing the gaskets with the new ones cause a leak? Also, doesn’t anyone know the proper torque specs to tighten all aluminum engine and intake manifold? I torque it at 30 lbs.

http://www.iccrents.com/ICC/Driver/IntakeManifoldGaskets.jpg

http://www.iccrents.com/ICC/Driver/IntakeManifoldGaskets2.jpg

[632 Regal]

Rick,

Just watching the videos I was thinking gasket leak or something not plugged in. Reading your last post here I would confirm my earlier thought. Those gaskets might work twice but I would use spray tack or something else and not reinstall the intake on used dry gaskets. The way it's jumping all over you may have a pretty big leak. 30lbs torque doesn't sound like a bad guess ;)

[Rick L]

Thanks Jeff and everyone. I ordered new gaskets since they were inexpensive. Hope that does the trick. And of course, check all vacuum lines again... :)



Rick,

Just watching the videos I was thinking gasket leak or something not plugged in. Reading your last post here I would confirm my earlier thought. Those gaskets might work twice but I would use spray tack or something else and not reinstall the intake on used dry gaskets. The way it's jumping all over you may have a pretty big leak. 30lbs torque doesn't sound like a bad guess ;)

[Kibokojoe]

Lets hear what happens