It's finnaly happening: Rough idle

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gsa60
Started learning about 480
Posts: 96
Joined: Tue May 21, 2013 10:18 pm

It's finnaly happening: Rough idle

Post by gsa60 » Sun Jun 12, 2016 5:14 pm

Hi guys,
So, since last year I've been experiencing some rough idle issues on my '91 Turbo.
At first it started as a puff here and there when idle-cold. It was like one or two a second, but very unnoticeable.
On the last 2~3 months it got very worse: the idle would not stop going up and down, between 500RPM to 1300RPM. It was like I was challenging the guy next to me on the traffic light for a race :? . As soon as I step on the throttle the engine would be stable (perhaps still a bit of puf). On the morning, the engine was very week on the first couple of meters.
One thing I did find out was: if I disconnected the MAF plug and then reconnect it again (with engine running), the engine returned almost to normal (still some pufs). So I bought a MAF from a member here but still no luck. So I think we can rule-out the MAF.

Oh by the way, reseting the ECU did not help.

I think today I finally have found the culprit: crankcase breather setup.

So, around 3 years ago my original crankcase breather valve broke off. I had a lot of trouble finding a replacement, which I failed. So I had to come-up with a solution by reading a bunch of posts (both here and on other forums). This is the solution I found (forgive the paint skills).

Image

So basically I've connected with a tee pipe the crankcase breather with the pipe that goes to the turbo to the intake manifold. I've placed a non-return valve on the entrance of the manifold so that boost pressure would not escape from the engine intake to the turbo-intake.

The tests I've done today:
1) connect the crankcase breather (c) directly to the turbo intake (b) and blanked the intake (a). Result: seemed a bit better but still a bit lumpy.
2) connected the turbo intake directly to the intake manifold and let the gas from the crankcase breather go to the outside.Result engine Idle seemed very good.

Finally, the question is: anyone knows what I'm doing wrong? does any of this makes sense? BTW I'm using a one-way valve like this one http://www.ebay.com/itm/10mm-3-8-Fuel-N ... 11&vxp=mtr which is 10mm (or 8mm of inside diameter), the tee pipe is the same width.
Why just now Is it giving Issues?

Also, I would want to avoid to the max running the car with the crankcase breather gas going to the atmosphere. For 1 there is horrible smell. And second, when my original breather valve broke I let the engine breath to the outside and after a month the engine was leaking oil from everywhere. It was a huge bill to repair that.

Thanks a lot for the help! and Sorry for the lengthy post.
Cheers

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AleksanderHugo
Started learning about 480
Posts: 54
Joined: Wed Aug 24, 2016 7:13 pm
Location: Lodz, Poland

Re: It's finnaly happening: Rough idle

Post by AleksanderHugo » Fri Apr 28, 2017 8:58 am

I join this topic, although I have a non-turbo 2.0 engine. I guess that on a non-turbo engine, the breather cannot cause idling issues, since the air from the breather connects to the intake before the throttle. Am I right?

Nevertheless, I am thinking about replacing my breather, since it lets some oil into the intake and seems to flood the throttle position sensor. Of course, there are no original breathers available, but I thought about using one from Renault:
http://m.ebay.co.uk/itm/321853196341

I do not want to disconnect my breather from the engine, before I have a replacement part available. Do you know if this Renault breather will fit?

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