Car won't idle after replacing vacuum pipes

adam928 · 01-15-2016, 09:58 AM

My ht leads had seen better days, so I thought I would replace them, and, as is often the case that lead me to thinking I may as well replace the vacuum pipes at the same time whilst I'm at it!

I'd seen a thread on here a while back where blue silicon pipe had been used, and thought I'd try that too!

Put it all back together, started first time, ran smooth, but idled at about 2000rpm! Then as it warmed the revs dropped, and it cut out! It won't idle now without cutting out!

Now, 2 things that I did notice that wasn't right, was the top vacuum pipe on the warm up regulator had a screw in it, and then the pipe was pushed on. also, the electrical connector on the front of the inlet manifold was connected, and hadn't been for many years, judging by the amount of muck on it!

I should say at this stage, I've had the car for about 20 years, but not really tinkered on it that much! It had had a recent engine rebuild when I got it, and never had issue with it. Also, I've only recently started to drive it again. I got it running after being sat for 5 years with just a new dizzy cap, plugs, and fresh fuel! It then passed its mot in September.

It was missing slightly, but the new ht leads seem to have eliminated that. It always idled ok before, even with the 2 issues mentioned! It did have a reluctancy to start when it was warm though, and wondered if the blanking off of the wum, could be the reason?! I've been back over the pipes, and all seem tight and secure, and ideas you guys, what I could have disturbed ? It's an 83 s version, I guess you'd call it a euro, as I'm in the uk!

Regards, adam

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adam928 · 01-15-2016, 10:02 AM

Also replaced the 8 rubber connectors to the inlet manifold, if relevant!

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Danglerb · 01-17-2016, 06:49 AM

Unless its made for vacuum hose use some of the silicone stuff will collapse and no air flows. Failing to idle sounds like less air is flowing at idle, ie former leaks sealed, places that should have flow, don't.

All I know about CIS is the need for a set of gauges to measure control pressures.

adam928 · 01-17-2016, 02:28 PM

Thanks for the info, I was sold the silicon hose as appropriate for vacuum hose use, but will need to double check I guess! Just freezing in my garage at the moment, so may need to put it off a couple of weeks!

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adam928 · 01-18-2016, 04:32 AM

The larger blue hose to the left, on the last picture, appears to collapse! So will source a better one, and see if that cures it!!

MPDano · MPDano's Garage

I use silicone hoses and they are fine as long as they vacuum hoses (thicker walls). I don't use one on the AAV like you did though. I think you are on the right track by replacing the collapsed one. As Mike says, get some CIS gauges, you will need these to get it right.

adam928 · 01-18-2016, 02:46 PM

Yes, my error, didn't realise the amount of pressure these had to cope with! Looking at the several ply hoses out there to replace this one!

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adam928 · 01-29-2016, 05:48 AM

Replaced that collapsed hose with a steel reinforced silicon one, and runs fine at normal running temperature! It's seems to idle a little faster than before, at about 1050 rpm.
Also, when cold, it still idles at just over 2000 rpm, until it warms up! Do you guys think the warm up regulator could be at fault, or something else maybe? I've seem you can buy repair kits for these!?
I've connected the electrical connector back up, and removed the screw in the warm up regulator...

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9two8 · 02-01-2016, 11:47 AM

Here,s a good "how to" re the WUR..,

http://www.ferrari400parts.com/Warmupregulatorrepair.php

adam928 · 02-01-2016, 12:35 PM

That's makes an interesting read! And certainly do-able!
It does state at the start, not suitable for wur with vacuum? Is there much of a difference?
Do you think the wur if the problem with the high revving too?

Cheers, Adam

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aluminum · 02-02-2016, 04:30 PM

"Replaced that collapsed hose with a steel reinforced silicon one, and runs fine at normal running temperature! It's seems to idle a little faster than before, at about 1050 rpm. "

The little bit higher Idle ( 1050 ) Most Likely is because with the replaced V. Lines you corrected a " Vacuum Leak "
If you want to slow the warmed Up Idle just turn the Large idle Screw slowly Clockwise to slow the idle . Suggest you Mark or Photo the exact Position of the Idle Screw before you turn it in and keep track of how far you move it .
The Idle speed when Cold is another Issue . Warm should be around 900 / 950
Lots of the 928 Idle quite High when Cold but it should Kick down after some Min's
Trick : To check for Vacuum leaks simply ( outside somewhere ) run a Garden Hose at low speed over all the Vacuum Lines / Areas with motor running at idle and if you find one the motor well slow down as it sucks a bit of water > IE you just found a leak

adam928 · 02-04-2016, 11:21 AM

Thanks all for reply's and help...
I kind of suspected I may have fixed a leak, causing it to run a little quicker when warm?!
Please excuse my lack of knowledge, but where is the idle adjustment screw, is it only visible with the air box removed again?
Also the resistance against the wur terminals is 54 ohms, does this point to the unit being faulty?!

The revs do kick down after a few mins, but I've never known them that high!

Thanks again!

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Danglerb · 02-05-2016, 06:55 PM

Front of the throttle body, big slotted screw.

adam928 · 05-04-2016, 12:28 PM

After a period away from the car, I've been forced to get it back on the road, so some alterations can be made to the house!

Taxed it on Monday, and put it back on the road. Problem I have is, it will not idle when it's warmed up... Think changing the collapsing pipe was just a fluke. I found the original Aav pipe, and put that back on. I'm also satisfied there are no leaks now in the vacuum pipes I've replaced!
I'm at a bit of a loss what to check now, could I have disturbed anything when I removed the inlet manifold?! Other than the replacement vacuum pipes and ht leads, there is no change to the motor, from where it idled with no issue!!

Thanks in advance...

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adam928 · 05-05-2016, 11:39 AM

So! Just dimantled the intake system again, to find I hadn't got the plenum seated correctly in the rubber connector ring

Put it all back together, idled fine!!!
I'll see what it's like to drive again tomorrow!