PLENUM CHAMBER

[dukeenfield]

Hi,I have just stripped down the induction system on my 1986 350i and wondered what would be the best sealant to use on sealing up the Plenum chamber and the trumpets. Also do you use any sealant os silicon grease on aluminium induction gasket? and what torque should the induction bolts be torque down to?.
I also thought about having the injectors cleaned.

[GreenV8S]

I don't know what the approved sealant is for the plenum but I would have thought any non-permanent sealant would do. Ordinary silicone sealant would probably be adequate, or blue hylomar if you have that available. There is no need to seal the trumpets into the trumpet base but you do need to make sure they can't come loose. If they are a tight push fit they would be OK fitted dry. Otherwise use a smear of sealent as an adhesive to hold them in. Not sure what the aluminium induction gasket is you refer to. If you mean the valley gasket that goes between the intake manifold and the heads, I think this is normally fitted dry. Cleaning the injectors is a good idea. I gather from listening to the experts that dirty / clogged injectors seems to be a more common problem over recent years, perhaps the fuel formulation has changed.

Edited to add: torque for the plenum bolts, not much, a few lb-ft, just firmly nipped up.

>> Edited by GreenV8S on Sunday 14th November 11:40

[dukeenfield]

Thanks for your help,I'm trying to sort out hunting and won't tick/over (no revs)when I have been on a run for 10 minutes,also revs tend to go up and down.thanks KEN.

[tallbloke]

Try cleaning all the injection associated electrical connections. Especially those connected with the throttle position sensor on the plenum inlet, and the 4" by "2 amplifier on the inner wing with all the yellow wires coming from it.

[dukeenfield]

Hi,thanks i will try that.

[60maxx]

Hi had a similar problem with mine when i bought it, after completing a full diagnostic check (im in the trade) i traced the fault to a corroding swirl chamber which links both the fuel tanks, this was partially blocking the fuel injectors over a period of time, solution was to replace swirl chamber and ultrasonically clean the injectors (did at work), what a difference ! starting, idling, performance, general running was greatly improved,
I would suggest having a full diagnostic on the engine/ fuel injection system and even flow testing the injectors, hope this may help.

[dukeenfield]

Thanks for imformation,I was going to get injectors clean,but to expensive at £20.00 plus vat each,so i will have to just hope they are ok.I took it to injection centre and I thought they would test properly,but they did'nt seem to know what they where doing and said it could be airflow meter,but couldn't be sure.They charge me a lot of money for nothing and its just the same as before.So I Thought best to try and sort it out myself.

[HarryW]

Daft question as you're in the midlands why don't you see if TVR Power will run a diagnostic on it for a small fee. Could even be possibily less than getting the injectors cleaned if they didn't need it .

Harry

[dukeenfield]

Good idea,I will have to ring them if can't get sorted,thanks

[Boosted LS1]

dukeenfield said:

Thanks for your help,I'm trying to sort out hunting and won't tick/over (no revs)when I have been on a run for 10 minutes,also revs tend to go up and down.thanks KEN.

Make sure the rocker covers are screwed down tightly and you don't have any air leaks into the plenum/throttle area after the throttle. Check the pcv hosing. Don't forget air from the rockers can be drawn in via the pcv system which has a really small intake restriction on the rocker cover to keep the engine in vacuum. Any other air being leaked into the engine will be 'false air' and will enter the plenum, leaning out your mixture.

Boosted.

[60maxx]

Yes I know this can be expensive, however, without the correct information, tools and equipment, the alternative of I shall try this and that !! can be an expensive and time consuming alternative too !
I may be able to help with flow testing and cleaning the injectors so as to help obtain a good base for further diagnosis, if your interested you can E mail me at [e-mail]