BX 16v / XU9J4 Petrol/Idle queries

VisaGTi16v · Post by **VisaGTi16v** » 25 Nov 2005, 20:21

Hi 2 questions regarding the bx 16v XU9J4 engine.

1. Just been reading the Haynes BOL and it states that pre 1991 16v's can only run on 97 RON Leaded petrol. Is this true? The engine in my Visa came from a 1990 BX and ive been running it on 97/98 Unleaded! It does have a ported head so it may have had different inserts fitted but im not sure.

Can anyone confirm if unleaded is fine on those earlier engines? I was told in the past that my old 1.6 8v visa gti was fine on unleaded

2. Looking at a 309 tomorrow with a XU9J4 in it from a 405 as a every day road car. He says most of time it starts and idles fine but when cold like now it wont idle for first couple of minutes without some help from the throttle then is ok. You cannot adjust the idle speed on them so im thinking its the idle actuator valve on top of the inlet manifold playing up which to quote the BOL again says, "controls the volume of air bypassing the throttle valve at idle thus maintaining a suitable idle speed during warm-up and a constant speed when the engine is warm"

Could it be that? There is no choke to speak of as far as I know as its all controlled by that, ecu and temp sensors. He says its fine after couple of minutes though. If it is this I will take the one from my Visa along when I view tomorrow to see if he will let me put it on it when its cold to test.

cheers

AndersDK · Post by **AndersDK** » 26 Nov 2005, 04:37

As far as I know there is only one BX petrol that can not run on UN-leaded as pr the listings. That is the old BX14 with the earlier Visa/Peug205 1.4L engine (type 150x).
But even this engine has been reported by numerous owners to run fine on UN-leaded until the car was written off for other reasons.

Have you checked with Gabor's BX-DY site pages ? AFAIR both BX 16V versions are listed on the fuelling pages.

The idle problem could be a leak somewhere that closes up when heat distributes from the cylinder head.

VisaGTi16v · Post by **VisaGTi16v** » 26 Nov 2005, 09:38

I thought it sounded a bit silly. I mean if the earlier 8v was fine then theres no way they would have designed the 16v to only take leaded.

Hmm that sounds worrying about the idling. You dont think its something as simple as the idle actuator?

citronut · Post by **citronut** » 26 Nov 2005, 10:49

isnt there an auxilary air supply unit for cold start
regards malcolm

VisaGTi16v · Post by **VisaGTi16v** » 26 Nov 2005, 10:52

hmm don't know. off to take a look at it now

Paul Mi16 · Post by **Paul Mi16** » 26 Nov 2005, 11:33

My experiences of the Mi16 engine is a follows based on having a 205 GTi with an Mi16 lump.

Only the cat engines can use unleaded, these engine have the Bosch 1.3 Motronic injection system. The 405 that donated my engine was run on unleaded when it shouldnt have been, and suffered from lumpy running and erratic tickover after about 2 years in the 205, but i also ran it on unleaded, knowing one day i'd have to take the head off. In the end I found a rebuilt engine which the head suitable for unleaded, which had cost £200 to do.

As for the idle/cold start problem, i'd suggest the ecu as the cold start function is part of the ecu. After that it would be the idle valve or maybe blocked or clogged breather pipes. It sounds a useful bargaining tool. Test data for the idle valve is available, and the earlier Bosch ML4.1 system was used on the on the the 2.0 8v Vauxhall's so parts are easy to come by.

Paul.

nick · Post by **nick** » 26 Nov 2005, 11:41

Somewhere I have a copy of a booklet Citroen produced & handed out at dealers in the early '90s, listing their models which could or couldn't run on unleaded.
This backs up what has been said already - the early BX 16V should use leaded only.

jeremy · Post by **jeremy** » 26 Nov 2005, 12:33

Certainlky up to 1989 the 16 valve was considered suitable for leaded petrol only. tha later one with a cat would have to run on unleaded and I believe has a knock sensor - which is probably part of the explanation for leaded only.

Engines without inserted valve seats like earlier BLMC Mini's will not run on unleaded as the valve seats melt and deteriorate very quickly. Unleaded engines have stainless valve seats which are impervious to the problem but engines with inserts which were designed for leaded and therefor have non-stainless inserts suffer from the melting and pick up problem to some extent.

In fact the general experience is that these engines will run on unleaded for a considerable time and that the best time to have it re-seated is when it has to come apart for another reason.

What metal was used for 16 valve valve seats I don't know. What I do know is that most are high compression and I would not expect it to run happily on 96 octane which i believe is what ordinary unleaded is. Shell do a higher octane fuel which may give better results. It may have been octane requirements that lead to the initial requirement for leaded - and this may have also suited the french petrol available at the time.

VisaGTi16v · Post by **VisaGTi16v** » 26 Nov 2005, 12:55

Thanks for the replies. Just had a look at the 309. It was only the first 30 secs of so that it needed a bit of help idling. Dont think I will go for it though (its on ebay) as it may not last long term. He said it used to suffer a lot from low oil pressure on long corners which is what they can do and so he replaced the oil pump and also the big ends etc but didnt get the crank reground, said it looked fine. It may well be but I dont think I will risk the money on it especially as the rest of the car was a bit tatty

Re: Petrol. When I got my Visas engine from its donor, the head was in a bit of a state, breaking up around the valves etc so perhaps this was due to being on unleaded. So as this was going to cost a lot to fix I just got a flowed/ported head on exchange at the time. Its only done about 2500 miles since then and mainly ran on super unleaded although did run fine on 95 sometimes even with fast road cams. I think I will start putting LRP in it though to avoid any long term damage

cheers