I have a 1991 (H reg) BX 19GTi. It uses the Motronic MP3.1 ignition system, - no CAT.
The Problem I have is that on 'mild' acceleration, it 'pinks' (pre-ignition) - On 'harsh' acceleration 'pinking' is not present.
Is there anything a DIY person with a multimeter and a few tools can do here? - or do I have to entrust it to a Citroen dealer? I would normaly want to adjust the timing a bit, but I understand this is not an option due to the ECU controling it all.
Regards, Paul.
'Pinking' BX 19GTi
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jeremy
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Have you checked basics like plug type? - might be wrongg heat range.
Otherwise make sure all your breather hoses are good and tightly fitted - possibly an air leak could weaken the mixture on one or more cylinders.
While the 8 valve GTi is relatively low compression have you tried a different fuel in it? I remeber in the days of leaded petrol I had a Scirrocco GTi and ran it exclusively on one of the major brands of fuel. Over a couple of weeks it went from beautiful to horrible and I was thinking a tuen up was necessary. I got 'caught short' one night and had to put another brand in - wow - just ran perfectly. The same brand would make my XJ6 pink as well - their diesel seems ok!
Shell sell a newish higher octane fuel which may help (Optimax?)
Jeremy
Otherwise make sure all your breather hoses are good and tightly fitted - possibly an air leak could weaken the mixture on one or more cylinders.
While the 8 valve GTi is relatively low compression have you tried a different fuel in it? I remeber in the days of leaded petrol I had a Scirrocco GTi and ran it exclusively on one of the major brands of fuel. Over a couple of weeks it went from beautiful to horrible and I was thinking a tuen up was necessary. I got 'caught short' one night and had to put another brand in - wow - just ran perfectly. The same brand would make my XJ6 pink as well - their diesel seems ok!
Shell sell a newish higher octane fuel which may help (Optimax?)
Jeremy
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alan s
- RIP 2010
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Paul,
I am not 100% sure that you are correct in saying you can't adjust the timing.\The reason I say this is that one of my sons bought an absolute doll of a TZi BX a year or so ago with only 90,000 klms on the clock. When I drove it, the damn thing was bucking & pinging and felt generally terrible to drive & the car had service records that said it had been serviced by a specialist with a good reputation. I spotted that the distributor had two bolts on it with slots in the base of the distributor, so I grabbed my strobe timing light, scratched my way through the myriad of pipes & wires at the front of the motor until I accessed the hole in the bell housing where I could see the flywheel & found the timing was waaaaay out. Readjusted it to where I reckoned it should be & it's never pinged or missed a beat since.
I don't know the type of system you have, but if the distributor has slots in its base, it's possible to adjust your timing.
I have been running on the highest octane available (98 octane) ever since & get terrific fuel consumption & performance almost up to the standard of my 16V
Worth a look in case yours is the same. Incidentally, the previous owners of my sons car were also told the timing was non adjustable.
Alan S
I am not 100% sure that you are correct in saying you can't adjust the timing.\The reason I say this is that one of my sons bought an absolute doll of a TZi BX a year or so ago with only 90,000 klms on the clock. When I drove it, the damn thing was bucking & pinging and felt generally terrible to drive & the car had service records that said it had been serviced by a specialist with a good reputation. I spotted that the distributor had two bolts on it with slots in the base of the distributor, so I grabbed my strobe timing light, scratched my way through the myriad of pipes & wires at the front of the motor until I accessed the hole in the bell housing where I could see the flywheel & found the timing was waaaaay out. Readjusted it to where I reckoned it should be & it's never pinged or missed a beat since.
I don't know the type of system you have, but if the distributor has slots in its base, it's possible to adjust your timing.
I have been running on the highest octane available (98 octane) ever since & get terrific fuel consumption & performance almost up to the standard of my 16V
Worth a look in case yours is the same. Incidentally, the previous owners of my sons car were also told the timing was non adjustable.
Alan S
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PJ
- Posts: 8
- Joined: 05 Jun 2003, 14:49
Alan,
Thanks for your reply - my earlier 19GTi had the type of distributor that you mention here - however, my current one has not got a distributor and rotor arm - it uses the 'twin coil and wasted spark' method (i think that's what it's called [:I]) Hence the distributor is just 'bolted' on in the traditional position as somwhere to put it! Moving it will have no affect on ignition timing!
Jeremy - you mention this 'Optimax' from Shell - a few other people rate this fuel as well - so may be I should find some and try it!
The Plugs by the way are the correct spec' - but they could probably do with a change. A few things to try.
Thanks.
Paul[:)]
Thanks for your reply - my earlier 19GTi had the type of distributor that you mention here - however, my current one has not got a distributor and rotor arm - it uses the 'twin coil and wasted spark' method (i think that's what it's called [:I]) Hence the distributor is just 'bolted' on in the traditional position as somwhere to put it! Moving it will have no affect on ignition timing!
Jeremy - you mention this 'Optimax' from Shell - a few other people rate this fuel as well - so may be I should find some and try it!
The Plugs by the way are the correct spec' - but they could probably do with a change. A few things to try.
Thanks.
Paul[:)]
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jeremy
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Homer
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<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by PJ</i>
Jeremy - you mention this 'Optimax' from Shell - a few other people rate this fuel as well - so may be I should find some and try it!
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
I had 4 BXs (3 1.6 petrol and a 1.9 petrol with a cat) <b>none</b> of them ran very well on Shell. Optimax wasn't around at the time though.
Jeremy - you mention this 'Optimax' from Shell - a few other people rate this fuel as well - so may be I should find some and try it!
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
I had 4 BXs (3 1.6 petrol and a 1.9 petrol with a cat) <b>none</b> of them ran very well on Shell. Optimax wasn't around at the time though.
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jeremy
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I haven't tried 'Optimax' myself as I'm currently running a couple of diesels but I think its rated at 98 octane. Ordinary (UK) unleaded is 96 and the GTi would have been designed for 98 - hence my suggestion that this fuel is worth a try.
To be fair to ordinary unleaded it sems to run well in many vehicles and isn't as prone to pinking as old leaded was.
While the 8 valve GTi isn't exceptionally high in its compression at 9.3 its in a range where ordinary unleaded may cause trouble.
My XJ6 at 8.75 :1 used to run better on the then available super + unleaded than it did on leaded. My Renault 21 (10 : 1) ran just as well on ordinary unleaded as it did on leaded (much to my surprise!)
Jeremy
To be fair to ordinary unleaded it sems to run well in many vehicles and isn't as prone to pinking as old leaded was.
While the 8 valve GTi isn't exceptionally high in its compression at 9.3 its in a range where ordinary unleaded may cause trouble.
My XJ6 at 8.75 :1 used to run better on the then available super + unleaded than it did on leaded. My Renault 21 (10 : 1) ran just as well on ordinary unleaded as it did on leaded (much to my surprise!)
Jeremy
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alan s
- RIP 2010
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I'm a bit of a high octane "junky" I suppose.
Where I am, I can get "Premium" unleaded" which all of our cars seem to run fairly well on.
I have used Optimax (98) in my sons TZi manual & it runs slightly better and I have also used BP Ultimate (98 also) in it & it is on par if not slightly better.
In contrast, my BX 16 Valve runs well on "Premium" (96 octane) yet the 98 stuff doesn't seem to make a scrap of difference to its performance.
Strangely enough, the greatest amount of improvement in any of our cars is in our series one CX 2400 Pallas c-matic...don't ask me why, but this car feels like it grows two extra cylinders when filled up with the 98 brew.
It's not imagination either; everyone notices the difference within about 5 miles.
Alan S
Where I am, I can get "Premium" unleaded" which all of our cars seem to run fairly well on.
I have used Optimax (98) in my sons TZi manual & it runs slightly better and I have also used BP Ultimate (98 also) in it & it is on par if not slightly better.
In contrast, my BX 16 Valve runs well on "Premium" (96 octane) yet the 98 stuff doesn't seem to make a scrap of difference to its performance.
Strangely enough, the greatest amount of improvement in any of our cars is in our series one CX 2400 Pallas c-matic...don't ask me why, but this car feels like it grows two extra cylinders when filled up with the 98 brew.
It's not imagination either; everyone notices the difference within about 5 miles.
Alan S
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Jon
Um, well an 8v BX GTi should run perfectly well on normal 95ron unleaded, and indeed the 2 I once owned many years ago ran just fine on this.
Lets go back to the original post from which we note that the car "pinks" on mild acceleration. Surely pinking/pinging will occur when the engine is under load, accelerating up hill, or using full throttle. You would not expect a car to pink on a light throttle would you?
To my mind this sounds more like some kind of fuel or ignition induced hesitancy. I would start by cleaning up the airflow meter flaps and body with suitable spray, then run some injector cleaner through the fuel system. Also check/change plugs and leads. If no better we could be looking at something like a duff water temp sensor which is giving the ECU false signals and making it run too rich???
Lets go back to the original post from which we note that the car "pinks" on mild acceleration. Surely pinking/pinging will occur when the engine is under load, accelerating up hill, or using full throttle. You would not expect a car to pink on a light throttle would you?
To my mind this sounds more like some kind of fuel or ignition induced hesitancy. I would start by cleaning up the airflow meter flaps and body with suitable spray, then run some injector cleaner through the fuel system. Also check/change plugs and leads. If no better we could be looking at something like a duff water temp sensor which is giving the ECU false signals and making it run too rich???
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PJ
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