crap running!

All aspects of tuning,modification and repairs to the BX 16valve.
ollie
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crap running!

Post by ollie »

As you know I have 2 of our beutifull beasts, one with 250K another with 150 K,
Problem is the 250K one runs nicely apart from high revs when the valve stem seals let it down, bit like the old CVH effect of a 6K rev limit when they fall off!
Drives beutifully otherwise!
But worse, the mechanically good 150K one has the standard crap idle and a slight miss at all revs, It does not appear to be a cylinder related thing, as it isn't rythmic, All ignition and associated electrics are new anyway from a previous problem and are fine.
What else would cause this?
I'm thinking: coolant temp sensor allowing overfuel - new citroen one 2 years ago, air flow meter, but it drives crisply otherwise, and have tried a spare, and the ECU which won't give any codes, fault or otherwise? is there anything else anyone can think of? otherwise I just start swapping bits complete car to car untill I find it!
next possibilities are throttle pot? and TDC sensor?

Ollie
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Timmo
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Post by Timmo »

ollie, as suggested to me over issues with my starting, have you had all the connecter blocks around the battery tray apart and cleaned up??? i did all of mine after a suggestion by a member and have cleaned and lightly vasalened them contacts and cable tied the plugs back together! It may not make the blindest bit of difference matey but you never know!
Timmo 8)

After all i am the Cornish one!

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ollie
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Post by ollie »

A good tip, but unfortunately these onlya ffect human operated items like warning lights, and of course the srater motor, alternator etc, however it has reminded me that the TDC sensor is in this area nd its connector may be covered in coolant....
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RobC
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Post by RobC »

my rough running only disappeared after i rebuilt my 150k engine! (don't worry i didn't rebuild it purely to cure the rough running, there were other reasons...) i did clean absolutely everything before i put it back together, so it was probably something like the throttle butterflies (which were dirty as hell and pretty sticky originally).
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Toddman
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rough idle

Post by Toddman »

You can check the TPD by testing it with a meter just keep making and breaking the micro switch and see how it goes if it makes/breaks 100% then obviously it is fine.
Well worth having the TB apart and setting the TPS acurately though IMHO.
The ICV also cause many problems by getting worn or gummed up so a good clean with carb cleaner thena lube with WD is always going to help.

On the ecu front I remember Robin having a very annoying misfire on ehis red BX, when idling every so often it would give a cough and eventually he found that a faulty connection on the knock sensor was to blame.
Is yiurs the early 4.1 system Ollie without any cat,lambda or knock sensor?

Also what combination of cam pulleys do you have as I have seen idles vary in smoothness according to the cam timing/

Cheers
Luke
Please call me Luke :)
1989 BX 16valve White 70k almost up to scratch
ed_straker
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Post by ed_straker »

wrong air possibly?!?!
Honda Civic Type S
ollie
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Post by ollie »

The crap idle does not bother me, its the missfire that does. have just dug out the spaer throttle bodies so will rebuild them for a swap.
Have no intention of rebuildingv the engine untill theres no car for it to go in! thern it can be done and get a proper control sytem for kitcar or such.

From the way it goes I reckon its got the best cam pulley set-up :twisted: and there shouldn't be too much wrong with it as I went to Pembrokeshire Sat am, 400 miles, 6 hrs including trafiic and collection, and still managed 40 ish to the gallon! that includes a few runs through the gears just cos it can.

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daaristieweer,wiedurft
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Post by daaristieweer,wiedurft »

have the same problems, and i didn't solve it yet. I asked it on different forums, including 405mi16, but we are the only ones i guess.....
When staring up for idling 40 seconds fine, and after that un uneven sound from the exhaust when idling. Also hasitating at 2500 rpm, and the engine is shacking at idling.

I checked and replace it all, except the fuel filter and checking the fuel pressure.......

Good luck, and please let me know....
Greetings, Jonne
bx16souppaes mk1
C4 HDI 110
ed_straker
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Post by ed_straker »

Could be the problem with my car: fuel filter changed, but didnt check fuel pressure and quality, so could be dirt or water in the tank.
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csg100
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Post by csg100 »

daaristieweer,wiedurft wrote: When staring up for idling 40 seconds fine, and after that un uneven sound from the exhaust when idling. Also hasitating at 2500 rpm, and the engine is shacking at idling.
Exactly the same problem on mine. Someone suggested the fuel filter and pressure check to me last night. May have to try that. But how would you check the fuel pressure?
Carl
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1990 Citroen BX 16v
1982 Rover 3500SE
1988 Volvo 360 GLT (for sale)
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Timmo
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Post by Timmo »

there are a new breed of pressure boost guage that has a gauge ont he top to show the pressure! although that may be a bit ott for a quick check but worth bearing in mind!
Timmo 8)

After all i am the Cornish one!

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ollie
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Post by ollie »

A good idea!, would have expected this to notice more at high revs when demand fotr fuel is greatest, but then logic rarely applies to a citroen!

Testing fuel pressure is a little tricky, you can buy a kit of guages but I guess any pressure guge and a T peice in the line would do, just need to be carefuill to get the fuel out after....

Fuel pumps are reckoned to have a limited life, I may just try a spare after comparing readings from the 2 cars.

The pressure is regulated by the return from the fuel supply rail, essentially a spring loaded diaphrgm on the end of the rail, I have a spare so may just swap complete, changing the o rings on the injectors at the same time!
In fact a blocked return would also play havoc with low rev return flow so had better check that too!

Injector pattern is also a possibility, but I can't easily check that!

ollie
AlanS
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Post by AlanS »

We've had most of these problems over the years and in most cases, it takes a lot of fiddling around rather than major technical conundrams to sort them out.
Here's a few suggestions for you.

Injectors:
The electrical plugs are usually fitted dry; we prefer to lightly coat them with silicone grease before fitting,. The reason being that the actual pins can slide back up inside the insulation when they're dry and tight. This can cause uneven idling due to non solid contact being made. If bad enough, can prevent car actually starting and on occasions can cause misfiring at high revs also, but more commonly causes problems at idle.
"O" rings on injectors can harden with age and can leak. Often the leak is more in the form of drawing air rather than leaking fuel; the latter being the usual source of underbonnet fires.
The holes in the head that the injectors fit into, I've seen almost totally closed over with carbon build up particularly on cars that have been driven a lot in a City driving environment.
Caps when popped off the end of the injectors often are full of crap causing spray pattern problems.

Stepper motor can cause problems if doesn't rotate freely. It can stick and create an erratic idle.

Ignition system: Seen so many caught with the coil having a conductive coating that earths out the ignition I've lost count. Wash the LT plug area with petrol, WD40, more petrol, more WD40, more petrol and then blow dry with compressed air. Keep doing it until you're positive there's no shorts between the LT and HT sides of it and that the + and - sections of the LT plug are definitely not shorting across. It MUST be removed from the car to stand any chance of success.

Plug leads: Again, can lull you into a false sense of security. One of the worst misses I ever had came when I fitted a new set of plug leads. 2 & 3 being the two potentially biggest offenders as they are of identical length even though the run length is different.
The problem arises from the shape of the end and the area they have to fit into. The long rubber extension to the end that fits on the plug usually will trap itself on teh porcelain and as a result does not allow the metal part to firmly attach to the top of the plug thereby causing the spark to have to "jump" to get to it's destination. Added to this is the square section at the top which is used to push the lead onto the plug. On particularly 2 & 3 these have to be fed in at a strange angle and the bunch of HT leads running in their channels can also be a problem as regards access goes.
Again, I use a coat of silicone grease or at worst silicone spray around the lip of the section that sits over the plug and a coat on the outside of the square knob where it fits down the valley. Press down until you feel an actual "click" as the lead attaches to the plug. I have often wondered if incorrect fitting to the plugs may be the cause of a few of the distributor caps and rotors that have burnt out due to the spark intensifying and loading up conponents further down the circuit.
Air leaks: can be a problem, although I did once remove my intake manifold once and had no gasket available to replace it with, so used a coat of silicone and bolted it straight on. It was another 2 years before I got around to fitting a new gasket, so manifolds as such seem pretty well made but some of the attached hoses can be worthy of inspection.

Hope all that is of some help to somebody. Not big jobs, in fact will possibly take less time to do those than it took me to type this. :oops: :oops:


Alan S
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thanuttiscotsman
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Post by thanuttiscotsman »

hi there,
i have recently solved similar problems with my car. i would check the following, dizzy cap, rotor arm and would try adjusting idle mixture. my car used to stall evertime i revved it up whether it was to 1500rpm or 5000 it died on return to idle every time. it also idled quite crap was eating fuel and constantly had smoke coming out back end. i have just cured this by adjusting the afm flap spring tension. i moved it round about ..well from one of the 512 marks on it to the next so probally 5 or 6 notches. and now she idles very steadily never stalls when i rev it and the fumes from the exhaust are clear as still water. im very pleased as i thought the head gasket was gone. i never thought it could be that before but it actually adjust the fuel mix considerably. now my afm is a re-con replacement which was probally tuned well to its previous engine but didnt agree with mine. so i would defo get the top off it and try adjusting it to see what difference it makes. its very easy as i done for the first time and its solved about 4 of my cars biggest problems.


cheers rossco
1989 BX 16v ph1 Big project chipped, k+N, scorpion s/s, weber throttle body, Nitrous injection

1990 BX 16v ph2 (now scrapped)
iain a
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Post by iain a »

...mmmm might try that myself.....idle speed is fairly lumpy for me aswell.....
oh bugger!! What now?!?
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