co readings very low

[pionte]

Van just passsed MOT, but the CO reading was very low @ 0.66 % and HC of 271 ppm.

I have always been unhappy with how the engine runs, apart from when at motorway speeds.It will sit at an indicated 80 - 85 mph really well, just needing light throttle to maintain speed, but low revs and pulling away it hesitates and since I have fixed all the exhaust leaks ( now totally gas tight ) there is no popping back or backfire .

Does the very low C O reading worry you ? It does me.... I am hoping to get this sorted as it annoys me

But what should I do? raising the mixture to run richer sounds the obvious place to start ?? from memory is it out to richen on carbs ? in on Fuel injection ?

1.9 DG pierburg 2e

[pionte]

I have been reading as many posts as I can , but I am still a tad confused about all the various parts.....





in this photo what is the vacuum unit at the rear called ? I think that the front one is the pull down unit and operates the front venturi flap for the choke or cold start ??

Haynes calls it a vacuum unit and Bentley doesnt know what a carburettor is....

The rear one im assuming operates the secondary go faster flap ?? when I do the ol suck test on the vacuum pipe it seems to work, ie it seems to operate a flap inside the plastic housing then stops and doesnt release untill I stop sucking... all good?? but , however hard I suck it wont actually open the secondary venturi flap.... so is there a problem inside this unit ? if i poke the screwdriver down and manually open the flap then revs rise and fuel is squirted .




its the one with the screw driver on that I am really unsure of .

[pionte]

okay, worked out what the rear unit does and it is all working as it should do.

adjusted the mixture using the old fashioned method ... by ear, happy with that now. still hesitates though.So will go through the procedures documented in other posts and see if things improve.

[kevtherev]

85 mph

good luck with that

[kevtherev]

what was the O2 reading in the gas test?

[pionte]

CO reading was very low @ 0.66 % and HC of 271 ppm.


after racking my brains and thinking back im sure carb engines should be 1.5 + or - .5 , so have adjusted by ear ( engine note raise fall etc ) Although I worked on Ford engines and some had the pierburg carb, I was more used to solex and ford VV carbs ... im sure I will get to the bottom of it. In the 5 years Ive had the van it has always been the thing that niggled me, Slowly im working my way through everything.I did a rebuild a couple of years ago but it didnt it out, i know that i am missing something... so one step at a time i guess.

Ive always found the engine very willing to rev I know they have a red line of around 5300 rpm... my daily drive Golf diesel runs out of usefull revs around the 4 k mark so in general driving I never bother to rev engines, but my wbx is far happier up the rev range than down around the 2k mark.

[123-jn]

At tickover when warm mine is around 1.6 CO running on petrol and around 1.8 on gas. AT 3500 rpm The CO is around 0.8 on petrol and roughly the same on gas. If I take it down to less than 1.4 at tickover it starts to get very lumpy and hesitates on acceleration . Check the accelerator pump squirts when you push the throttle all the way also.

[pionte]

thanks for the info jn, the accelerator jet does squirt, I may whip the carb of tomorrow and clean the jets... just in case.

I really dont think that there is an air leak anywhere.... I would of thought that the HC readings would have been higher , interesting that you experience hesitation when your CO readings fall below 1.4 , without a guage I cant be sure what mine is now.. I will re adjust by ear tomorrow and see what happens.

[Ian Hulley]

I wouldn't be doing '85' very often or we'll be seeing a lot more of you in Technical

Ian

[pionte]

im loving the fact that the swear filter seems to block the word F O R D ...

Ian and Kev, I know that people get nervous about running these Engines at high RPM ( 4 -4.5k rpm ) but I am more comfortable with spinning the engine rather than risking knocking the big ends out by continued low rpm high throttle opening , Ive been with people who's engine is trying to jump out of the engine bay and the whole vehicle shudders as the engine try's to respond to too higher a gear .

Ive only ever blown one engine up, that was a F O R D crossflow Kent 1660 race engine, I hadnt run it in properly and the rings werent bedded in. ( im not counting the Ford Focus TDCI with complete Common rail injector failure , bad tunning chip caused that one )

But if it does go bang I WILL come and ask your advise

Oh and round here with the traffic I barely get more than 50....