Van hesitant and low co readings

Post by **Die Bulli Familie** » 18 Feb 2006, 19:25

My van is slightly hesitant whilst accelerating when the engine is warm but not up to running temperature. I've checked the timing, replaced fuel filter, cleaned carb, etc.

At the MOT last week I noticed the CO reading was very low, maybe I have an air leak on the inlet? Does anyone know a good way to check for inlet leaks? I've been spraying WD40 expecting it to pass through the engine if there was a leak but I can't find a leak.

Approximately how far out should the mixture screw be? mines about 1.5 turns from fully in. If the mixture is lean then I should screw it in shouldn't I?

I had my van running sweet today, with the mixture screw about two turn out, then after stopping and re-starting it didn't run right.

I think I'm looking in the wrong area, anybody suggest some things to check?

The engine is 1.9 DG with the pierburg 2E3

Post by **Hacksawbob** » 18 Feb 2006, 19:52

I've heard that vacuum can develop in petol tank, unlikely put try get up to temp them take off petrol cap see if there is a woosh of air as you take it off. Also obvious but. best way to prevent leaks is to replace all the vacuum hose then you know for sure, 10 min job. dont know about mixture screw I'm affraid.

Post by **futurecut** » 19 Feb 2006, 21:20

Mine had similar symptoms and was cutting out a bit but i adjusted the idle speed as i think mine was a bit low. I think it's generally supposed to idle a bit faster than the other engines.(900?ish) now it feels like the choke is always on a bit (it isn't) and bus is lively. Idle speed isn't too fast tho', think it's just me noticing the diff between it being too low and now.

Post by **HarryMann** » 20 Feb 2006, 10:32

My van is slightly hesitant whilst accelerating when the engine is warm but not up to running temperature.

Could really be all sorts of things, though someone who's had same might narrow it down, for this engine.

You don't seem to be suspecting leads or plugs, so presume they have been changed. When engine getting up to temp, can go through pahses of running either excessively weak or rich, so needs a good strong spark at these times, esp. under acceleration when cyl pressures are higher.

Have you checked the carb throttle spindle for wear?

Post by **Die Bulli Familie** » 20 Feb 2006, 10:46

Yeap, I've changed plugs and leads, they had no effect.
I haven't yet checked the trottle spindle for wear, how much wear is too much?

I set the van slightly richer at idle, if definately sounds better but it's still hesitates (slightly) when I pull off in 1st gear, I'm getting to the point of just living with it.

I'm considering stripping the distributor down just to make sure everything is ok there.

Does anyone know how much vacum the engine should generate at tickover?

Post by **HarryMann** » 20 Feb 2006, 11:05

Perceptible wear over and above mintest rock in spindle? If you want to check effect, you might try some grease of vaseline around the spindle bushings if you can get it there... not partic. definitive.

You are now saying that this hesitation is just when you pull away in 1st, so if this is not in other gears, and its when you let the rpm drop down to below 1000 as the clutch comes up then as suggested above, try increasing the idle speed slightly - as engine wears, partic. carbs, engine won't idle or come off idle so smoothly?

Yes, it does sound like a carb or small inlet/exhaust leak...
Vacuum at idle, no idea, and it varies so much not partic. reliable for diagnosis maybe. Also possible small blockage in an emulsion tube or jet, sometimes can be cleared by blocking inlet with hand as engine passes through that particular rev-band... flat palm of hand, and then whip throttle open as if accelearting away, creates high vacuum that can pull much through - very effective on the Weber style progressive twin chokes. Bit of knack to it.

Post by **Aidan** » 20 Feb 2006, 19:34

check the flexible vacuum hose for the brake servo that comes off the inlet manifold - it is internally reinforced with steel which eventually rusts and the hose becomes porous and gives these symptoms. If you have it on an analyser then tightly wrapping your hand around it will change the reading if this is the problem - tape it up for the short term and replace if necessary.

Post by **HarryMann** » 20 Feb 2006, 19:44

Could really be all sorts of things, though someone who's had same might narrow it down, for this engine.

told you someone would start getting specific - good tip there.

Post by **Die Bulli Familie** » 21 Feb 2006, 09:01

I checked the vacum take off for the brakes, initially I thought it wasn't on tight enough although after refitting it didn't make any difference.

The gas analyser I borrowed was playing up so that didn't help, I'm trying to borrow another one.

In my mind I'm either not generating (loosing) vacum, or the distributor isn't responding to vacum.

It would be nice to have some figures for the required vacum alhough I understand there can be variances.

I'm driving my other van today and I really notice the difference, I had thought of living with the fault but now I want to get to the bottom of it.

Thanks for the help, anymore with anymore?

Post by **HarryMann** » 21 Feb 2006, 12:38

Vac advance/retard normally both start about 90-160 mbar (70-120 mm Hg)

Fully done by 200-280 mBar (150 -210 mm Hg), maybe 360mBar (27cm)(MV engine)

Vac advance and retard normally typ, 10~15 degrees

So you should be able to see at least 200mbar, maybe up to 400, depending whether you're measuring at throttle body or manifold.