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Engine problem

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Engine problem Empty Engine problem

Post by DaveyA Yesterday at 5:00 pm

I've had problems with the EGR valve ever since I got the van. I had it cleaned one time and it has been fine up until last week while on my way to Scotland for a break. Engine light on and poor performance, erratic idle etc. Once on site, I called out the AA just to confirm the problem which they did. With the help of the site owners who knew of a reputable garage I booked it in and got the valve replaced. All seemed well after I tried it out on the road, all faults cleared and it goes like a bat out of hell, much better than it ever did. But as I made my way back to the site I noticed that it was very hesitant on light throttle and quite jerky sometimes when pulling away. If I gave it some welly it took off strongly. I contacted the guy who did the job and he came out to me and checked for any faults with his diagnostic tool. It was all clear, no faults showing. He suggested it might be trying to do a regen, and said to give it a couple of rides out and if it was no better he could connect to it and force a regen. I've been out again today and it is much the same. It has loads of power if I drive it hard, keeping on the throttle all the time. But just tickling the throttle when easing off to cruise it starts to gently "flutter" is the only way I can describe it. It never had this behaviour before and I just wonder if anyone has some knowledge of it. It seems a coincidence that it has appeared with the fitting of the new valve. It wasn't a cheap one and was brand new in the box. I'm wondering whether it could be a faulty valve, these things happen. Any thoughts on whether a regen would help. I really warmed its backside after the valve was fitted and again today, I'm not sure under what conditions it might initiate it's own regen. I'd be grateful for any thoughts or advice.  Many thanks.
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Engine problem Empty Re: Engine problem

Post by Roopert Yesterday at 5:34 pm

Regen is a cyclic process, so whether it needs one depends entirely on how much soot has built up since the last regen.

Typically there are two types of regen: passive and active. The former happens when there is significant soot load (but not enough to yet need an active regen) and long high-speed (or high revs) driving causes the DPF to get hot enough to start burning without any need for an external input.

Active regen is initiated by the ECU when it calculates that the soot level is above a preset threshold, by comparing the pressure at each end of the DPF. I think on the Boxer there is a separate additional injector, and this is activated when the DPF temperature is high enough? The VW T5 works in a slightly different way, in that it injects extra fuel into the cylinders during the exhaust stroke (no extra injector needed), but the overall effect is the same - the unburnt fuel hits a catalyst at the front end of the DPF and heats the exhaust gases so much that the soot gets hot enough to burn, and most of it burns away, leaving a small amount of ash residue.

There's not really any point in forcing a regen unless it actually needs it. On my T5 it's possible to read the ECU data and find out how many miles since last regen, and what the calculated soot load is - so you can roughly predict when the next one will be due after a while. Yours probably does the same, but it may not be well documented. If you have been doing long-distance high-speed runs recently, it's very likely to have already done a passive regen if the DPF was only partially full.

One further observation: on my T5 I have noticed a "flutter" effect when on the overrun while the DPF is undergoing regen - but there are few other signs that it is regenerating, other than slightly higher idle revs and a lot more heat underneath.

Having said all that... your symptoms seem to point to an EGR valve that is sticking partly open, and is only shutting fully with more throttle than it should need. It would be interesting to find out whether the replacement EGR is a factory part, or an aftermarket one. In the VW T5 world, some aftermarket EGR valves seem to cause more trouble than the factory ones...
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Post by Roopert Yesterday at 5:42 pm

One further point: on the T5, I'm fairly sure that you need to run an "adaptation" procedure when the EGR valve is replaced. This allows the ECU to "learn" the fully closed and fully open positions. Do you know if the Boxer requires a similar procedure and, if so, whether it was done?
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Engine problem Empty Re: Engine problem

Post by DaveyA Yesterday at 8:11 pm

Thats very interesting, thank you. I watched him fit the valve and I don't think there was any procedure carried out, maybe just to see if there were any more fault codes showing. It wasn't a dealer part but he said it was OEM spec, I recognised the name on the box it came out of, I just can't recall it now. I must admit I drive the van "sedately" normal times and possibly this doesn't help matters. My own instinct says its a faulty valve, but difficult to easily prove. Would it not show as a fault if it was partially open?
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Post by DaveyA Yesterday at 8:21 pm

I forgot to mention that it was worse this morning when I started it from cold and drove off the site for a test drive. Once on the open road and I could accelerate it seemed ok.
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Engine problem Empty Re: Engine problem

Post by Roopert Yesterday at 11:39 pm

DaveyA wrote:Would it not show as a fault if it was partially open?

I don't know enough about how it's operated on your specific engine to say. By analogy with the T5, the system changed drastically over the years, starting with a vacuum-operated mechanism which had no way to feed back anything about actual valve position, to a motorised system with feedback about actual valve position. The former probably wouldn't register a fault under any likely conditions, and the latter probably wouldn't if it needed adaptation and that had not been done.

The big problem is that Peugeot sell these parts at an extraordinarily high mark-up, so there is a lot of money to be made by the Chinese aftermarket parts makers - and it seems that some don't care too much whether their copy works very well. I think they calculate that if they charge £60 (versus the ~£200-400 of an OEM part) there's enough money in it for them as long as more than half the buyers can't be @rsed to return a product that doesn't work very well...
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