xsara 2.0 HDI (2000) surging problem

[froggman]

Hi, I am hoping somebody can help me with this fault that has developed with my old xsara, first I will give some background info.

About 2 months ago, the motor started, for want of a better description, "surging" whilst under load. It is not apparent for the first couple of minutes driving and is worse going uphill. I took it into my local garage, who have always done very good work (albeit it not cheap). The son said straight away it was a pipe for the turbo which goes behind the engine and I had to book it in. 2 weeks later, I took it in and he tested it with his diagnostics computer, whereupon he changed his mind and said it was a fuel supply problem, because the fuel pressure was not steady. He changed the fuel filter, no change, so kept the car to test further. I returned the next day, to find the garage owner had decided the catalyst was blocked, so he took the car and thrashed the ****s out of it to clear it (which I wasn't too happy about), then said it is ok now. I took the car away and it broke down on the way home. I have a code reader so read the code (P220 - fuel pump problem). Took it back to the garage, where the owner tested it again, this time agreeing with his son that it was a fuel supply problem. Kept the car in, saying it was a faulty fuel pressure regulator. The next day, he said that was not the problem, it was definitely the low-pressure fuel pump. This went on for over a week, with a different diagnosis each day (always definitely!) Eventually they decided it was a fuel injector sticking open causing a drop in pressure on the rail, so I stayed there while they changed 2 injectors, said it was fine now. I took it for a spin and it was not much different than when I first took it in. After arguing with the garage owner (he would not agree that there was still a problem), paying a 600 euro bill for all the hours spent on it, I took it home and decided I will fix it myself.

To my thinking, although I am not a qualified car mechanic, if there was a fuel supply problem, surely the faster I drove it, the worse it would get? It will go to any speed I like (although not smoothly) and stay there for hours. The motor feels more like it is trying to accelerate (like the turbo kicking in), then changing it's mind, then trying to accelerate again in about 2 second intervals (very consistant), rather than having a drop in power every 2 seconds. I hope I have explained that ok? I have found someone else who had the exact same problem, on another forum, but unfortunately never gave an update.

I changed the MAF sensor about a year ago, which had failed. I have tried unplugging that, but it made no difference to the surging. I also bought some injector cleaner "Injection 5" and have nearly used the tank of treated fuel, with no discernable difference. Unfortunately I only have a code reader, not a diagnostics setup, but with an engineering background, was wondering if I could tap directly into any sensors with a meter to monitor what is happening?

I appreciate you taking the time to read this novel! I hope there will be someone out there with some helpful advice. I haven't really got the money to just start replacing components to narrow down the problem, I would rather be sure first.

[Paul-R]

The LP fuel pump failed on our Xsara HDi back in 2012. The pump either works or it doesn't, there was no (for us) in between state where the pressure went down. I was able to get going very temporarily by banging the bottom of the fuel tank under the pump but this did not last long. In the end the pump was replaced with a new one.

There's a slightly longer post on it here: viewtopic.php?f=2&t=60197&sid=b5f5f749f ... 33#p576191

[froggman]

Yeah, I just have a gut feeling that it isn't a fuel supply problem, more a sensor or control issue. Thank you for the info anyway.