Strange Issue After Pump Adjustment

[ally406]

I did the LDA mod, but the pin that the LDA actuates got stuck. To unstick it, I had to remove the throttle arm so I could open an access panel and push the pin back out. I moved it back and forth a few times with WD40 until it was free. I reassembled everything and that seemed fine.

From cold, the engine starts easily and idles at around 1,000rpm like it always has done. However, when hot, the idle can drop as low as 800rpm and the engine hunts seriously. It's also very smoky at idle and difficult to start. Another thing I notice is that as I press the accelerator pedal engine rpm does not rise initially, then all of a sudden I get 2,000 rpm, like a dead spot at the start of the pedal.

As it's fine from cold, I thought this was timing related. As it's a 406 with a semi-ECU controlled pump, have I disturbed something timing related on the pump? I thought it might be veg related, but it's just the same on pump diesel (in fact, possibly worse!)

I hope you don't mind a 406 interloper, but this seems to be the place to ask!

[RePT]

My car doesnt like to idle between 1100 and 2000 either, it too is a dead spot.

Are you running veg?

You could take ur idle cable out and only have one idle, which sits at 1100 rpm(i run veg)

[Piggy]

I have no experience of tuning the semi ecu controlled ones...but I would have thought it would mess up it all as the ecu has some control still

[Tom]

Did you remove the throttle arm?

[dturbopeck]

Sounds like the throttle arm is just alittle out,

[ozonehostile]

you can ajust the hot and cold idle on a bosch pump, its the upside down T shaped piece on the side of the pump with two screws on either side, you can wind these screws in or out to adjust the hot and cold idle

[Piggy]

dont think thats an issue...my idle when warm is about 800rpm and it purrs

[ozonehostile]

dont think thats an issue...my idle when warm is about 800rpm and it purrs

I don't think I've ever heard anyone refer to an xud as purring before haha
Usually when you think xud, clatter comes more into mind

[cwspellowe]

Sounds like throttle arm to me too.

I'm assuming you didn't remove the top of the pump at all, and you definitely didn't touch the governor? If so, only thing it can really be is the throttle arm. The ECU-controlled part of the pump controls timing, so if something's been disturbed on the throttle arm to affect fuelling at idle the ECU will be reading default values which will be mechanically out if the arm's out by a spline or two.

Just my thoughts anyway. Rip it off and fit a mechanical pump ftw.

[ally406]

Sounds like throttle arm to me too.

I'm assuming you didn't remove the top of the pump at all, and you definitely didn't touch the governor? If so, only thing it can really be is the throttle arm. The ECU-controlled part of the pump controls timing, so if something's been disturbed on the throttle arm to affect fuelling at idle the ECU will be reading default values which will be mechanically out if the arm's out by a spline or two.

Just my thoughts anyway. Rip it off and fit a mechanical pump ftw.

I've been pondering this since my post and I think this is correct. The mistake I made was not marking the arm before I removed it. I turned the shaft to normal idle speed and just refitted the arm. Now it makes sense, the angle sensor on top of the throttle arm must have some effect on the injection timing, and the arm won't be where the ECU expects it to be! I will report back after some fiddling.

[ally406]

I finally managed to take a look at this today, after having a CV joint to change, oil and filters to do! I took the arm off again, turned the shaft until the engine was idling normally. Turning the shaft even a little bit further would raise the engine speed past normal idle. I refitted the arm, but the problem still persists when the engine is hot. I've read a bit more and found that the angle sensor on the arm is to do with the EGR, it has no effect on timing.

What confuses me is the dead spot between 1,000 and 2,000 rpm. I press the pedal and get nothing....nothing....nothing.....2,000rpm. It makes the car difficult to drive at low speed. It doesn't do this when cold

[Piggy]

very weird....very weird.

I agree with MrKillGTturbos....fit a mechanical pump and then remove the egr!!