sticking acceleration on 405 1.9TD

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kelvin
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sticking acceleration on 405 1.9TD

Post by kelvin »

I have recently bought a 1994 405 GLXTD estate with all kinds of lovely extras (and an alarm system that actually seems to work). At the same time, I discovered this brilliant forum, which has given me several hours of fascinated reading already!
I would appreciate feedback on a couple of queries though:
1) For the first few minutes on starting from cold the accelerator tends to stick slightly and the engine revs don't drop when my foot comes off the pedal. I suspected a sticking cable so disconnected it and squirted in WD40, but it seems to slide beautifully anyway and the pedal works fine too. The return spring on the diesel pump also looks fine when I work it manually. The problem goes within about 15 mins, though I must say the revs seem to drop rather slowly once I take my foot off the gas, compared with my old 305 1.9 diesel estate. Any thoughts please?
2)The car cruises beautifully and quietly but makes an annoying hum cruising at around 50mph. Above and below that band the hum goes. It sounds like it comes from the back, and I wondered if it might be ageing baffles (?) in the rear exhaust box. Its not a bid deal, but seems odd in an otherwise sophisticated car. Has anyone any experience of the same thing?
Stuart McB
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Post by Stuart McB »

The noise question could be tyre tread pattern noise. Had this aon Ford Focus sounded like the bearings were shot but only at50mph, new tyers sorted this out. As for the slow return, has it got one of those return shock absorber looking things on it?
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fastandfurryous
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Post by fastandfurryous »

The slow return is a characteristic of the 405 with the return damper on it. Initially, I was going to remove mine, but it works well. If you are booting it, and then abruptly come off the accelerator, instead of getting a nasty driveline shunt, it comes off smoothly. I think it allowed the use of softer engine mounts, so I would leave it well alone. To check it's working properly, push the lever on the injection pump to "max acceleration" (with the engine off) and see how long it takes to return. It should be back to the idle stop in just under a second. If it snaps back (which I doubt) then it's shot. If it takes a week and a day to return, then it's probably gummed up with road dirt, and would benefit from a good squirt of wd40 on the chromed shaft. (under the plastic cover.. it's just like a tailgate strut with a cover over the chromed bit)
Does it matter what gear you are in to get the annoying hum? I have resonance from my 405 at certain engine speeds, which is a biggered exhaust. Noise at a certain speed can only be down to tyres, wheel bearings, or possibly a driveshaft bearing. Does it sound like tyre noise, or bearing noise (they sound distinctly different)
David.
kelvin
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Post by kelvin »

Thanks for your quick replies Stuart and fastandfurryous. Yes, the pump has a return damper on it and the return action works smoothly, in a second, as you mention. Common-sense still tells me the problem must be a sticking accelerator cable, so I think I will have to investigate it more carefully.
As for the annoying hum, I will have to listen more carefully and report back to you. I didn't know tyres could cause such a problem, but for your info, the tyres look pretty new. Is it a question of them being worn, or the tread pattern being inappropriate??
For the moment, I favour the buggered exhaust theory. I presume we are talking about the rear half, which has a box with (I assume) baffles in it??
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fastandfurryous
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Post by fastandfurryous »

If your accelerator pedal returns to idle in about a second then there is no investigation to be done... this is how it's supposed to be.
You can check for a stiff accelerator cable by disconnecting it at the acclerator pump and letting go of the inner cable. The weight of the accelerator pedal should be sufficient to (slowly) pull the cable through. By then pulling on the inner cable, you should be easily able to pull the accelerator pedal back up to it's idle position. I have yet to experience a stiff accelerator cable, and I get the feeling there's nothing wrong with yours.
A cream-crackered exhaust would resonate at the same engine speed, regardless of road speed (well.. ok, at 5 different road speeds for the 5 different gears). If it is the tyres, this often gets quieter in heavy rain, as the water on the road has a damping effect. Conversly it may get louder on a concrete surface. If the noise is present regardless of road surface conditions, I would be looking towards a bearing somewhere.
David.
kelvin
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Post by kelvin »

Had a closer look today at the sticking accelerator and it appears to be due to the top of the pedal mechanism catching on the plastic trim beneath the dashboard. Should have looked more closely the first time!
kelvin
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Post by kelvin »

David-
thanks for your last reply, which I missed on my screen before sending the last note about the accelerator issue. Had a long run yesterday and confirmed the hum is definitely an engine/exhaust note which is heard in 3rd 4th and 5th. On paying closer attention I would say it's just that the engine has a 'rough' spot at around 2100 rpm. I have driven cars before which seemed to have rough spots and sweet spots at certain speeds, due, I assumed to the kind of driving (e.g lots of motorway)they had mostly had. At least, that's what I assume, though I do not have a detailed knowledge, only DIY skills. Does this make sense? Short of changing the exhaust, which doesn't look old, I think I may just have to get used to it for the time being.
A bit more advice please on another topic. I broke down yesterday on my way to catch the ferry to the UK! A bayonet-fitting hose at the bottom of the plastic radiator-filling unit (bolted to the side of the rad)just broke from its mounting. The actual mounting had sheared off the filler unit and I found traces of glue where someone had tried to bond it back. I limped home and have had the unit out and heavily re-made the joint with epoxy putty until I can get a new unit from a scrappy (if they'll part with it without having to buy the whole radiator). I can't however see any provision for run-off from the filler unit in case the system is overfilled and gets hot. Is there any overflow set-up on a 1994 405 TD? Sureley if there was no safety-valve arrangement, the system could do great damage??
Thanks again for your helpful comments,
Kelvin
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fastandfurryous
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Post by fastandfurryous »

Hmm... as far as I was aware, the "filling unit" (expansion tank?) was integral with the radiator on these. Certainly mine is (and I have the idiot bayonnet fittings too). I did try once to fit an earlier 405 rad with normal hose-clip fittings, but it won't fit due to the size of the expansion tank. The later "Bayonnet" style rad that we both have is made of a fairly brittle plastic, which I'm sure hardens with age. If you've had a bit break off already, I'd go on the safe side and get a new one. I don't think they're too expensive.
There is indeed an overflow on the 405 rad. If you look in the filler neck, there's a hole in it, pointing towards the offside wing. That's it. Nothing more grand than that. The filler cap is a pressure cap. Not a very clever arrangement to be honest. Another case of being built down to a cost. Personally, I think the 309 cooling system arrangement was far better. I may yet alter my 405 to have a high-up expansion tank, and actually allow it to bleed properly (it's a swine sometimes to get all the air out) Early in the life of the 405 I remember there was concerns about overheating and poor radiators. I think it's just a bad layout which lends itself far too well to air-pockets.
Bad luck about the breakdown!
David.
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