L Series surging idle

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cookm

New Member
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Hi everyone,
Well I'm still getting used to the new Freelander diesel (1999 model), but I'm definately not happy with the idling. It seems OK just after starting but when warmed up it gives a kind of surge (very short increase in revs) above its nominal 950rpm approx every 2 seconds. It is happening rhymically, not randomly. It's just like someone blipping the throttle briefly.
I've spent a good hour or so scouring Google about this. I've tried cleaning the MAF sensor but no difference. And the air filter looks like new. I tried removing the injector pin lift sensor (just for fun) and it idled normally then - trouble is it then pushed out loads of smoke when the throttle was increased! So I guess that sensor must be OK?
Any ideas guys? There are loads of other sensors/valves connected to the ECU (as the Bosch fuel pump is a bloomin fly-by-wire type) which may have developed a fault - but which is the most likely contender..?
Many thanks!
Martin
 
The air intake,on top of the engine could be clogged.The Y shaped thing gets clogged with oil and crap.To take it off you'll have to break the gasket.
I'm no mechanic,but when I took I was putting my engine back together I cleaned it out with jizer because it was totally clogged.I had to buy a new gasket but if I was doing it again I'd use shoe box cardboard and a bead of gasket seal.
If it wasn't such a bastard to get to I'd recomend checking the crank position sensor.
 
Hmmm...are the CP sensors prone to failure? Can they be tested in situ? I wish there was a way of testing all the sensors via the OBD connector (like on some more modern cars), but I'm led to believe that unless you use a Testbook or Rovacomm thingy then it's not possible on the older Freelanders :-(
 
Latest update:

I've now checked the CPS (waveform OK), TPS (measured OK on ohmmeter), air filter (OK), Y-shaped manifold (was dirty but now cleaned out), No.1 injector sensor (OK), changed the fuel filter, and checked the priming bulb (no obvious leaks)...

BUT THE ENGINE STILL SURGES!!!

It's a rythmic vroom, vroom every 2 seconds or so and it only starts once the car has been revved at all. If you just start it up and leave it idling it doesn't happen...:mad:

Any more ideas?

Thanks,
Martin
 
If all the sensors check out, then it's possible that it's the load on the engine that's changing rather than the input fuel being changed.

Anything unusual in the electrical system?

It could be a heavy load that is periodically removed causing the engine to surge until the fuel is reduced.

Something like a split charge unit with a self resetting breaker connecting a near short; disconnecting then trying again.

It could be other ancillaries dropping in effort required too - air bubble in power steering loop passing through the pump, or maybe the air-con compressor being odd.
 
Hmm..interesting theories, phlebas. I'll investigate along those lines.

Can't be an EGR problem though, as I've disconnected the MAF sensor in the inlet duct (following recommendations from others). That made no difference at all to the idling or to the normal running...
 
Could still be the EGR valve mate, if the valve isnt sealing properly on its seat or is stuck open then it will effect the engine.
Disconnecting the MAF does not ensure that the valve is closed. I tried the same, including pluging the EGR valve vacumn hose with no effect. Still the rythmic lumpy idle and smoke.

Only when I gave it a good clean, did the engine respond better. Much better low torque and much less smoke.
 
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