1999 Land Rover Freelander 2.0XEDI "surging"

[solardb]

Hi, I brought a 1999 Land Rover Freelander 2.0XEDI, knowing it had mechanical issues.
The Engine misses at regular intervals on idle. Is not so much a miss , as more of a reverse surge. Most of the time it revs freely with no load on . However , when you try to drive it , it jerks and sputters form idle to about 1800rpm, between 1800 rpm and 2500 rpm it runs beautifully, about 2500 rpm it starts to miss again , but no where near as bad as below 1800rpm. It is baffling how it runs so well around the 2000-2500rpm range, which corresponds to 80- 100 km/h.
I have put a new air filter and fuel filter, to no great improvement. I also blanked off the egr valve , again no improvement.
i took it down a back road, and let it rev to 4000 rpm or so in 3rd gear, it didnt like it at all , and dropped to 60-70 kmh. When I got back there was a noise like a police siren coming from the engine , probably from the tutbo area. The next day the noise was gone.
Any ideas on what is wrong?

[woko]

There is another fuel screen in the banjo bolt on the inlet of the injector pump.

Noise could be a leaking manifold gasket. Intake and exhaust are the same gasket. The engine ecu will try to adjust for different readings between MAF and MAP sensors if leaking. Check for leaks.
The MAF and the coolant temp sensor can cause surging. Disconnect each individually and go for a drive. The radiator fans will run at full speed when the ECT senor is disconnected. Check wiring going to injector pump. It can chaff.

Do you have access to a Hawkeye or similar to read codes?

Sent from my GT-I9295 using AULRO mobile app

[solardb]

Thank you Woko. Should disconnecting the maf sensor bring the engine warning light on? It doesn't.
Where is the map sensor?
I will try disconnecting and driving later on today.
Having the codes read is probably the next step.i have a rennac scanner for my prius , I will see if it can be registered for landrover.

[woko]

Disconnecting the MAF won't bring on the engine light. The MAP is mounted on the fire wall behind the air filter. There are 2 there. One is Map the other is for egr The one on the drivers side is map. The one on the pass side Egr

Sent from my GT-I9295 using AULRO mobile app

[solardb]

Thanks. Haven't had a chance to get back to it yet.

[solardb]

Progress !
Disconnected the temp sensor, as you said the fans come on full bore.( well they sort of ramped up , but were full bore within a minute).
Disconnected the maf sensor wires. It idles smoothly.
Took it for a drive, massive improvement. There is now only a single miss around 1500rpm under load. above 2500 rpm there is still a miss , maybe just a single one but it repeats occasionally. Its now actually driveable.
I see I havent followed your instructions and tried them individually, I will try that now.

[solardb]

The Temp sensor has the most effect. With that disconnected, it runs reasonably well, a miss around 1500 rpm , and another around 2700-3000 rpm.
I have reconnected the maf sensor and it seems to make little difference to both been disconnected.

does this mean the temp sensor is faulty, or is it the circuit it is feeding into ?.

[woko]

If it makes a difference for the better it will be the sensor. I have replaced a few of these. The part number is ERR2081

[solardb]

thanks , have ordered one off Ebay.

[solardb]

Sensor has arrived. It measures 3.5 Kiloohms resistance on a NZ winter morning , probably about 10 degrees celcuis. Putting it in a cup of boiling water, the resistance reduces to around 0.5 Kiloohms, or 500 ohms. I would say it is a 5 kiloohm NTC thermistor.
Might be helpful for anyone wanting to check their sensor.