Thread: Won't go over 60km/h

Originally Posted by discorevy

Bit late to the party, Yes, you'll need to do the FPR, but that's not going to be the issue.
Quick squiz at the log tells me your MAP sensor is probably U/S, either that or the wiring to it has too much resistance. More likely sensor though.

What does it read ( turbo pressure ) at idle since you cleaned it?
It should never read negative on a Turbo diesel unless.

major blockage in intake ( It would be reluctant to rev at all if that was the case )

Compressor wheel fallen off and blocking intake ( see above )

Sensor fault ( It's a delicate petal, that's probably over 20 years old )

Went out and plugged the nanocom in, its reads -0.21 at idle. The airbox to turbo is completely free of any blockages, the hose was replaced a few years ago with a silicone one.

I will take off the intercooler hoses again and have a another look, but they looked fine and didnt see any obvious problems other than a smear of oil.

The MAP sensor i cleaned a few weeks ago so all the logs are since its been cleaned.

I highly doubt its something major like compressor wheel falling off, as i have driven it for a few weeks now. Like i said earlier its fine after 2000rpm, before hand is completely dead. Also this was not an issue before i replaced the fuel pump. Before the pump packed it in, it would launch off the lights, you gave it some boot and it would go hard, now its like a 5sec delay before it decides to do anything. The car starts fine, idles fine.

Had the car for 7 years and this is not normal at all

Maybe I wasn't clear, as was just a blurb on what people should look for in relation to diagnosing a negative pressure reading.

Replace your MAP sensor, it is stuffed

This will cause your problem

Yeah my bad, i was just replying to what you asked, Ie the boost at idle. I guess i will now buy a map sensor and hope this fixes my issues. Just stressful as i have sold my house and need to start moving out and having a car not working doesnt help much.

Originally Posted by Noisy

Went out and plugged the nanocom in, its reads -0.21 at idle.

That reading is a boost calculation made by the ECU by extracting the AAP from the MAP reading, you need to read the manifold pressure in kPa from "inputs fuelling" to see the MAP sensor's direct output, there is sucction in the inlet manifold with engine running so if the boost is low or there is a resriction on the line a negative boost reading doesnt necessarily mean that the MAP sensor is fubar. Remove the sensor to be in the air, let it plugged in and see the kPa output, if it's equal with the real ambient pressure shown by a barometer that negative reading is not a sensor issue. However if it's old it's not a bad move to fit a new one to be 100% ruled out just dont buy some cheap aftermarket, go for Bosch if you dont want to spend on a genuine LR which would be the best.

if you clean the sensor you must spray well iinside the bottom of it as that small hole near the probe to be free of muck cos there's the pressure sensor, shown with the arrow, the probe is for IAT

Originally Posted by sierrafery

That reading is a boost calculation made by the ECU by extracting the AAP from the MAP reading, you need to read the manifold pressure in kPa from "inputs fuelling" to see the MAP sensor's direct output, there is sucction in the inlet manifold with engine running so if the boost is low or there is a resriction on the line a negative boost reading doesnt necessarily mean that the MAP sensor is fubar. Remove the sensor to be in the air, let it plugged in and see the kPa output, if it's equal with the real ambient pressure shown by a barometer that negative reading is not a sensor issue. However if it's old it's not a bad move to fit a new one to be 100% ruled out just dont buy some cheap aftermarket, go for Bosch if you dont want to spend on a genuine LR which would be the best.

if you clean the sensor you must spray well iinside the bottom of it as that small hole near the probe to be free of muck cos there's the pressure sensor, shown with the arrow, the probe is for IAT

Just came inside to say i did some more looking around in the nanocom and found some new menus to look at, and just found the inputs fulling menu, i have only been looking at the instruments part.

Manifold pressure in the input fulling had the reading at 77kpa

Ambient pressure was 101

Also i gave the sensor another really good spray and got it right down in the hole and still read the same

Then after reading this post i went out again and removed it from the manifold while plugged in and it read 77kpa both with key on and a quick start and idle to check.

I ordered a bosch map sensor this morning after discorevy said it was stuffed, and being most likely the original i guess replacing it was best.

Originally Posted by Noisy

Then after reading this post i went out again and removed it from the manifold while plugged in and it read 77kpa both with key on and a quick start and idle to check.

Then beside discorevy's good guess you have the evidence too that the MAP sensor is fubar

Originally Posted by Noisy

Yeah my bad, i was just replying to what you asked, Ie the boost at idle. I guess i will now buy a map sensor and hope this fixes my issues. Just stressful as i have sold my house and need to start moving out and having a car not working doesnt help much.

Hopefully selling the house offsets the not working for a while.
At least a MAP sensor should get your car back to how it should be and while it's not ideal to diagnose without having the car in front of me, I'm 90% sure.

Let us know how how you get on

Originally Posted by sierrafery

Then beside discorevy's good guess you have the evidence too that the MAP sensor is fubar

Nothing to do with guessing. I have been working and hopefully improving these for 20+ years so might have some experience.

If you have vacuum showing at idle then chances are you MAP sensor is out of calibration ( or a blockage, wiring etc )

While it's good that you help people out with electrical diagrams and diagnoses from Rave and other internet sources, my advice to you would be not to under estimate some people, especially those that have worked on ( and have appreciated ) the TD5,for a couple of decades, and there's a few on here.

You have been trying to contradict my posts for around 8 years.
If you think the TD5 should show Vacuum at idle, and you're obviously interested in them, then maybe ask the mechanic who does the work on your Landy to school you on them.

If the O.P. was to follow your guessing, he'd be replacing way more than necessary and yes, I do realise some workshops throw parts rather than properly diagnose as well.

To be honest there were 2 separate issues here. The first was the fuel pump was dead, and i think while trying to diagnosis that problem i have caused this problem, and my reasoning is this. I was low on power so i did the first and logical step (in my mind) and that was clean the sensors and see if that fixed it, but i think what happened is the 20+ year old sensors didnt take kindly to the cleaning and thus broke. So when the fuel pump was replaced it fixed the original issue, but the now broken sensor caused the low power on take offs. This makes the most sense to me because before the pump died the car was driving perfectly fine.

So once the new map turns up hopefully it will be back to how it was, or better, but i will take how it was