Td5 Flat spot on take off and hard to start cold since new head fitted

[Davetd5]

Hi Folks,

Got the td5 running the other day after fitting a new head (pressure test showed old one was cracked in #1 inlet port). I went with the chinese head my engine shop sold me for $1850 and it fitted on with no problems.
But since restarting I have a flat spot on take off and its hard to start first thing. Takes a couple of goes then runs rough for about a minute while pumping smoke out the back (possibly unburnt fuel). Once its hot it starts first thing all day. Any ideas?

The thing I'm more concerned about is that it has a big flat spot on take off, especially on any incline.
Its dead from idle (750rpm) til 1000 rpm when it'll start to take off, once going it improves after 1500rpm and then it takes off over 2000rpm and will rev really well up to 4000rpm.
But its near dangerous trying to find a gap at a round about or turning uphill at an intersection from a stopping start.

So I either have two problems or one.
It wasn't like this before I changed the head. I'm an ex mechanic (but I'm older and slower now.)

Yesterday I fitted a brand new VDO MAF sensor and it improved it significantly in the top rev range. Battery is brand new.
I cleaned the MAP and Ambient Air Temp sensors the night before with contact cleaner.

I'm going to rebleed the fuel system when MrsTd5 gets back with it this arvo, then change the fuel filter (and rebleed system again).

Then I'll reconnect Nanocom Evo and check Throttle position sensor voltages.

What's next?

I'm thinking possibly the injector seals or washers are leaking overnight into the combustion chamber (I used genuine parts) causing the hard start when cold?

Piston 2 was about 2.5thou lower than the others, so do I have a slightly bent rod causing lack of power on take off? It wasn't this gutless before I removed the head and I drove it the day before disassembling, so I'm doubtful on that one.

Any other ideas? Cam timing seemed to line up ok, I've pulled the rocker cover to check.
Injector wiring loom is new (non-genuine)

Thanks in advance
Dave

[thai_tiger]

Are you happy with the injectors were correctly adjusted

[Markf]

Hmmm. Interesting. I have exactly the same issue since I had the head replaced by the local stealer. The head came from Turners. They took five (yep, you read that right) tries to get it up to tolerable. At each attempt to get it right they replaced the injector washers and O-rings. Fuel consumption is up by one to two litres / 100km and it's down a bit on power. Before the head replacement it was able to easily able to maintain 110kph up a local test hill but now it'll drop back about 5kph. Like you, from idle to about 1200rpm it's got about as much acceleration as a fully loaded road train.
It's a bog standard 10p engine with the EGR still in place. Intercooler is nice and clean, boost solenoid is new as are the MAF and MAP/AIT.
I suspect that the hard cold morning starts could be due to glow plugs but I haven't as yet had them out to test. When I get to it I'll replace them but I suspect I'll see no difference.
The stealer suspected the fuel pump so they replaced a genuine two week old pump with a new one without consulting me (which they still expect me to pay for).
I still reckon that it's got something to with the injector washers but I can't be certain.
My problem, being retired and on a fixed income, is that I can't afford to take it to an indy and say "diagnose and fix" so I'll live with it for the time being as it's still nice to drive and it's never let me down apart from sundry flat tyres and an alternator.

[Davetd5]

Are you happy with the injectors were correctly adjusted


I think so, I was very careful when adjusting them, and the Nanocom has the cylinder balances running fairly evenly.
Still, its easy enough to check if I pull the rocker cover off. Thanks

[Davetd5]

Hmmm. Interesting. I have exactly the same issue since I had the head replaced by the local stealer.

Yes interesting. I can't help think that having the battery disconnected for 6 weeks has made it lost any adjustments its made to compensate for worn sensors.
I lost count of how many Falcons I've had to reset base idle speed on after replacing the battery because the ECU loses its tune, and I wonder if something similar has happened here whereby there's some fault that the ECU had been compensating for. That certainly seemed to be the case with the MAF

[Markf]

[deletia]

That certainly seemed to be the case with the MAF

Mine being a 10p engine the MAF is only used for EGR control so as expected changing it made no discernible difference although there was a placebo effect just after I changed it.

With my Nanocom I've recorded the data on a trip from Moe to Melbourne and back (two lots of about 120km's) and had a look through it for any anomalies but nothing sticks out apart from the occasional bit of rogue data (RPM 7,000, temp 140degC, etc). Cylinder balance seems good (+8 to -5 when cold and +or -5 when hot) at idle.

Before the head change I could just floor it from below idle and it'd just take off smoothly, albeit slowly. If I do the same thing now it jerks and bunny hops. I used to able to let the clutch out at idle and floor it and it'd take off smoothly. Now I need a few revs above idle to be able to be sure it won't stall.

[onebob]

Mine being a 10p engine the MAF is only used for EGR control ....

.......actually the MAF signal is also used by the Auto Trans if your D2 is so equipped[emoji6]

[discorevy]

I got a call from a local workshop a couple of weeks ago asking if I could come in to sort out the same symptoms after they had fitted a head , turns out the mech had lined up one of the holes in the flywheel for the crank sensor instead of the slot when doing the cam timing , so check the cam timing again.
Sometimes it pays to take it to an actual Land Rover specialist, or at least in this case someone familiar with TD5

[thai_tiger]

Discovery TD5 Turbo Lag
(https://www.aulro.com/afvb/technical-chatter/125031-discovery-td5-turbo-lag.html)
Sorry this post didnt cover what i thought but a common mistake is to set the injector adjustment on the heel of the cam.

[Davetd5]

Its fixed!

Big shout out to discorevy, yes it was the cam timing! Reset it and the thing goes as well as it ever has.

I'd misplaced the tool for locking the crank I'd made out of an air hose fitting so in my unthinking haste I had just used an unmodified male fitting and jammed a 6mm allen key in there. (bad move as the crank wasn't lined up correctly)

So tonight I cut the top off the airline fitting, drilled it out and used a 8mm drill bit to lock the crank.
Only about a third of the slot in the cam was visible through the hole, so it was retarded by about 4mm on the cam sprocket.
Reset it and it fired up no worries cold and takes off like a beast.

Thanks again discorevy, and to anyone else who is experiencing a flat spot on take off and poor cold starting after head work - recheck your valve timing!