2.25 petrol rough idle

Popped my 1985 LR 90 2.25 petrol to my brothers house round the corner to tune it up as it was running rough on idle. We set the timing first, plugs looked clean, so a spark was good.
Cap looked loose fitting and the rotor arm was all over the place so...
1 new distro cap. Not fixed
One of the cheap leads came apart so..
1 new set of leads. Not fixed
Electronic ignition did not rotate on advance...very odd so
1 new complete distro with electronic ignition. Not fixed.
checked webber carb, this is new, all was good there.

One thing we noticed, the vacuum pipe from the carb still had vacuum on tickover? Did not know this should be the case and can only imagine it may be why it's running rough.
Considered taking the rocker cover off and checking the valve timing to look for clues of maybe a loose cam or timing chain woes, but the darkness came, so I'll leave it for another day.

so driving the 2 miles home last night and it got rougher quick. 1mile on and it stopped, it seemed like it was not getting fuel. One tow home later and left to stand for 10mins, it ran...still lumpy but ran. Now, the other week I did a service and noticed the fuel filter bowl had brown **** in the fuel, so a new filter went in. When I get home from work today I will check that bowl again, then maybe blow out the main jets in the carb and check the fuel flow from the pump. Maybe the failure last night is a seperate issue as it never happened before. I'll be happy to go back to the lumpy tickover for now.

Thought i'd pop it on here to get other opinions. Any other suggestions are gratefully recieved.
edit 27/7;
The plot has taken a left turn now. I cleaned the fuel filter, (that was clean fuel now), added an inline filter to keep an eye on in front of the carb. Fuel pumping through lovely and clean and at a good rate. Pull each jet out and cleaned it, they were fine. it ran rough on tickover still so I took it for a spin, then it died up the road...this time it would not start at all.

Pause for back story; when I first got this a few months back, I was happily driving when a fire started under the bonnet. This turned out to be a shonky wiring job on a security switch under the dash that someone fitted and it shorted out the wires going from the coil to the carb and caught alight. I fixed those wires and made the shonky wiring good for now with the view to remove said stupid switch another time.

So, with that in mind, whilst waiting for a tow, I noticed the shonky wiring came from a harness that goes around the back of the engine, that has damage too.
I then ran wire direct from battery to coil and see if I got a spark, no spark. I'm thinking it could be 2 things.
1) The coil is trashed, what with all the shorting and trouble it's had, not suprised
2) the new distro I fitted with electronic ignition is actually faulty...hard to believe but I'm told this can happen. I may fit the old coil again and see if that works to eliminate that issue, or swap out the little red pickup sensor....these have been known to be faulty out of the box.....I know, hard to believe this one.

I rewired the ignition to the coil and fitted the old distributer, this seems to have fixed a non starter issue. but I still have the lumpy tickover.



PS: anyone have the timing for this 2.25 engine, the LTP3003 manual is a bit expensive to get this week! We set it as TDC as per other manuals but were left a little perplexed as to if this was right or not. Be nice to have reference to the dynamic timing. In any case, I think the timing is not the issue here.

Brown in the bowl Better have a look in the tank.

1. Buy manual for proper maintenance - try eBay/Amazon for a second hand copy, they're only a fiver.
2. ensure fuel system is crystal clear, new fuel and filters, no blocked lines.
3. make sure distributor is 100% good [do not buy cheap parts, go to the Distributor Doctor for correct parts].
4. set up timing correctly.
4. set up valves clearances.
5. clean and set up carbs.
6. take for a good run to your preferred watering hole, sit back and enjoy.

Job done.

First of all, drain the fuel tank and look inside. If it is rusty, remove the tank and clean it out. To clean rusty fuel tanks I use 5 litres of white vinegar and 2-3 table spoons of baking soda. Pour the mixture into the tank, seal it and shake the tank vigorously for a couple of mins, leave to stand for 5 mins and repeat. Then empty the tank and rinse thoroughly and leave it to dry. I have sometimes used a 2 part epoxy tank sealant called Flowliner but if the tank is not too corroded I usually don't bother.

After sorting the fuel tank I would then check the fuel lines are clear and remove, dismantle, and inspect the fuel pump. While I have it dismantled I would refurbish the fuel pump with one of the refurb kits that are widely available. If you have an inline fuel filter I would also replace that. After the fuel pump I would turn my attention to the carb. Remove and dismantle it and check all the jets are clear, check the float height is correct and check for any wear or play in the throttle spindle. If any part looks worn or corroded then get a refurb kit for the carb and rebuild it.

Having now eliminated a fuel problem I would check the cylinder compression. On a cold engine you should see around 120 psi but this will vary. The important bit is that all the cylinders are within 20 psi of each other. A common problem is the head gasket failing between cylinders 2 & 3. If the compression is fine then you need to look at the ignition system. If you have abnormally low compression on any cylinder then take the rocker cover off and check the valve clearances. If the clearances are ok but you have low compression then take the head off and check for burned or leaky valves and a cracked or warped head. A failed head gasket should be easy to spot. If you can't see any problems with the head or gasket and have low compression, then take the head to a specialist for pressure testing and refurbishing. When you refit the head re-check the valve clearances as the new gasket will have a different thickness to the old one.

After eliminating any fuelling problems and with good engine compression you need to check the ignition. Start by getting the timing roughly correctly set. Set the engine idle speed so to approx 700 - 800 rpm. I use the charge light as a guide, I adjust the idle speed until the charge light is just glowing slightly or flickering if you have uneven idle. Disconnect the vacuum pipe from the carb and cover the hole. Attach your timing strobe and set the timing to approx 6-10 degrees btdc, this may be best guess if you still have uneven idle. After setting the timing, check your plugs, just because they look clean, it doesn't mean they are sparking correctly. Check the gap and check they are actually sparking strongly and correctly between the electrodes. If you have a weak spark or sparking anywhere other than between the electrodes, then replace the plugs and check. if still no joy check the leads are correctly connected and replace if they are in any way worn, corroded or the insulating is cracked or split. If you are still having problems, you need to look at the dizzy and coil. Check the vacuum pipe is fitted and is not leaking or kinked. Check the distributor shaft for any play, either rotational or lateral, if there is any play, replace it, I have had a new distributor fail within 6 weeks so just because it is new, it does not mean it is good. Check the distributor cap for cracks and worn or burned electrodes and check the rotor arm for wear and play. Ideally I would fit a known good distributor and compare them. I would now check the coil, check the leads between the coil and dizzy are in good condition, any joints are tight and that they are no longer than they need to be. If you can, check the coil with a known good one, but I would probably change the coil as a matter of routine. After this, and assuming you have a properly running engine, you can set the ignition timing accurately. I use 99 octane petrol only and have set my timing to 10 degrees btdc at about 750 rpm.

Having checked all of these you should now have a properly running engine. If not I would then look at things like a worn timing chain or crank and camshaft wear. The thing I have found with these engines is that poor running rarely has a single cause, it is most often a combination of several thing becoming worn and out of adjustment. Unless the engine is very high mileage, or you have oil pressure problems then the problem is unlikely to be anything internal or serious, it is most likely to be one or more ancillary parts providing fuel or spark. Just eliminate one cause at a time, fuel, compression and spark and don't assume that a new part is working correctly, always try and compare it to a part that you know works correctly.

Also - you know there's a secret filter at the carb union? That one got me.

boguing said:

Also - you know there's a secret filter at the carb union? That one got me.

Click to expand...

Wait, for petrol there's another filter?
There's one at the pump and there's a tub in the engine bay on the bulkhead....not had that apart yet, is that the one you mean.

I have a haynes book of b'llocks but not a petrol one, so it's useless for this issue.

#2 here. Sneaky isn't it?

boguing said:

#2 here. Sneaky isn't it?

View attachment 322650

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That's a single choke weber. Not sure mine has that. I will have a look though. I remember my old singer has a brass gauze hidden there on a twin setup and that caught me out once.
Image below showing new carb next to old one. Had to fit a new carb, I find carburettors quite perplexing and simply easier to fit a new one.


Hmmm, just googled it and it may be hidden under there. Might be worth taking the top off the carb to check, you never know.
Good call. cheers. I'll add it to my list of things to check when next on my ramp.

Sorry, I assumed it was the same carb as the S3 has, and yes, you've found the right picture!

So, getting back to the rough idle issue (after a bit of tinkering with some shody wiring). What distributor should go in the motor. I tried a brand new one (made of chinesium), but the rotor arm had a massive gap to the pickups in the cap, whilst problem solving I decided to refit the old one. Mainly because, it's running now and I need to regroup.
Meanwhile, whilst I have a ton of things to look at to solve this, I would like to get a new distro due to a couple of reason.
1) The current one, when you suck on the vacuum pipe, it does not turn the plate that the little sensor (red in my case), therefore I cannot see how it can advance the timing. The new one does, as expected on any vehicle I have worked on, very odd. I cannot see another way the vacuum is supposed to advance it without moving the base plate and sensor. This is not causing it to run rough on tickover as the short time I had the new distro working, it still ran rough, though it may contribute
2) The old distributer is all a bit shonky really, the cap has a terrible fit and can't help with trying to tune timing when I get to that level of fine tuning.

Had a quick look on ebay and have seen a couple of distros for sale. There's a Lucas Type 25D and a Lucas Type 45D, I'm reluctant to jump in and get what seems to be the right one without understanding things a bit more. I already know that there are different advance curves that the weights define.
does anyone know a good place to start to get a decent distributer that suits the 2.25 engine? Or am I stuck with the same cheap crap that churned out. The best place I can find is Accuspark, they do the complete kit if I like, at least I'll have a good starting point.

I have one of these distributors fitted: https://www.paddockspares.com/etc5835eblack-distributor-electronic-black-cap.html. It works perfectly well, much better starting and more accurate timing than my old points distributor. I am not surprised that sucking on the vacuum advance pipe does not seem to do anything on the distributor, the vacuum you can pull by sucking is far less than what the engine produces. The best way to check is to put a timing strobe on the engine. Rev the engine with the vacuum pipe attached and see how much the timing advances then disconnect the vacuum pipe and rev the engine again and compare the timing change. If there is no change then the vacuum advance isn't working. You will always get some advance when you rev the engine as there are weights inside the distributor that advance the timing slightly through inertia.

Dorset_dumpling said:

I have one of these distributors fitted: https://www.paddockspares.com/etc5835eblack-distributor-electronic-black-cap.html. It works perfectly well, much better starting and more accurate timing than my old points distributor. I am not surprised that sucking on the vacuum advance pipe does not seem to do anything on the distributor, the vacuum you can pull by sucking is far less than what the engine produces. The best way to check is to put a timing strobe on the engine. Rev the engine with the vacuum pipe attached and see how much the timing advances then disconnect the vacuum pipe and rev the engine again and compare the timing change. If there is no change then the vacuum advance isn't working. You will always get some advance when you rev the engine as there are weights inside the distributor that advance the timing slightly through inerti

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I agree with all of that, but the electronic pickup is mounted such that it cannot rotate no matter how much vacuum you put on it...very odd. There's a brass pin that rotates, so maybe there's something missing or it advances a different way but the little red sensor will not move even with a screwdriver behind it...in the end, I'm going for a new one anyway, I have long term plans for this LR and it's going to take me a couple of years before I start doing long trips in it, first I need to know what's what, so it'll be triggers broom eventually. So a new one makes sense.
As an engineer, I look at the 'paddock', 'craddock' , 'britpart' units, all very cheap and certainly functional, however, I cringe at some of the shortcuts they make, I get it, I design bits for cars and everything has to be done on a budget.
That said, I have many other issues to solve first.

Accuspark means new distro, cap, coil, plugs, leads.....£109. Well worth it. It's the 45D. It won't solve the rough idle but will satisfy my 'what-if-it's-that-shonky-bit' thought.

I have a 110 2.5 petrol.
I had all the same problems as you, it took me ages to figure it out.
In the end it was crap in the carb, I sent it off for a refurb and its been fine ever since.
Also, make sure the 2 solinoids that go into the carb are working, iirc, 1 is idle control, the other is fuel shut off when the ignition is switched off.

I also fitted a k+n type air filter, the pipe from the air filter to carb was rotting and allow debris to get into the carb.

landrover11019 said:

I have a 110 2.5 petrol.
I had all the same problems as you, it took me ages to figure it out.
In the end it was crap in the carb, I sent it off for a refurb and its been fine ever since.
Also, make sure the 2 solinoids that go into the carb are working, iirc, 1 is idle control, the other is fuel shut off when the ignition is switched off.

Click to expand...

Whilst that is an area to look at, I had the problem when I brought the LR last year and brought a brand new weber carb...issue still there. I have cleaned it out anyway to make sure, it is not the carb, of that I'm sure. My next thing to check will be the valve clearance, because at the same time I can check if there is any backlash on the cam shaft via the timing chain. Maybe the timing chain is loose or the oil pump that pushes against the tension belt may be worn....etc....
I have a couple of half decent books coming to go along side my useless haynes book of b*llocks, maybe that will guide me better.
Itching to get the LR back in the garage so I can get to work but the garage is being used for a couple of parties and this is irritating as hell. Normally do this kind of work in the winter months.

The books turned up. It is TDC static or under 600RPM with strobe. Nice to have a couple of decent books though, so I can have a good look at things.
Fitted accuspark distro, leads and 3 pronged plugs. I knew this would not solve the issue but they needed replacing anyway. Have a new coil coming, well, had one but realised it's not a ballast line so need to swap it for a non ballast. But at the end of the day it runs rough on tickover...seems to just drop now and then. It seem to run ok at around 30° BTDC (don't know exactly, I have a cheap strobe with no angle adjuster on it). So wound it round to close to what is in this picture (TDC) and it's the same, refs cleanly as usual etc...
Something is loose somewhere, so next job (when I get my garage cleared), is to take the rocker cover off and go through the gaps, at the same time, I'm told to check for backlash, this may hint at timing chain or tensioner.

Dorset, I appreciate your long comment and keep reffering to it. eg; pressure testing, that is also next on my list when I have her back in the garage.

OK, got back to the old girl after lots of other projects got in the way. Been using her regular and still have the rough idle issue. So with her in the garage I have today and next Saturday to tinker with her and try a few more things.

I checked the tappet clearances, they were all tight, so I loosened them a little to 0.010", (that said, I might recheck when warm as I now get a little bit of rattle), whilst there I checked the movement of the rockers when rotating the engine, there appears no backlash at all, I really don't think it's the timing chain tensioner.
One thing I did different though, and that's following a manual, when setting the timing roughly, I rotate to TDC, (when number four cylinder has both valves rocking, then set the distro to fire on 1. As usual, ran like a 2 cylinder donkey, so rotated it back round to around 20 or 30 degrees, ran fine. I really think the cam shaft is fitted wrong here or has the wrong cam shaft or something, as the position of TDC for firing 1, is not right.
I did fit a new rocker cover gasket as the one fitted by the previous owner had a ton of glue on it...what is this obsession?
Next I will check the compression of each pot and have yet another look at the fuel filters etc....
Maybe I'll get a video up here of it running next.

PS: my brother acquired another one from the same year, a proper mess, rusted through and through, not salvageable, guess what, it ticksover fine. FFS. Might be easier to swap out the bloody engine at this rate.

I can't buy into the camshaft timing being 30 degrees wrong - it probably wouldn't run and I'm pretty sure you'd be clashing valves and pistons. Distrib shaft wrong assembly, maybe, but that, like the crankshaft, isn't really going to get worse.

Have you checked the entire fuel line for blockages. Crud in tank blocking the pickup and any other filters and joints.

I did a compression test, 115,125,125,125. Nothing outrageous there. I did a dry test but feel that this is not the issue so did not bother doing a wet test.

Regarding cam shaft, let me explain better what I mean. If the person who last assembled the engine put the chain between the cam shaft and crank out by one tooth, that would cause all sorts of conflict and possibly what I'm seeing here. I think next weekend I'll be checking that next. Should not be a hard job and be nice to take apart anyway and fit a new gasket...guessing there's a **** load of red glue there too!
I'm 90%sure it's not fuel, I fitted an inline filter just before the carb temporarily so I can keep an eye on that, it's clean and a good supply to the carb. Fuel from the tank is clean, new filter, It's a new carb and I've cleaned the jets out a few times and found nothing, I'm convinced it's not fuel. The fact that the distro is 20 or more degrees out tells me it's timing related. Maybe a wrong cam shaft is fitted, but for now, checking the cog alignment is an easy step before I get into that.
I rebuilt a rootes 1725 engine a few years ago, went from cast to ally head, ordered cam, assembled carefully and noticed that was wrong before I got to installing engine, so I can imagine someone getting that wrong, considering the bodges I've seen to date, it's worth checking them cogs are aligned right.