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dirtydiscov8

New Member
A while ago i posted about my 97 disco 3.9 v8 not revving past 3500rpm when hot.

Since then it has been to 3 different garages and none of the could find any fault. I have bout and used a steve heath diagnostic tool which only once has shown code 48, stepper motor/intake air leak/ base idle. it is wired right as shows faults when u unplug something.

I've changed various parts now and im getting very frustrated with it.

Disco has a crower 50229 cam, magnecore leads and adjustable fuel reg.

So far...
Fuel pressure set at 38psi as recc by rpi
new fuel filter
smoke test to check for air leaks
new throttle pot
speed sensor
base idle set
fuel flow rate checked
fitted known good steeper motor and fuel pump
coolant an fuel temp sensor
spark plugs
magnecors
lucas cap and arm
ignition timing set and re checked
also been through the ecu plug with a multi meter referencing a rover test book and getting the correct reading for inject resistances and everything!!!

I hate throwing money at car's but no one can find any problems!!

Any one got any idea's or know of any good rover v8 mechanic types in the herts area???

It's that or it becomes an exspensive new years eve bonfire!!!

Any help much appreciated, Thank you please!!
 
Is this something that just happened or was it by chance after changing
some thing ,after a service ect .
 
Always seemed to lose power at about 3k when hot. Shortly but not straight after the cam change it got worse.

When cold it will happily rev to 4500rpm. It seems I be relate to the heat build up in the engine bay not the actual engine temp. Say it can sit half on the temp gauge and be fine but if sitting in traffic and I imagine the engine bay temp increases it worsens.
 
There is a post on here from Tig 9619 same problem as you after changing
his cam have alook may help.
 
sounds to me like the cam followers are not set up right

when hot valve stems and cam followers expand ( get longer) thus if the camshaft fitted is thicker the valves wont totaly shut correctly when hot ( expanded ) thus loseing compression and putting the engine into limp mode stopping it revving over 3500rpm

get the valve and camshaft clearances checked there should be 2 different measurements one for cold setting and one for hot

when theyre set correctly for cold the engine needs running to hot the rocker covers removeing and cross examineing with the hot settings if theres a difference adjust them when its hot as all valves will expand at different tolerances and rates such as the older valves for leaded fuel are softer than ones for unleaded engines and so will expand less or more coinciding with how old or hard the valve stems are
 
Let's start at the top the only good followers to fit are the genuine dealer supplied ones period!
Again the only good ignition parts are dealer only period!

Plenty of the aftermarket say it's gen spec but it ain't most on here know the supplier!
Go back to basics the fpr will over pressure across the whole rev range not good
As you have said it is not showing any faults you can dismiss the electrical and look at the mechanical.
Have you got lambdas fitted what is the feed back when revving?
 
I was trying to say the same as Johny curt I just do not know as much as him ,but I been told you need to check the preload on some cams(feck
knows what that is).
 
Thanks for some good input. My thoughts were with the followers. Sometimes it will be fine till i rev it hard then it will start playing up and seeming to lack power. They don't make any nasty noises though i would have thought they would?

If i go down the route of fitting genuine followers would i need to replace the already new camshaft too!!

I did set the pre load when i fitted the new cam but it was on a cold engine though.

i do have lambdas but i wouldn't know how to check there feed, tried it with a non cat tune resistor fitted too, still had the exact same problem.
 
you have got the ignition timing right ? and it's spoton all the way up the rev range ?
 
Ignition timing is set at about 8degree btdc. Runs up smoothly to being all in at about 30degree at about 3000rpm. Tried advancing an retarding to no avail.
 
vougese39 said:
Let's start at the top the only good followers to fit are the genuine dealer supplied ones period!
Again the only good ignition parts are dealer only period!

Plenty of the aftermarket say it's gen spec but it ain't most on here know the supplier!
Go back to basics the fpr will over pressure across the whole rev range not good
As you have said it is not showing any faults you can dismiss the electrical and look at the mechanical.
Have you got lambdas fitted what is the feed back when revving?
Click to expand...

Just got a fault code of stepper motor/intake leak

Now i know i don't have any intake leaks, used a fancy snap on smoke testing machine and all was well. Tried a known good stepper motor from mates range, same problems. Possible for non oem lifters to throw this code up by creating poor inlet pressure or something.

Someone pass me some straws to clutch at!!!!
 
Just a thought.... I'm no expert, but having just changed the cam on mine I found accurately checking the preload was a nightmare - really fiddly and difficult to do conclusively - so I did the best I could and crossed my fingers...!

Anyway, to my point. A relatively easy and cheap way to TEST whether the preload is an issue (as opposed to measuring it) is to install some rocker shims and see if the issue improves. Turner Engineering do a set at a very good price. It wouldn't involve anywhere near as much dismantling to just get the rocker shafts off, shim them a little (equal shims on each pedestal of the rocker shaft), then put it back together and test it. It avoids the full strip-down, and might get you nearer to a solution without having to spend a fortune.... (Make sure the oil holes of the shims line up with the oil holes in the pedestals!).

Like I said, I'm no expert, but I can't see that you could cause any damage trying that method. I'm sure I'll be shot down in flames if I'm speaking rubbish, it is just a thought.
 
I believe boycie may have hit the mail of the head. Unless the cam and followers are genuine parts for your specific vehicle you must check the preload after fitting a new cam/followers. You may want to have a look at the article at RPi Engineering - V8 Engines. As johnny curt mentioned, if the preload is incorrect you will almost certainly get power loss due to incomplete valve closure as the engine warms up.
 
Right, after putting some thick oil addative crap in it it greatly improved the revving problem, so i figured it was definitely the lifters. Went out and got some rhoads lifters and adjustable pushrods (turtled i know how much a ball ache pre-load is this way makes it much easier). Fitted all that this afternoon, went really well...some would say too well!!

Filled it up with fluids gave everything a double check, cranked it over and.....sweet f/a, nada,nothing,kaput!!!

Checked i had fuel, it had plenty. Double, no tripple checked all connections to coil and all plugs i had removed, all good.

Pulled out a plug, wet with fuel but would it spark,arc to anything...nope!!! Got the timing light out and clipped it to all ht leads, no strobing. Tested power to coil, good 12v.

Got another coil just incase. Still nothing. Right you little tit i thought so i put a different dizzy on it but still nothing!!

Now im thinking the pick up in the dizzy is working as it must be sending the ecu the right signal via the coil to tell the ecu when to inject.

During the work today the dizzy wasn't removed, just took the cap off with all leads attached to it and re fitted. ( firing order is correct )

Surely it has to be the cap or arm at fault?! Any ideas?
 
Tried that too. I did try it last as £90's worth of week old magnecors really shouldn't fail!!

The cap's only ben on a week to, not it's not genuine lucas but really, can taking it off an re-fitting it make it die? I've got some genuine oem caps at work i'll being trying tommorrow
 
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