Thread: 3.9 EFI Flat spot / slight misfire

Originally Posted by Hobbes

I've been trying to find some of those nylon combs with fixing hole that separate the HT leads - no luck at the usual Repco/Supercheap outlets - anyone know an off the shelf supplier?

There are several different styles of lead separator on ebay, one of them might suit you...

Well, spent the day removing, cleaning and repositioning the LT cabling and the HT runs.
Following good old audio engineering practice I made sure that cables crossed at right angles, or at least had some air between them.

End result appears to be that its worked! Lot smoother at idle and no weird drop outs around the 2k rpm point. Next step will be shield those cables as per Philips advice.

Welcome Kevin, and yup. a dodgy track on the tps is often the cause of the described symptoms. Fortunately it wasn't in this instance..so a few bucks saved..

Chris

Replaced the amp, plenty of heat sink paste behind it, the old one, was nearly dry.

All the HT leads, I've covered in 3/8 plastic cable shroud pre - cut, so at least they don't touch now, when they go onto the rocker covers all HT lead spacers seem to do the trick.

So far so good, now no great misses' or hesitation, in fact it feels a lot better of the button now.

Started to look at the TPS the red cable is the feed back to the ECU. therefore needs the + (volt meter) on it, then to ground, you will generate a error but a disconnect of the battery will clear it with no issues. resistance when disconnected should read around 5000 ohms.

Doesn't look like i've got to the bottom of it yet, got on the highway this morning, and still there, after the amp change.

I know my dizzy checks out OK, timing is correct, dizzy cap & rotor arm, capacitor, plug leads coil are all new.

My only thought is even thou the TPS checks out OK, it could be on its way.

But something so simple as a cracked plug, could it give that fault, but my understanding is, it would occur at idle all the way up to 4,000 rpm etc.

What would a iffy injector show, apart from reduced power?

Keep at it Jimbob292.

I thought I would update that I replaced the old leads last night and replaced with the Magnecor KV85s from my other Rangie and I can not detect a miss while driving any more.

I found the connection at the coil was broken... as in the metal came out of the lead jacket and stayed inside the coil when I removed the old wire.
So I think it is safe to assume that it was probably the main cause of the problem.

Re routed the wiring a touch more (but not yet shielded and ground it) and at present there is no stutter even with the AC on... but now I have come to realise my AC doesn't work at all, just warm smelly air!!!

Thanks for the advice so far guys and again hope you find the cause of your problems Jimbob.

Hi Grimace,

I can say I'm going to win, its just a matter of time

It still puzzle's me the slight miss, at 2000 - 2100 rpm 95 km/h, but when the Disco is stationary, it doesn't do it, i can slowly increase the rev's up to 3,000 rpm sweet as a nut, surely that would that show a fuel demand issue, either way the saga carries on.

Completely checked over all the brake servo hose, crankcase breather hoses again, for cracks and such like, nothing.

Flushed the crankcase breather with petrol, pretty clean anyway, but worth a shot.

Removed the TPS, cleaned as best i could with CRC electrical cleaner, also the main cable, put a little copper ease on the mating spindle to throttle valve, hylomar around the gasket and refitted.

At the weekend will pull all the plugs again, check the colour and see whats happening, last time, they were all white, so bang on the button, mixture wise, that will rule out the injectors etc.

I have some RN12YCC that have never been used, bought them by mistake, they should be OK in the engine to run as test to rule out the other plugs?

I also plan on clearing the MAF out of this equation as well, I've also removed that plug, sprayed with CRC cleaner, and gave all the terminals a slight twist, so they mate a lot better in the connector. I have some CRC MAF cleaner, so will give it a good clean as well.

Its my understanding that a faulty MAF will throw up the check engine light, likewise the TPS & other temp sensors?

As for the TPS looking at getting a new one, is the next part in this equation, tbh called a few LR dealers in the UK and part # ERR 2263 is no longer in production, the Lucas code on the side is 215AS this is the type, the model # is 70408A.

Checked out the RS Components web site,
Buy Rotary Encoders Rotary position resistive sensor,5kohm Vishay 971-0002 online from RS for next day delivery.

the nearest is part# 319-310 but you need a 90deg movement, where as this one has 130 deg

If you can find one below 200 GBP you on a winner for sure!

Finally making some progress.

Removed the fuel filter last night, replaced with a new one, added 500 ml of 3M Fuel System cleaner.

Replaced the plugs with another set of Champions,

left bank.JPG
Left bank left to right piston 2,4,6,8

right bank.JPG
Right bank left to right piston 1,3,5,7

A couple of the plugs didn't look good, these have only done around 2,000 k/s after the 210,000 service, likewise with the fuel filter.

Took it for a run, perfect through the gears now, no flat spot @ 2K rpm

Life's now peachy for once!

The symptoms came back again yesterday.

So took the hit and took the tank out this morning to check for any crud, when i took it apart here's what i found a broken neutral on the pump.

Could have turned out nasty if i hadn't have checked it out.