95 Disco V8i struggling to accelerate, "bucks" a bit when taking off.

[Seretical]

Just today, I was driving my disco back home and I pulled up at the lights. As I went to take off and I pressed the accelerator in, it just started bucking along, almost like it was going to stall or like it was running out of fuel. I also noticed it was pretty rough when idling, almost "bumpy". I had just under a quarter of a tank left so I thought that might be an issue, so I pulled in to the next petrol station and gave it a full tank.

Started it up, and once again the idling was bumpy. Pushed the accelerator and it's still doing it, all the way home. And it felt like it was only getting worse. That brings me here. I suspect it's most likely a fuel problem. I just don't know what.
I went through my service records and I haven't found anything related to the fuel system so that's not good news, I know that much. I believe my vacuum advance is not functioning properly, and I am not sure about the state of my MAF sensor. Truth be told, I don't know where to look or what to do. I'm not planning on driving it out of fear that it'll die while I'm on the road.

Any V8i Disco owners had this issue? Or is anyone able to shed some light on this? Hoping this is relatively easy and inexpensive to fix
Thanks

[grey_ghost]

Has the in-tank fuel pump been replaced? Those were the symptoms that I experienced when the pump on my 89 V8 RRC died.

Typically the pumps last about 150,000 - mine went at 225,000.

And check the usual - fuel filter, plugs, air filter, etc

[AK83]

could be something really simple like vacuum line loose or cracked. Can cause same symptoms.

[Rick1970]

If you have a IR thermometer (heat gun), run it over the 8 exhaust ports on the manifolds (engine running from cold)....easy way to pick up which cylinders are missing. If ignition related, could be plugs/leads of those cylinders, or dissy cap/rotor.
Well worth replacing the fuel filter, if it's missing at idle, a quick squirt of some flammable arosol in the intake may help diagnose......should pick up if fuel related, stay the same if spark related.

As well as fuel pumps dying, the hose in the tank can also split and cause very low fuel delivery and pressure.

[discomatt69]

check plugs and leads, pull one at a time with a pair of pliers while it is idling, if the idle gets worse its not that lead or plug,if it doesn't make much of a change you have found the issue.
How long since a decent service, if a fair while replace plugs , leads, cap if worn, and fuel filter, all service items.
If the problem persists my guess its either fuel pump or air flow meter related

[Porker]

Thanks for the replies as this is my son’s discovery. I checked for vac leaks, checked fuel pressure (32psi) fixed the vac advance also checked the maf. I had previously pulled the plugs just after he purchased the car and they were in as new condition and also indicated that the mixture and timing was good.We haven’t been able to get the fault to happen again so I’m am wondering whether it is a fuel level issue, as a number of years ago I had a similar fault with a split gauze pickup on the end of the fuel pickup in the tank. Is this possible with the Discovery in tank pump?
We are planning on getting a replacement pump for it anyway as a spare part to carry along with the other spares. Thanks Paul.

[redmond]

[QUOTE=Porker;3154698]Thanks for the replies as this is my son’s discovery. I checked for vac leaks, checked fuel pressure (32psi) fixed the vac advance also checked the maf. I had previously pulled the plugs just after he purchased the car and they were in as new condition and also indicated that the mixture and timing was good.We haven’t been able to get the fault to happen again so I’m am wondering whether it is a fuel level issue, as a number of years ago I had a similar fault with a split gauze pickup on the end of the fuel pickup in the tank. Is this possible with the Discovery in tank pump?
We are planning on getting a replacement pump for it anyway as a spare part to carry along with the other spares. Thanks Paul.[/QUO had same problem spent weeks checking all the stuff was magnetic pickup in dizzy wire had broken would start then stop splutter also changed module to a bosch as lucas one has a habbit of letting you down

[4bee]

[QUOTE=Porker;3154698]Thanks for the replies as this is my son’s discovery. I checked for vac leaks, checked fuel pressure (32psi) fixed the vac advance also checked the maf. I had previously pulled the plugs just after he purchased the car and they were in as new condition and also indicated that the mixture and timing was good.We haven’t been able to get the fault to happen again so I’m am wondering whether it is a fuel level issue, as a number of years ago I had a similar fault with a split gauze pickup on the end of the fuel pickup in the tank. Is this possible with the Discovery in tank pump?
We are planning on getting a replacement pump for it anyway as a spare part to carry along with the other spares. Thanks Paul.[/QUO had same problem spent weeks checking all the stuff was magnetic pickup in dizzy wire had broken would start then stop splutter also changed module to a bosch as lucas one has a habbit of letting you down


Taken in a load of water contaminated fuel prior to the 2nd load he mentioned? A decent dose of Metho into the fuel Tank was always my Pre- Winter safeguard.

[Rick1970]

Need to check fuel pressure with and without the vac hose connected to regulator…… at idle fuel pressure should raise when hose is removed, drop back a bit when regulator sees manifold vacuum.
At very least, replace fuel filter.
Maybe drain fuel and remove fuel pump from tank for a visual…..could have got a dose of bad fuel.
98 fuel seems to go bad quick if left sitting, had this issue a few times with a bike (left sitting for 3 weeks from a full tank and would barely run…..drain and replace fuel and all good)

[johnp38]

Maybe drain fuel and remove fuel pump from tank for a visual…..could have got a dose of bad fuel.
98 fuel seems to go bad quick if left sitting, had this issue a few times with a bike (left sitting for 3 weeks from a full tank and would barely run…..drain and replace fuel and all good)

98 fuel is meant to be the longevity king and 91 the use me asap type, I have run 98 in my generator since new (2004) and it has been started once for testing since the big SA blackout when the towers went down (3 years ago ?) and it was on for a few hours that night. And even then it had also been sitting for a year or more not started.

My small engine shop person recommended 98 for the petrol driven stuff that sits around a bit between uses too.

Always interesting hearing others experiences.

[Traco]

Sounds like it may be a duff TPS. You can measure the resistance on these with a digital multimeter. New improved versions are available from ACT, Mark Adams and RPI also sell these.

[nzajg]

Hello. You may by now have solved your fault. However, I have a 95 DI V8 which had a similar intermittent condition, which I called a fibrillated spasmatic fault. It ended being the Throttle Control sensor. These are very costly to replace, worth more than the truck itself. To repair I carefully removed the back with a narrow fret saw and carefully picked out the resin packing to expose the wiring that had partially dislodged itself. I resoldered the wires (micro surgery), thus avoided having to enter the front side of he sensor. I then reattached the back with gasket paste. The D1 runs well.
Regards Tony G, NZ