RR classic 3.9EFI bogs when gas is applied

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TimoTS

TimoTS

Active Member
Posts
143
Location
Netherlands
My Range Rover idles but when I apply the gas it sometimes bogs, sometimes completely sometimes almost completely, all injectors are cleaned, what could this be? It idles good, fuel filter?

I’ve attached a recording of it happening.Video of bog

Every time it drops in rpm’s it’s me hitting the gas.
 
So, from your attached video we see that the engine at idle of around 1750rpm, then there’s a few blips of the throttle and then after the revs drop slightly below the idle speed, then will increase back to 1750rpm… yes?

Also unfortunately i’m confused with your statement “when I apply the gas it sometimes bogs, sometimes completely sometimes almost completely, 🤔
 
discool said:
So, from your attached video we see that the engine at idle of around 1750rpm, then there’s a few blips of the throttle and then after the revs drop slightly below the idle speed, then will increase back to 1750rpm… yes?

Also unfortunately i’m confused with your statement “when I apply the gas it sometimes bogs, sometimes completely sometimes almost completely, 🤔
Click to expand...
When i blip the gas, instead of rising in rpm it drops, and sometimes dies. Only when i apply it slowly it rises normally.
 
When once my 3.9 had a intermittent time with it it’s idling I put Redex Petrol System Cleaner into the tank and the issue never returned, maybe using supermarket petrol (which I still use) caused the issue so a fuel cleaner is still used once a year.

With my 3.5 a clogged crankcase breather caused engine stalling, so I cleaned the pipe and flame trap in petrol, (a top tip from the dealers service dept) the cleaning the breather was listed in the main dealer service and replacing the flame trap sometimes, servicing by the book every 3000 miles or so when I had the time to take it in.
And no issues in the ten years of ownership till l sold it with just over 100k miles and just after a camshaft replacement. ☹️

So at first keep things simple 😊
 
discool said:
When once my 3.9 had a intermittent time with it it’s idling I put Redex Petrol System Cleaner into the tank and the issue never returned, maybe using supermarket petrol (which I still use) caused the issue so a fuel cleaner is still used once a year.
So at first keep things simple 😊
Click to expand...
I also put supermarket E5 in my 3.5efi because, apart from keeping the ethanol percentage as low as possible, the pump price is only a few pence higher than the E10 from BP/Shell/Esso used in our old BM.

Both cars had a dose of cleaner earlier this year, difficult to tell if the engines saw any actual benefit but the application(s) won't have done any harm.
 
Bogs when giving it gas........ check vac advance is working, check throttle pot for base voltage, resistance and scaling. Might be worth checking ignition timing while you're at it, I found a bit of extra advance worked well. BTW best diagnostics for 14CUX is understand what it's trying to do (or not) then use a multimeter. If you really want to get in to it, vacuum testing and compression testing can tell you a lot. Rovergauge is OK provided you understand what it tells you, I used to use an EcuMate which was quite useful. HTH
 
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