off the top of my head check all the breather hoses between plenum chamber and rockers and ensure no leaks between maf and plenum? maybe its sucking in air somewhere. Mines done that a few times.
1995 4.6 Hesitating before revving up ?
Evening,
I'll start by saying this is an amazing site ! I've spent many hours researching different things about my p38...but never posted :clap:
My 4.6 v8 had it's head gasket burn through from cylinder 5 to atmosphere, sounded like a blowing exhaust manifold which i originally thought it was. So i've had both heads off, had them fly cut, tested and reassembled it.
But i'm having a problem - when it's sitting idling - if you press the accelerator it seems to hesitate (bog down a bit) then rev's up :think: I had guess that my air flow meter was a bit tempermental before the head gasket fault, so a new one has been fitted. Also fitted new spark plugs & leads.
Can anyone give me some suggestions on what i can look for to try and sort it ?
Cheers
Gordon
I'll start by saying this is an amazing site ! I've spent many hours researching different things about my p38...but never posted :clap:
My 4.6 v8 had it's head gasket burn through from cylinder 5 to atmosphere, sounded like a blowing exhaust manifold which i originally thought it was. So i've had both heads off, had them fly cut, tested and reassembled it.
But i'm having a problem - when it's sitting idling - if you press the accelerator it seems to hesitate (bog down a bit) then rev's up :think: I had guess that my air flow meter was a bit tempermental before the head gasket fault, so a new one has been fitted. Also fitted new spark plugs & leads.
Can anyone give me some suggestions on what i can look for to try and sort it ?
Cheers
Gordon
1 - 11 of 11 Posts
I'd check all connections again, plug out plug in but inspect for any signs of residue of sorts.
Possibly crank or camsensor...
Possibly crank or camsensor...
This doesn't help, but mine intermittently does exactly the same thing. While it's doing it, I also get a very low idle speed and stalling. It never seems to do it first thing in the morning though which seems a bit odd. It usually only does it after starting the engine when it's warm...
It's recently (last couple of days) got much worse for some reason.
I've had a new MAF which seemed to fix it for a while. More recently the adaptive values were reset in the ecu again which seemed to cure if for a while, but it's back again now and it's REALLY irritating especially in the snow!
Guy
It's recently (last couple of days) got much worse for some reason.
I've had a new MAF which seemed to fix it for a while. More recently the adaptive values were reset in the ecu again which seemed to cure if for a while, but it's back again now and it's REALLY irritating especially in the snow!
Guy
So where did the Maf come from ?
You dont mention which engine you have, year model..... if its pre 99 then I would say two things, 1 HT leads 2 idle control valve on throttle body, maybe throttle position sensor but I doubt it.kooky_guy said:This doesn't help, but mine intermittently does exactly the same thing. While it's doing it, I also get a very low idle speed and stalling. It never seems to do it first thing in the morning though which seems a bit odd. It usually only does it after starting the engine when it's warm...
It's recently (last couple of days) got much worse for some reason.
I've had a new MAF which seemed to fix it for a while. More recently the adaptive values were reset in the ecu again which seemed to cure if for a while, but it's back again now and it's REALLY irritating especially in the snow!
Guy
99 on then that too could be HT leads along with idle control motor (Bosch) though I've yet to see a bosch idle control motor go
Maybe consider unplugging the fuse box and check the connections on both plugs and lugs where they connect...
I am assuming GEMS going by the thread title..viperover said:You dont mention which engine you have, year model.....
Sorry about that. I forgot I hadn't set a sig up.
Mines a 98 4.6 HSE with lpg (ie GEMS). The MAF was a brand new (cost a bleedin fortune too) oem one. Previously it had an aftermarket one on it so I'm guessing it's had this problem before but throwing replacement MAFS at it doesn't seem to fix it.
I'll have a look at the idle control valve - I've been reluctant to touch this though as it's only held in with one screw - the other has been snapped off in the casting. I guess I ought to get this drilled out and redone at some point.
The last time it was serviced, the chap mentioned that the MAF was almost out of limit but I didn't understand what he meant. Anyway, he reset the adaptive values and it was fine again for a while.
The low idle part of the problem is fairly intermittent, but the hesitation is much worse when the idle is playing up - the first part of the throttle movement will actually cause it to stall unless you push it further where it reluctantly picks up again (if that makes any sense).
Apologies to the OP - didn't mean to hijack your thread!
Guy
Mines a 98 4.6 HSE with lpg (ie GEMS). The MAF was a brand new (cost a bleedin fortune too) oem one. Previously it had an aftermarket one on it so I'm guessing it's had this problem before but throwing replacement MAFS at it doesn't seem to fix it.
I'll have a look at the idle control valve - I've been reluctant to touch this though as it's only held in with one screw - the other has been snapped off in the casting. I guess I ought to get this drilled out and redone at some point.
The last time it was serviced, the chap mentioned that the MAF was almost out of limit but I didn't understand what he meant. Anyway, he reset the adaptive values and it was fine again for a while.
The low idle part of the problem is fairly intermittent, but the hesitation is much worse when the idle is playing up - the first part of the throttle movement will actually cause it to stall unless you push it further where it reluctantly picks up again (if that makes any sense).
Apologies to the OP - didn't mean to hijack your thread!
Guy
If the HT side of the ignition system is in good order the only other thing that springs to mind is if the stored closed throttle voltage is too low.If its less than about 0.6v this will cause hesitation or stalling from idle.The stored and actual throttle voltage can be seem on Testbook.
Cheers. Pretty sure the HT is ok. I'll see if i can get the values read. Does Rovacom show the same values?allyv8 said:If the HT side of the ignition system is in good order the only other thing that springs to mind is if the stored closed throttle voltage is too low.If its less than about 0.6v this will cause hesitation or stalling from idle.The stored and actual throttle voltage can be seem on Testbook.
Guy
Thanks for the replies... It turned out to be a faulty air flow meter.
Gordon
Gordon
1 - 11 of 11 Posts
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