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Discussion Starter #1
Hello everyone ! I have searched and searched for answers but I am still having no luck. I am hoping someone could point me in the right direction.. please bear with me as I am writing this on mobile
So I have owned a 1996 4.6Leaker Range Rover p38 for 2 years I am proud to have working eas system might I add :) fixed it all myself and am comtrable with it .
I would like to add in that I only use 93-94 octane in this veichle as well.
So to get to it ...
I have been having a bad idle recently in the last few months ( I have rarely been driving it since the condition has appeared
the problem problem/ the engine will choke itself of air when I use the accelerator or directly tug the throttle cable. It will start fine and run good (it will stay at 900-1000 rpm for 2-3 minutes cold start and than after that my rpm will slowly get lower (thinking it's because of my engine temp rising and etc (normal from what I understand) ) but it countinues to lower at idle until it goes low enough to stall itself out .when I use the accelerator pedal to (give gas) it completely chokes out and my idle rpm drops to zero and it will stall if I don't let off of the throttle pedal
So over the last month I have replaced my fuel pump, alternator, throttle position sensor, stepper motor, new spark plugs and new wires and I have also replaced all correded wires going to my battery, alternator, starter, fuse boxes also new battery rated 850cca ( also have checked evey fuses in engine and under passanger seat).

I am also getting fuel and spark %100

I have taken off my intake manifold and have cleaned it and resealed it . No air leaks that I can detect and all my vacuum lines appear to be in good condition)
I am honestly realy stuck on this problem and I would appreciate it if anyone has ran into something like this can lend me some knowledge and insight.

I do also have RSW solutions software. (Love it, recommend it) I have no engine codes etc .
 

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It sounds like your RSW software has been ineffective in tracking this, no?
 

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Discussion Starter #3
Yes It has been ineffective at this problem I am having yes . The vehicle has not giving me any check engine lights or gearbox fault etc. But the software also displays live data from the becm and eas system as well as read and clear faults, reset adaptive values, reprogram eas ride heights, etc.
A few codes came up when this bad idle first started happening about 2 months ago.. I read them : iacv valve strepper motor open circuit (driving cycle *) I can't remember the others unfortunately. I cleared them thinking the problem would go away or it was just bad voltage from battery . Codes haven't reappeared even when stalling at idle .
 

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Idle is controlled by the IAV stepper taking signals from the air flow sensor and TPS. It won't be an air leak, not unless it is a huge one, as that would normally cause high idle not low. You say you replaced the stepper (I assume you mean IAV), was this with a brand new genuine one or a second hand one? Did you clean out the passages to it before fitting it and did you then reset the adaptive values? I assume the RSW software is capable of doing this?
 

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Discussion Starter #5
Richard g - yes I do mean the IAV (directly beside the TPS) on intake manifold correct?
I bought a genuine second hand one . I cleaned the intake manifold, butterfly valve, passage ways with carb cleaner . I did NOT reset my adaptive values yet (but I can and I will today to cross it off the list) . The veichle seem to idle fine when cold for 2-3 mins but once it reach operating temperature (coolant temp needle in the center of temp gauge) it will begin to idle slower and go as low as 350rpm.
Changeng the gear seletetion from park-drive etc does not affect rpm in anyway

I am leaning towards a bad MAF or a camshaft position sensor ( but it idles okay while cold now leading me to believe it may be a temp.related sensor due to stalling when engine is hot) engine will start , idle for a few seconds when hot after stalling as well. But will die quickly
 

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Normally when cold the idle will be higher, around 1,00 rpm, dropping down to 600 when hot. It sounds like yours is just down so it starts off low and as it warms up drops too far. Adaptive value reset may well do it. If it doesn't, try unplugging the MAF. If nothing changes that's the problem.
 

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Discussion Starter #7 (Edited)
So I reset my adaptive fuel valves. I Let it sit and idle at around 750rpm for about 10-15 mins .The car will now idle at operating temperature and won't stall out ( hooray!). I am still getting alot of hesitation and it will cut out immediately when I give it throttle while idling . When I open the butterfly valve manually (giving it more throttle) and then let off the throttle /butterfly to let it go back to its shut/idle position I hear a pop noise ? Sounds like it is coming from my airbox tbh.. but worried it's a missfire as it will idle rougher and shake but than go back to the standard idle . I was born missing my right ear.. so I am half deaf and listening for noises for diagnostic purposes is not my specialty by any means. I have not tried to drive it or anything. ( I know it's going to stall as I leave my driveway) It seems when I give it throttle either way slowly or quickly it cuts out and becomes hesitant.. unplugging my MAF while it is running will adjust the rpms sliglty but stays idling. Cuts out and hesitation when given throttle with MAF plugged or unplugged
I am hearing alot of air rushing around my airbox/ air tube while it is idling . But as I adjust the throttle open using my hand where the throttle cable goes the air rushing/vaccum noise dissapears(and it than wants to stall) until I release the throttle and the Rpms will go back up and idle fine again
Also no codes or check engine light have came on .
I appreciate your input, Richard Thank you
 

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Sounds like the mixture is too lean.

Something to look at (as I found with mine), check the air silencer boxes (those funny shaped plastic boxes that hang down towards the LH manifold from the induction pipe). I found mine had melted through on the bottom, so the engine was getting unmetered (and unfiltered!) air straight into the induction pipe from there. The MAF might be doing its job, but if you are getting air in here, then you may well be running lean, which would cause hesitation, backfiring etc.
 

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That's a very good suggestion, any air getting in after the MAF but before the throttle will give the symptoms you have. If it is a problem with the air silencers, then they aren't strictly necessary. They are there on one of my cars but have been cut off and the holes blanked on the other and it doesn't seem to make a lot of difference. Or your MAF is faulty, GEMS MAF will respond to a good clean with carb cleaner. What does your diagnostics show as the airflow?
 

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Discussion Starter #10
Richard and dtoyne: i cleaned the MAF sensor realy good with carb cleaner. I also took of my induction pipe and had a good look No cracks or holes . I than took out all my sparkplugs and examined them. All good there . All wires are on snug and tight. . I started it up. Idles fine now even at operating Temp. I have noticed that I can slolwly increase the throttle and the Rpms will go up to 1000rpm BUT if I give it throttle a little quicker or try and go above 1000rpm it will cut out and want to stall . Unfortunately the RSW software can not measure the airflow . Unfortunately due to work I won't be able to have another look at the veichle for another week and half or so ( no big deal it's been sitting for 2 months) . I will still be active on this website browsing the 1258 or however many pages there are on p38's . I may try and convince my twin brother to have a look at this problem. He is a journeyman mechanic . I really do appreciate the input and suggestions from you both . I will make another "reply" on this discussion when I have looked over the engine again when I am back, and able to bring an updated status report. In the meantime I hope everyone has a good day or night !
 

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if you have reset adaptive values just drive it , it will relearn what's right , it could take a week or so to readjust to proper running mode depending on your driving habits.
 

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Something you might try would be to do a hard reset. If you disconnect one of the battery cables and touch the cable ends to each other, this will cause everything to go to default values. DO NOT SHORT THE BATTERY TERMINALS TO EACH OTHER. Disconnecting the battery cable and then touching one to the other will cause a hard reset. Hold them together for a count of 20. Then reconnect and see what happens. All of the work you have done will change the "scratch pad" or adaptive values, and a default may clear things up and create a new "ground zero." Ray
 

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Sorry Ray but disconnecting the battery and shorting the leads together on a P38, no matter how long you leave it for, will only cause you to have to reset the windows and sunroof. You cannot reset anything in the engine ECU, or any other ECU for that matter, by disconnecting the battery, only by using diagnostics to reset the adaptive values which he has already done.
 

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Dear All,
On a related note, after fitting the nozzles for an LPG conversion which involved removing everything down to the injectors the car restarts and will rev but will not idle. initialyy it was rough at all rev ranges but as the fuel rail filled etc it got better but its still got that rough idle after a few minutes running.

My question; How long after a fuel rail off job should i expect it to run rough?
seconds, minutes? does it need a run to re-calibrate?

as ever many thanks for your experience.

i want to have some idea before i start checking all the various connections and joints.

many thanks
Paul Cundy
 

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Has someone mentioned looking at the evap canister purge valve to see if it is stuck open causing a weak mixture? Once again, downstream of the MAF.
 

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I take it by the description of your IACV that it is a GEMS engine, with a 4.6 written on the top of the intake manifold.

If that is right, and based on your descriptions, I have to ask if you may have lost the oring between the front portion of the intake from the air box and the MAF?

FWIW you're doing the right things in the diagnosis so checking on some of the 'silly' stuff is next in line.
 

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Discussion Starter #18
Hey everyone . I would like to add yes it is gems and LHD . Im from Canada eh? I am still away from veichle but I would to thank TATS for the link. I am reading it at this very moment very helpful even for future things.
As for your question cunpr: the link that tats has posted has information I think may help you as well. I saw some stuff about .... I just read on page 19 that some/long term adaptives values could take up to 50 miles or so.. but that's if working on ECM it says SO PLEASE don't quote me .
Dtoyne: another good suggestion thank you. Never even came to my mind I will give that a look here in a few days when I am back!
WaltNYC: yes it is a 96 GEMS 4.6. my mistake as I never specified it was a GEMS . And ORING?! Haha I honestly don't recall ever seeing a oring there..opps. I will have to check . Thank you for the suggestion . Now I am curious and anxious as ever to check
 

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My question; How long after a fuel rail off job should i expect it to run rough?
A couple of seconds if that. As soon as you turn the ignition on the fuel pump runs for about 4 seconds and then also runs while the starter is turning the engine. If you were to turn the ignition on and pause before turning to start, that should be sufficient to get the fuel rail back up to pressure. I would suspect, as you have had it to bits, there's an air leak somewhere. How have you plugged the LPG nozzles so you don't have a huge air leak on each cylinder?

Simply by taking the manifold off and putting it back on, shouldn't have affected the running at all.
 

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This may sound too simple, and you seem to know your way around the air system, but nobody has mentioned decoking the inlet air bypass tulip valve, the first symptom of which is lumpy idle then stalling at launch from traffic lights.
 
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