P38A 4.0hse won't rev

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Wazzajnr

Wazzajnr

Well-Known Member
Posts
2,391
Location
Chorley
Hi guys,
OK, the rangy is now in Czech, no issues driving it down of note.
Fuel economy (debateable) was about 22mpg which I was fairly happy with.
Now, the only issue I have is that at wide throttle opening and high (above 3000rpm) it doesn't seem to want to rev. It sits lovely on the motorway at 80mph,and if you tickle the throttle, it flies, however, if you floor it, it makes much noise but doesn't really go well.
Now I'm down here I've had a play on the hills and if I drive it on the selector with up to 1/3 to 1/2 throttle, it's like a rocketship (well as much as a 2t offroader can be expected to be) but as soon as you floor it, it just starts to sound rough and not really go anywhere.
I have nanocom so any suggestions as to what readings I should be getting would be appreciated.
To me, it feels almost like it's over fuelling.
On a side note, many years ago I had a opel commodore with a straight six and that was the same. I eventually traced that to the cam timing being out by one tooth. Would this be a possibility with the V8?

Cheers in advance.

P.S. There is a track from the pub to my house through the woods. I wonder how long before I prang it avoiding Mr Czech plod!!!
 
Had something similar years ago, it was a blocked non return valve in the tank breather.That caused a vacume in the tank, so much so that the tank was deformed. Worth slackening the filler cap, see if it makes a difference. Hope it's something simple.:)
 
tomcat59alan said:
Had something similar years ago, it was a blocked non return valve in the tank breather.That caused a vacume in the tank, so much so that the tank was deformed. Worth slackening the filler cap, see if it makes a difference. Hope it's something simple.:)
Click to expand...
Thanks for that, I'll give it a try and see how it works. Cheers
 
Check your spark plug leads for breakage and voltage leaks, also if you have an electric test meter check your plugs (unless new) for resistance. Plugs and wires can break down under load and heat. If you have a scanner for the car Tha provides live data and can record, take the car for a drive while recording live data, then you will have a reference to any problem at any speed. Check out the obvious stuff before diving into the technical void.good luck
 
Mark Piercy said:
Check your spark plug leads for breakage and voltage leaks, also if you have an electric test meter check your plugs (unless new) for resistance. Plugs and wires can break down under load and heat. If you have a scanner for the car Tha provides live data and can record, take the car for a drive while recording live data, then you will have a reference to any problem at any speed. Check out the obvious stuff before diving into the technical void.good luck
Click to expand...
Cheers Mark, I'll check it out.
 
Right, tried with fuel cap off, no different.
To be fair I've no idea when it was last serviced so I think that's my first port of call.
I'm thinking I might bring it back to the UK this trip then I can do a few bits to it between now and November when it's due it's MOT.
I was really looking if someone had a list of "normal" figures to look for on a healthy engine.
One more thing is that it does smell quite rich at idle but I've been a diesel guy for years so maybe I just forgot what petrol exhaust smells like!!!
 
Sure someone on here can share some values from Nanocom at idle or maybe an ODB2 reader might even work with the engine.

Mark's suggestions look a good place to start though.
 
Check your fuel filter, I've had cars in before with a strong smell of fuel needing a filter change. Not guaranteed diagnosis but maybe a hint in the right direction
 
OK, thanks guys. Still would like some nanocom numbers to point me in the right direction though.
Cheers.
 
MY 4.O LTR WAS RUNNING THE SAME EXCEPT THAT WHEN I TRIED TO USE THE KICKDOWN IT SEEMED TO BE HOLDING BACK. I TRACED THE PROBLEM BACK TO A DIRTY MAF SENSOR. QUICK CLEAN WITH ELECTRICAL CLEANER AND THE DIFFERANCE WAS AMAZING. 5 MIN JOB AND SO MIGHT BE WORTH A GO !!
 
I vaguely remember reading about the maf sensor causing this behaviour before which was why I was asking for some numbers from nanocom. I've checked the readings and they do go up and down but no idea if it's by the right amount.
Also thought I read that you can clean the maf on gems but not thor??

Anyway, bit of an update. Last week just before I was due to leave, there was a rattling which turned out to be the left hand back box had broke off at the joint. As a temp repair, got a local guy to weld it up. Reason I mention this is that when I tipped up the backbox, loads of catalyst honeycomb fell out. (black as hell I might add)
Now, questions.
1. I assume this honeycomb should only be in the cats at the front?
2. Could the honeycomb have broken up and be restricting exhaust flow? If so, would that show up in any readings?
3. If I took the cats off and broke out any remaining honeycomb, would that cause further issues or would it run fine, albeit not as "green"
4. Suggestions for best suppliers of the following.
Spark plugs
Plug leads
Full exhaust minus centre box but including cats
Maf sensor
Air filter
Fuel filter

I noticed on one site it lists about 10 different plugs ranging from 2 quid to 20 quid each.

Cheers.
 
No you can clean the MAF Sensor you just remove it from the plastic housing but remember to use electrical cleaner or you can get a proper MAF sensor cleaner. DO NOT USE WD40.This leaves a residue which dirt will stick too. By the sound of it the cats are shot and should be replaced. You can decaf the engine if you really wanted to but would suggest you didn't. One thing not to skimp on on the V8 is plugs and leads. I would advise platinum plugs from NGK. Any decent outlet will supply these but off my head you could try britpart or island 4x4.
 
Ruby Range said:
No you can clean the MAF Sensor you just remove it from the plastic housing but remember to use electrical cleaner or you can get a proper MAF sensor cleaner. DO NOT USE WD40.This leaves a residue which dirt will stick too. By the sound of it the cats are shot and should be replaced. You can decaf the engine if you really wanted to but would suggest you didn't. One thing not to skimp on on the V8 is plugs and leads. I would advise platinum plugs from NGK. Any decent outlet will supply these but off my head you could try britpart or island 4x4.
Click to expand...
OK, thanks for the info. What is the likelihood of the maf being forked? Reason I ask is that I'm probably going to send a box of parts out to fit next time I'm there, (new cats and back boxes being one and plugs and leads being the other)
Now, if I'm sending a box of bits, adding a maf into the box is no great heartache if there's a chance it's knackered. However, if cleaning it is almost guaranteed to fix it then saving over 100 notes would be very welcome.
Reason I want it sorted is I'm bringing it home for a bit as I've missed the deadline for importing it to Czech plates so it will have to come home for an mot.
 
Although you will often hear a garage say that the MAF sensor has gone it is actually not a common item to fail. There is a thread on the net were a reputable garage has confessed that if a sensor is regularly cleaned ie every 60000 miles it is almost a life item. Take it off and look at the silver metal thin strips. If I remember correctly there are 3 on the engine you have. You can see quite easily if they are firstly all intact and secondly if they are dirty. If intact I would clean them off by just giving them a really good clean with a cleaner. You will be surprised how much muck comes off them especially if your engine has done big mileage or worked in dusty conditions. Leave it to dry for 20 mins before refitting and starting the engine.
 
OK, I'll take a chance on not buying a new one for now then, just take a bottle of cleaner with me (I have plenty, I'm an electrical engineer!!!)

Hopefully, the combination of a good service, new exhaust, plugs, leads and a clean MAF will fix it and make the journey home more pleasurable.

To be fair, on the motorway, most of the time, it's fine. At 80mph, just a light increase in throttle and you're past anything quite quickly, it's just if you're on a long steep drag and need to boot it, it just doesn't have the poke it should.

As soon as I have more info, i'll update you all.

Cheers.
 
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