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        General >> Problems >> 'Fluffy' from low revs
        
(Message started by: PJDavis on Oct 9^th, 2010, 3:10pm)

Title: 'Fluffy' from low revs
Post by PJDavis on Oct 9^th, 2010, 3:10pm

Something that has become noticeable just the last few days. Cold or Warm, Air'con off or on, from idle if I hit the throttle quickly the car 'fluffs' (hesitates slightly) before picking-up cleanly. I sat stationary to see when this occurs. From Idle if I rev quickly it hesitates for about 500rpm. If I rev with medium throttle I get slight hesitation. From 1000rpm the problem is slightly better but the same. From 1250rpm if I rev quickly there is a slight hesitation, but with just half throttle it pulls smoothly. From 1500 rpm if I hit the throttle very quickly I get a very slight hesitation, any other throttle opening from this speed and it's smooth. From 1750 rpm I can hit the throttle as quickly as I like and it revs smoothly all the way to the line.
When driving, the car is great above about 1500rpm, it pulls smoothly and quickly to the red line and changes up as expected in 'S' or 'E' gearbox mode. Below 1500rpm I have to go easy on the throttle to keep it smooth.
There's been no change in the petrol consumption, I took the plugs out and they are all nice and greyish/brown, the wire-loom that runs around the plugs and to the camshaft sensor is replaced by new stuff, any work done on the car to do with plugs replacement etc. Was done 3000 miles ago. Can't think of much else to say, I haven't been fiddling with the car at all recently.

Any thoughts? I'm away to Spain for a week the morra, so might not reply for a wee while.

Peter.

Title: Re: 'Fluffy' from low revs
Post by Mike H on Oct 9^th, 2010, 4:42pm

Might be you're getting the beginnings of what I had. At risk of sounding like a scratched record, ;D a new MAF cured it. (As it did also a "dodgy" autobox, see elsewhere).

I believe these MAF's stop working properly after a certain age, and all our cars are getting pretty old now. Ergo I'd be suspicious of a 2nd hand one as well. Just IMHO of course.

Title: Re: 'Fluffy' from low revs
Post by Mike H on Oct 9^th, 2010, 4:43pm

PS what state is the air filter in?

Title: Re: 'Fluffy' from low revs
Post by PJDavis on Oct 9^th, 2010, 5:15pm

Hi Mike

MAF looks nice and clean. Air filter replaced about 6000 miles ago, and it's clean too. MAF is pretty expensive though aren't they? I would hate to spend a pile of cash on a new MAF for it to be the same! OK just looked on ebay and found a new one for £50. I'll think on that when I get back from Hols.

Any other suggestions are more than welcome!

Title: Re: 'Fluffy' from low revs
Post by Mike H on Oct 9^th, 2010, 5:47pm

Depends, what engine is it? Mine was £52 from BuyPartsBy but that's 2 litre 16V.

Yes I know, cleaned mine, looked good, but seems that could mean nothing. Problems just getting worse so I thought for £52 worth a try, if turns out not to be that then could sell on on eBay or something. Nope, that was indeed it.

Thing is, there's a tiny weeny thing that is electrically heated up (a resistor) and another tiny weeny thing whose resistance is altered by the hot resistor, depending how much air is blowing over it (a thermistor). If you think about the stress of being heated up / cooled down over years I'm not surprised if the characteristics go off kilter

Title: Re: 'Fluffy' from low revs
Post by PJDavis on Oct 9^th, 2010, 6:07pm

Mike

Mines a 2.3. Done 92k miles. The right number of MAF sensor on ebay for £50. One other thing my car needs is a change of thermostat. But I figured if the car is doing it at all temperatures, that would make little difference.

Peter

Title: Re: 'Fluffy' from low revs
Post by Mike H on Oct 10^th, 2010, 1:03am

I concur! ;D Nah I think it's PCM can't make the fuel mixture right so is "experimenting", 'least that's how I figured it, so like is suddenly too rich or lean. Remember carburettor cars when you pushed the choke out too early? Is that like the "hesitation" you're getting?

When that fails the PCM resorts to open loop fuelling mode which is when it clears. Proof of the pudding is unplug the MAF which forces open loop fuelling see it that makes it better.

Only going by my own experience mind you.

Title: Re: 'Fluffy' from low revs
Post by PJDavis on Oct 10^th, 2010, 2:03am

OK Mike

Much to my wife's distress, I have just done an experiment. Started the car, and much as I hate blipping the throttle when the car is first started, it revs cleanly when cold. However, as soon as the initial start is passed, and before the temp gauge has moved much, it starts to hesitate when blipped. Disconnecting the the four wire plug from the MAF seems to make the problem slightly worse if anything, or hardly any difference. I was trying to think of what the hesitation is like. It's not as bad as an old fashioned 'choke-out' situation, more like an old fashioned car that is too far advanced. Kind of : Brrr-brooooom!

:-/

Title: Re: 'Fluffy' from low revs
Post by Mike H on Oct 11^th, 2010, 4:09pm

Nah I meant drive it with the MAF unplugged, has to be properly warmed up first.

Maybe symptoms not as acute as mine were, all I can say is was worse in Summer compared to Winter. While still cold hardly did it if at all. Hot Summer's day was terrible on a long journey. Which led me to suspect running too rich after fully warmed up (while cold was OK, plus doesn't go into closed loop fuelling [using the MAF] until properly warm, I think), air filter was indeed very dirty. I've gone into detail elsewhere, basically lots of new bits later, all cured, including "dodgy autobox", which wasn't at all ;D

If it ain't that after all, anyone else got any ideas?

Title: Re: 'Fluffy' from low revs
Post by Highlander on Oct 11^th, 2010, 4:17pm

Engine loom/coilpacks/airleak/cracked manifold, throttle body needing a clean?

Title: Re: 'Fluffy' from low revs
Post by PJDavis on Oct 12^th, 2010, 6:53pm

I'll change the MAF sensor, once I get back home, then I'll go on to what Stuart suggests. Of that, I've changed one coil pack, I could change the inlet manifold because I have a spare, I don't think it's the engine loom because I've had a good look at it, and I'll clean the inlet to the system. I'll let you's all know. I'm enjoying the 'rain in Spain' just now!

Title: Re: 'Fluffy' from low revs
Post by PJDavis on Oct 16^th, 2010, 11:32pm

Now that I'm back at the 'ranch', I'll drive it with the MAF off and I'll tell ye's how I got on. I'll do it the morra.

Title: Re: 'Fluffy' from low revs
Post by PJDavis on Oct 21^st, 2010, 8:48am

OK up-date time. I managed to get a new MAF for a reasonable price, £50. I noticed it wasn't a FORD item, I wonder now if this makes a difference, although the seller did assure me it was specifically for the Scorpio 2.3.

I had previously covered the other suggestions of coil changes and plug-leads, but to no avail. It was my intention to fit the new sensor, and then clean the throttle body with Carb' Cleaner. I had not long changed the loom, and figured that with the car behaving poorly only below 1750rpm it would probably not be a cracked manifold.

Well, I fitted the new MAF sensor and the car was worse! The car was very much more hesitant below the same 1750rpm, and would stall if I was quick enough on the throttle, those coupled with even light throttle use making the car 'fluffy'. I immediatly suspected the new sensor to be duff, and this seems to be the case.

Of course I'm still using the car regularly and thought the best thing would be to fit the original sensor back on, seeing as the car was performing better with it. I had previously given the original sensor a clean, but obviously it wasn't enough. I proceeded to give the original sensor, "The clean of it's life", with a spray-can of Carb' Cleaner that really blasts the stuff (that smells like 'thinners') into every orfice in the sensor. I gave it a shake about and dried it as best as I could, then fitted it back on.

The car seems to now be ok at all revs! Took it out for a run and it's back to it's usual self. Is there any particular rule about fitting the sensor back on? E.g. fit it whilst it's running, or fit it then the wires, or connect the wires whilst it's running?

I have sent the company that supplied an e-mail, I suspect they will want to replace the item rather than refund it, that's OK as long as the next new one works. Has anyone had the same experience with a new one, and can anyone provide a suppliers name that's reasonable and reliable?

One other question, is it wise to strip the couple of screws off and clean in behind that metal plate inside the sensor? Also to remove the plastic top off the wire casing and clean in there too?

Peter

Title: Re: 'Fluffy' from low revs
Post by Simmo on Oct 21^st, 2010, 12:06pm

I would have thought it was simply a case of cleaning the sensor as described Here (http://www.fordscorpio.co.uk/cleanmaf.htm). I think the less you interfere with the connectors etc the better and simply re-fit it, connect up and start the car as normal. The ECU will take a short while to 'learn' the new settings but after a few miles of varied driving it should sort itself, as indeed yours appears to have done. There is no doubt that the MAF does have a major effect on the running of the car as without it working correctly the ECU tries to compensate by adjusting other sensors.

Title: Re: 'Fluffy' from low revs
Post by Tompion on Oct 21^st, 2010, 1:17pm

I always take the black box off to clean the wires as it’s easier to clean around the back of the components. However the wires are very thin so it rather depends on how good people are at working with relatively delicate items.
I use a different cleaning technique, but I’m used to working with fragile items hence I won’t post the way I do it.

It’s the heating up of the wires that cause them to get dirty. There should be no real need to clean inside the body of the MAF, it should stay clean.

I have 2 second hand MAFS that I bought on Ebay for under a tenner each, I keep one cleaned on the shelf and just swap the black boxes over every few months.

Searching on Ebay for the part no often works best for second hand ones as they are used on other vehicles.

It can take a few miles to re-learn the output from a new or cleaned MAF.

Title: Re: 'Fluffy' from low revs
Post by Mike H on Oct 27^th, 2010, 12:51pm

Sounds the new MAF was wrong type.

Also mustn't have any air leaks round it, the hose fittings that is.

Title: Re: 'Fluffy' from low revs
Post by PJDavis on Oct 27^th, 2010, 1:24pm

The chappy that sold me the MAF insists that his one was the right one with the right number. I actuaully found one off a Mondeo in my work! Gave it a good clean-up and it works fine on my car. (It's the same part number) I took my original one off again and gave it a good clean-up and it's fine now, car pulls like a train again. The chappy on the internet said that he gets one in a while that just doesn't want to work. He is sending a replacement, I'll just keep it as a spare.

One thing that I've heard, one MUST disconnect the battery, whilst replacing the MAF sensor. Is this true?

Title: Re: 'Fluffy' from low revs
Post by Mike H on Oct 27^th, 2010, 1:42pm

Hope not cos I didn't! ;D

Interesting about the odd duff new one though, suppose it must happen but you'd think there'd be some sort of QC

Title: Re: 'Fluffy' from low revs
Post by Tompion on Oct 27^th, 2010, 3:36pm

on 10/27/10 at 13:24:26, PJDavis wrote:

One thing that I've heard, one MUST disconnect the battery, whilst replacing the MAF sensor. Is this true?

No need, but I expect it's just because the new values from a clean/new MAF need to be learnt, but it'll do that anyway.