Airflow meter adjustment

[neal1980]

Hi all I hope somebody can help!

I think my airflow meter may need adjusting to give me sum performance back and economy its dreadfull!, A friend very kindly NOT! adjusted it trying to get the emissions down on my car, now its not running right and doesnt seem as responsive. Am i right in thinking my cats are probably shot? another mate has told me that as its cat controlled you cant adjust emissions, is this correct? If so does any one have any clue to how many turns I should adjust my airflow meter so at least its sum where near correct, i assume its working cause when i disconnect the plug it stalls, so must be doing summat i figure?...my car is a 96 (n) Chimera 4.0....

And also I keep hearing about temperatute sensors being replaced to cure excessive fuelling, i rarely drive it hard and cant believe how much its using...Has anyone replaced this and found it helped?

Apart from that, brilliant car wouldnt change it for anything!...Well apart from the new sexy Tuscan Convertible!...

Thanks all

[HarryW]

The hotwire AFM (5AM) is trimmed for either cat or non cat installations. It does affect the tickover CO but in a cat car the close lop control will do that as well. To ensure that the trim pot (the screw thingy) is the right area for the closed loop comtrol circuit (lamdas) to do their job it needs to set around 1.75V.
Check out the rpiV8 site here, it gives the wires to be measured www.rpiv8.com/carbs-2.htm#4.6airflow if you do not have a voltmeter then I suggest you get someone to do it for you [hindsight-mode-on] tip - if you ever adjust anything always count the number and direction of the turns, if all else fails you can then return it to original [hindsight-mode-off].

Harry

[shpub]

All well and good but as the range is quite wide it is really only a best guess. Ideally it should be set up with a gas analyser so that the emissions can be checked. The emissions can be controlled from the ECU is it is modded but the closed loop system is ultimately responsible. The problem is that the closed loop system is not always used and then it depends on the mapping which in turn depends on having the correct information coming into the ECU.

Basically the twirly thing should not be touched and left alone once it has been set up.

[neal1980]

HarryW, thankyou very much for your advice, That link you gave me is brilliant, will give it a try in a min when i find my multi meter...Will post results...

Do you have any advice regarding the Temperature sender?

Thanks
Neal

[PeterC]

Do you have any advice.....?

Yes, with respect don't meddle with things that you don't understand, leave them well alone. If in doubt get an expert to sort it.

I know this costs money, but believe me the potential consequences of what you are doing makes the servicing fees of little consequence.

Items at risk include:
Cats - through over fueling
Valves - through weak mixture
Pistons and valves - through pinking
Wasting petrol - at nearly 90p per litre!

If you notice a problem have an expert look at it. When you meddle you are simply addressing the obvious symptoms which may not be the problem anyway. A classic example of this is the known weakness with the temp. sender which gives rise to all sorts of problems with running (search previous posts for details)

I post this reply to discourage others from reading such posts on PH and attempting DIY tweaks and wrecking their engines/cars in the process.

[neal1980]

Thanks for your advice Peter, I actually found Harryw information to be spot on, indeed after looking at the voltage it was out by nearly 2 vaults, having just tweaked it to its required range its much much better, seems smoother and returns to idle much quickly. Quality!..BTW You would have to be stoopid if you didnt know what pinkin sounded like.....

I enjoy messing around with my TVR all infomation posted on here is for advice only, you decide to use it or not..

For the record the guy who adjusted it worked at TVR for over 3 years!...So who knows what knowledge the "experts" at some TVR garages actually have!...

Thanks all

[HarryW]

PeterC normally I would agree with you on this topic but the original post said that a helpful friend had tweeked it so I was pointing him in the direction of a free available web site to put it back to the right area. As stated the lambda sensors will take over from this point forward.
BTW It should be noted that these only control the mixture sub 3000/3200rpm, above that they are open loop and this is where the damage can occur very quickly if you ignor pinking etc.

Harry

[neal1980]

The link really helped me set the airflow meter up as near as possible, was also going to check the throttle position sensor, on that website the wire colours are different to what they are in my TVR?

Any idea to what colours on the tvr throttle position sensor will tell me what voltage its producing?

Thanks

[taylormj4]

I've also noted that the voltage on the airflow meter is out but when the adjustment screw is turned, it has no impact on the measured voltage.
I've been told by a dealer that on the CAT cars, the adjuster is disconnected to stop you fiddling!

Is that true, or is mine bust?

Matt