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Zetec hunting and ?running lean


DWaldie
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Had another tinker this morning and made some discoveries along the way (and fixed the car 😁)

 

So, connected Easymap (and found it has three pages!). It says "Lambda Control Disabled" and, as soon as I touch the accelerator "TPS not stable". Swapped the TPS for another I had lying around (thanks John 👍) and it ran even worse.

 

From my limited knowledge, I had been thinking it was a throttle or lambda issue as I had disturbed both. I have read in other threads about "zeroing" the TPS at tick over, but Easymap said it was at zero already! By chance, I though nothing to lose by adjusting the physical tickover screw. Adjusted up: no difference. Adjusted down and, voila, problem sorted. Ticks over as sweet as a nut, and revs cleanly. Hope that helps others who might come across a similar problem. Clearly, by cleaning the throttle body, I had changed the air flow.

 

Just a few remaining questions:

 

I assume Lambda Control Disabled means it has been turned off?

 

Do I need to do anything about the TPS not stable? It was the same with both TPS.

 

Is there a way of adjusting the tickover screw from behind? I used some needle nose pliers on the threaded side 😱

 

With Lambda control off, am I going to get the car through the MOT?

 

Is it going to be a dry winter so I can make use of my 4000 miles policy 😉

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Its been a while since i had an MBE ECU but just be very careful when tinkering with the TPS. I ended up needing a full remap when I messed up my settings!

 

As for lambda- as mentioned, most tuners  turn it off, so that sounds normal. No idea how it would affect emissions because I’m lucky enough to have a Q reg, so it’s never even been a consideration 😁

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1 hour ago, Kingster said:

Its been a while since i had an MBE ECU but just be very careful when tinkering with the TPS. I ended up needing a full remap when I messed up my settings!

 

As for lambda- as mentioned, most tuners  turn it off, so that sounds normal. No idea how it would affect emissions because I’m lucky enough to have a Q reg, so it’s never even been a consideration 😁

In the end I didn't need to unlock the map. Just used Easymap for diagnosis. Thanks for all the help

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Well, yes, but you physically removed the TPS, this is not a trivial thing to do on MBE ecu’s, though it sounds like you may be ok. How did you align them, when you refitted them. (The normal technical e is to do it by physically adjusting the TPS, (by turning it), till it matches a pre-set Voltage.

 

 

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1 hour ago, Dave Eastwood (Gadgetman) - Club Secretary said:

Well, yes, but you physically removed the TPS, this is not a trivial thing to do on MBE ecu’s, though it sounds like you may be ok. How did you align them, when you refitted them. (The normal technical e is to do it by physically adjusting the TPS, (by turning it), till it matches a pre-set Voltage.

 

I admit I found it odd that when adjusting the throttle screw there was no change in the voltage or indicated throttle position. I noticed with both TPS there was some slight play between the socket and the spindle on the throttle spline. I assume the tiny adjustment I made on the tickover screw was within this amount of play. I read that the MBE only identifies 15 positions of movement in the throttle spindle from closed to fully open. Not exactly high precision.

Once the snow melts, I'll take it out for a spin to double check, but it seems back to its usual self.

Thanks for the help and advice. Easymap is much better than a crappy OBD reader 👍

 

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Great! 15 steps is relatively course, however, the gaps are interpreted when it comes to actual map control, so it's not as bad as it sounds. Plus, with MBE, (others have alternative ways to do these things), the Voltage values for the TPS aren't directly linked to the 15 steps on the TPX axis on the fuel and ignition maps.

 

One of the things that makes the MBE ECU's very powerful in what can be achieved with them, is also part of what makes them extremely difficult for the enthusiast to use; many of the raw incoming signals, such as TPS are fed into what is effectively a conversion table/map, and it's the output of this that drives the main maps you'd edit when tuning a car. So in the case of the TPS, can effectively make the ecu more sensetive to small movements off idle, which is where big changes in engine response occur, and less sensetive once the throttle is fairly wide open.

 

BUT, this also means, (with an MBE of this generation at least), you ABSOLUTELY must not change two or more settings at once on the throttle settings, or you can essentially loose where the real 0 throttle opening is compared to where the maps think it is. At this point, as Chris said, sometimes the only answer is to re-map.

 

So if changing one TPS for another, for example. You should make a note of what it's raw output Voltage is, before removing the old one. Then, swap them over, and rotate the new TPS on it's mounting, untill it reads the same Voltage. DO NOT adjust the throttle stop/idle screw during this process, as that is your temporary reference point, for where the ECU thinks the throttle is when closed.

 

Wear can cause the TPS to be a little loose on the spindle, and if it gets more than just a tiny amount can be a problem.

 

Idle screws on the Weber style throttle bodies from both Jenvey and Omex, (and maybe others too) are notorious for slipping over time. It does pay, (depending how often the car is used), when doing its annual oil change service, say, to hook up a laptop, and compare raw Voltages to last time's, so that you can tweak it if necessary.

 

 

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48 minutes ago, Dave Eastwood (Gadgetman) - Club Secretary said:

BUT, this also means, (with an MBE of this generation at least), you ABSOLUTELY must not change two or more settings at once on the throttle settings, or you can essentially loose where the real 0 throttle opening is compared to where the maps think it is. At this point, as Chris said, sometimes the only answer is to re-map.

😭😭😭 yup

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Again, that's really helpful to understand. I'll connect up and take some reference readings for future. I'll also back up the map once more and move it to my desktop PC so I know I have it.

 

I've been in touch with a local tuning company. I mentioned I was using an "old" MBE system and he gave me the impression they like them. They tune rally cars but not sure if that makes a difference.

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The MBE ecu’s have always been really good, BUT, they seem targeted more at very low volume manufactures, like Westfield, Caterham, (who still use them, but of course, the current models) etc. I seem to recall TVR used them at one point, too.

 

Because of their extensive “table within a table” structure,  they allowed skilled/knowledgable rolling road operators to create a small volume production car standard map, for their range of cars.

 

At the same time, the software exposes just enough of the basic fuel and ignition maps, that a simple competition car standard map is also not to difficult to create on the dyno, or of course, to alter after engine tuning.

 

The tricky grey area, is where enthusiasts want to start tinkering with more advanced functionality. It is in there, but it’s almost like the mapping software was deliberately designed to be as obtuse and tricky as possible, to do some of these things.even to the extent of not always using fairly industry standard names/terminology for some stuff.

 

Setting the TPS up is a classic example of this. But so is configuring more in-depth Lambda control of maps, etc.

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