Cool - first problem with Kermit

Goodo - we have a misfire and a problem with Kermit. It started mostly on the overrun, now it's reached the point whereby low load / low engine speed causes a kangaroo effect.

OBD-II reports a freeze frame fault code 0108, that my guide says, "Manifold Absolute Pressure / BARO Sensor High Input."

It's not something I can fix myself :) but I'm guessing that this is the funky little sensor that, heh, senses atmospheric pressure...?

Can anybody tell me what this does in English?

Reply to
DervMan
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Exactly what it says on the tin: It senses air pressure in the inlet manifold, and from that (along with air temperature and mass or air flow sensors) the ECU can work out the load on the engine and it's fuelling requirements - much the same way as you'd use a vacuum gauge for driving economically. If the sensor itself is kaput then it'll need replacing, however these sensors are usually mounted separate from the engine itself and connect to the inlet manifold via a small bore pipe. It would be worth checking this pipe and it's connections for leaks or obstructions before blaming the sensor itself. Also don't forget to check the electrical connections to the sensor - if one or more of them are bad or dirty (maybe due to water ingress?) then this could also register as a sensor fault...

Darren

Reply to
Darren Jarvis

Aye, and on the Fords they double up the purpose of the sensor, the MAP sensor measures air pressure before you start the engine, and then senses the air flow into the engine. If you travel up to any serious altitude in a Ford you do actually have to stop occasionally to let the enngine management recalibrate air pressure.

Reply to
Andy Hewitt

Bizarre. I know the original L-Jetronic had a mechanical air flow meter (or two in the case of the V6 engine), but later systems used a 'hot wire' mass sensor, temperature sensor and pressure sensor. Not sure how a pressure sensor could measure air flow - unless you mean the two sensors share the same physical housing and can't be replaced independently...?

Darren

Reply to
Darren Jarvis

Ford use two systems. The hotwire system is self calibrating, and does not need to measure atmospheric pressure anyway Ford call this MAF (Mass Air Flow). It measures the actual air flowing into the engine *before* the throttle butterfly.

Ford also use a sensor connected to manifold vacuum and call it MAP (Manifold Absolute Pressure).

This second system is not measuring how much is actually flowing, as with the hotwire system, it only measures the amount of pressure in the manifold *after* the throttle butterfly. As such it need a frame of reference to work from, and then it calculates the air going into the engine. When you initially switch the ignition on, it is measuring normal atmospheric pressure.

All of the Zetec engines use the hotwire MAF system, but AFAIK all the OHV engines use the MAP sensors. CVH engines use either.

One thing you can check is that the vacuum pipe to the MAP sensor hasn't got soft, and is collapsing under load. If it is, you need to replace it, and bung a standard one way valve in the line too.

Reply to
Andy Hewitt

D'oh - aye good call. And sure enough, moving the wiring results in the engine nearly stalling when idling. So I suspect I have a loose connection.

Now the down side to this is that the TMAP is next to the strut brace and the wiring is under it...

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shows the engine bay. The TMAP is at the back of the manifold... :-/

Reply to
DervMan

Thanks for the tips. The strut brace is, like, seriously in the way of this funkiness. :-/

I seem to recall something about use of WOT re-calibrates everything?

Reply to
DervMan

Please explain the logic of the one-way valve - surely with one fitted it would prevent the sensor detecting changes in the inlet manifold air pressure (either negative or positive depending on which way round the valve were fitted)???!

Darren

Reply to
Darren Jarvis

You fit it to prevent fuel getting sucked up into the sensor, it happens a lot on those - quite a standard mod on the Fiestas.

Reply to
Andy Hewitt

In message , Andy Hewitt writes

They have actually reverted to using a MAP sensor in the 1.6 zetec Focus engines since about 2003.

Reply to
Paul Giverin

Not a one way valve, its just a fuel trap.

Tim..

Reply to
Tim..

Now we have another fault code - 0181, Fuel Temperature Sensor A Circuit Range / Performance.

It might be a vacuum leak...

Reply to
DervMan

As an update.

The TMAP sensor appears to be producing duff information. When driving along the manifold pressure goes from normal up to full on (107, heh I don't know what the scale is) and then back down again. This causes one hell of a surge from the engine... repeat. Lots. The car is almost undriveable around town but it's better at a cruise. Not superb, mind...

Is there anything else that can cause this reaction other than a duff TMAP sensor or the wiring loom? I've cleaned the ICV, no effect (barely any crud in there either, heh).

Reply to
DervMan

Its broken - tear it out - but the 1.7 Zetec in there....

Reply to
DanTXD

Only sensor that usually buggers up is tps one.

Sugest you have a wet plug and socket on some part of the loom. It does not need to look wet to give grief! Have you been near a pressure washer lately? (last couple of weeks)???

Take ALL apart, dry for several hours each with fan heater or hair dryer, and I bet it goes away... Been there before.

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Reply to
Burgerman

Like you've realised, this is because the EMS is not getting a sensible reading from the MAP. Either the sensor or the wiring is wrong.

Well sensors are generally either faulty or dirty, and wiring can be intermittent. Beyond that it's unlikely that the EMS is faulty and you don't want that to be the case anyway.

One last thing you can try, force a retrain by disconnecting the battery. The EMS will be reset and will have to relearn all the compensatory thingamies. It'll run rough for a bit until it does. If it is software related, this will generally clear the problem, but I wouldn't expect it to help. Remember to clear the DTC after you've fixed things to see it if comes back, it'll keep being there until you do and people have been known to replace sensors a second time when the DTC continues to be reported because they've not actually cleared it.

Reply to
Questions

Have they really. My God!.

Reply to
Andy Hewitt

Yes it is, it's a valve they use to

Reply to
Andy Hewitt

LOL!

Reply to
DervMan

Exactly. Having the TMAP go is rare.

Nope, other than driving through rain. I don't use pressure washers, heh.

It's worth a shot, thanks. Me-laddo is almost undriveable so I'll get around to this at the weekend.

Reply to
DervMan

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