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Hi just got a fiesta tdci, it idles rough in the morning, read on here glow plug ? How do I test them what reading should I get on my multi meter, thanks in advance

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9 hours ago, Sirrias said:

How do I test them what reading should I get on my multi meter

Glowplugs are not so easy to test on a multimeter. They have a very low resistance, and draw around 10A each. So they will look like a short circuit to a multimeter. Also as they are usually all connected in parallel, one high resistance one will be swamped by the others, unless they can be disconnected & tested individually. I have tested them using a clamp-on current meter, that can measure the high currents without breaking into the circuit, but that is not a very cheap option.

In this weather, glowplugs should have little effect on starting, common rail diesels usually start ok without them down to quite low temperatures. Some engines use them for emissions control, but then a warning lamp will usually light if they are bad.

I would suspect other causes such as MAF sensor, or the EGR system (EGR valve, Throttle valve and possibly intercooler bypass valve on the 1.6TDCI) before removing the glowplugs to test/replace them.


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No dash light so not sure it would be a glow plug, new to fords so do they suffer from bad connection issues, I'll clean maf/map sensors, can I block off the egr without any problems ? On my fiat it was fine

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3 hours ago, Sirrias said:

can I block off the egr without any problems

This engine uses a throttle valve as well as the egr valve. The egr opens to allow exhaust gas into the inlet, and the throttle may partially close to ensure the inlet manifold pressure is lower than the exhaust, to obtain the correct flow.

If the egr is simply blanked, there may be a small performance loss, and the warning lamp may come on. If the lamp comes on, it will prevent dpf regenerations, leading to a blocked dpf eventually.

It is ok to blank it off for diagnostic purposes, to see if it is causing the rough idle, but if you keep it blanked off, check for side effects. It may be necessary to alter the mapping of the ECU for permanent blanking.

If you have a Windows laptop, or possibly an iOS or android tablet/phone, then a program called Forscan can display, log and graph live readings from most engine sensors, including MAP & MAF, and egr & throttle valve positions. The only cost is a £15 adapter (ELM327) (Bit more for wireless ones for iOS & android). It is a powerful diagnostic tool, though may need a modicum of technical knowledge to install & interpret the results. If you are interested in this, I can post more info.



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5 hours ago, Sirrias said:

yes please post mor info

Forscan is a powerful Ford specific system, Cost £15.00 for the interface. Needs a computer of some sort. (COM port, USB, bluetooth or WiFi interfaces available). You will find a lot about ELM327 & Forscan on this site, which together provide a very comprehensive diagnosis & maintenance tool. James (jeebowhite) has done a nice guide: http://www.fordownersclub.com/forums/applications/core/interface/file/attachment.php?id=21196

For an ELM327 adapter, see

Wireless ELMs are also available (bluetooth & WiFi), but are often not as reliable as the wired ones. Also they are rare in the "modified" form which is needed to access the 2nd Ford bus system. This 2nd bus is the MS-CAN bus, and links all the car interior electronics like door modules, and the BCM (aka GEM).

Your existing ELM may be sufficient to use, although it probably will not have the MS-CAN switch. But it can access all engine functions without that.

The Forscan programme is free (in Windows format) and you can get it from


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Thanks for all your input it's been invaluable, here's a weird one can't find an aux input any ware so bought a kit off eBay and pulled the cd radio out and there's a plug in the space where my new kit should fit anyway pulled the plug out plugged in my kit and I now have MP3 😊

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