mg zr 1.4 chugging idle

[rapidyellow]

so I bought another mg zr

seller had replaced head gasket

on driving it home, it was chugging at idle in traffic, and it used loads of fuel

I disconnected the front lambda and it ran great and idle was better too

discovered that it had no thermostat, so that was installed during the week

new lambda came today, put it in

connected back up and its still chugging at idle

don't know what to look at next, and the earache has started from the mrs so I need it sorting!!


this pic shows some of the various sensors


1. inlet air sensor? if I unplug this with engine running it stalls

2. ?? if I unplug this when engine running nothing changes

3. throttle position sensor. if I unplug this with engine running it idles high and constant

4. and 5. temp sensors, theres two of them but the plugs are different and cant be wrongly plugged in, unplugging them when engine running makes the temp gauge stop working, and the fan come on

6. lambda sensor, new

7. cam shaft sensor, unplugging when engine running doesnt seem to change anything, I had a spare one so swapped it, no different.


engine light isnt on, no fault codes, no pending fault codes. [engine light was on when running with lambda unplugged, but thats cleared now]


HELP!!!

[fordperv]

Replace the ecu coolant temp sensor it's probably gone faulty telling the ecu it's -20 or something silly like that iirc it's a brown plug but I may be going senile

[DavidB]

Turn key on (don't start engine).
Press throttle pedal to floor five times.
Turn car off and then try starting.

This resets throttle position on ECU.

[rapidyellow]

Nov 29, 2014 15:57:06 GMT DavidB said:

Turn key on (don't start engine).
Press throttle pedal to floor five times.
Turn car off and then try starting.

This resets throttle position on ECU.

thanks, have tried this but no different



temp sensor - any way of testing it?

[DavidB]

The inlet sensor (brown plug) gave me similar woes!!

[reliantscimitar]

Hi here

can you look at the engine temp in live data via the obd socket?

cheers - mike

[awoo]

might just be air in the system, are these the honda engine ones? as it was a common problem and dead easy to sort out.

just leave the cap off the radiator and let the engine idle for 10mins or so, squeeze the hose to the rad to help it along, top up the water as required, let the bubbles out etc.

might sort it out.

i had this on my crx and it cured it nicely

[rapidyellow]

Does anyone know what the thread size is on the temp sender on these?, because i could swap it from our other ZR but would need someting to quickly plug or screw into the hole to stop it losing significant coolant, as I would be doing this with a cold engine perhaps I could use the solid slug that tends to form in a kitchen / bathroom silicone nozzle? the "good" car would not be run but would just donor the part to test with in the duff car.

have found a few bodged things around the engine, IF the timing belt was out, would this have a similar effect on the idle?

[georgeb]

No 2 could be your idle air control valve?

On my 4.6 with erratic idle, I took both the IAV and TPS off, gave them a good clean with carb cleaner and toothbrush and that sorted it out. I also have a tool to re-set the ECU adaptive values for mine, which I did after cleaning, I assume there's something similar for the MG?

[Midas]

Starting with basics are you sure the plugs, leads and coils are ok? I've got an entire injection system for one of these knocking about, including sensors if you get stuck for bits.

[rapidyellow]

Nov 30, 2014 11:04:44 GMT Midas said:

Starting with basics are you sure the plugs, leads and coils are ok? I've got an entire injection system for one of these knocking about, including sensors if you get stuck for bits.

yes, basics all covered

what sensors have you got

will start switching parts from our other mg 1.4 on wednesday

[Midas]

Off the top of my head inlet temp, water temp (gauge sender) and water temp (ECU sender).

[SauceDoctor]

1 is the MAP sensor
2 is the Idle Air Control Valve

4 and 5 are the temperature senders. I can't quite make out from your picture which way round you've numbered them, but the "underneath" one is for the ECU, the other one is for the gauge. If you pull the connector off the underneath one with the engine running, the rad fan should kick in (that way you'll know you've identified the correct one)

BMW (yes!) part number B13.62.1.433.076.
MG Rover part number MEK000030
Intermotor 55478
Fuelparts WS1120
Alternative BMW part number 1 433 076

My own Rover 25 was running like a pig until I switched mine. The car was under warranty at the time (2005) but I fixed it myself as the Rover dealer was USELESS.

EDITED to add: sorry, I told you the wrong way round for the sensors, but it looks like you figured that out anyway.

[rapidyellow]

I think the top connector [re: temp sensors] was the one what made the fan come on, this one has two wires in it

the other only had one wire, so most likely thats for the gauge

tomorrow afternoon I am going to take off the idle air control valve and give it the once over, and will take out the map sensor too just to have a look

I am told that my engine is "hunting" at idle, odd term but there you go, to me its just another way of describing the problem, one post I read on a forum at work today was that the cam timing could be out, so I will check that.

Wednesday I will have access to the other ZR so will attempt to switch over some sensors just to see.

[DavidB]

I reckon the brown temp sensor is the problem.

This one:



(obviously this is broken).

[rapidyellow]

so I was going to swap the temp sensor from our other car today but got to it with a spanner and it would have taken longer than I thought it would

so thought I would look at the cam timing via the belt

well I think I have found the problem, can I have other opinions please? - I put a ruler across to show that I could not line up the marks which to my mind should mean the ruler/straight edge goes through them all and the centre of the bolts - ?

[froggy]

If you had a vac guage it would show up if the timings out and being map sensor based low vac is usually under load so it will be rich .

[DavidB]

Timing looks OK. If it was one tooth out, you'd notice, but it's hard to see from the angle in the photo.

I did this how to ages ago.
You should have a look at the bottom pulley to see if that's pointing to the notch on the plastic cover:

forums.mg-rover.org/blog.php?b=808

[Dorset_Clive]

On my 1.4 k (the white one in my sig) I once managed to jump SEVEN teeth on the timing belt (rough rally!!) and the engine still ran but wouldnt rev beyond about 3000rpm, so not sure if half a tooth out would make a difference.

When you say the engine is 'chugging' what do you actually mean? Is it just at idle and completely alright across the rest of the rev range?

It does sound a little like the idle control valve. Is there any chance the inlet manifold or the cam/rocker cover has been changed? On the older (distributor) K's there is a subtle difference between some of the rocker covers, with some having a large internal diameter breather and others small. The only difference is the inside dia of the spigot on the cover, so it is really hard to spot. Fit a 'big' dia cover with a 'small' dia inlet manifold ICV and it all goes to ratshit!

[rapidyellow]

so today was the opportunity to see about this cam timing, it was tough to even consider doing it with frost on the ground and the car frozen, out in the back yard with no under cover, back garden mechanics, just like it used to be..

did what was needed to get to the belt, lined up crank timing mark, the cams were way out

crank timing mark, I slightly adjusted it after this pic to be more central to the line above the two dots


cam timing marks


re alighned the timing and turned it over via the crank bolt a couple of times, all good, so put enough things back together to start it and


PERFECT!!

idling lovely and smooth now, just how it should

final build up, tools away, off we go, just lovely.

thanks to anyone who has offered suggestions, got there in the end at minimal cost.