MG & Rover - XPower Forums banner

1 - 16 of 16 Posts

·
Registered
Joined
·
7 Posts
Discussion Starter #1
My car: MG ZS+ 110 1.6L 2004/05 model
Mileage: 98,000

Problem/s:

1. While driving the car jerks when coming off and on the throttle, even when I do it slowly. You can feel the engine like rock twice. This isn't when changing gears just crusing in any gear and feathering the accelerater pedal. Particularly does it when the car is naturaly de-acelerating under engine braking and then I want to come back on the pedal.

2. Idle feels lumpy, can feel it through the car

3. Whilst sationary, once the car is warmed up and idling at normal 750~800 rpm if I very very very gently start to open throttle and I mean a tiny bit at a time the revs don't start going up and the car will feel even lumpier like its struggling. If i keep squeezing the throttle (a tiny tiny bit more) eventually the revs will shoot upto about 1800rpm. As soon as it does I hold the pedal steady but the revs will then fall to about 1250 then hunt up and down about 50~100 rpms around 1500rpms. It seems if I try to hold the revs anywhere from idle to 2000rpms it doesn't know what to do and hunts a bit. It's like theres no gradual between no throttle and a bit of throttle

Any ideas? There has to be a common problem here as others have reported the exact same symptoms (with no resolution). And my CRX had the same problem (never got to the bottom of it)

Thanks in advance :)
 

·
Registered
Joined
·
7 Posts
Discussion Starter #2
I should point out that in the last 12-months its had a lot of new stuff. Including a lot of work done. But I think it's always been like this.

HG Done
New pistons (had piston slap)
Cams replaced with MGTF 135 cams
Plastic Inlet mani replaced with used MG 1.8 Alloy mani
K&N panel filter
New plugs, leads & coils
New CTS
New Fuel filter
New thermostat
New cambelt and tesioner
New waterpump
New oil strainer
 

·
Registered
Joined
·
1,194 Posts
3. Whilst sationary, once the car is warmed up and idling at normal 750~800 rpm if I very very very gently start to open throttle and I mean a tiny bit at a time the revs don't start going up and the car will feel even lumpier like its struggling. If i keep squeezing the throttle (a tiny tiny bit more) eventually the revs will shoot upto about 1800rpm. As soon as it does I hold the pedal steady but the revs will then fall to about 1250 then hunt up and down about 50~100 rpms around 1500rpms. It seems if I try to hold the revs anywhere from idle to 2000rpms it doesn't know what to do and hunts a bit. It's like theres no gradual between no throttle and a bit of throttle
Check your throttle body for any evidence of oil, give it a thorough cleaning if there is as theres a good chance your throttle needle is sticking.

have you adjusted your throttle cable recently?
 

·
Registered
Joined
·
7 Posts
Discussion Starter #4
No I haven't why? I have the allominium TB by the way not the plastic one. I have been meaning to take a look inside it though. Where is the throttle needle? or what is the throttle needle?

Thanks
 

·
Still not cured of MG addiction
Joined
·
7,110 Posts
I think I'd be looking at the engine mounts which could cause some of the problems you're finding. But then is that the root of the problem - it sounds like the engine isn't running right.

I'm sure I remember someone with a 1.8 ZS having similar problem on this forum. Try these maybe:

http://forums.xpowerforums.com/showthread.php?t=52227&highlight=lumpy
http://forums.xpowerforums.com/showthread.php?t=40933&highlight=lumpy

Both talking about coolant temp sensor. Is your car getting up to temperature according to the dash gauge?
 

·
Registered
Joined
·
7 Posts
Discussion Starter #7
TB will be the big metal looking object connected directly to your induction setup [panel/open cone] a quick search should give you enough tips on how to give it a clean.
I know what the TB is, just wondering what/where the throttle 'NEEDLE' is? Thanks
 

·
Registered
Joined
·
7 Posts
Discussion Starter #8
I think I'd be looking at the engine mounts which could cause some of the problems you're finding. But then is that the root of the problem - it sounds like the engine isn't running right.

I'm sure I remember someone with a 1.8 ZS having similar problem on this forum. Try these maybe:

http://forums.xpowerforums.com/showthread.php?t=52227&highlight=lumpy
http://forums.xpowerforums.com/showthread.php?t=40933&highlight=lumpy

Both talking about coolant temp sensor. Is your car getting up to temperature according to the dash gauge?
Yes mounts have crossed my mind too but can't help thinking there's something just not right about the engine or running of it. Also it wouldn't explain problem no.3. And yes the temp on the gauge is perfect but thats controlled by a seperate sensor not the CTS

Should the mounts even be worn on a 04/05 plate??
 

·
Commission Number 000744
Joined
·
2,651 Posts
Maybe the idle air control valve needs cleaning out?
When you decelerate this is open til about 1500rpm (iirc) then closes to correct opening - maybe if its sticking it could give your problem :dunno:

Assume this is what is meant by "needle" in above post? Part has "V" pointing to it in pic. Easiest way to remove, due to limited access, I found was small torx bit and ratchet spanner. Inside its basically a cone on a threaded spindle, ecu powers it to correct position to give correct idle speed for engine load (if you have A/C on, HRW etc)
 

·
It's a big fan
Joined
·
3,218 Posts
"Plastic Inlet mani replaced with used MG 1.8 Alloy mani"

- have you still got all the sensors correct? The early alloy ones had a different sensor setup, it may have been bodged to get it working... I would be tempted to put the lightweight plastic one back!
 

·
Registered
Joined
·
1,315 Posts
"Plastic Inlet mani replaced with used MG 1.8 Alloy mani"

- have you still got all the sensors correct? The early alloy ones had a different sensor setup, it may have been bodged to get it working... I would be tempted to put the lightweight plastic one back!
Yeah as above, not all the alloy inlets are compatible with the MEMS 3 in the ZS, there is no performance gain either just a 5kg weight penalty.

Your problem sounds to me like a faulty throttle position switch as its sounds like its fueling on MAP without sensing the throttle moving off idle. There is no such thing as a throttle needle on a K series so I dont know what the other poster means. Unplug your throttle position sensor, if it makes no difference to the cars running then its most probably the fault.
 

·
Registered
Joined
·
7 Posts
Discussion Starter #12
Maybe the idle air control valve needs cleaning out?
When you decelerate this is open til about 1500rpm (iirc) then closes to correct opening - maybe if its sticking it could give your problem :dunno:

Assume this is what is meant by "needle" in above post? Part has "V" pointing to it in pic. Easiest way to remove, due to limited access, I found was small torx bit and ratchet spanner. Inside its basically a cone on a threaded spindle, ecu powers it to correct position to give correct idle speed for engine load (if you have A/C on, HRW etc)
Already cleaned the IACV, maybe dodgy though but its an expensive job to buy a new one to find it doesn't make any difference. I have also had it on a diagnostic machine, only fault that came up was the TPS but I had unplugged it with the engine running a few days prior to having the test so I expected it to come up so it doesn't prove anything, stupid me! It could be faulty though
 

·
Commission Number 000744
Joined
·
2,651 Posts
Already cleaned the IACV, maybe dodgy though but its an expensive job to buy a new one to find it doesn't make any difference. I have also had it on a diagnostic machine, only fault that came up was the TPS but I had unplugged it with the engine running a few days prior to having the test so I expected it to come up so it doesn't prove anything, stupid me! It could be faulty though
Did you clean the bit you can't see - when you take it off there is the cone which can be covered in crap but more important really is the threaded part behind cone. Filled mine with carb cleaner then with finger and thumb over holes gave it a good shake (Ooo er), quite a bit more crap came out. Did this a few times and also tried leaving it for a bit to stand with cleaner in, though it evaporates fast so can't leave it all that long.

A few weeks ago there was someone on ebay selling TBs complete with IACV and throttle pots cheaper than you'd just get the IACV
 

·
Registered
Joined
·
7 Posts
Discussion Starter #14
I cleaned the IACV quite thoroughly like you described really a few weeks back. Didn't make any difference.

I've just cleaned the TB today and given some of the sensor connectors a dose of the old WD40 again. Will see how it goes, think it's still gonna be same if so I'm going to take a chance and buy a new throttle pot/TPS and IACV as they both could be causing the issues. Found a good bit of info on here about them - http://wiki.seloc.org/a/Category:Engine

Worth a read
 

·
Registered
Joined
·
5,326 Posts
Firstly I would be looking an the basics,

Plugs, coil packs etc and temp sensors etc just to make sure there isn't a fault there.

As already said on Plenum, no advantage, but possible issues for compatiblity.

Air leaks too, did you use new seals etc, fit correctly? etc

I would also say you are making it almost impossible for this engine to run properly by making all these hardware changes but not re-mapping the ECU to cope. Cams, bigger TB etc, ECU is totally out of its depth at best so its never going to run as well as it could.

We would be looking at £300 ish to remap it properly but TPS is sounding like the main cause of the running issue you have.
 
1 - 16 of 16 Posts
Top