ZX, rough and weak engine.. HELP !!

Mads · Post by **Mads** » 18 Sep 2003, 14:22

My 92 ZX 1.4, 170.000km has developed engine problems. The engine runs rough, and esspecially when starting cold and damp it has problems with low power and misfiring. It idles OK but rough when warm.
It stars OK both cold and warm, but the engine tends to stall when the load is removed (cold engine). Sometimes it idles at +2000rpm when cold (I guess this is what it is supposed to do) at other times it settles at the 800rpm. even if it is cold.
I have:
* Changed rotator cap, Leads, Spark plugs
* Checked the vacuum system for suspect hoses etc.
* Changed fuel and air filter
* Had the injector out (no apparent problem) and I ran a bottle of injector cleaning liquid through the system..
No improvement [V] except to the turnover at the local spare dealer[}:)].
I have not had the ECU fault codes read (Haynes computer code book on order, hopefully it will arrive shortly and be a lot better than what seem to be the general opinion of this forum) but I am getting desperate fixing the fault before winter (and the Danish MOT) [B)]!!
If anyone can give me a clue where to look I will be very grateful..[:D]
Thanks in advance
Mads

CITMAN · Post by **CITMAN** » 18 Sep 2003, 15:46

Is you car an injection model if so i think you need to get those fault codes read. If its a carb it might have a problem and may need an overhaul if you need any more help let me know through this post and ill get back to you.

Mads · Post by **Mads** » 18 Sep 2003, 15:59

It is an injection model and I do hope to be able to get the codes out shortly..

Mads · Post by **Mads** » 18 Sep 2003, 16:00

It is an injection model and I do hope to be able to get the codes out shortly..

AndersDK · Post by **AndersDK** » 19 Sep 2003, 06:27

Hej Mads -
2 wellknown buggers to check :
1) The engine 2pole temperature sensor - which is ONLY used for the ECU. Quite easy to recognise - as there aint that many 2pole sensors on the engine itself. Usually the sensor's connector plastic piece is either blue or green in colour.
Should be located near the thermostat housing - or at least into the cylinderhead waterways somewhere.
Either the sensor is kaput for good - or the connector/cabling is corroded/dodgy.
This sensor is the "choke" device for the ECU.
It's a NTC resistor - high ohm's on cold - my guess approx 5K ohms at approx 10deg temp.
Get's low ohmic - approx 200-500 ohms at hot engine.
Check it out !
2) The throttle potientiometer.
see this thread :
http://www.andyspares.com/discussionfor ... IC_ID=4093

Mads · Post by **Mads** » 19 Sep 2003, 12:42

Thanks to CITMAN and Anders for the qualified advice. I will be back with an update next week, when I have had a go at getting the codes out and checking the sensors Anders mentioned.
Mads (97Xantia 2.0,16v, 92ZX 1.4i)

Mads · Post by **Mads** » 27 Sep 2003, 17:42

Got the fault codes out today using the dashboard light and a few yard of cable. See:
http://www.tramontana.co.hu/citroen/fuel/test.html
Very ease and cheap [;)]
No fault codes however [V][?][:)]
Checked the CTS: OK, high resistance at low temp and low at high temp.
The throttle potientiometer seems not so easy to get at, I'll probably remove and clean the throttle housing next [V]. and check the sensors there.. but I don't feel convinced it will cure the problem.
Any bright ideas ???? please !!
Thanks in advance
Mads

AndersDK · Post by **AndersDK** » 27 Sep 2003, 19:55

While removing the throttle housing - check the ATS sensor the same way as the CTS. It's got the same functional characteristics - which you may also find on Gabor's BX-DIY site (tramontana etc).
Otherwise it may be time looking for any false air problems - while you're there. This may also be caused by any dodgy/rotten vacuum hoses controlling the inlet air.

CITMAN · Post by **CITMAN** » 27 Sep 2003, 22:56

As your a fellow zx 1.4 owner I have a question for you. Is your engine noisy when the engine is started on a cold morning and then quietens down when its warmed up. Becuase i have been told this is a chracteristic of the engine and just wonder if any other owners of 1.4s have suffered from this knocky noise which occurs when driving the car when its cold.

jeremy · Post by **jeremy** » 28 Sep 2003, 01:38

Is this a case of good old fashioned piston slap?
Jeremy

CITMAN · Post by **CITMAN** » 28 Sep 2003, 02:43

I havent got a clue what piston slap sounds like but it has been making the noise since the car was in its youth at 20000 miles and has been like this ever since it know on 80000 miles and uses a little oil approx 200 to 300 ml per 800 miles.

Mads · Post by **Mads** » 28 Sep 2003, 23:32

Honnestly I haven't noticed any particular noisiness on cold mornings so I am tempted to say rubbish. Then again I'm not that athletic till after 9.. so I'll have to get back to you next time it has been really cold and freezing.
Mads

jeremy · Post by **jeremy** » 29 Sep 2003, 03:10

Piston slap is the noise made by a slack piston in its bore. It is often heard on startup before the piston has expanded to its running size. It is not a heavy knocking noise.
Jeremy

CITMAN · Post by **CITMAN** » 29 Sep 2003, 14:37

I have thought maybe its piston slap, but the noise is more noticeable when you pull away and accelerate, but if I rev the engine to 4000 rpm it fades away. The noise has been there since the car was in its youth with 20000 mile on it and hasnt got any worse, it now on 80000 miles. If it is piston slap remind me never to look after an engine like I have with this one ever again i.e. oil changes every 3000 miles or 3 months, with quality oil.
Just changed the oil and put 15w 40 castrol magnatec in it to see if it quietens it down when its cold. When it warm the motor is smooth.

Mads · Post by **Mads** » 29 Sep 2003, 18:15

I double checked engine noise this morning, and honestly I couldn't detect any noticeable difference between cold and hot and the general level seems OK. My engine is however not in top shape as you know, so..
Mads
PS: I'm using 10w40 oil.