Help! 1.4i Nova Misfiring

[Clairelouisekeech]

Here is the lowdown:

He starts fine from cold and warm/hot.

- Runs fine at cold till temp gauge gets up onto blue.
- At low revs, on turn into new road for instance in 2nd gear, he jumps and coughs and misfires with loss of power till revs rise about say 2500rpm (Haven’t got a rev counter, so guessing a bit!), when normal power resumes. A good blast in 2nd, up to 3rd, and third higher revs would be ok.
- It is basically at low revs, under load, chronic misfire as if only on 3 cylinders, until revs pick up or load is lightened.

Status of engine: -
- 1.4i Nova, 1991, J Reg
- 45000 miles
- Have had it nearly a year with faultless motoring
- New spark plugs fitted 42500 miles, but now very black
- New HT Lead set fitted 44570 miles
- New rotor arm and dizzy cap fitted 44713 miles
- Heater not very hot in winter months
- Air filter looks clean and new (but obviously over 1 yr. old). No obvious blockages or dust built up areas

Things I still need to check: -
- Rubber inlet hoses in and around air filter to engine
- Clean up and re-check spark plugs
- Fit new thermostat, water pump, and maybe cambelt cause I’ve been told that’s what powers the water pump. This is a major job for me, and hope to complete week beginning 01/07/2013


Any thoughts greatly appreciated.


Cheers
Claire & Marty

[kent14sr]

Check for air leaks around the inlet side - manifold gasket, throttle body etc and also the brake servo vacuum pipe, especially where it joins the servo.

Have you done a compression test?

[meritlover]

does this have a lambda sensor? if so, check/replace it
check/replace the CTS
do a compression test.
check/replace thermostat. it will not be the belt or waterpump but these should be changed around 55-60k which is soon. you could take the opportunity now or wait. if its the original belt, change it now.
if it misfires at idle, stick a stroble light on each plug to see if its the spark thats dropping out and work back from there.
check vacuum hose between manifold and MAP sensor for leaks.
dont assume a black plug means its running rich, it can be caused by a spark missfire carbonising the hot plug with unburned fuel.

it will either be something simple, or something very major.

[Adam]

Ignition coil/module. Change the whole thing. Had same problem with my old astra 1.4.
Or the actual distributor, the sensor on it is what the ecu works off.

Both are cheap and easy to replace with 2nd hand bits.


It will have a lambda but can't see it being that tbh. Engine cold and under load =open loop

[meritlover]

as said...testing the spark with a strobe light will prove/test the trigger and LT/HT circuit.

[meritlover]

It will have a lambda but can't see it being that tbh. Engine cold and under load =open loop

...yes, but a poorly lambda can cause the plugs to fowl on frequent short runs...which leads to fowled plugs and miss fires.

[Clairelouisekeech]

Thanks everyone for your suggestions. Will give these a go this weekend.

[meritlover]

Thanks everyone for your suggestions. Will give these a go this weekend.

how did it go?

[Clairelouisekeech]

It didn't.....ended up having to replace our other car's brake discs and pads! Bloody cars! We had to get one car driveable as I'm due to give birth in 2 weeks.

Quick question on this Lambda sensor.....would a warning light come on the dashboard if the sensor is faulty?

[Clairelouisekeech]

hi all, marty here.

so on sunday i re-checked all 4 spark plugs. set the gap to 0.7-0.8mm, put some WD40 in the hole of the engine, and around the plug, and refitted.

also took the air filter housing off, so i could clearly see the carb, checked all rubber pipes, including the 2 fuel ones going into the right hand side of the carb. No perished air pipes to be found.
checked visually, all elec plugs on the engine that i could see. all seem to be ok, and seated correctly.

so my only unknowns, are now,
1. ignition coil (Just bought a new new one on ebay),
2. thermostat (have one, and new water pump and camblet, to change all at once, but not a job i can manage right now due to lack of time)
3. lambda sensor.

just seen new lambda on ebay for under £20, so if new ignition coil doesnt sort things, that'll be my next option.

any thoughts on that lot gang, would be much appreictaed. i'm nearly out of ideas.
oh and, have looked inside rocker, and on dipstick, no whiteness or signs of head gasket issues. the car has only done 44000 miles!!!

cheers,
marty.