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.

[Clairelouisekeech]

So, have now fitted new ignition bits and still misfiring under load and uneven idle at tickover. The only unknowns now are lambda, head gasket, fuel pump and thermostat........any ideas greatly appreciated guys.

Claire & Marty

[jimbob-mcgrew]

wow - due to give birth in 2 weeks and your working on cars. you've just earned some renegade points from me :)

you said in the first post that your spark plugs were black. that might indicate it is over-fueling or the ignition timing is out.

are the 2 cambelt markers on the lower crank, and the upper cam pulleys set in synch ?

[Clairelouisekeech]

Hey jimbob-mcgrew........I could go along with this but it's my hubby that has been doing most of the work :o) I do tinker though. I will forward your comments on to Marty :o)

[Clairelouisekeech]

Hi all.

marty here.

so have resorted to desperate measures, norm the nova is up for new head gasket, head skim, cambelt, water pump, and thermostat.

latest things i've tried are: -
Lambda sensor
coil
ignition module

on top of : -
spark plugs 2500 miles old
new ht leads
new rotor arm
new dizzy cap

i'm out of ideas. apart from havent got round to checking plugs with strobe light yet.

tired of his grumpyness!!!

marty.

[novahotrod]

Is it carb or injection? Could be dodgy pierburg carb! They seize up. Set ignition timing. Check cam timing also basic compression test. Possibly burnt out valve? We're you based I've got 4 1.4 engines sat in the workshop we could swap bits out of. If its injection also check little filter in feul inlet! They block up. Wind a screw in to it and pull it out! Bin it and fit an inline filter.

[Clairelouisekeech]

Hi novahotrod, sorry for delay in replying, I will pass your suggestions onto the hubby. It's an injection engine. I know he is tearing his hair out on this one......last weekend he replaced the MAP sensor and that hasn't fixed it..........running out of things to replace now. I have just driven it in this horrible wet weather and as soon as it warmed up it started playing up and was just so bad when trying to speed up. The other day the engine mgt light came on so he took it to local garage to plug it into ecu but they don't have the kit for such an old car!

[Clairelouisekeech]

Hi novahotrod sorry but my hubby has just asked me to ask you......how does he check the valve clearances as the engine is an overhead camshaft so the tappets aren't on the top......cheers. He says fuel filter has been checked......

[meritlover]

..how does he check the valve clearances as the engine is an overhead camshaft so the tappets aren't on the top..

he cant.

[Novasport]

Coolant temperature sensor. Would over fuel when hot so would be why it runs OK when cold and at higher rpm.
Cheap component to start with.

[Clairelouisekeech]

Oh :o(

[Clairelouisekeech]

Thanks Novasport I will let him know. They are only £6 on ebay so worth a try.

[meritlover]

the tappets are hydraulic and are 'self adjusting' which is why the clearence cant be checked.

do you have videos of him miss-firing so that we can hear this distressed nova engine and help diagnose the issue?

[meritlover]

Coolant temperature sensor. Would over fuel when hot so would be why it runs OK when cold and at higher rpm.
Cheap component to start with.

you're right. im pretty sure i suggested that about 4 months ago too.

[chrisd1986]

I had this issue on my 1.6 16v and it was low fuel pressure

[dgbnova#1]

crYes Chris could have it there low miles crap old fuel so filter could be clogged again cheap swop think it's on driver side of tank it is on external pump cars worth a try

[jimbob-mcgrew]

pop pop ka-boom ker-bang bbwwoooorrhTT-wuT

[dgbnova#1]

Thanks Novasport I will let him know. They are only £6 on ebay so worth a try.

What's your location as someone may be close enough to have a look for you!

[meritlover]

i have a coolant sensor you can look at if you like.

[Novasport]

Thanks Novasport I will let him know. They are only £6 on ebay so worth a try.

You need part number 90510183. If you search that number on eBay, they are as little as £4.79 inc postage!

[Clairelouisekeech]

ok thanks all. marty here now. Not sure if claires put on...but my mate who MOTed Norman last month said the emissions were non existant and i should be getting 100mpg on what the emmissions were reading! lol. having said that, old set of spark plugs were more black than anything...which suggests over fuelling right? To be brutally honest, in the words of a scotsman...ma heed is fooked on the whole issue! dunno whether i'm coming going or just been.
i've also done a compression test (with the engine at cold) which came up with normal readings.

new cambelt, thermostat and water pump last month have quickened the beggining of the misfire...i figure cause the thermostat now works, and temp gets warmer quicker. i'm sure all the symptoms are linked...just need one of you nova genius's to fit the final piece of our jigsaw :-)

so new things to try...coolant sensor, fuel filter...fuel pump.?. There is "an issue" with the fuel tank in that it leaks when full to the brim, but i fixed that problem 2 MOTs ago by...not filling it to the brim! Ha ha ha. Where is the fuel pump? is it elec or mech? dear god hopefully mech on this age of motor. we're in portsmouth BTW gang...anyone know a nova legend nearby?

cheers, marty (&Claire)

[chrisd1986]

Lift the back seats up and its inside the tank, ive also had issued with these tanks rotting inside and surrounding the pump in crap and causing low pressure

[meritlover]

spark plug colour is propably the worst gauge of mixture ever.

its an indicator of incomplete combustion which can be caused by an over lean or rich mixture. for instance, a lean missfire means there is not enough fuel to burn with the amount of air in the cylinder...but there is still some fuel there. The fuel is then left over or deposited on the plug which carbonises and turns it black. also if there is a miss, the plug never gets to operating temperature and cannot self-clean...so it turns black.

checking fuel pressure is easy on the MPI engines, just attach a suitable gauge to the schraeder valve on the end of the rail. check under prime, idle, and under load.

[Clairelouisekeech]

ok all thanks for yer info. fitted new water temp sensor today in inlet manifold, and made no difference at all grrrrrr!!!
lifted rear seat briefly and yes can see top of tank, 13mm hose i guess to front of car, and a flange fitting about 100mm diameter, with lots of 8mm hex head bolts securing it. so whats the deal? undo all bolts and lift it all out ? would it be an idea to do it when exhaust not hot?
cheers.
marty.

[meritlover]

start by measuring the fuel pressure and checking for kinked or collapsed fuel hoses.

another quick way would be to remove the fuel return hose and check there is a healthy flow going back to the tank. stick it in a fuel can for example and watch. if you get a decent flow, it means the fuel rail is at the right pressure (unless the regulator is knackered) if its just dribbling out then this would indicate a fuel supply/pressure problem.

[Clairelouisekeech]

ok merit lover thanks for that mate. where do you mean the fuel return hose ? under the bonnet or at the tank? I had my garage mate check things out at fuel tank when he was looking for the original leak...i';m starting to wonder if this problem started after he'd done that...? and may have clamped on a hose when he refitted the tank...will ask him.
if i disconnect the hose under the car before it goes up to the engine...i guess that'll check flow on that bit from tank wont it. Will try and have a go tonight or at weekend.
how can i measure pressure up closer to the engine? disconnect the fuel in to the carb and crank engine (only briefly obviously as dont want fuel spraying everywhere!!!).
cheers, marty.
PS Been offered a L plate Celica 2 litre GT for £500...with the nova playing up...its very hard to ignore such a nice jap motor 2 doors down offered to me.... :-(

[meritlover]

IIRC there is a stinger on the fuel rail which looks like a tyre valve for fitting a gauge.

basically the pump pressurises the fuel rail and the injector pressure is controlled by the FPR. because it controls at back pressure, if you remove the return hose (doesnt matter whether at the FPR or at the tank) if you get flow you will know that the minimum pressure is being delivered to the injectors (because the excess pressure is 'bled off' to the tank).

what carb? is this an SPI?

[dgbnova#1]

Think he means throttle body/carb as it sits like a carb

[dgbnova#1]

[QUOTE=Clairelouisekeech;2195468]ok merit lover thanks for that mate. where do you mean the fuel return hose ? under the bonnet or at the tank? I had my garage mate check things out at fuel tank when he was looking for the original leak...i';m starting to wonder if this problem started after he'd done that...? and may have clamped on a hose when he refitted the tank...will ask him.
if i disconnect the hose under the car before it goes up to the engine...i guess that'll check flow on that bit from tank wont it. Will try and have a go tonight or at weekend.
how can i measure pressure up closer to the engine? disconnect the fuel in to the carb and crank engine (only briefly obviously as dont want fuel spraying everywhere!!!).
cheers, marty.
PS Been offered a L plate Celica 2 litre GT for £500...with the nova playing up...its very hard to ignore such a nice jap motor 2 doors down offered to me.... :-([/QUOTE


Did you omit this from ure details earlier on as don't recall it I would plumb for anything around the tank if it was off , twisted pipe , collapse as said earlier filter inside tank blocked

If you take the return off at the tank put a bottle under it and if you get a good Flow its a good sign

[meritlover]

Think he means throttle body/carb as it sits like a carb
i know that, i just wanted to be clear on whether its SPI or not. most of the diagnosis i was giving was my assumption that it was an MPI...but then you know what they say about assumptions......

[Clairelouisekeech]

Ok all thanks for latest info. have chatted with my mechanic mate and he assures all things tank went back ok in regards to pipework. he didnt check inside tank so i will do this as soon as.
it is a single point injection, so i now know wat SPI stands for lol.
You guys are all focused on fuel...my mechanic and i are curious though as the car runs ok at cold.?. So fuel not an issue then, when i would think its asking for more than normal temp operating. How can this be explained? Would build up of fuel overnight supply enough for first few miles, then start to get low on fuel feed as the journey contniues? What choke related items are on the engine that could go wrong?
many thanks all, determined to get this sorted as i do love my retro nova and the celica is an import so apparnelty not so cheap to run as a 1991 british nova!! :-)

best regards,
marty.

[Clairelouisekeech]

dgbnova#1, where is the return pipe on the tank? Cant take tank off at home so that would mean another garage bill :-(

[Clairelouisekeech]

Please, please, please is there a NOVA expert near Portsmouth that would be willing to come and help Martin sort this car out? He's replaced soooo many parts now and it's still running like a dog. I am willing to pay in cash or drink!

Thanks
Claire

[dgbnova#1]

Return should be the pipe on the pass side of the car underneath but best way to cheak is look at the underneath and it should go straight into tank,

Your pump should be under the rear seat so lift it up or out even better and it's under the black plastic cover behind driver

[dgbnova#1]

Ok all thanks for latest info. have chatted with my mechanic mate and he assures all things tank went back ok in regards to pipework. he didnt check inside tank so i will do this as soon as.
it is a single point injection, so i now know wat SPI stands for lol.
You guys are all focused on fuel...my mechanic and i are curious though as the car runs ok at cold.?. So fuel not an issue then, when i would think its asking for more than normal temp operating. How can this be explained? Would build up of fuel overnight supply enough for first few miles, then start to get low on fuel feed as the journey contniues? What choke related items are on the engine that could go wrong?
many thanks all, determined to get this sorted as i do love my retro nova and the celica is an import so apparnelty not so cheap to run as a 1991 british nova!! :-)

best regards,
marty.

On tickover and when cold will use less than when on demand and these are easy things to check that's y we suggest them

[Clairelouisekeech]

ok then mate all good cheers. just worried i'd given you all duff info or wrong info. bit concenred bout how to get that pipe off under rear seat, but am sure i'll manage. best to do it with exhaust cold though yea?
thank you all. marty.

[dgbnova#1]

Yes cold is best but not to important have you changed filter yet? It's pretty easy to do the pump removal when you see it

[Clairelouisekeech]

RIGHT GUYS JUST TOOK A BUNCH (sorry caps on) of photos, and can tell you all that there are 2 pipes running from tank to engine on drivers side, one going through a cylinder type thing, the other coming from above tank somewhere. the two pipes then connect to the carb (as i call it), one in pass side front, the other passenger side back. then...i just found something new on my car...a 3rd pipe (return i'm guessing), which goes from pass side of tank to a large-ish bottle type thing insdie front pass side wheel arch????? then that connects up to the front of the carb...
will try and get photos on here tonight, will be frowned upon if i attempt it tonight. thing under rear seat has a elec plug with brown and blue wires, and the one pipe. should i discoonect this pipe before removing the assembly up? really dont wanna (a) spill fuel everywhere, and (b) have to take the take out again :-((

cheers all. marty.

[meritlover]

post a pic of the distributor and its alignment with the notches on the head.

[Clairelouisekeech]

ok all how on earth do i upload a jpg on here??? have pix of dizzy, fuel tank 3 pipes in/out and carb...HELP.

[Clairelouisekeech]

All, please see photos on Flickr....

https://www.flickr.com/photos/106968474@N05/

[Clairelouisekeech]

Great work Wifey!! ok gang, so pictures 1 and 2 are passenger side and this pipe goes to pass front wheel arch cannister thingy.
Pictures 3-5 are drivers side, pipe with red stripe on i guess goes up to the under rear seat connection. not sure what that silver cylinder is, but i know that & the pipes around it are new cause my mate replaced them trying to fix the original leak of fuel.
picture 6 is the 2 pipes from drivers side of tank, connecting to the carb.
7, picture of whole engine incase anyone was wondering what type it is.
8, cannister under front pass wheel arch, pipe goes back to pass side of tank, and other pipes go into engine bay up to carb in...
9, pipe from carb to cannister front wheel arch.
10, under rear seat.
11, my rough sketch of what pipes go where from tank.
12-13 pix of distributor as requested.

cheers all, really hope someone can advise on this.
Marty.

[meritlover]

have you tried running it with a strobe light on the king lead to see if its a lean or electrical missfire?

try plugging the vac hose from the canister to the manifold/throttle body. if i remember, there is a thermo switch instead of a solenoid to open up the canister purge when the engine is up to temp.

do a function test on the lambda sensor before considering changing it out.

[Clairelouisekeech]

jeez mate. are we not thinking its a clogged up fuel sender unit now then? its a brand new lambda. havent done a strobe test on it yet, cause the dizzy hasnt been moved since the trouble began.
not sure what you mean by "try plugging the vac hose from the canister to the manifold/throttle body" either. sorry... :-(

[Clairelouisekeech]

guys, whats the latest? gonna attempt to take the fuel sender unit out tonight...if i can get the pipe off. initial attempt wasnt successful... :-(

[meritlover]

gonna attempt to take the fuel sender unit out tonight...if i can get the pipe off. initial attempt wasnt successful... :-(

why on earth do you not just pull the return off the throttle body, shove a temporary hose onto it and into a gallon fuel can?

surely doing a strobe test will confirm whether its and ign or fuel issue and half your fault finding work?

these EFI units are so primitive there are only a handful of things it can be:

In:
IAT
CTS
MAP
O2
Octane plug
cam pickup/trigger

out:
spark trigger to coil ignitor
single injector
idle valve


if you confirm you have a consistant spark, good fuel pressure, correct cam timing, good compression then you will find the fault. you can probably cross half those things in the list off if you've replaced them.

[Clairelouisekeech]

alright merit lover keep yer shirt on.
just taken tank sender unit out, once i took the feeder pipe off there was pressurised fuel at the connection...is this normal? that pipe goes through an inline filter (Newly replaced) then up to the carb connection. I notice a filter on the end of the sender unit, it does blow through so is obviously not totally blocked...but worth replacing i'm guessing if its 23 years old.?. it maybe a cause of incorrect amounts of fuel going to engine.?.

no more time today...let me know your thoughts.

new pictures on http://www.flickr.com/photos/106968474@N05/

[meritlover]

alright merit lover keep yer shirt on.

O_o

i was only trying to help.

[Clairelouisekeech]

soz merit lover but thought "why on earth do you not just pull the return off the throttle body" was a bit intense. i havent got ideal car fixing conditions or time so you need to be gentle with me on here ha ha ha. very tense times.
got sender unit out, could not blow into, but did suck ok. now thats off, and engine cold, gonna blow through from engine today to see if the fuel line from tank to engine is blocked. there was pressure build up when i disconnected hose at sender unit...is this normal?

[Adam]

Have you got another distributor you can try?

Sorry havent read every reply, did you replace the ignition coil and module under it?

[therealnovaboy]

Id check for air leaks around the inlet/TB. It might not leak until its pulling on load so you might need to physicaly remove it to check the gaskets.

Sounds like a fueling issue going by the emissions.

[Clairelouisekeech]

Hi adam thanks for your ping. havent got another dizzy at present. do work with a guy who's daughter in law is the daughter of a scrapyard owner, and it was on a shoping list i gave him on friday, so hope to get one soon.
yea mate ignition coil and module under it, brand new replacements. also replaced MAP sensor, leads, plugs, rotor arm, dizzy cap. i havent checked the timing with strobe yet as despite having the gear...i'm a little unsure how to do it. must read up on instruction manual. cheers for now.

[Clairelouisekeech]

hi therealnovaboy, thanks for your ping, i like yer thinking but this would mean the car being off the road for a day or 2 and i need it at the moment even if it does run like poop. i was looking at the SPI/inlet manifold assembly at the weekend, is it all one part? couldnt see a join/gasket between the two.

i did take the fuel tank sender unit out at weekend, blew through pipe from engine, cleaned funny shape filter on bottom of sender unit, and replaced. all was clear and normal.

i have a gasket set, maybe i'll take the inlet manifold off then mate. cheers. marty.

[Clairelouisekeech]

my other thoughts with the airfilter off at weekend...could the throttle sensor fail? Like wise the elec plug in thing directly under the air filter on top of the carb assy?

[meritlover]

it could do, yes.

its just a potentiometer on 3 pin plug. you can test it with a meter.

would be easier to swap out the whole TB assembly with one from a corsa 1.4i or similar.

as therealnovaboy said, it could be an air leak. the TB is held on with 2 long 6mm studs with a gasket on the underside where it meets the manifold flange.

[Clairelouisekeech]

ok many thanks merit lover. will have a look tomorrow lunch as busy tonight. work gets in the way of car maintenance!!!

[Clairelouisekeech]

ok all this mornings efforts...
1. tighten all nuts on inlet manifold gasket. got at least 1/8th of a turn out of all of them.
2. took out idle sensor and gave it a clean up, was a bit black but nothing untoward really.
3. took off throttle sensor but nothing to clean up really.
4. took out sensor thingy in top of carb directly under air filter. had fuel in it. and couple of filters which looked fine.

started her up, and after 5 minutes of idleing, still a little cough when i dabbed the accelerator, which is a bad/usual sign!

so just the dizzy to change now...

[meritlover]

you havent mentioned lambda sensor.

[Clairelouisekeech]

Changed a few weeks ago mate.

[Clairelouisekeech]

just fitted a different dizzy off a G reg cavalier, which had exact same serial number dizzy as mine. fitted it on nova, started first time, but once warm...same &*%$ing result though, cronic misfire under load at low revs :-(
close to just selling it aas it is and cutting my losses. its givin me a high blood pressure now! Bored of it. thats the whole elec system changed that i can think of. ONLY things not changed now are throttle sensor and whatever sensor it is under airfilter on SPI assembly. close to tears!!!
Jason W, a mate said to me that this engine does its own timing (within reason) through the ECU, so no need for a strobe light...would you disagree with that? cheers for now, marty.

[dgbnova#1]

Pm sent

[meritlover]

Double post