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Jerking issue C14NZ engine

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Jan 11, 2025
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Hi all,

I'm from the Netherlands, unfortunately there isn't really an Astra owners club (we have a few Opel owners clubs, but the forums do not have a lot of life in them).
In the 90's it was a very popular car and also it was car of the year and the most sold car for "years". Also my grandpa had one (the 1.8 GLS) and as a little kid, back then, it was a very modern car!

After searching for months I found out the UK has a great Astra MK3 owners club and community.
I own an '95 MK3 Astra Caravan for years. For us it's an Opel Astra "model F", because before we had the Kadett (A to E).
It has done 305.000 km's/109k miles. So yeah, it's one of the lonely survivors. Most of them are on the scrapyard because of the rust or the engine has seized. Mine has almost no rust, engine running ok until some months ago.
It has the C14NZ engine, so yeah, it's slow. I have it for 8 years and it didn't cost much then, it never has given any problem until some months ago. Just simple maintenance and nothing special really... Give it a new belt, cooling radiator and even a new clutch!

Long story short; a couple of months ago, around the 300K mark, the engine quit. I was 200 km's from home. Turns out the fuel pump blew.
The garage in Belgium could fix it, but it was very expensive (no details, haha)! I had no other choice. I never had any issue with the car, so it was worth it.
They fixed it, I drove home.


Since then, the engine lacks (more) power. It stutters/jerks (don't know the right word).
It should have a top speed of 155 km/h. Years ago it was possible to go above 160. Since the fuel pump issue, it's more like 140 max!
Also, the acceleration is bad. It jerks, it doesn't accelerate in a straight line. Some time ago I had two bikes on it, 4 persons (like every year), but it was even difficult to maintain 100 km/h on the motorway (I must say it was going up a hill a little).

I still don't want to bring it to the scrap, so I threw some money on it, fitted a new fuel tank because the other one had a leak (required for the MOT sadly). I suggested just fix the fuel tank by close the little gap/hole with some welding maybe, but the MOT in the Netherlands is very strict! Also it had a very minor CO (lambda) issue, it was a small hole in the exhaust, they told me.

Because I still have the issue of the engine jerking (after replacing the fuel pump), I replaced almost everything I could get my hands on (it's cheap!)
- Spark plug, spark plug cables, distributer and cap
- Ignition coil
- Airflow sensor box (on the bulkhead)
- Idle motor (did have the idle issue but solved with changing this one)
- Coolant temp sensor at the back (it does not overheat, goes to 90/95 degrees Celcius and stays there, summer or winter)
- Lambda in the exhaust pipe on the front
- The fuel pump
All from noticeable brands like Delphi, Bosch.


The mechanic at home checked the fuel pressure and also the new fuel pump was of an "A" brand, and they told me it was fine. They still know how to work on old cars.
I can fix some issue my self but some things I need my home mechanic.


I checked the vacuum hoses, they are replaced years ago and have no leaks; however, I'm not sure if they are connected properly , maybe the Belgium garage did not know how to put them back.
At the back one leads to the airbox (left one), the right one leads to the front again (and clearly has a vacuum), the one on the front goes to some kind of vacuum valve close to the airflow sensor.
I checked pictures of the same engine and they look the same.

There was no noticeable oil consumption, however, last time I needed to add some liters, but it's more like 1 liter per 5000 KM, so think it's OK.
Also, no coolant consumption, non, zero, never, same level for years, no sludge under the cap.
There is no noticeable smoke coming from the exhaust.
The only smoke is somewhat black smoke of unburned gas, while idling and giving it some gas. It stutters a little and if you keep pumping, engine keeps running but stutters somewhat and some black smoke is coming from the exhaust.
The stuttering is below 3000 rpm and above it's not noticeable, however, it lacks some power I guess at the top end. The engine idles fine and also runs fine if you are not accelerating.

The end muffler has been removed years ago and it's one big pipe from the middle muffler. It was a cheap fix then (muffler came off).

I bought an OBD2 dongle but I'm guessing it's too new and does not work. Red something about the paperclip method, but did not tried it yet.
Also, good to mention, there is no check engine light! I had it once, on a long road, ascending for kilometers, could not go above 90 in 3rd gear, making like 6000 rpm, at the end the light came on, after making a turn it went out.

I always gas up the car with premium fuel (we call it Super 98, unleaded 98 RON). the dirty one, never BP Ultimate or something like that.

Some suggestions I got, maybe the catalytic converter is "full". But the engine ran fine until the gas pump blew. Another thing is there is not enough pressure at the exhaust end. But also, it ran fine. Maybe the camshaft, but still, it was okay back then.

I must say some months ago I changed the lambda sensor in the exhaust manifold at the front; and it runs better, but not as good as it was. I have some power back, it can reach 150 on the motor way, but it's still jerking below 3000 rpm and noticeable when driving through town, and also with a little load, like 4 persons in the car. If I remember correctly the engine had power at the lower end, and pulls really good for such a little engine, it pulled to 4500 rpm with the sweet spot at 3000 rpm and above 4500 the power ran out.


I do not use the car that many anymore because I have other cars, but I have it for years and don't want to bring it to the scrapyard yet, it has a new MOT and this year I think I can give it an MOT for 2 years because in the Netherlands you can do that if the car is older then 30 years.

Sorry for the long post, maybe someone has a suggestion. Want to have it in the family until my son has his driving license (6 years, left, it's a long time...).

Thanks!
 
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have you checked the fuel filter is facing the correct direction? Also check the fuel pressure while driving? run the line all the way into the car and hold the gauge. There is a very big difference between static fuel pressure and fuel pressure underload!
 
I fitted a new fuel filter and pretty sure it's in the right direction, also the "jerking" was the same before and after the fuel filter change.
I guess the pressure is measured at stationary, should the fuel pump pump harder if the gas pedal is pressed? As far as I know there is some kind of fuel pressure gauge at the injector housing, is that correct?
I have cleaned the injector housing and also the throttle valve and everything around it with carburator spray... But it was already pretty clean.
Also checked for a vacuum leak, was thinking maybe the rubber ring between the injector housing and the air filter housing above it (leading to the air filter box), was leaking... But it seems pretty solid... I did start the car without the housing and the injector appears to be doing it's job. No dripping.

The only thing what has been changed is the fuel pump... So it's most likely it's the fuel pump itself. But it was pretty expensive to replace, and the distance is to far to make a point out of it. They speak French and not a word English or Dutch (and my French is very bad).... Most French speaking do not speak another language apart from French (or they don't want to). I tried via a translator app but they were pretending they did not understand (yeah right).

In the Caravan model the fuel pump is somewhere on the fuel tank, and the fuel tank has to be removed unfortunately...
 
yea you have changed the fuel pump twice now though haven't you? thats how i read it?

So the fuel pump shouldn't work harder as such, but fuel press should stay at least the same under throttle, usually it will actually rise because the regualtor will be a rising state type of reg.
 
The fuel pump has been changed one time. Since then I have the issue... So you should say, it's the fuel pump. But the pump itself has been checked and the mechanic says it's okay.
After this almost everything has been changed. It runs a little better, but still it's somewhat jerking in lower rpms.
The air hoses are replaced, just not sure if they are in the correct place, checked pictures of similar engines (like the C14NZ but also the C16NZ), and seems to be the same.
The mechanic says the engine runs fine but because of the mile age it can be a little rough. So maybe it's more like a higher mile age issue?
There is not much to replace anymore, the only thing(s) I can think of, are the fuel injector (but has been cleaned), I have a new rpm sensor but the bolts of the old one are rusted, so could not get it out.
Don't have the issue above like 3000 rpm. I call it jerking, but you also can call it stuttering, it feels like it does not get enough fuel, but it's only a juddering, if it does not "fire" one time on one cilinder.

I hoped it rings a bell by someone, like someone had the same issue before. It's like a project, I don't use the car that often, so I want to figure it out myself. I spend like a 1500 euro's already (450 for the fuel pump at this Belgian mechanic (or I needed to left the car and it went to the scrap)), and like a 1000 for all the things afterwards (incl. a brand new fuel tank), but hey, I have it for 8 years and never let me down, it went to France, Germany, Switserland, everwhere.

Some say... It's the last of it's kind (in the Netherlands), do not think it will become a classic, but Opel fan's saying it's like the only one left.
 

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