Fuel starvation on full throttle

[cavalier1990]

Hi all

This is something I've noticed with this engine and never really got to the bottom of it. There isn't any actual running problems per se, but if you sit in the car at tickover and then slam the gas pedal to the floor, it picks up but misfires on it's way up, then clears.

As most of you know I've replaced everything that you would replace like ignition components, fixed any vac leaks, fuel filter, injector flow tested, new idle stepper motor. I replaced the fuel lines with the 8mm plastic tubes a couple of years ago and wondered if maybe the fuel lines were constricting the flow, but from what I see this fuel pipe is a kind of standard replacement for most smaller engine VXs.

If it was the fuel pipes then I wouldn't be too bothered as I'm not a boy racer (honest!) and only really notice it when doing as I described. I don't think it does it when you floor it when driving on load but I'll need to try it again.

Cheers

Andy

[vexorg]

Does it do it on full load rather than full throttle, like 2nd or 3rd gear, from lower revs, and full throttle through the rev range?

If it's just in neutral then it's common for modern cars to cough and get confused as they are not meant to be racing cars, just good family everyday on the road cars.

[cavalier1990]

Does it do it on full load rather than full throttle, like 2nd or 3rd gear, from lower revs, and full throttle through the rev range?

If it's just in neutral then it's common for modern cars to cough and get confused as they are not meant to be racing cars, just good family everyday on the road cars.

I'm pretty sure it does it on load as well. Haven't fully tested that theory yet, sometimes it jerks a little if I pull away in a higher gear, like 2nd away from a junction, one of those ones you can keep moving and don't need to stop fully. Once I get tracking fixed on Saturday I'll try it in first 3 gears see what happens.

[James McGrath]

Any progress with this?
Could be a fuel pump issue. Might be worth testing the fuel pressure. Should be 2.5 bar at the fuel rail from memory.
I had terrible problems on my Dad's 2.0 CD with this, this sounds similar.

How many miles has it done?

[vexorg]

Fuel pressure will be 2.5 or 3 depending on the engine. Then it'll have the mainfold vacuum subtracted from it. Best to pull the vac line from the regulator to test it.

[Robsey]

I have seen this before on many diffrrent cars and it is not really a problem as such.

It is just the ecu struggling to go from idle to full throttle (full pressure fuel delivery) in an instant.

A bit like asking you to go from a gentle stroll to flat out sprint....it just does not happen that easily.
Or is it that I am knocking on in years ? - lol

Regarding fuel pressure, which engine?
If it is the C18NZ, then it runs at a lower pressure than it's bigger multi-point injection counterparts.

2.5 to 3 bar sounds like the mpi pressure.

[vexorg]

I always loved that about carbs, that instant response when revving the engine.

The c20let has a moment from idle if you rev it too fast, if the engine is anything above idle then it's not far off an instant response.

[cavalier1990]

Any progress with this?
Could be a fuel pump issue. Might be worth testing the fuel pressure. Should be 2.5 bar at the fuel rail from memory.
I had terrible problems on my Dad's 2.0 CD with this, this sounds similar.

How many miles has it done?

130,000 or so on this now. To be honest I never done anything with it as it was otherwise running fine, and had other things to contend with. It also seems to be very intermittent problem, and it's not often I can the car like this. Funnily enough I did notice it yesterday, I had a wee jab of the wah wah pedal for a few seconds and it done this misfire as it was pulling, like having a duff plug lead or spark plug, I then backed off and tried it again, and it was fine.

Leads are relatively new, so are plugs, and so is the coil and cap. Can only think it it something carb related or fuel pressure. Fuel filter could maybe do with a change it's been a few years since that was done.

[James McGrath]

Is it on your 1.8?
Yeah, the fuel pressure will be lower than 2.5 bar. Probably around 1.5 to 2 bar I reckon.

As Robsey said, it could just be the engine not being able to respond quick enough to the sudden opening of the throttle.
On these engines there is only a inlet vacuum gauge (MAP sensor) and no proper airflow sensor (MAF sensor).
This is a bit imprecise, especially considering it relies on vacuum hoses to operate which are probably a bit old and crusty by now.
There is however a throttle position sensor which should let the ECU know the throttle has been opened very quickly.

I'll have to do a test on my 1.6 (a very similar engine to your 1.8) and see if it does the same thing.
I haven't driven it regularly in years but from memory it was very responsive compared to the C20NE, always thought the C20NE was a bit rough compared to the 1.6.

I doubt it's anything like the injector being dirty or dirty valves, not at 130k.

[cavalier1990]

Is it on your 1.8?
Yeah, the fuel pressure will be lower than 2.5 bar. Probably around 1.5 to 2 bar I reckon.

As Robsey said, it could just be the engine not being able to respond quick enough to the sudden opening of the throttle.
On these engines there is only a inlet vacuum gauge (MAP sensor) and no proper airflow sensor (MAF sensor).
This is a bit imprecise, especially considering it relies on vacuum hoses to operate which are probably a bit old and crusty by now.
There is however a throttle position sensor which should let the ECU know the throttle has been opened very quickly.

I'll have to do a test on my 1.6 (a very similar engine to your 1.8) and see if it does the same thing.
I haven't driven it regularly in years but from memory it was very responsive compared to the C20NE, always thought the C20NE was a bit rough compared to the 1.6.

I doubt it's anything like the injector being dirty or dirty valves, not at 130k.

I had the injector tested not that long ago and it was 100% no problem with it. I did think it (ECU etc.) would catch up after a second or 2 but it seems to do it for quite a while, maybe 4 or 5 seconds. I kind of grit my teeth as I don't like doing it too long especially when the engine is going to start thrashing higher revs so it may actually do it longer than 5 secs. If I do it a 2nd time after that it is usually ok, which to me points to maybe a fuel starvation issue. Wondering as well that the new (over 5 Years ago now) fuel pipes I put in to replace the crusty old rubber ones, are maybe a tad on the thin side, although I'm sure it was the standard recommended replacement, 8mm plastic pipe 3434701 replacement. Actually had a wee dig there and for the 18CNZ this fuel pipe is listed for the engine compartment, although I don't see an underbody section for the 18CNZ on the catalog, only for 16/20. I imagine the fuel pipe underbody would be the same though.

https://opel.catalogs-parts.com/#{clien ... group:17-1}

Will get round to replacing fuel filter soon, especially as been using e10 a bit now and it hasn't been changed in maybe 4 or more years.

[Robsey]

The main underbody fuel line is rigid cunifer.
8mm copper microbore plumber's tubing will do the same job.

As for the rest of the hoses.
All are 7.3mm bore (for a snug fit) ethanol resistant rubber hose.
There are a few places that do ethanol proof hoses, but if using ebay, then buy carefully - suppliers quote "upto 100% ethanol", but that means any amount, as little a 5%.

The only place that I know guarantees 100% ethanol is a VW specialist near me called Brickwerks.
Highly recommended, trustworthy, and reliable.

https://brickwerks.co.uk/product/fuel-h ... e-7-3mm-2/

For those with Carbs... they also stock Pierburg 2e3 parts and gasket sets.

https://brickwerks.co.uk/product/carb-r ... rburg-2e3/

Be aware though - They are VW specialists, so cannot offer any advice about Vauxhall applications.

[cavalier1990]

As a quick note I ran some liqui moly catalyst cleaner through the 1.8 today, might be imagining it, but felt a little more punchy, I was in 5th and I thought I was in 4th as it felt like it would when pulling in 4th, but was actually in 5th. I didn't run the whole lot through as was using a normal squirty bottle, and as it got to the bottom it was getting harder to keep the scooshing going as the bottle was at an awkward angle. I was in B&Q today and they were out of those pump pressure sprays, which is what I really wanted, so going to do a bit of online shopping for one of those bottles. I want to run a few cans through it over the next few Weeks.

[Robsey]

In the 1.8, I would expect that you would be able to use this like you would a carb cleaner -
Just pour it down the inlet of the "glorified" carb.

I could see it being a lot trickier on intakes with a MAF sensor, rather than the SPi's MAP sensor.

In that case you would need to remove the air filter and squirt into the air-intake box for the 8 valves,
Or detach the intake hose from the air box before the MAF sensor on the 16 valves.

https://www.liqui-moly.com/en/gb/cataly ... .html#7110

I think any system cleaner followed by an "Italian Tune Up" would probably perk up the engines in these older vehicles.

Be nice to see if / how much the car has improved over the next few weeks.

On a cynical note - it will be hard pushed for your car to be as fuel efficient as mine - I have not put a drop of fuel in for 30 months.

Nowt like a SORN to save fuel.

[cavalier1990]

There has been a few times where I did think i was in a certain gear say 4th, but thought I was in 3rd due to the response, and went to change up but realised it was already in that higher gear. This is due to the response in the gear feeling like I was in a lower gear. I was in 4th the other day, but thinking I need to change down to 2nd, thinking I was in 3rd, and it was starting to struggle a bit, so seems to be pulling a little better as well.

I got the proper liqui moly spray bottle so can run the rest through and maybe one more bottle just for good measure.Whether it helps with emissions is the 24K question. I've also got new seals for the injector coming as it seems to me like it's leaking out fuel a bit. When you look down the intake you can see a stream of fuel going down the walls of the inlet, when it should just be a mist straight down onto the butterfly valve. In saying all that the engine seems to be no sign of overfuelling, but it maybe the fuel is getting through as unburnt as the problem at MOT was HC I think that's unburnt fuel particles.

[cavalier1990]

I noticed this again the other day, really bogging down when pulling away quickish from lights. Seems to be on warm up, making me think it's the CTS, but then I did check the values of it on the video I recorded when I had it connected to opel scanner and it seemed to fall into suggested ranges. That was when it was fully warm though. Being a bit more specific it appears that it is missing on load, like pulling away, for say 3 or 4 secs then it picks up.

[Robsey]

I do hope it isn't like "Easy Start" syndrome.
By which I mean that once you have used Liqui-Moly, the car will play-up when you don't use it on a regular basis.

[cavalier1990]

I do hope it isn't like "Easy Start" syndrome.
By which I mean that once you have used Liqui-Moly, the car will play-up when you don't use it on a regular basis.

It's been doing it well before using liqi-moly. Going to need to rig up the opel scanner again and check the CTS values when it's warming up. something I've not done is check fuel pressure. I can't think why that would cause itonly at warming up, but just more out of curiosity, that and a fuel filter change as that hasn't been done for quite some time, especially with the advent of e10, which I have used but try an avoid it.