Dodgy misfire

[tiger1983]

1999 single plug vts
No fault codes showing

I've got a weird misfire that will start after the engine has warmed up and up to around 3k revs before it will disappear.

I've replaced,
Crank sensor
Lambda
Green temp sensor
Plugs
Fuel filter
Tried 2 different coil packs

Also compression tested, 170 across all 4 cylinders.

Checked injector spray today, all firing with apparently a good spray but I had noticed a dodgy connection to cylinder 3 which is the actual injector plug that wobbles and the loom is still making a good connection so this could be a possibility but at the moment that injector has been seen firing.

What else to check?

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[saxokid100]

Ive only ever had misfire on vts"s when the coil packs are worn out..

[Alex]

Does it miss when idling?
Bit tricky unless you have an infrared thermometer but if you can find which cylinder is missing I'd swap the injector over with one of the others.

I had a misfire which was an injector failing when warmed up.

[tiger1983]

Replaced all 4 injectors today after the plug on cylinder 3 literally snapped off but still missing at around 3k

I didn't give it chance to warm up properly and check if it misses on idle today as I knew I could recreate a misfire at mid range revs but last week (before I took parts off the car) it did miss after it had warmed up and would disappear after 3k revs

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[Synister]

I'm getting the exact same thing on my 1.3 rallye. Misfires at 2800-3200rpm then clears up afterward.

My oil and water both smell of fuel though so I'm assuming mines head gasket related.

[tiger1983]

I checked that on mine today, no smells of fuel...I have already compression tested mine aswell.. today was spent checking my timing as it looked like inlet was slightly out, turns out the angle I was looking made it look out, timing is spot on

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[tiger1983]

Starting to suspect a fuel supply problem....can anyway point me in the right direction to testing the fuel relays and pump.
I swapped the relay from under the ecu for another one and it seems to have made a slight difference so now want to start testing parts, also can a pump be tested through the Rev range as it seems to play up at around 2500 revs

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[Synister]

I'm replacing my fuel filter tomorrow after I put half a tank of Forte advanced formula gas treatment through it. I'm hoping that will clear it up for a while until I get around to doing the headgasket (As I'll do the waterpump, timing belt, tensioner, exhaust and inlet gaskets at the same time).

Mine sat for a year in an old shed and has 123k miles on it, the exhaust and inlet gaskets look like the original items from 1996 so I'm hazarding a guess that the head has never been off it.

[Synister]

Have you lifted the injectors out individually and tested that they're spraying alright?

[axsaxoman]

disconnect injectors while its running --one at a time
and that will prove if its injectors +/or electrical supply to them
have you checked enmissions when its missing --
does it have cat fited? -4 branch manifold with probe only in one pipe?

[tiger1983]

What would I be looking for as I pull the plugs?

I've recently replaced all 4 injectors along with the loom as cylinder 3 snapped the plug off, all were firing fine (every 2ms on idle) before replacing but not actually witnessed them firing since replacing but scanner is showing the fire rate as still 2ms (scanner is for OBD2 but it's actually a single plug ecu).

The car has failed it's mot twice on emissions, high carbon and high hydrocarbon but we did notice when the Revs got higher and the misfire disappeared, the levels dropped fast but soon as the car goes back to the test rev range the problems come back straight away.

The car is a vts conversion, 99 plate engine (last of the mk1 I believe), completely standard other than k&n panel filter Inc cat fitted, single lambda sensor on the whole system on the manifold, according to citroen, that year only had the one sensor.

List of jobs already done/replaced
New lambda.
New green temp sensor.
New oil & fuel filters along with oil change.
New crank sensor.
New air flow sensor (snapped old one).
Tried 2 separate coils and witnessed both sparking when plugs are ground to the rocker.
New plugs.
Timing checked, lined perfectly.
Compression checked, 170 across all 4 cylinders.

Main aim is to sort the misfire so the hydrocarbons come down which in turn we're hoping the rest of the emissions meet the target pass zone.

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[axsaxoman]

now we get a story --its a "bitza"
was it a later 8v converted to vts ?
what you done with fuel lines +reg ?
not telling the whole story is never going to give the right picture when trying to dianose by long distance
std vts ex manifold or after market +where is the probe mounted?
cat fitted --genuine or cheap after market one ?
full spec of car before conversion and whats been changed or i,m not bothering to reply again

[tiger1983]

Car started off as a 96/97 (N plate) completely standard 1.1 spi engine, already had feed and return lines as a 1.1.

The vts engine has come from a 99 (T plate) both single plug ecu.

It's basically been a re shell of a vts into a 1.1 shell. This has included interior and engine loom swap, fuel pump swap, dash and dials swapped, you name it I've changed it to the point the only thing original on the car now is the shell and windows.

Engine wise. Everything other than filter is completely standard, standard vts manifold, under floor cat supplied by euro car parts so I have already been told they're one hit wonders but a change is in the pipeline once the misfire is sorted before the next attempt at emissions. Lambda sensor is mounted in the manifold just before the join to the down pipe so it receives the reading from all 4 cylinders.

Also fitted the original abs system only thing that didn't get transferred over was the power steering due to pedal box not fitting the bulkhead.
As I say, it's basically a 100% completly re shelled vts other than no power steering.

Checked injectors again, they're firing, also pulled each plug and instant change in engine straight away, lumpy running.

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[stevo67]

Lift the fuel pump out give it a little tap with a rubber hammer,then put it back in situ.If the problem goes away then it's a good chance that the pump is at fault.

[tiger1983]

Lift the fuel pump out give it a little tap with a rubber hammer,then put it back in situ.If the problem goes away then it's a good chance that the pump is at fault.
Guess you mean somewhere along the body of the pump not directly on the top? Planning on buying a pump from a breaker over the next few days, if it sorts the problem then will be replacing with brand new soon after

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[axsaxoman]

"Checked injectors again, they're firing, also pulled each plug and instant change in engine straight away, lumpy running".

If it was already mis firirng when you removed each injector plug in turn -surely it ran worse or better when certain ones were taken off ?
what is your defintion of a misfire -on 3 cylinders If running on3 then you must be able to find which by removing injector plugs --3 of them will make it run worse --one will make no difference or just running rougher than you would like -which could be whole lot of other things .
has it ever run smooth since the conversion ?
what rpm does it idle at ?
have you adjusted throttle stop to make it idle ?

[Gandi699]

now we get a story --its a "bitza"
was it a later 8v converted to vts ?
what you done with fuel lines +reg ?


in regards to the fuel lines, the j4/mk1 vtr setups in saxos/106s ran a fuel return but whilst some of the range later on had a return and reg on top of the tank without the return on the rail.I believe citroen then used a similar setup on jp4. Why did the vtr mk1/vts keep this setup when others were changing over to the tank mouted regulator and return (which I assume is cheaper for a manufacturers point to produce)

[stevo67]

Guess you mean somewhere along the body of the pump not directly on the top? Planning on buying a pump from a breaker over the next few days, if it sorts the problem then will be replacing with brand new soon after

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Yes the body mate & if it runs properly afterwards you'll know it's a faulty pump.Which will need replacing.:drink:

[tiger1983]

"Checked injectors again, they're firing, also pulled each plug and instant change in engine straight away, lumpy running".

If it was already mis firirng when you removed each injector plug in turn -surely it ran worse or better when certain ones were taken off ?
what is your defintion of a misfire -on 3 cylinders If running on3 then you must be able to find which by removing injector plugs --3 of them will make it run worse --one will make no difference or just running rougher than you would like -which could be whole lot of other things .
has it ever run smooth since the conversion ?
what rpm does it idle at ?
have you adjusted throttle stop to make it idle ?

I'd need to retest the injector plug pull as it's been abit of a hectic weekend with my son being ill but if I remember right, all 4 caused the engine to run lumpy, I will recheck that as soon as I can but since the new injectors went in, the engine sounds better but can still hear the same rumbling/bubbling sound as there was during the previous emissions tests and the movement in the engine as if it's surging.

When I first finished the conversion, the engine was running well until it decided to start stalling on approach to junctions/roundabouts....soon as I dipped the clutch on approach, the engine would stall. The scanner through up mixture adjustment lowest point which I was advised was to do with the lambda sensor, this was replaced along with the green temp sensor at the same time. That stopped the stalling to some extent, it would try stalling but would end up saving itself, I then did another check and saw the injector firing times were out, cylinders 1 - 3 were firing every 2ms, cylinder 4 was reaching 17ms! Changed the crank sensor and it seemed to solve the injector times but then it failed the emissions. After further inspection, I found several splits along the injector loom (on the rubber elbows), a plug wobbled on injector 3 which later snapped off the injector completly so I replaced the loom and injectors.

As for rpm at idle, it will sit comfortably at 850, I have wondered if this is too low as all my previous cars have been more at the 1k area but this is my first ever vts.
As for the throttle stop, I'm guessing that's the tiny little screw at the cable pulley? I haven't touched that myself but a few people have mentioned adjusting it and see if it makes a difference, only reason I haven't tried that is due to not having a torx small enough to fit.

Can you confirm, I have been reading things saying about some saxos had a regulator in the tank, is that the case on an 1.1 spi? Also seeing as I have changed the fuel pumps over from the 1.1 pump to the vts pump (straight swap between cars), that should of solved any regulator issues as the only regulator I know of now is the one on the fuel rail itself.

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[tiger1983]

Yes the body mate & if it runs properly afterwards you'll know it's a faulty pump.Which will need replacing.:drink:
Will try this at the same time as retesting the injector plugs!

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[tiger1983]

An update....after replacing fuel pump I still had the misfire so I went on and replaced map sensor, knock sensor and idle control valve....finally the misfire has gone!!
Only thing in the engine bay now that has not been replaced for brand new is coil pack so if it reappears anytime soon, I know all it can really be is coil until I replace that in the next week or 2.

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