Umm, Is It Normal....
- Thread starter Doo
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is it constantly miss firing during idling/running or just when it's hot or cold?
Only when it's hot. Cold she's smooth as silk. I'm thinking it could be a fault with my recent Bosch O2 sensors, but why?
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can anybody lend you a coil pack to help eliminate the fault?
can anybody lend you a coil pack to help eliminate the fault?
Waiting to hear from a mate who bought two 38's.... But world a coil only miss when warm and only upon load between 800rpm & 1500rpm? Soon as I ask for a little more, she's willing. I don't even need to floor it, just a dribble more.
Ummm, how do you mean do the same?
Cold or hot, floor it and she's off like a Greyhound after a hare!
Cold, smidgen of throttle and she's smooth as a baby's bum/
Hot, touch the throttle a tad and the stumbling is worse than Morris & the Minors St St St Stutter Rap... Trying to pull away from the lights or a junction is a proper mission. Stumble, stutter, hesitate... FOOT DOWN and she's off like a rat up a pipe.
Cold, as above and she's sweeter than a pot of honey.
I agree with Saint, I don't think this is O2 sensor related.
My guess would be throttle position sensor or an inlet leak. My logic being as follows so that anyone more knowledgeable than me can either tell me I'm talking rubbish or confirm my theory.
1. Throttle position. With the throttle fully released, the ECU tries to keep a stable idle (750rpm from memory)
As you feed on the throttle, the position sensor doesn't register a change because the track is worn most at that point but the butterfly valve is open allowing much more air in. The ECU tries to handle this but can't. More throttle and we get a good reading and off we go.
Conversely, we get a reading from the pot telling the ECU we're not at idle but the butterfly isn't open so it's starved of air and goes over rich. Same result.
My merc occasionally does the same and I know there's a small dead spot on the throttle pedal sensor. It's a fly by wire diesel but it does confuse it occasionally and cause similar symptoms.
2. Air leak. When cold, there is excess fuel injected across the range to compensate for the cold engine so it can cope. When warm, the leak is a big percentage of air getting into the engine but not being registered by the MAF but at higher revs or wider throttle the leak is a smaller percentage which the ECU can compensate for based on the o2 sensors.
Could also be that under higher vacuum of wider throttle, the leak seals itself.
In the old days, the way to find it was spray WD40 around the inlet tract whilst idling and listen for any change in engine note.
I think either of these is more likely than the ignition side. Yes, it could be a coil pack failing when hot but I would expect that to manifest across the range when hot.
My guess would be throttle position sensor or an inlet leak. My logic being as follows so that anyone more knowledgeable than me can either tell me I'm talking rubbish or confirm my theory.
1. Throttle position. With the throttle fully released, the ECU tries to keep a stable idle (750rpm from memory)
As you feed on the throttle, the position sensor doesn't register a change because the track is worn most at that point but the butterfly valve is open allowing much more air in. The ECU tries to handle this but can't. More throttle and we get a good reading and off we go.
Conversely, we get a reading from the pot telling the ECU we're not at idle but the butterfly isn't open so it's starved of air and goes over rich. Same result.
My merc occasionally does the same and I know there's a small dead spot on the throttle pedal sensor. It's a fly by wire diesel but it does confuse it occasionally and cause similar symptoms.
2. Air leak. When cold, there is excess fuel injected across the range to compensate for the cold engine so it can cope. When warm, the leak is a big percentage of air getting into the engine but not being registered by the MAF but at higher revs or wider throttle the leak is a smaller percentage which the ECU can compensate for based on the o2 sensors.
Could also be that under higher vacuum of wider throttle, the leak seals itself.
In the old days, the way to find it was spray WD40 around the inlet tract whilst idling and listen for any change in engine note.
I think either of these is more likely than the ignition side. Yes, it could be a coil pack failing when hot but I would expect that to manifest across the range when hot.
I will see if there is an air leak, but as you suggest, if it was the coils, the whole rev range would be affected, more so under load as in up a steep hill (which I traverse every day).
Throttle pot is a possibility, but not convinced as this engine was replaced under warranty 27k or so ago and I am told it was an entire engine. Surely the would have supplied everything??
Who knows, but at 94k on the car, she's otherwise immaculate.
Throttle pot is a possibility, but not convinced as this engine was replaced under warranty 27k or so ago and I am told it was an entire engine. Surely the would have supplied everything??
Who knows, but at 94k on the car, she's otherwise immaculate.
myfirstl322
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A replacement engine AFAIK is just that, an engine, no ancillaries like throttle body, starter, alternator et al, just an engine, maybe just a short block sans the heads even.
Only folks I know who sell complete 'crate' engines with EVERYTHING on it are the Americans, or Forces suppliers.
Only folks I know who sell complete 'crate' engines with EVERYTHING on it are the Americans, or Forces suppliers.
I'll need to ask Hamish, but he told me the whole engine was replaced. I asked if it was the short motor, but no, it was "everything" although I'm not sure what everything meant.
So, how do I test the TB? I could get Hamish to do it with his fabuloso tester. Any cheap ways on a Rangey?
So, how do I test the TB? I could get Hamish to do it with his fabuloso tester. Any cheap ways on a Rangey?
The throttle pot should just be a potentiometer similar to the height sensors so you should be able to check it with a multimeter. I'm travelling at the moment so can't look up the pinouts.
Just a thought, the throttle body is prone to coolant leaks, this could also maybe be letting water into the engine? Or water getting into the pot?
The throttle body was pissing out coolant (onto three plug leads on left bank) which is what I originally thought was causing my misfire (that's what it feels like, damp plugs). But that's all fixed and hasn't lost a drip in over a month. The coolant bottle level is the same. Never occurred to me that it could leak internally. I'll check it out. I'll do a MARRS and Pump Up The Volume til the drum beat goes like this...
Maybe borrow mates adventure camera and mount it near the EAS pump/valve body housing and see if there are any leaking sparks under load. A bit of fun if nothing else
Maybe borrow mates adventure camera and mount it near the EAS pump/valve body housing and see if there are any leaking sparks under load. A bit of fun if nothing else
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When my cam sensor started to go on my Omega it would do odd things when hot. Then one day it just failed altogether and left me with no power so no steering and limited braking on a steep and twisty lane!
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my 2.0i omega used to do that! Sorry I sold it..
myfirstl322
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No need to apolgize
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PPP38vouge
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Hi Doo,
My daily, ( Ford Focus 1.6 zetec ) was running as sweet as usual then one day it started to misfire like what your RR, I replaced a few things like idle control valve , new air filter , cleaned out throttle body and a few other bits, but it still ran rough, I drove it like this for about a month then the last thing I change fixed the problem, it was a duff spark plug, 3 of them were the correct colour but one was a lot darker so knew it had not been sparking properly, not saying this is what's causing your problem but it may be worth a try.
Hope this helps.
Paul.
My daily, ( Ford Focus 1.6 zetec ) was running as sweet as usual then one day it started to misfire like what your RR, I replaced a few things like idle control valve , new air filter , cleaned out throttle body and a few other bits, but it still ran rough, I drove it like this for about a month then the last thing I change fixed the problem, it was a duff spark plug, 3 of them were the correct colour but one was a lot darker so knew it had not been sparking properly, not saying this is what's causing your problem but it may be worth a try.
Hope this helps.
Paul.
Planning to take her to my mate Ian as he "bought" them so may be able to get an exchange if there is a problem.
But surely a duff plug would be duff all the time, not just when reached normal running temp??
Was reading all manner of stuff about porous engines, bad liners and pressure problems... Shat mah pants if I'm honest
I can see all of my problems being that
What are the chances of my "replacement" new engine being a top hat type? It was replaced under warranty I should imagine about a year before she was laid up! So perhaps 2010/2011 or thereabout....
