350I refuse to work correctly
Discussion
Hello guys,
Something is really wrong with my 85 350I : I've checked/replaced everything I could, including NOS rotor arm and dizzy cap, plugs wires, coil, electronic module, spark plugs, but the problem doesn't change.
It start first time most of the time, but, rapidly (but not always, as it seems to be an intermitent fault !) it run roughly, as if one (or more) cylinder is missing, except at idle, where it run smoothly most of the time…
This morning, during a 50Km run, she started to run smoothly, then more and more roughly, then again correctly at the end of the run, for the very last Miles.
New NGK spark plugs are incredibly white (lean ?), so it's not excessively rich, if I'm not wrong
From behind, the smell of unburned fuel is terrible, according to a friend who was following me with his 911 .
Sometime, she work well, then start to run on 7, or 6 cylinders, without evident reason.
Engine is healthy, compression are okay, so it must be an injection or ignition problem, but I don't know what to do, please help me !
Something is really wrong with my 85 350I : I've checked/replaced everything I could, including NOS rotor arm and dizzy cap, plugs wires, coil, electronic module, spark plugs, but the problem doesn't change.
It start first time most of the time, but, rapidly (but not always, as it seems to be an intermitent fault !) it run roughly, as if one (or more) cylinder is missing, except at idle, where it run smoothly most of the time…
This morning, during a 50Km run, she started to run smoothly, then more and more roughly, then again correctly at the end of the run, for the very last Miles.
New NGK spark plugs are incredibly white (lean ?), so it's not excessively rich, if I'm not wrong
From behind, the smell of unburned fuel is terrible, according to a friend who was following me with his 911 .
Sometime, she work well, then start to run on 7, or 6 cylinders, without evident reason.
Engine is healthy, compression are okay, so it must be an injection or ignition problem, but I don't know what to do, please help me !
Hi BD, the spark plugs are new NGK (the previous ones were of 2 different brand), so Don't think they could be the problem.
I've change all these bits, one by one, because that's the spares parts I have in my garage, so the cost was nil : I checked if it was better or not between each change, you know the result.
The fuel filter is new, pump seems to be good, if it was dead it should be dead permanently, don't you think .
I've check the timing with a strobe, it's perfect.
Please, no, not the ECU…..
I've change all these bits, one by one, because that's the spares parts I have in my garage, so the cost was nil : I checked if it was better or not between each change, you know the result.
The fuel filter is new, pump seems to be good, if it was dead it should be dead permanently, don't you think .
I've check the timing with a strobe, it's perfect.
Please, no, not the ECU…..
BIG DUNC said:
How are the fuel pump and filter?
ThisPlugs showing a weak mixture means not enough fuel getting into the chambers = Low fuel pressure or something far more drastic which is very doubtful due to the fact that the fault comes and goes
It's also doubtful that there is lots of unburnt fuel coming out of the exhaust unless the valves are sticking open on occasion which is very doubful
Is the smell of fuel possibly coming from a leak somewhere?
I would be checking fuel pressure before getting more involved
There is something else that could be happening but this depends on what your ignition system consists of - If the distributor is of the centrifugal advance type (Very likely will be) there is a possibility that the bob-weights are sometimes sticking and throwing the timing out
These are only my thoughts and i have been known to get it wrong at times but....
Good luck in finding it
Perhaps the vacuum advance isn't working properly, this could give the same symptons as sticking bob-weights, if the plugs are sparking too soon anything could happen
Is the vacuum advance ok, perhaps the base plate that it moves is sticking or the vacuum advance unit is keeping the plate over when it shouldn't be
Does the timing always check ok after high revving the engine?
Is the vacuum advance ok, perhaps the base plate that it moves is sticking or the vacuum advance unit is keeping the plate over when it shouldn't be
Does the timing always check ok after high revving the engine?
Thanks PS, that's serious food for thoughts : I'll have a look in the distributor tomorrow, and see how I can make an adaptator to check the fuel pressure whilst the engine is running.
The fact that it is a non permanent problem is rather reassuring me, but it's more hard to solve !
I just realised : we (me and friends) were having some fun on small rurals roads here in Northern France, but my tank was fuel 100% full.
On left (rather rapid….) bends, the fuel smell was evident, due to fuel coming out of the tank, by the fuel filler or anything like that : the smell my friend was talking about could be coming from this leak, eventually.
The fact that it is a non permanent problem is rather reassuring me, but it's more hard to solve !
I just realised : we (me and friends) were having some fun on small rurals roads here in Northern France, but my tank was fuel 100% full.
On left (rather rapid….) bends, the fuel smell was evident, due to fuel coming out of the tank, by the fuel filler or anything like that : the smell my friend was talking about could be coming from this leak, eventually.
Edited by chris59 on Sunday 24th February 19:32
I'll remove the sensor tomorrow to check it, but don't expect to find one locally.
Hopefully it will not be the Ecu, but if it is, will one from a Range Rover work (same question about the sensor) ?
Is it normal that the engine can run (with no obvious difference) wihile this sensor is disconnected ?
Hopefully it will not be the Ecu, but if it is, will one from a Range Rover work (same question about the sensor) ?
Is it normal that the engine can run (with no obvious difference) wihile this sensor is disconnected ?
Engine Temperature Sensor.
This is a classic case when it's failing intermittently.
If the resistance goes too high (or open circuit) the ECU overfuels terribly.
You can use the LR one if you're abroad, there's a part number somewhere maybe on the parts list.
See here:
https://www.pistonheads.com/gassing/topic.asp?h=0&...
This is a classic case when it's failing intermittently.
If the resistance goes too high (or open circuit) the ECU overfuels terribly.
You can use the LR one if you're abroad, there's a part number somewhere maybe on the parts list.
See here:
https://www.pistonheads.com/gassing/topic.asp?h=0&...
Edited by adam quantrill on Sunday 24th February 23:04
Yeah I didn't spot it in your list. Also it's a good idea to double-check the resistance of this sender at the ECU multiplug - you'll have to look up which ECU pins are the right ones.
This will eliminate the wiring loom introducing a bad connection.
After all this and your last checks the ECU might cause problems, I and others have had some success with re-soldering the joints in the ECU printed circuit board. This procedure takes an hour or two.
This will eliminate the wiring loom introducing a bad connection.
After all this and your last checks the ECU might cause problems, I and others have had some success with re-soldering the joints in the ECU printed circuit board. This procedure takes an hour or two.
Adam et all, the sensor is not on this list because I replace it last year, trying to solve another malfunction, who finaly was a simple "sticking" (not every time, one more intermittent fault !) carbon contact in the middle of the (repro) dizzy cap.
Back this morning to the original, 34 years old Lucas sensor, and the car seems to be running fine once hot.
I've got the filling to fall from a sky scraper : 'till I'll touch the ground, everything's fine at the moment…….
Back this morning to the original, 34 years old Lucas sensor, and the car seems to be running fine once hot.
I've got the filling to fall from a sky scraper : 'till I'll touch the ground, everything's fine at the moment…….
Well, Adam, it failled right from the start, considering I nearly didn't used this car since the fitment of this new (plastic, you're right !!) crap sensor (bought from RB, btw).
So, persevering was the only way to follow, these cars deserve some patience…..
Now she's back in my garages, along my 2 others TVRs, about 35 Triumphs and several other toys…..
I'l follow your link again, to see where to buy a good one, just in case the old sensor decide to give up…..
So, persevering was the only way to follow, these cars deserve some patience…..
Now she's back in my garages, along my 2 others TVRs, about 35 Triumphs and several other toys…..
I'l follow your link again, to see where to buy a good one, just in case the old sensor decide to give up…..
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