350i randomly running poorly
Discussion
Good Morning Gents,
Here is the issue for the group;
One of the guys here in the states that has a 390i has had this problem for a while now and I started to experience it in the last 400 miles or so.
While driving, and for random lengths of time the car will start to miss and run s
tty. Accelerating and decelerating is not an issue but just driving along at a set speed seems to cause the engine to miss. It also looks like the fuel usage goes way up and is obvious by the smell and residue on the back of the car.
On the 390, they have changed temp sensors, added a fuel regulator, looked into the timing and other things that I'm trying to get a list of.
There doesn't seem to be an correlation to weather, temp, amount of time driven or fuel type used. It just randomly starts and stops. It might be 5 minutes or, like yesterday the majority of the trip back from Woodwork, nearly 2.5 hours.
Have any of you guys on that side of the pond had this issue?
Any and all suggestions would help. I don't really want to start changing things till the problem goes away. So with the vast experience of the group, the correct solution might pop up quickly!
Charlie
Here is the issue for the group;
One of the guys here in the states that has a 390i has had this problem for a while now and I started to experience it in the last 400 miles or so.
While driving, and for random lengths of time the car will start to miss and run s
tty. Accelerating and decelerating is not an issue but just driving along at a set speed seems to cause the engine to miss. It also looks like the fuel usage goes way up and is obvious by the smell and residue on the back of the car.On the 390, they have changed temp sensors, added a fuel regulator, looked into the timing and other things that I'm trying to get a list of.
There doesn't seem to be an correlation to weather, temp, amount of time driven or fuel type used. It just randomly starts and stops. It might be 5 minutes or, like yesterday the majority of the trip back from Woodwork, nearly 2.5 hours.
Have any of you guys on that side of the pond had this issue?
Any and all suggestions would help. I don't really want to start changing things till the problem goes away. So with the vast experience of the group, the correct solution might pop up quickly!
Charlie
It could be any number of things. Analysing such faults is very difficult with the amount of information given. My advice would be to check the simple and less costly things first. Fuel pressure, quality of spark, timing, ignition leads, coil, distributor cap, stray spark, ignition module etc. From your description though, I would hazard a guess and say there could be an air leak. Spray something like penetrating oil in the air around the engine when warm and running to see if engine note changes. You'll be surprised how badly these engines run with an air leak.
Tony.TCB.
Tony.TCB.
So if it's happening when you are travelling at a constant speed vs speeding up etc i would want to check 2 things
The throttle pot is giving a constant signal, you can test this with a multi meter to ensure its a smooth signal (the early versions can be rebuilt as the carbon track does wear)
There is also a carbon track in the air flow meter. So try another afm from a friend or something and see that if that changes anything
Just my 2 cents :-)
The throttle pot is giving a constant signal, you can test this with a multi meter to ensure its a smooth signal (the early versions can be rebuilt as the carbon track does wear)
There is also a carbon track in the air flow meter. So try another afm from a friend or something and see that if that changes anything
Just my 2 cents :-)
Edited by gmw9666 on Monday 23 May 15:32
Hi...
Do you know the fuel pressure at idle and WOT on the adjustable FPR?...Does it have a gauge?
Have you run the car out of fuel at any time?
If the car can accelerate passed this then i doubt if it would be a "Tracked" issue like the throttle pot...AFM...If its air leaking then this would be more noticeable on start up and acceleration...A failing CTS could do this especially as its using more fuel and not getting burnt...Worst case scenario is a cam but don't go there yet....However first check to see if the ECU plug is firmly connected...Give it a firm push to see if it clicks in anymore...Trust me even an amount you would think insignificant can cause what you think is a huge problem...Back firing...Strong smell of fuel..Cutting out...But it can also do what you are describing...It happened to me some miles from Belgium on a French motorway that fined heavily for breakdowns...There was no recovery and they tow you to a police compound where they charge 1000 euros as well as a obstruction fine on a motorway which is that again if i recall...Luckily for me i was with a knowledge veteran Wedge group and we were able to pull over on a farm entrance.
The ECU plug was out by 0.05mm but still caused a mis-fire at constant speeds..Acceleration was fine....I now have cable ties as tight as i can pulling the plug on to the unit just in case...
Failing that i would wipe clean the distributor cap..Check condition of rotor arm and movement on dissy spindle..If you get a chance remove the dust cap and spray some electrical lube in there as the weights can stick, Allow to dry and always replace the dust cap.
Inspect the spark plug leads and if they are old then replace with a good quality set, The recommended Landrover Disco 1 EFI are fine....Make sure the king lead is long enough as the standard sets do not allow for this...TVR parts ltd do as they are aware of this issue....Although most will supply an extra length king lead at no extra cost.
Check that the plug is firmly home on the resistor on the inner wing...Again i use a cable tie as mine is a bit loose...
Top left of picture.
Check the paste on the ignition amp is still there..You should be able to physically see it..If not then its two screws and some thermal/Heat-sink paste...
Clean all connections including the ECU male and female pins carefully...The CTS & Thermotime plugs..Dissy cap..Resistor plug...AFM plug...
Always remember to test every time you change or replace a part otherwise you will not know what caused it and how not to avoid it again....I clean my connections up a least once every 2 months with some contact electrical lube...Never scratch them up with a rough file...Always use a fine emery board or nail file and an old toothbrush.
Most of these Wedge issues are actually a simple fix...Not all obviously but just be methodical and always test after anything you do....
Hopefully a cheap fix
Cheers
Ziga
Do you know the fuel pressure at idle and WOT on the adjustable FPR?...Does it have a gauge?
Have you run the car out of fuel at any time?
If the car can accelerate passed this then i doubt if it would be a "Tracked" issue like the throttle pot...AFM...If its air leaking then this would be more noticeable on start up and acceleration...A failing CTS could do this especially as its using more fuel and not getting burnt...Worst case scenario is a cam but don't go there yet....However first check to see if the ECU plug is firmly connected...Give it a firm push to see if it clicks in anymore...Trust me even an amount you would think insignificant can cause what you think is a huge problem...Back firing...Strong smell of fuel..Cutting out...But it can also do what you are describing...It happened to me some miles from Belgium on a French motorway that fined heavily for breakdowns...There was no recovery and they tow you to a police compound where they charge 1000 euros as well as a obstruction fine on a motorway which is that again if i recall...Luckily for me i was with a knowledge veteran Wedge group and we were able to pull over on a farm entrance.
The ECU plug was out by 0.05mm but still caused a mis-fire at constant speeds..Acceleration was fine....I now have cable ties as tight as i can pulling the plug on to the unit just in case...
Failing that i would wipe clean the distributor cap..Check condition of rotor arm and movement on dissy spindle..If you get a chance remove the dust cap and spray some electrical lube in there as the weights can stick, Allow to dry and always replace the dust cap.
Inspect the spark plug leads and if they are old then replace with a good quality set, The recommended Landrover Disco 1 EFI are fine....Make sure the king lead is long enough as the standard sets do not allow for this...TVR parts ltd do as they are aware of this issue....Although most will supply an extra length king lead at no extra cost.
Check that the plug is firmly home on the resistor on the inner wing...Again i use a cable tie as mine is a bit loose...
Top left of picture.
Check the paste on the ignition amp is still there..You should be able to physically see it..If not then its two screws and some thermal/Heat-sink paste...
Clean all connections including the ECU male and female pins carefully...The CTS & Thermotime plugs..Dissy cap..Resistor plug...AFM plug...
Always remember to test every time you change or replace a part otherwise you will not know what caused it and how not to avoid it again....I clean my connections up a least once every 2 months with some contact electrical lube...Never scratch them up with a rough file...Always use a fine emery board or nail file and an old toothbrush.
Most of these Wedge issues are actually a simple fix...Not all obviously but just be methodical and always test after anything you do....
Hopefully a cheap fix
Cheers
Ziga
Will do Ziga.
I was just out rolling up my cover and putting it away and opened the bonnet to take a look around. I pressed in on the plug on the ECM on the left front fender and it moved in. Feels a bit like it should move in since it is sort of springy.
Anyway, I noticed a small ground strap from one of the mounting legs which led down under the air cleaner and I found that it wasn't attached to anything! Probably not good. What should it be attached to?
Charlie
I was just out rolling up my cover and putting it away and opened the bonnet to take a look around. I pressed in on the plug on the ECM on the left front fender and it moved in. Feels a bit like it should move in since it is sort of springy.
Anyway, I noticed a small ground strap from one of the mounting legs which led down under the air cleaner and I found that it wasn't attached to anything! Probably not good. What should it be attached to?
Charlie
It could be the old injection ECU solder problem. When mine suffered from it, it overfuelled like a b1+ch and would only run properly with foot hard down (i.e enough air to match the petrol that was going in!). Overfuelling on that scale will cause rough running on an even throttle. To give an idea of the problem, my car used half a tank in 93 miles.
The flapping earth strap is more likely part of the interference suppression system as the airflow meter (on the inner wing/fender) is earthed via the wiring loom back to the rear of the left-hand cylinder head with the other injection earths.
The flapping earth strap is more likely part of the interference suppression system as the airflow meter (on the inner wing/fender) is earthed via the wiring loom back to the rear of the left-hand cylinder head with the other injection earths.
Re soldering the circuit board is a bit extreme, especially if you have no experience in undertaking such a task. The circuit board on any electronic device is very delicate and a drop of solder in the wrong place can cause severe damage. What I normaly do with any circuit board that's failing, is to give it what I call the 'circuit board service'. To do this you need a 1/2" clean soft paint brush, a vacuum cleaner and a short garden hose. Put the short garden hose in the end of the vacuum hose and tape it up with duck tape so that when you turn the vacuum cleaner on, it will give a powerful suck through the garden hose. Now open the circuit board in question and thorghly brush and vacuum at the same time taking care not to damage anything in the process. Make sure when you finish that all parts of the circuit board and inside the casing is clean and as new. Now put it all back together and try it. Using this technique I have saved many circuit boards and brought them back to life. Though I've never tried this on the ECU, I can see no reason why it should be any different to other circuit boards. Many people are under the impression that the solder on the circuit board has split, but in reality, what happens in most cases is that the dust gets in there and settles, thus short circuiting the board. It's easy to do and much safer than dropping solder at random. You may be pleasantly surprised.
This information is given in good faith and no responsibility is accepted. Finally, good luck.
Tony. TCB.
This information is given in good faith and no responsibility is accepted. Finally, good luck.
Tony. TCB.
Edited by ElvisWedgely on Tuesday 24th May 22:23
ElvisWedgely said:
Many people are under the impression that the solder on the circuit board has split, but in reality, what happens in most cases is that the dust gets in there and settles, thus short circuiting the board. It's easy to do and much safer than dropping solder at random. You may be pleasantly surprised.
This information is given in good faith and no responsibility is accepted. Finally, good luck.
Tony. TCB.
Sorry Tony, in this case sadly the problem is often almost exactly what you claim it isn't. There are a few issues at work, one of which is that sometimes the weight of the larger components makes them move around with vibration which frets the leadout wires within the solder until it fractures. Poor soldering technique is another (the classic 'cold joint') as is acidic flux which reacts with the component wires. You can also have a reaction with damp in the air, this is why most PCBs wear a nice lacquer. If the lacquer's applied post-soldering it's even better although it can be a pain for fault-finding as you have to dig your meter/scope probe tip through the coating to make contact.This information is given in good faith and no responsibility is accepted. Finally, good luck.
Tony. TCB.
I was once told that Lucas sub-contracted the ECU assembly out to (effectively) home workers which is an easy way to miss poor soldering technique. Whether it's true or not I don't know but it might explain some of the problems.
These aren't high-density boards by any means so it's quite easy to avoid bridging joints when soldering. I wouldn't advise a complete novice to have a crack but what you can do as a start is take a nice high-powered magnifier to the boards (the track side of both boards is exposed when you remove the top and bottom covers, which you will of course do with the proper tools, unlike some monkeyed ones I've worked on
). Even an inexperienced eye will soon get an idea of the average joint condition so when you spot one that looks grainy and crystalline or better still, has an obvious crack around the component lead, you'll know you're on the right track. The ECUs aren't static -sensitive like modern microprocessor stuff so as long as you don't breakdance or moonwalk on your nylon carpet in your onesie beforehand you should be fine.Incidentally a quick and dirty trick to check for poor joints on these ECUs (assuming the car is driveable even if rough) is to have the ECU on the passenger seat and clout the case with a screwdriver handle whilst driving...
Wedg1e said:
Sorry Tony, in this case sadly the problem is often almost exactly what you claim it isn't
Yes. I know what you are saying and soldering may be required in extreme cases and hence why I said in most cases. Maybe I should have said in some cases. It is however a lot easier and simpler for someone with little experience of soldering to try the cleaning process first before getting the solder and heat gun out. I have had success with circuit boards with just a clean up but if there are obvious cracks in the solder then your method of running solder over these joints may be needed. Like anything else, it's worth trying the easy route first.Tony. TCB.
Edited by ElvisWedgely on Wednesday 25th May 00:44
Wedg1e said:
Incidentally a quick and dirty trick to check for poor joints on these ECUs (assuming the car is driveable even if rough) is to have the ECU on the passenger seat and clout the case with a screwdriver handle whilst driving...
Spot on Ian....I know someone who wasn't aware of this but did exactly that...They sent their ECU away and it was rebuilt and given a 25 year guarantee ...They needed to see it first to make sure they had all the correct resistors...I think they had to send it to their Birmingham branch...Sometimes they have to send them to India to be repaired...Not bad though for £180.His Wedge now runs really sweet...Sounds happy and uses less fuel.....Happy days....
Mine was checked over by a good friend and any dry joints were re-soldered...I do have a receipt somewhere that states the ECU was rebuilt in 2006.
Here is his workstation...
I think the ECU was scared cos it done a little poo...
The blue arrows indicate dry joints.
Cheers
Ziga
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