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Discussion Starter #1 (Edited)
hi, after fitting a new crank sensor, everything seemed ok, but the engine misfires pretty bad when on the move, only when up to running temperature though? but never cuts out and idles fine., although the sensor was bought for a 164 3.0 24v , could it be that it's the wrong one? does anyone know which is the right crank sensor for a 164 '95 3.0 24v? I bought this one, bosch 0261210047, also how would I find out the engine code for my car as this was an issue when enquiring about the sensor.? this engine code might help in finding the right part.
 

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Your crank sensor has nothing common with your misfires. your problem is lean mixture. check for air leaks and recheck fuel pressure. hint: with warm engine you have less fuel injected, thus, leaning mixture.
 

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I've not really looked at your other thread on this, as I'm not familiar with the 24V cars, but I know the 12V cars are prone to air leaks in the induction system. The rubber pipes that go along the back of the plenum to the idle speed control valve are prone to cracking and letting ai in. Likewise the big convoluted pipe between the airflow meter and the plenum (especially at the bottoms of the corrugations where the oil tends to sit). Have you checked those?
 

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Discussion Starter #4
hi avo/thott, when I replaced all the plugs and coils, all the plenum fittings and pipes vacuum pipes, etc came off and were cleaned, and checked for air leaks, I have sprayed around these pipes with the engine idling after re-fitting, because I had the same thought, and there is no difference to the tick over, which is fine btw, i'm now thinking maybe the air mass sensor, is there anyway of checking/cleaning that?
 

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hi avo/thott, when I replaced all the plugs and coils, all the plenum fittings and pipes vacuum pipes, etc came off and were cleaned, and checked for air leaks, I have sprayed around these pipes with the engine idling after re-fitting, because I had the same thought, and there is no difference to the tick over, which is fine btw, i'm now thinking maybe the air mass sensor, is there anyway of checking/cleaning that?
Hi
Stuff like that can be cleaned with isopropyl alcohol aka isopropanol
 

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I insist on fuel pressure test. Im motion, under high load, with vacuum hose disconnected from fuel pressure regulator, to see only pressure drop from some kind of faulty.
 

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hi avo/thott, when I replaced all the plugs and coils, all the plenum fittings and pipes vacuum pipes, etc came off and were cleaned, and checked for air leaks, I have sprayed around these pipes with the engine idling after re-fitting, because I had the same thought, and there is no difference to the tick over, which is fine btw, i'm now thinking maybe the air mass sensor, is there anyway of checking/cleaning that?
I forget which pins, but two of them will be a variable resistance depending on the position of the flap inside it. An old analogue meter on Ohms is best for checking. As you move the flap, the needle should move smoothly. If it's jerky, the track inside is probably dirty or worn away. Someone on here might know which pins. That said, I think I've randomly probed mine and I haven't damaged it! Loads of videos on Youtube about rebuilding them. You just have to cut through the sealant on the plack plastic lid to get it off.


I've checked fuel pressure under load in the past, simply by putting a T piece into the fuel line and running it under the back edge of the bonnet to a pressure gauge taped to the wiper arm so I can see it from inside the car.

Do you have your old coil packs still? Might JUST be worth swapping the new nes ne at a time for one of the old ones that you know to be good.
 

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Discussion Starter #8
I forget which pins, but two of them will be a variable resistance depending on the position of the flap inside it. An old analogue meter on Ohms is best for checking. As you move the flap, the needle should move smoothly. If it's jerky, the track inside is probably dirty or worn away. Someone on here might know which pins. That said, I think I've randomly probed mine and I haven't damaged it! Loads of videos on Youtube about rebuilding them. You just have to cut through the sealant on the plack plastic lid to get it off.


I've checked fuel pressure under load in the past, simply by putting a T piece into the fuel line and running it under the back edge of the bonnet to a pressure gauge taped to the wiper arm so I can see it from inside the car.

Do you have your old coil packs still? Might JUST be worth swapping the new nes ne at a time for one of the old ones that you know to be good.
hi avo, the car has over 100,000 miles on the clock, this year I have spent quite a lot of money all ready, on various items , abs pump, abs electronics, steering rack, new alternator, and bits and bobs, it seems to be never ending, but my 25 year old cloverleaf is pretty well sorted and probably a keeper, I know what your saying about trying to re-furbish the mechanical air mass senor, but today again I bit the bullet and ordered a new bosch one from Italy, not a bad price either, thanks for your input it's very welcome, I will keep you all posted on the outcome of this . I bet it's the fuel pump or something after all this. anyway the history file is building up.
 

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Ouch! Still, with these cars, spares are drying up all over he place now, so at least you've got a good one for the foreseeable future!
 

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Without some diagnostics you run the risk of disappearing down the wrong rabbit hole. While there are many potential causes of a misfire, I am struggling with the timeline you describe. For absolute clarity, can you confirm (or otherwise that this is what happened please:

Car was running fine, no misfire, no problems.

Car stopped running

New CPS fitted, car runs again but now has misfire.


Are there any other stages/steps in there that we should know about?


If you had diagnostics, you could at least see if the ECU has logged any CPS issues, or any others for that matter. It may be possible to fit the necessary parts to activate the in-built diagnostics on your car. Some came with a push button on the column (I think) and a light which gave flash-codes for stored faults. I made up a very simple switch and bulb setup for pulling codes on a 12V 164 ECU. Really not sure if the 24V has that or not. Also possible is that your ECU will give you the codes if you do the throttle pedal pumping trick (my 155 V6 did and I think that had the same ECU you do???) Try it - start with ignition off, then switch ignition on (but don't start engine), then rapidly pump the pedal all the way to the floor 5 times (fully off to fully on) then release it. If it worked, and the ECU supports it, the MIL lamp will do a sequence of flashes. You have to be quick to catch it - don't hang about with the ignition on before jumping on the pedal. If you get flash codes, we can go from there. For reference, a sequence of 4 sets of 4 flashes means all clear.

A common cause of misfires on the 24V is slipped cam timing - did anything happen around the time you diagnosed CPS failure that could possibly suggest you investigate that as well?

Another very common issue with the 164 is the fuel leaking inside the in-tank pump assembly. This one has been well documented, but basically, there is a short length of fuel hose inside the in-tank unit between pump and outlet at the top which ages and leaks. The first sign is usually difficulty starting after the car has sat for a bit (residual fuel pressure drops away meaning it has to run the pump for a bit before there is sufficient fuel pressure to fire the engine). Eventually, you reach the point where it can't sustain adequate delivery at higher demand.

The AFM is pretty reliable but can indeed wear. I fixed one on a 12V 164 some years back by carefully shifting the ceramic substrate so the wipers moved on an unused section of the track. I did have to mess with the calibration a bit after doing it, but it wasn't too tricky. Long time ago though, so don't ask me for details! I'm sure that linked vid will cover it.
 

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Discussion Starter #11
hi, chris, this is what happened, the coolant was changed, then the car was driven say 3 miles and it just cut out at 30mph, and wouldn't start again, had to be trailered home, I thought maybe some coolant had got on the electrics, the next day, the car would start ok on a cold engine but cut out as soon as it warmed up after the thermostat had opened, and wouldn't start again that day. next day ok from cold, but cut out when running temp, this went on and on, until it was suggested that the crank sensor must of failed, so a new one was fitted, and bingo the car ran again, but with a pretty bad/alarming misfire at 60/70 mph, not so bad tootling around, in fact I went to the Trafford centre today in her and she ran almost perfect along the m60 for a couple of junctions, with minor juddering, I just can't put my finger on it, I will try that pedal test, to-morrow, thanks for the input.
 

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A fails-when-hot CPS is common enough, so a good diagnosis there. Confirmed by it running again after the new CPS of course.....probably!

Another common issue with these is a bad connection to the water temperature sender. Not 100% certain it affects 24V cars, but on the 12V, the loom was tight where it connects to the ECU water temp sender (not the gauge one, it's nearby, but not the same device) This can cause problems as the ECU thinks the car is stone cold if the connection goes bad. It can be intermittent too, for extra joy. This is probably worth checking, if only to eliminate it - locate the 2 pin AMP connector on the stat housing, disconnect it, peel back the rubber boot and carefully inspect the terminals. Make sure they are properly locked in place in the connector shell and are clean.

Does seem suspicious that the problems started after a coolant swap. Can't imagine what could have been done during that procedure to cause the sort of problems you are seeing, but I suppose almost anything is possible. A reputable place did the work?
 

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Discussion Starter #13
chris, the pedal depression 5 times didn't work, I cleaned all the contacts including the earth around the stat area as you said, but still had the misfire, today I unscrewed the petrol cap and noticed as always the air escaping , the car seemed to drive ok after that, I have a theory that when the tank becomes about half full, that a vacuum might be happening in the air space above the fuel, that might cause a restriction of fuel to the engine, what do you reckon? I also have the new air mass sensor to fit in the new year, so I will keep you informed.
 

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chris, the pedal depression 5 times didn't work, I cleaned all the contacts including the earth around the stat area as you said, but still had the misfire, today I unscrewed the petrol cap and noticed as always the air escaping , the car seemed to drive ok after that, I have a theory that when the tank becomes about half full, that a vacuum might be happening in the air space above the fuel, that might cause a restriction of fuel to the engine, what do you reckon? I also have the new air mass sensor to fit in the new year, so I will keep you informed.
Yes, that can happen. There should be a breather to let air into the tank to replace the volume of fuel that has been used. Usually, it is routed through a rollover valve so that if the car overturns, the fuel doesn't leak out of the breather. I guess it is possible that there's a blockage in it. Mine fell apart. It's a plastic valve at the top of the offside rear wheelarch, cable-tied to the filler neck. If the pressure in the tank falls appreciably below atmospheric, the fuel pump might not pick up as well as it should, resulting in low fuel pressure. Do you not the get misfire when the tank is full? If it's half full now, try driving round (carefully) for a bit with the filler cap off.
 

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Discussion Starter #15 (Edited)
thanks avo, i'll check that valve out, I also wonder if I could drill a small breather hole through the filler cap, because once the tank is filled, ie, "the petrol caps been off" the car seems to run ok for a while. i'll check that valve out first though, much safer I suppose.. don't want petrol fizzing out of the filler! had a quick look at that breather pipe, it's coloured blue, with a one way valve fixed between it, is it easy to remove? for cleaning or replacing, must go into the top of the filler pipe somewhere. how did you remove it? thanks again.
 

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Sorry, not been here for a bit.

Shame it didn't respond to the pedal trick. Must be too early and ECU for that one. Might be worth investigating the simple bulb & switch diagnostic.

I know coincidences happen, but given what happened, I'd still be focusing on things that have changed recently - CPS being one of them.

Have you checked that the crank pulley is good and tight, and also, that as the engine rotates, the gap between the trigger wheel and the CPS is constant?

Did the new sensor come with the bracket, and if so, is it identical to the old one, including having the dowels that locate it accurately?

Confess I'm clutching at straws here....
 

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thanks avo, i'll check that valve out, I also wonder if I could drill a small breather hole through the filler cap, because once the tank is filled, ie, "the petrol caps been off" the car seems to run ok for a while. i'll check that valve out first though, much safer I suppose.. don't want petrol fizzing out of the filler! had a quick look at that breather pipe, it's coloured blue, with a one way valve fixed between it, is it easy to remove? for cleaning or replacing, must go into the top of the filler pipe somewhere. how did you remove it? thanks again.

I didn't have to take it apart - it fell apart! Can't remember but I think it was relatively easy. Just wash the mud off the filler neck and you'll see it all. Three (I think) hose clips. Be careful, the plastic in your might be brittle and it might fall apart like mine did (I just replaced mine with a simple T piece and made a mental note not to drive the car upside-down...

One thought however. Yours might be different. Mine is pre-cat, so the tank breather system is very simple. Yours is likely to breathe through a canister of charcoal powder somewhere. It is there to absorb fuel vapour that evaporates through the breather when the car is parked up in the sun. There will be another pipe going from it to the engine (inlet manifold or plenum, I guess). There will be a solenoid valve which, when the engine fires, will open for a few minutes to allow the engine to suck air backwards through the carbon canister to purge the fuel vapour out of it, leaving it ready to absorb more, the next time the engine is started. (Of course, this canister could be anywhere. It doesn't have to be near the filler neck).
 
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