Buttonman

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About 4 weeks ago I wrote in and asked about the engine hesitating repeatedly when I was trying to keep at an even speed when it was hot. A crack in the IACV that opened up when hot was suggested but I have just fitted a new one and made several trips with the same result that the engine cuts out at any even speed. The old one made an intermittent high pitched buzzing sound, the new one doesn`t. Starting is OK and tickover was and is uneven at between 750 and 880 rpm, fast when cold but slows when getting warm. When I put my foot down it picks up immediately but with a sudden pick up and then accelerates without hesitating. When decelerating there is no hesitating or lurching either. There is about 11mm slack in the accelerator cable. Before this happened I had replaced all the hoses as they were as old as the car and one had burst. The thermostat and hoses were replaced as a set. A new temp. sensor was fitted (like for like) as the gauge showed normal even when the engine was boiling and no warning lamps were lit. The downhill light sometimes comes on for some reason. Even tho`I am an old analogue driver I wanted to find out a bit more about these probs so I bought a Bluetooth diagnostic reader. It told me that there was a problem with the CPS that I have just cleaned and that there was intermittant misfiring of the ignition system. Also a result that read TID:$04 CID: $02 test incomplete or dependant test failed. Both coils and leads and plugs were replaced by the previous owner in Aug 2018 (car used little since) and I have just cleaned and adjusted the plugs and cleaned all relevant wiring connections. I am way out of my depth when it comes to car electronics having had the same car for more than 40 years, none in that, not even a digital clock. Any help or advice would be appreciated.
 
About 4 weeks ago I wrote in and asked about the engine hesitating repeatedly when I was trying to keep at an even speed when it was hot. A crack in the IACV that opened up when hot was suggested but I have just fitted a new one and made several trips with the same result that the engine cuts out at any even speed. The old one made an intermittent high pitched buzzing sound, the new one doesn`t. Starting is OK and tickover was and is uneven at between 750 and 880 rpm, fast when cold but slows when getting warm. When I put my foot down it picks up immediately but with a sudden pick up and then accelerates without hesitating. When decelerating there is no hesitating or lurching either. There is about 11mm slack in the accelerator cable. Before this happened I had replaced all the hoses as they were as old as the car and one had burst. The thermostat and hoses were replaced as a set. A new temp. sensor was fitted (like for like) as the gauge showed normal even when the engine was boiling and no warning lamps were lit. The downhill light sometimes comes on for some reason. Even tho`I am an old analogue driver I wanted to find out a bit more about these probs so I bought a Bluetooth diagnostic reader. It told me that there was a problem with the CPS that I have just cleaned and that there was intermittant misfiring of the ignition system. Also a result that read TID:$04 CID: $02 test incomplete or dependant test failed. Both coils and leads and plugs were replaced by the previous owner in Aug 2018 (car used little since) and I have just cleaned and adjusted the plugs and cleaned all relevant wiring connections. I am way out of my depth when it comes to car electronics having had the same car for more than 40 years, none in that, not even a digital clock. Any help or advice would be appreciated.
Thanks for your response. I spoke to the previous owner before I saw your response and he suggested clearing the codes and go for a drive as he thought they could be from 2018 and that was why the coils and leads were replaced. I went for a long drive and there were no fault codes stored in the ECU when I looked on return. Does that mean there are no faults anywhere or is there a fault in the ECU as even the CPS is not mentioned. The incomplete test is still there and if there is a fault with the CPU would that cause the cutting out? Starting to get a bit fed up as we want to use the car to try to shake off some covid related cabin fever.
 
What engine is it? 1.8L K4 or 2.5L KV6.

A lot of running issues can be put down to poor fuel pressure, as the filter clogs up in time, but is seldom replaced, as it's in the tank.
 
What engine is it? 1.8L K4 or 2.5L KV6.

A lot of running issues can be put down to poor fuel pressure, as the filter clogs up in time, but is seldom replaced, as it's in the tank.
Thanks for your reply. It is a 1.8 K4. Would not be surprised if the filter had never been changed, the timing belt I changed last year had done over 150000km. Am almost tempted to put the old temp sensor back in and see what happens as the car ran ok but with a squeeky IACV and a slightly uneven tickover. Have enclosed the results of the lambda test. If one of the tests could not be completed does that mean the sensor is on the way out or is already there?
 

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If the ECU isn't returning any current codes, then it's not detecting any current issues.

I'm not sure what the tests the diag is performing, but the test that isn't complete is potentially a post cat O2 sensor test, which is often delayed, and rather random in nature. If it is the post cat O2, then it's of no consequence, as it's an emission requirement, nothing more.

It's definitely worth changing the fuel filter, but be aware that there are several different designs (different pump manufacturers I believe), which aren't obvious until the pump is out the tank. I just change the whole pump assembly, as it saves trouble later on.
Also you need to be careful removing the pump, as it uses the BMW style threaded securing ring, which can be a real pain to refit, once removed, unless you have access to the specific tool for fitting it.
 
If the ECU isn't returning any current codes, then it's not detecting any current issues.

I'm not sure what the tests the diag is performing, but the test that isn't complete is potentially a post cat O2 sensor test, which is often delayed, and rather random in nature. If it is the post cat O2, then it's of no consequence, as it's an emission requirement, nothing more.

It's definitely worth changing the fuel filter, but be aware that there are several different designs (different pump manufacturers I believe), which aren't obvious until the pump is out the tank. I just change the whole pump assembly, as it saves trouble later on.
Also you need to be careful removing the pump, as it uses the BMW style threaded securing ring, which can be a real pain to refit, once removed, unless you have access to the specific tool for fitting it.
Thanks for your reply and suggestion about the fuel filter. The first test result was for bank 1 sensor 1 or vice versa. While the test was running the moving line was really jagged and irregular. Have had a new fault reading for the cam. Pos. Sensor. Am tempted to replace that as it has shown up before. Are there any other sensors that can cause the hesitating at a steady speed. The car has its MOT in Sept so I want it to be shipshape. I am self employed and have time now to do repairs but might not have time in then. Is it worth cleaning the throttle body and MAS?
 
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