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JMG

Knock sensor problem ?

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Hi all,

I have a problem with my 1990 Turbo SE.

Since about one year I have boost problems, ECU often limit boost to 0.65. And for the last few months, I had never got boost above 0.65.

I have had the chargecooler impeller changed by my mechanical on 2006 but I decided to check it 6 month ago to be sure it is not its fault again (what an awfull job, I needed 3 hours to remove it and replace it). It is perfect. Once replaced and refilled I tried to unplug the outlet hose and it flows good. So I tried to run the car hard, keeping at full throttle and 0.65 boost, then stoped, put my hand on the chargecooler, it was cold. So it is not this.

Unfortunately I was not able to use freescan because my serial cable only gave me the data which do not need interact.

3 weeks ago I saw LEW has released an usb cable and ordered it. I now have it and have used it with success.

I do not have check the engine while driving because my steering rack is about to break (I ordered a new one from SJ and will not drive until it is replaced) but I check the engine at warmup cycle with the car stopped. I just have started the engine and let it warm until the fans start then stop the engine. I tried this 2 times (not the same day) and got the same results.

The AF ratio gets from 12.9 and raised 14.6 at about 73 deg C of water temp. After that it never changed. The BLM cell is always 111.

MAP varies between 0.45 and 0.57. BattV varies between 11.8 and 13.2. IAC starts at 131 bup falls slowly until 8. Knock retard is always 0 but knock counts start at 12, stay at 12 for a few seconds, then start to grow at a very high rate and this never stop after (about 1 or 2 new knock every second and after 5 minutes, it has looped 3 times at 256, this means near 1000 knocks in only 5 minutes). Spark advance begin at 29.9 but falls slowly and is 8.9 at the end of the test.

I don't thing there could be as knocks at 1100 RPM with a MAP of 0.50 and and a AF ratio near perfect of 14.6 with an engine which seems to be in good health. But to be sure I unplugged the 4 wires with the engine cold and checked them (they are Denso irridium and have about 15000/20000 miles). They are in very very good state, no wear at all on the electrods and just a little light grey/yellow deposit. I think electrodes would be in very bat state, if not destroyed, if there were as many knocks.

So I think the knocks do not exist. But is it the knock sensor which is dead or can it be other things like mechaninical noise which makes the sensor thinking its knock (my valves tappets are a little noisy) or electrical leaks on the ignition or other things ?

If it is do someone know a simple way to access this sensor, it seems to be very hard to access. I have unmounted the boot in the rear and it keeps very hard to see between the many hoses and impossible to get to it with my hand.

The last question, are the low IAC and low spark advance normal ?

I join the complet freescan log of the second test.

Thanks in advanced for the answers.

idle_warm_2.zip

Edited by JMG

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My knock sensor became over sensitive with age (as yours probably is), my knock count would reach 200 in one minute or so, with the check engine light on almost permanently. I obtained mine from Malcolm (Espritism) on the day Troy took over the stock, so might be worth finding out how much one shipped from Troy would be.

To gain access I did as you and removed the floor, but then removed a few wires , it wasn't easy but with a pair of adjustable grips I managed to move it, them undo it fully by hand.

Best of luck

Andy

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Strange, my check engine does not light, and no error code is set by the ECU.

And I know it works because 2 weeks ago one of the 2 screws which maintain the IAC had been lost, creating a big intake leak and a bad idle (2000 RPM when warm), and the check engine lighted and the code 35 was set (code 35 = bad idle).

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without looking at the log file, you mention the coolant temp at 73 deg C. is that as high as it gets on freescan?

if it doesnt go higher, the thermostat seems the culprit possibly.

try a new one for a triumph dolomite sprint etc, 82 degC

ecu needs to see 78 degC at least before it allows more boost than 0.65bar

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No it is good. I just said the AF ratio gets to 14.6 when the coolant temp gets to 73 and do not change after, but the coolant temp continue to raise (until 86 on this log).

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Jean-Marc,

Did you reset the BLM values in freescan and have the ECM relearn? If not, go to the advanced menu in Freescan with the key on and engine off then hit the reset BLM. Also, you may consider trying a new knock sensor. They are a standard GM knock sensor and should be easy to find with the abundance of Opel cars in France.

Artie


89 White Esprit SE

...a few little upgrades....

93 RX7.....Silverstone

....slightly modded...Muahaha...

New Addition:

1990 300ZX TT......Hmmm

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Jean,

I had exactly the same problem about a 18 months ago. I spend hours trying everything to solve it.

It is going to be one of the following, do these in order.

1. Change the knock sensor.

2. Change the ECU use your existing memcal

3. Change the memcal.

My bet is that it is the knock sensor input stage in the ECU that is gone. That's what it was for me.

Dermot

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Jean,

I had exactly the same problem about a 18 months ago. I spend hours trying everything to solve it.

It is going to be one of the following, do these in order.

1. Change the knock sensor.

2. Change the ECU use your existing memcal

3. Change the memcal.

My bet is that it is the knock sensor input stage in the ECU that is gone. That's what it was for me.

Dermot

Many thanks, Dermot.

I do not think it is the memcal since it has been changed from a #3 to a #6 some months ago and the boost problem had started before (I thought it was the chargecooler again at this time).

When you say "the knock sensor input stage in the ECU", do you mean the wire from the sensor on the ECU connector ?

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I have checked the ECU connectors and what is around. I have find several unplugged wired or connector but not found any items to connect them.

I have taken 4 pictures and, for a global view, I have paste them side by side on a single picture which I join to this message.

I have numbered the unpluged things I have found and I have also named 2 strange things 'A' and 'B'.

1) orange wire (in the air, not isolated)

2) black wire (in the air, not isolated)

3) white 2 pins female connector

4) big 4 pins female connector (in the same place that all the connectors that go to the rear relay and valves box)

5) a wire not connected at any side (5 is a 2 pins rectangle brown female connector, 5a is the other side, one pin metallic plain connector not isolated, 5b is where the wire is attached, the wire is green)

6) black 2 pins female connector which was under the big air intake hose (green wires)

I checked the wires on the four ECU connector, all are well attached.

I don't know if some of these unplugged things may plugged somewhere or if all of that is normal.

post-601-1204590581.jpg

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When you say "the knock sensor input stage in the ECU", do you mean the wire from the sensor on the ECU connector ?

I guess Dermot means part of the ECU that reads the input from the sensor rather than the wire leading to it, so in effect part of the pcb.

Andy

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