Engine hunts when hot

[lancepar]

TV8 said:

I have a good original Lucas 5AM somewhere if you get stuck (and a bunch of other TVR goodies to move on).

Located near Bromley

Graham

PH says you don't permit emails! How does one contact you?

Lance

[spitfire4v8]

The earliest cool spot is immediately behind the radiator on the tvr engine bay .. moving the afm forwards initially brings it closer to the exhaust manifold so making things worse.
I've no idea on response times, but any extra delay should be seen as a bad thing I would imagine.

[LenChim]

OK a bit more information from my car, first off I thought I would have a look in the AFM so I took the castings off each end and had a look down the hole where the wire and resister are, it all looked a bit dusty so I gently blew it out, then I injected some paint thinners through it and blew it out again, after several cycles of this I could then see that the wire looked like a coiled spring not a solid lump. Reassemble and put it back om the car.
Voltage test red/black -ve blue/green +ve ign, on, 0.352v. Engine running 1.98v. Engine hot 1.74v.
I took some pictures of the screen running the Rover Gauge. Cold, Hot and at 3000 rpm.The last one is of the state of the floor after running, this I suspect is due to the temperature and the fact that the car has been started many times now without going for a run to clear it out.

[LenChim]

[LenChim]

[TV8]

lancepar said:

Graham

PH says you don't permit emails! How does one contact you?

Lance

I have checked and I do permit emails. Try grahamb at btinternet dot com

[ChimpOnGas]

spitfire4v8 said:

I've had a canems car in with running issues and that too turned out to be the MAP sensor

Sadly this doesn't surprise me at all, I recommend everyone with a Canems system replaces their cheap Chinese map sensor with a quality sensor from NTK and relocating it too as it gets wet where the installers place it.

The next items to replace are the cheap Chinese waterproof fuse holders used on the Canems installation, they are very poor quality items and a breakdown waiting to happen.

Don't ask me how I know





Not good

Edited by ChimpOnGas on Thursday 12th December 16:32

[blitzracing]

Couple of things -Your short term trim is hitting 100% on one side, which is wrong, it should be cycling around the mid point. This means either the long term trim has not been set up as the battery or ECU has been disconnected recently (?), or a sensor is a mile out and the long term trim is at 100% and run out of range. To reset the long term trim (if its near 0 at present) you have to let the car idle for at least 2.5 mins when hot (above about 90'c) and you should see it slowly move as the ECU learns the new setting. Once its stopped moving, the short term trim should then cycle around the mid point. The lower the long term trim, the better the map and sensor data is for your engine, and on a TVR 30%or below would be a good value. As for the AFM reading- set it to direct, it should read between 32 and 35 % at idle- Id expect a 4.5 to be midway between these 2.

Edited by blitzracing on Thursday 12th December 16:41

[ChimpOnGas]

spitfire4v8 said:

I'd like to see the AFM replaced with a MAP sensor though, mounted somewhere cool rather than the heat-affected AFM position right over the exhaust manifold .. I might give that a go one day

A lot of modern cars use both an air flow meter (air mass meter) to give it its correct name and a MaP sensor, like this the AFM is doing 99% of the load sensing function 99% of the time because an AFM measures true air mass which is advantageous for many reasons.

The addition of a MaP sensor is just there as a fail safe and to help detect vacuum leaks engine side of the throttle butterfly that are undetectable by the AFM, the combination of Both an AFM and a MaP is therefore the best setup.

MaP sensors are fine but as I've found to my cost their quality can vary greatly, the thing is while these cheap Chinese junk sensors are typically £15 you only need to pay £27 for a proper Japanese quality NTK MaP sensor!

A MaP sensor has such an important job to do why anyone would risk fitting a no name Chinese copy to save £12 on their engine management installation is completely beyond me

[lancepar]

TV8 said:

I have checked and I do permit emails. Try grahamb at btinternet dot com

Hi Graham,
Yes you do today but not when I previously tried, hense the message, must be a pistonhead gremlin, I'll get in touch.
Lance

[LenChim]

blitzracing said:

Couple of things -Your short term trim is hitting 100% on one side, which is wrong, it should be cycling around the mid point. This means either the long term trim has not been set up as the battery or ECU has been disconnected recently (?), or a sensor is a mile out and the long term trim is at 100% and run out of range. To reset the long term trim (if its near 0 at present) you have to let the car idle for at least 2.5 mins when hot (above about 90'c) and you should see it slowly move as the ECU learns the new setting. Once its stopped moving, the short term trim should then cycle around the mid point. The lower the long term trim, the better the map and sensor data is for your engine, and on a TVR 30%or below would be a good value. As for the AFM reading- set it to direct, it should read between 32 and 35 % at idle- Id expect a 4.5 to be midway between these 2.

Edited by blitzracing on Thursday 12th December 16:41

Ok, before I started the car today I looked at the fault codes and cleared them. As I did not clear them before the last run not sure that they are relevant.



I also looked at the "Battery backed RAM Contents" Not sure what they mean or if any are incorrect.



Ran the engine to 90C idled for 3 min. MAF @ Direct, Lam Trim LT.

[LenChim]

Then I switched to short term Lam, it was very variable.
ODD EVEN
-28 -13
-24 -20
-39 -16
-23 -22
-40 -19


Then I took a pic of the LT Lam


I also looked at the "Fault code file" again and it said the the "Air control stepper motor was at fault" But that was probably due to the fact that I pinched off the air pipe to it to reset the tick over with out the ACSM coming into play so it was having a sulk.

[blitzracing]

All the results are a bit contradictory- long term trim is stuck at -100 %. This means the lambda out puts are always at over 1 volt and not switching for the ECU to do this. A high AFM output would do this as the AFM / Map data would add more fuel with a higher voltage, but on the surface the readings are not far out. Yet we also have a fault codes for both lambda probes and low fuel pressure, which is completely the opposite, as this would be 0 volts from the probe.

Dont worry about the stepper fault for now.

Its time to get a test meter out- and measure the Lambda probes directly. Have a read here:

http://www.g33.co.uk/img/fuel/14cux-fault-finding....

Obviously probing about with test meters is very time consuming ( Although educational), Id still see if you can beg borrow or steal an AFM as its an easy bit to swap out, and then do an ECU reset by unplugging and replugging it to reset the trim values to zero.. Then take the car for a run so its hot , and then let it idle for a couple of minutes at idle to allow the ECU to readjust the long term trim, and see what the readings end up as.

. I have seen some really odd readings like this when the inlet air pipe collapses, as it alters the inlet vacuum and this alters the injector pressure, so the ECU gets its knickers in a real twist as its not programmed to look for a fault like this.

[spitfire4v8]

What I would add is that the fuel map doesn't look like any 450 chim I've seen to date (though there are a few versions).
The closest I can find is a Morgan 4.6 which has the richer areas around the 2nd and 3rd rows.
Your fuel data goes much richer than I would expect around tickover and cruising.

Also your used cells do appear to be a bit further down the table than I would normally see (though you've got soft cell* off so I can only go off the MAP percentage which appears to be at around 34 - other eighties bands* are available) .. at 3000rpm with no load I would have expected that to be a row higher .. possibly suggesting you're running with too little ignition timing... I would be checking that anyway, and also getting a known 450 Chim chip in there and see what happens.

[LenChim]

Ok the latest screen shots;.

Right I have got the car hot 90c ish let it idle for 3 min. the screen shots show the results Short term trim is about mid point but the log term is -85/-57, the AFM seem to be ok at 33%.
The car seems to run ok, no shunting but runs out of revs at 5000rpm, seems to ether run out of fuel or sparks cant really tell which, I replaced the HT leads about 3 months ago.
I have to say that getting the car up to temp is a problem when running around, I changed the stat to a 82C unit some time ago may be I need to go to 88C. The Ignition timing is set at 8 deg BTDC with vac off at 1000 rpm.I also need to change the temperature gauge sender as only reads 70C at about 90C eng temp. Only gets to 90C standing in the garage.

[LenChim]

[blitzracing]

Even though RoverGauge only reads trim to 3400 rpm, you can still pop a meter on the lambda output to get a passenger to read the voltage directly. It should cycle between 0 and 1.2 (or so) up to 3400, then stick at around 1.2 volts or slightly over to peak RPM. If you are running out of fuel it will drop to 0 volts. Problem is a bad misfire also looks like a lean mixture, so the results may not be that different. If you want to diagnose HT faults, and old style Crypton tuner is the way to go where you can monitor the HT wave forms. Shorts show as low HT, and open circuits show as higher voltage spikes. Mind you it may cost you as much to diagnose as swap all the suspect bits out. Its a pity Gunson used to do a brilliant HT tester with a simple LED bar display for the HT voltages, that tells you a lot, but have long since been out of production.

[LenChim]

blitzracing said:

Even though RoverGauge only reads trim to 3400 rpm, you can still pop a meter on the lambda output to get a passenger to read the voltage directly. It should cycle between 0 and 1.2 (or so) up to 3400, then stick at around 1.2 volts or slightly over to peak RPM. If you are running out of fuel it will drop to 0 volts. Problem is a bad misfire also looks like a lean mixture, so the results may not be that different. If you want to diagnose HT faults, and old style Crypton tuner is the way to go where you can monitor the HT wave forms. Shorts show as low HT, and open circuits show as higher voltage spikes. Mind you it may cost you as much to diagnose as swap all the suspect bits out. Its a pity Gunson used to do a brilliant HT tester with a simple LED bar display for the HT voltages, that tells you a lot, but have long since been out of production.

OK Christmas is over so I have made the plug assembly's to go in line to check the lambda out put and ran the test today. The outputs were good once the engine had warmed up. On the road the at constant speed they seemed to cycle ok, decelerating and accelerating but at about 3300RPM they switched off zero volts.
So the question is were do I go from hear? I don't have a Crypton tuner, as I said I have replaced the HT leads but they are tied together. I did take the cap of the dizzi and clean it and look for cracks, tracking lines etc. It does not sound as though it is misfiring. I have rechecked the fuel pressure its ok, also when revved hard but I can not test it under load (no rolling road).
Any suggestions.

[QBee]

LenChim said:

.......I have replaced the HT leads but they are tied together. ...........

Should they be tied together? I always keep mine apart.....

[spitfire4v8]

In the olden days when we used to run ht leads with little shielding then it was good practise to run them separated, these days it matters not a jot. Plenty of manufacturers run latter day cars run with ht leads crammed into a central channel in the cam covers with no issues whatsoever. If you have any misfires it's because the lead is breaking down rather than any routing issues.