Hej,

my 3,4 C2 have developed a severe full throttle hesitation(hick-up)above 4k rpm. Also the CEL comes on indicating Lambda out of range (lean on both banks) at very light throttle and warm running.,

I have checked the data using the Durametric monitoring and the Lambda value is generally around 1.00 as it should be but after the CEL is lit it indicates a value of 1,25. The car still runs ok at this point.

All in all the car runs ok with about 50% of the throttle but feels choked (to much air) on higher throttle openings. The engine runs stronger if you back out of the throttle (less air) at high rpm.

I have changed the fuel pump and filter (failed to find the fuel pressure measuring point though).

I have also seen that TPS only indicates 69% at full throttle which is a little weird, I therefore changed the TPS but was given the same result, still 69%

So I wonder what next?, shall Durametric display 100% TPS?
what is the effect of a stuck Variocam solenoid?, at what rpm does it activate?, the signal in Durametric indicates a solid 3.0 degrees throughout the range so no change there

:-/

Help anyone?

 

Low power at full throttle is normally associated with incorrect/restricted air/fuel OR restricted (stopped up) cats. Since you have some faults codes to help, start there.

Test fuel pressure.

Disconnect MAF sensor and drive ...NOTE: will set MAF faults

Monitor MAF specified valve vs actual value

Inspect MAF sensor for cobb webbs, leaves ect. Can be an issue especially after changing air filters.

ASSUMING you have E-gas, manually open butterfly and see if you get high 90's% percent throttle value( if you cable throttle just floor the pedal)

More detail for your lamda readings will be necessary for further help

 

I have only looked at the CATs from the exit side and they looked ok there, I'll give them a look before the cats as well.

I'll measure the fuel pressure as well.

I'll give it a go to disconnect the MAF

Regarding the TPS (my car has mechanical throttle), it registers 69% at full throttle. I have inspected the throttle flap itself and it is fully open at 69%.
The weird thing is that when I remove the TPS and turn it by hand I still only get a max 83% which is still too low. I have tried both the old TPS and the new and they both record the same numbers so I do not think I has an issue at the TPS itself.

I will do a run and make a log

Regarding the MAT, I assume you mean that I should compare the Actual MAF towards the Specificated MAF which is the calculated number shown by Durametric right?, if so the the calculated number is way too low, (or the measured is too high)
However isn't the calculated number(Specified MAF) based the parameters of TPS, temperature and RPM? which means that if the TPS value is way wrong then the Specified MAF will be way wrong too?

Is the ECU dependant on the measured MAF or the differentiated calculation between the MAFand the Specified MAF, basically it uses the Specified MAF as base and then adjust the mixture with the difference between measured MAT and specified MAT?

As I said earlier, Lambda values behaves correct for both banks at around 1.00 until something goes wrong then it becomes 1.25 which is too lean

 

You are exactly correct, IF the TPS is wrong, the specified MAF will be wrong also.

The DME uses TPS, Temp, and RPM, for the specified MAF table and is the predicted MAF value, but the DME uses the actual MAF value for the air/fuel ratio. IF the actual and specified values are too far apart it is supposed to set a fault code, but I have seen faulty actual MAF readings that were quite a bit off and no codes set.

The TPS should have three wires, one 5v wire, one ground, and one signal return wire. Test for 5v, and a good ground, something doesn't sound right with the TPS, should get a signal of over 90%..(above 4.5v)

I suspect you have a wiring or ground issue..

 

I'll check that,

I did a log this morning, it has a very low sample rate but you clearly see what I mean.
The first 15 minutes is the school run hence the low Throttle opening, it ends at about 7:53 (long idle period) after that I am picking up the pace a little.

I have sampled the MAT and specified MAT values and you can see the massive difference between the two, should these two values follow each other?.
The car runs really well with about 50% throttle(gas pedal procentage, not TPS) all the way to the red line but any more throttle opening and it feels choked.

Lambda is mostly behaving as I expect, but the Measured MAT is vey high compared to the throttle opening but this must be due to a failure in the TPS somewhere.
Still though there are a number of samples in the measurement where the RPM is around 3000, TPS is above 25% in where the Lambda is bottoming out at 1,25, a clear lean situation.
I guess to have such a situation occasionally is not a problem but when they become too persistent the ECU will log an error.

I'll measure the voltage at the TPS end tonight.

 

I measured the voltage at the TPS end, 0; 5 and 5,6v respectingly.

After some more logging it looks like the lambda sensors show high values (1,25) after the car is restared hot after a 10min shut off, the cat has then lowred in temperature by 200degrees to around 250C

it takes a while for it to come back up over 350-400C but then it measures correctly again.

 

I looked at your log, The specified MAF and actual MAF are way apart..

Also I see that your TPS % never got over 67%, that is a problem. You should be able to see the actual TPS voltage on Durametric. Typical value should be .7v-.9v at closed throttle and 4.1v- 4.5v at full throttle, and should go up smoothly as throttle is depressed. If not within this range check the voltage directly at the TPS sensor on the signal return wire.

 

Ok, ill hunt for the TPS setting in durametric

 

I can not find any TPS voltage in Durametric, only %