Strange Boost Leak

[S2central.net]

As a quick test, why not bother another MAF and/or swap lambda probes with another car.

In saying that - seems odd it only behaves badly when up to normal temp - would be worthwhile measuring resistance across water temp sensor at rear of head which ECU uses for this. If it always thinks the car is cold then it could mess things up at part throttle.

Its often hard to root cause these things remotely.

[jonnaz]

its a 3b so dosent the ecu get the temp from the MFTS and its a temp guage sender on the head? the MFTS is new so is the lambda sensor and i have tested a new maf on the car and still it surges.

keep the ideas coming tho as i am baffled and will try anything to fix it.

i might pull the TB off and take it to bits.

Thanks

[S2central.net]

3B or otherwise - ECU does NOT read water temperature from MFTS on the water rail - it gets it from the sensor at rear of head (G62) - has a white housing on it.

Temp guage signal comes from MFTS - so does a couple of high temp alarm signals but ignore those for now.

See if you can read resistance across G62 - I have reference data on it at S2central.net you can compare with.

[prj]

Try different MAF and disconnect lambda.
Your ECU will not go to limp mode without lambda.

[jonnaz]

resistance across g62 at about 30°C is 1.38 ohms. i also measured the IAT resistance and that is 506 ohms. acording to the data sheet on s2central.net sugests the reading on the g62 is a bit low.

good tip on s2central using a connector with wires attached for the g62 test

i am goin to try measuring the resistance at operating temps.

[S2central.net]

G62 is 1.38ohms or 1.38kohms ????????

[jonnaz]

sorry kohms

just measured at operating temps g62 0.238 k ohms, IAT 511 ohms.

[S2central.net]

G62 and G42 seem to be OK then...

When you swapped MAF over - did you also reset the ECU (by unplugging it for ~30 seconds or pulling MOTOR fuses) ?

[jonnaz]

it was a while ago but prob not .the car flys if you put your foot down no boost cut or stutter its just at 1100 rpm where the problem is. i will try get a hold of a MAF again. but would a faulty maf not cause poor running all the way through the rev range?

how does the fuel cut off work as it is like the injectors are sutting off and on.