Whoa-a Cable throttle body has to have a throttle position sensor .I think Atrox was describing how to clean it .That is a basic .

 

Yes it has a tps, but there is nothing to clean on the sensor. he is referring to the electronic throttle body.

I replaced the tps with a spare and cleaned the cps. will drive it in a bit and see.

 

Well i swapped tps and thought i had it with an intermittent crank position sensor. no dice. cleaned all sensor connections. maf reporting normally.

Here is a video. 1 min and a restart later and it revs clean

 

Did you log the MAF voltage and compare between good and bad runs? The MAF values in kg/hr could be substituted values. Only the voltage is the raw measurements in Durametric. I still suspect your MAF and tune.

 

Can you compare throttle position voltage or % at wot after restart to a failed occurrence ? A marginal wire connection or bad ground could act like this .The big clue is that a restart clears the condition -whatever is wrong gets reset . Someone who knows the dme might have more insight .That is a good question for Softronics .

 

One more thought.......have you checked fuel pressure and flow ? This is a stretch but if the fuel pump starts pumping air it would diminish performance -also a faulty pressure regulator .I recently replaced my pump on the volume test you could see a combination of air and fuel -new pump all fuel .

 

I tend to agree that its some maf to dme glitch. i did not test raw voltage. what sort of result would indicate a problem?

Throttle position was the same before and after. no change there.

The fuel pressure regulator is mechanical so i dont believe that is an issue. fuel pump flowing air is interesting, but it seems odd that it would happen precisely after 30 min and would always happen at the same rpm regardless of load. you would think at easy throttle the fuel demands would be much lower.

The repeatability of this makes me go back to my dme glitch assertion.

Thanks guys for all the great suggestions

 

Actually with return fuel system the pump is constant -the only variable is the return .I may be way off but I think you could have a fuel delivery issue -starting with the fuel filter and working back .

 

I have seen cases where the MAF signal has drops out (goes to zero intermittently). To see that, you have to log with the highest sampling rate with only a couple of variables selected such as rpm and MAF voltage (so not to degrade the resolution).

 

thats true, but the mechanical fuel pressure regulator would control that on a vac signal, which I checked.

Fuel filter has maybe 2k miles on it.

I hear where you are coming from, but fuel filters don't reset after a restart. If the fuel pump was flowing air, why wouldn't it do so for the first 30 min?

What about variocam? would a bad actuator cause something like this without a code? Cam deviation at idle when hot is like 1 and 2.3 or so.

 

^^^ as said the sampling rate of the monitor is key....some sensors need a lab scope on them to really really read them for a glitch [my snap on scope has a glitch mode just for this]. i suggested looking at 02 sensors/injector on time to rule out fuel when the event occurs .

 

Maf voltage approx 3.9 at 6200rpm, no fluctuation or change when issue occurs
voltage above 13.6 at the obd port
tps remains steady when this occurs
02 sensor readings were inconclusive
Occurs in neutral at a stop as well as in gear
Occurs at damn near, if not exactly, 30 minutes after start
ignition timing does not change. at part throttle its about 30 degrees, closer to WOT its more like 20 degrees
ECT was between 196 to 208 degrees
rpm reading does not disappear during the issue

Maf, TPS, and CPS replaced with new or known working


maybe its just me but I'm going with Occams razor here....gotta be the tune/dme

 

Agreed.​

 

TPS steady -is the voltage the same between ok running and the event ? I assume you have all the evap stuff connected ? Will the Durametric report fuel tank pressure ?
I still think you have a fuel delivery issue .Here is why :The repeatability of the failure .The fuel pump runs at one speed -how the car is driven has no effect .For the DME to fail at the same time interval is dubious -

 

i wanted him to monitor the 02 sensors to check for a fuel problem [lean] he should have seen the ecm trying to get fuel in the motor by increasing injector time on,backing off the timing etc AND a cell but i think we both agree a couple more hours checking the fuel system is called for before yanking the ecm out .maybe a fuel pressure tester in line while road testing could help but it will not show volume,remember these cars pop a cel for a loose gas cap so i think the ecm should see a tank venting problem [key word should].