I am having an odd issue, where my Z behaves perfectly normally when started and will drive without issue for 3 to 4 minutes, after which time it has alot of difficulty building RPM or accelerating below 4,000 rpm in 1st gear, 3,000 rpm in 2nd gear & 3rd gear and 2,500 in 4th & 5th gear. It does not matter if I use light, partial or full throttle, either way the Z seems bogged down and can only build rpm very very slowly when under the above indicated RPM ranges. Once I (very slowly) get past the indicated RPM ranges the Z drives without issue again, until I change gear and then it will again struggle until it gets above the RPM spot in the next gear. Furthermore, if I pull the car over and stop for a few minutes, when I restart the Z the problem is no longer there for a minute or two, but it will reappear again after one - two minutes. The problem happens regardless of engine temperature - it will happen when the engine is cold and it will also happen when the engine is at normal operating temperatures. Does anyone have any ideas what this could be and how I can go about fixing it? So far I have cleaned all electrical connectors in the engine bay, replaced the temp sensor & temp sensor connector & replaced the TPS. The fuel filter was changed about 12 months ago. Air filter changed less than 6 months ago. I am getting code 55 - no errors. My Z is a TT slicktop, converted to manual with an na rear subframe/diff. Any help would be appreciated.
AFM should be functioning properly, going by the voltage readings on ecu talk, however I have a spare AFM which I will hook up tomorrow to see if it fixes the problem.
Btw, the TPS gives a voltage of 0.44-0.46 at idle, however I just took the Z for a drive & ecu talk shows the voltage under acceleration to rise, drop slightly then rise again, for example with accelerator pedal depressed or being pushed in at a gradual rate the voltage went from 2.02 to 2.30 to 2.10 back up to 2.54 (numbers only general & vary depending on how deeply I depress pedal but same pattern persists). Is this rise, drop, rise of TPS voltage normal or is there a problem here? I would think that the voltage should just be going up & not down in the middle as this would indicate the throttle closing somewhat?
There's crap on your tps. Foot flat should show solid numbers . Slowly depressing the pedal should show the readings climb cleanly. Good job finding it Replace, enjoy.
check connectors to TPS. strange one. I agreed with the voltage diagnosis that the TPS was the most likely cause. I would suggest you check the connectors for signs of green material in and around the TPS connections. Next I would check the ECU connector under the passenger floor. I am not at my pc now but I think the TPS goes to the ECU. It definitely looks as though the TPS voltages are erratic at some points. If changing the TPS does not change the voltages smoothly then there are few other causes. When did this occur? Was the car fine until this happened or did you get the car with this issue? MichaelZ
I cleaned the connectors when this problem first occured, there was a fair bit of green gunk on the TPS & connector, which I scrubbed off. My Z had been running great for a long time and then this suddenly just happened all of a sudden, after I had a heater/coolant hose at the back of the engine replaced & a coolant flush. Will check ecu connection next as reccomended as there us no further corrosion on the tps connector
Did you check the other connector downstream of the TPS? There's the onle that plugs in to the connector itself, and from memory there is another connector that runs alongside the passenger side of the plenum. Otherwise have you checked your timing? It's a long shot, but retarded timing could account for sluggish response. I sincerely doubt it would cause the range of problems that you have described but if you're running out of options...
Yep secondary tps connector cleaned but wasnt corroded. With base timing, it is sitting at 19-20deg at idle. Could this be causing it? I know that base timing normally should be 15deg? Mine may have been changed when I had it nistuned? Unsure as I did not check base timing before & after tune was done about 6 months ago
Sounds like the common problem of wrong plugs, TT's use a longer plug than the NA model due to the turbo's running con-caved pistons. If the wrong plug has been installed you will get hesitation until your at higher RPM.
Which plugs are we talking about here? So I can check. Thanks tho not sure that this is the case as when problem started no plugs had been changed?
Thanks will give this a try. I assume that you mean the earths on all the plugs? How would I do this? I have a multimiter but not sure how to use it? Has heaps of different settings
Solution!!! After trying just about everything elde I unplugged the O2 sensors. Success! Problem has dissapeared & runs much smoother now. However it feels like I have lost heaps of tourqe. Would unplugging O2 s do this? I get that fuel economy would suffer but didnt expect power to drop. Still on same 17/18psi like before
My bad. Boost is hitting a max of 14/15psi and not coming on as early as before. Must have accidentally reset the EBC. Problem still fixed though
