I have a wierd issue with my Z that has persisted for over a month or so. On the first start up of the day, my Z runs way too rich. On a hot day it is just barely driveable, but on a cold morning it is basically undrivable. The car chokes and struggles to rev due to the excess fuel, occasionally will also have "popping" sounds from the exhaust. Even on a warm morning, with the car warmed up to around 70ish deg, and driving for several this still happens . But if I turn the car off, let it coast for 4 or 5 seconds and then turn it back on, the problem dissapears and she runs like a dream again. This also fixes the problem on even the coldest of mornings, with the Z below operating temp. What is going on here? What is the cause? How do I fix it, and why am I able to overide the issue via restarting the car? To help in diagnosis, my Z is a 1989 manual TT, stock ECU chipped and tuned, reasonable fuel usage for its power level (244rwkw). Serviced every 5,000km.
Sounds like something is kicking her into knock map on startup. Run your error codes and see if it can pin-point the problem. Could be the usual culprits like the CTS or the Det sensor. Re: the restarting the car fixes the issue, does this only work if the car is warmed up? Or does it work with temps below 65deg? *if* it only work when warmed up, then it's a glitch somewhere within the CTS circuit as below 65degrees your in a form of knock map and it may be that the ecu only registers the higher temps once you restart it. It could also be the sender itself giving a false reading so remove it and give it a good clean. It doesn't answer the undrivable question tho. There may be an issue with your TPS showing high throttle numbers vs the actual air available, coupled with a rich mixture could make things difficult. A Any work done on the car lately?
Restarting the car will fix the problem even when it running below 50deg, it is quite puzzling. And when I say undriveable on first start on a cold day, it really is. It's normally good enough to get out of the driveway, but wont rev over 2k rpm, and feels very clogged and slow due to too much fuel. Once I get 200m down the road it struggles to rev at all! Pull over, and turn off engine, count to 5 and restart and it runs fine for the rest of the day. The only work that was done before this problem presented itself has been a heater core bypass and having boost leaks diagnosed and fixed, and a power run on the dyno to check how power was holding up. I will see if I can check for error codes on my lunch break.
There are a number of possibilities...all electrical, seeing a restart cures the problem it's going to be difficult to test whats working and whats not. Does it idle? If so try this tomorrow morning Start the car and ensure that the symptoms are still present. Leave the car running and pull the CTS plug and squirt some inox or similar into the pins. Replace it, ensuring it's on nice and tight. Test. Pull the AFM plug, squirt some inox or similar into the pins. Replace it. Test. Do the same with the TPS plug, the 3 pin plug attached to the front of the TPS. Now if one of these work clean out the plug properly and tighten the female pins up. It may not neccesarily be the plug, and if your symptoms represent themselves the next day then it may actually be an issue with the sender, or possibly, but improbably the ecu.
Thanks for the advice Andy. Yes it idles fine on start up. Where is the CTS plug located and what does it look like? Is there a diagram in the tech section? And further noobness, what is inox? Thanks again.
On the top alloy water pipe coming out from the block (at the front) there are 2 electrical connectors. The one on the left (has 2 pins) is the CTS, the one on the right is for the temp gauge. When you pull the CTS plug the auxiliary fan will kick on, probably one of the most common cause of over fueling in these cars to date. It is interesting though that it can cause massive over-fueling in some cars and not noticeable in others.
