Need help with my S13

[jim3798]

Hey guys I need some help with my S13.

I will give a quick back story to the car. I bought the car used last year and have been chasing wiring problems since the day I got it. It is an 89 coupe completely stock atm and is a 5 speed. It ran pretty good when I fist got it but always idled at around 1500rpm. After driving it for a while things started getting worse. It got to the point that the car just wouldn't start at all unless I pushed the gas pedal to the floor and cranked it for a minute which led to replacing all the vacuum lines which seemed to fix the starting problem.

Now comes the big problem I am having. The car is now idling at 2500-3k. I have replaced the MAF and TPS to no avail. I have done some searching and am now looking to pull and clean the IACV. There is another issue that has me confused though. The plug that goes straight into the TPS only has two wires (if looking at it bolted on, it has the bottom two and from what little I have found, the top wire in theory should be a ground). the TPS I put in still had the plug on it and that plug had 3 wires..... I have looking and looked but I can't seem to find this third wire in the harness any were and I am starting to wonder if there actually is a third wire in my car. I have tried looking but can't really seem to find any info on this. Could someone please clarify if there should be two or three wires plugging into my TPS and if there is anything else I should check/adjust?

I could really use some advice on this as this is my first real project car. I hope I covered everything and apologize for the long post.

[idlafie]

Use the SEARCH function here on Zilvia & see if you can find a link to download a OEM FACTORY SERVICE MANUAL from here on Zilvia. The factory service manual will tell you how many wires the TPS should have - check the wiring schematic - and what each connect to. I don't recall exactly, but I think the 89 has three wires, ground, ECU, and not sure if third is power or what....its been a while since I've seen one & I can't recall....that's what the FSM is for....

Cleaning out the IACV should help with the idle issues. Also check the Engine Coolant Temp Sensor & it's harness all the way back to the ECU. The ECU expects a signal from the ECT sensor tell it if the engine is hot or cold. IF the ECU doesn't get a HOT signal from the ECT sensor then the ECU thinks the car is still cold & tells the injectors to dump more fuel into the combustion chamber, hence the higher idle. Factory Service Manual explains it best...having to do with Smog & car going into "Closed Loop"

Anyhow, hope this helps....

ID

[rollout240]

^^^ agree. i had a similar issue with my SR. the coolant temp sensor was busted. i changed it and completely changed the idle on the car. no more bogging and high rpm idle.

IACV is a factor too. If its dirty it may not be reading properly. Check also that you are getting power to all those sensors. If it is an electrical problem and for some odd reason something isnt getting power then well you know. car wont function correctly.

good luck.

[rollout240]

Nissan 240SX Wiring Diagram (1990) | Circuit and Wiring Diagram (http://www.wiringdiagrams21.com/2009/01/10/nissan-240sx-wiring-diagram-1990)

there is a link to pdf files on the 240sx wiring diagrams.

good luck

[jim3798]

Thank you very much for the info guys and sorry for a late reply. I got into a pretty bad wreck(not in my 240SX thankfully) and haven't been able to get to the computer much less work on my baby. heh. I will get the manual and check the sensors. The IACV was pretty dirty and cleaning it did help quite a bit. Again thanks for the info. I am still pretty new to working with cars.

*edit*
After looking at the FSM and the diagram linked by Rollout (thank you again guys) it looks like the third wire in question runs (if I am reading this correctly) from/to the automatic transmission control unit. since mine is a manual transmission with no sign's of a swap, it would seem that it doesn't use/have that wire.

[rollout240]

cool man. hope everything goes well and that everything is cool from the wreck man!