S13 Hesitation

[richcoosa19]

Hello everyone,

I have an 89 240SX (S13) SOHC 2.4. I have a problem with the car running and starting rough. When the car starts either it runs perfectly, or it hesitates during take off. The even wierder thing is when the car descides it doesn't want to start I remove the fuel pump fuse from under the hood, and turn the engine over and it will start and run for a minute or so. This makes me think the engine is simply running too rich, however I really have no clue how to tell this. I have replaced the throttle position switch, fuel pump, and cleaned my K&N filtercharger air filter. I found a vacuum hose that was broken, and replaced that too with no resolve.

I can be driving the car after starting smooth, and will turn rough. I do notice that if the car is idling smooth, I can be listening to it and it will kinda rev up on it's own. This is a dead giveaway that it's going to act up now. When I hit the accelerator, it hesitates and acts as if it's going to go dead and then revs. The EXTREMELY WIERD thing is that if I unplug my throttle position sensor, everything seems to work fine even though it lacks pickup through the vacuum system. But still it will not start sometimes even with the TPS unplugged, keep in mind I changed the TPS too.

I thought it may simply be bad wiring to the fuel pump, so I hot wired my fuel pump, still no suffice. I'm almost convinced it's some kind of vacuum line problem, but I really don't know. Can someone lead me in the right path?.....please.....

[J_Spec_NiTeMaRe]

http://www.240sx.org/faq/index.html



Clean your coolant temp sensor contacts and make sure your MAF is working right. Then service your AIV valve. If it's not gone after that, troubleshoot with that link.

[richcoosa19]

I found and fixed the problem. On the intake manifold, there is a plug infront of all the injectors that wasn't making good contact , I replaced the plug along with resoldering the wires and voila, like a new one.