Originally Posted by rustcollector

Not sure about the 4.0 engine as I have a turbo diesel, but I build fuel injected race engines so do have quite a bit of experience with many types of manufacturer fuel injection systems.
The symptoms you have described sounds very much like you have a fault with the cold starting system.
Now virtually all injection systems have one of to types of cold start devices fitted.
Option 1. The 6 cylinder 4.0 engine you have may have a seventh injector fitted to the inlet manifold so it injects extra fuel and acts like the choke system on a carb. It gives more fuel until a certain temperature is achieved and then shuts off. This is often controlled by a very cheap engine block mounted temperature sender that sometimes has a dual function in that it supplies info to the guage on the instrument cluster. If you have noticed wierd temp readings on the dash, it may well be this little devil . It is usually this cheap little sender that is the culprit.
Option 2. The inlet manifold has a bypass system. Sometimes part of the manifold but more usually a seperate device made of moulded plastic or cast aluminium. It is a rotary valve in a tube.
This works by being in the open position when the engine is at normal temp so the engine is drawing say 95% of it's air through the inlet system fom the filter and the other 5% through the valve that is piped of after the filter and rejoins the inlet manifold near the throttle body. For a cold start, the valve is closed, so the engine gets an artificially rich mixture as it still injects the same amount of fuel but is receiving 5% less air. So it still acts like a choke on a carb. The valve is sometimes operated by a water feed and a bi-metallic spring and sometimes(more common) by a small stepper motor. The valve usually siezes and 99% of the time it does this in the shut position so the vehicle is always in cold start mode, thereby running rich and difficult to start when warm. It can be removed from the vehicle (noting which way round all the pipes go and take the multiplug wire off. Clean with an aerosol can of carb cleaner and a toothbrush. (use the wifes, not your own!). Replace and hey presto!

As I say I am not overly familiar with the 4.0 6cyl engine but I would bet it uses option 2.
I hope this helps.
Darren.
Feel free to ask me any other questions.

Originally Posted by Peeper

I was under the impression that the IAC, TPS, and an injector problem would throw a code. Am I wrong? I am about at my wits end on this, I don't want to wear out a perfectly good starter, and plus it running rich can't be good. I've already thrown money were I didn't need to i.e. Map Sensor, New Air Filter, Fuel Pump... I just don't know what else this could be with it not throwing a code.

Originally Posted by 98jeepsrt6

i Dont think those will through a code they just go bad.. Also i was wondering if you have done a compression test, just to see how your compressions are. The idle air control, regulates the amount of air coming into the throttle while the engine is at idle... The TPS basically reads the throttle butterfly position and will send signal to ECU and will help determine fuel trim..

Also have you checked rail pressure? Since you changed the pump just check if its giving good amount of pressure at the rail.. Injectors.. are you getting fuel into the cylinders??

This is silly Q but when you did the plugs and wire did you put the wire in the correct order?

Originally Posted by Peeper

Oh and did another fuel pressure test last night, it was at 45 at key on, 50 idling, and dropped to 20 in roughly 30minutes, that's why I checked injectors. Injectors will cause a vehicle to not start when warm, but cold it will start all day. Rough idle, strong smell of gas, hard start, and declined gas mileage. I thought for sure I had a bad injector, but appears not to be the case.