Wont start w/o fluid, runs on high RPM's on Neutral

[Lord_Explorer]

Hi eveyone,
I'm new here, just concidering to buy Explorer '94 2WD.
Engine has 125000 and wont start with out starting fluid.
Once it starts, runs on high rpm 2000 on neutral and about 1200 after engaging the gear. The regulation screw is all the way out so no more adjustment there. Any ideas if this is a small thing or the engine is about to finish?
Many thanks!
YouYou

 

[awood]

Just a quick guess...The idle air control valve (IAC) is what controls combustion air at idle (since the throttle plate is closed at idle, air has to come from somewhere). The computer will open/close the solenoid as needed, providing air to the intake manifold. In my mind, the IAC may be stuck open, making it too lean to start, and giving a too fast of an idle after starting. I suppose it could be a vacuum leak too. There are some vacuum lines that are hidden behind and under the throttle body and IAC/EGR feedback sensor area. Sort of a common area for leaks.

 

[AlphaTX]

I just finished diagnosing my father in laws 91 Ranger with the 3.0 that had the exact same issue.

His problem was that the air intake tube was old, brittle and falling to pieces. When we first got the truck, the idle was high. I simply removed and cleaned the Intake Air Control (IAC) valve. You'll see it easy enough as a cyndrilical looking thing on the throttle body/ intake plenum with a 2 wire electrical plug. It is a two piece unit comprised of a solenoid that pushes on a plastic coated rod in the tube. This rod can get gummed up which will cause it to "stick" open, or some small debris can also lodge it open. This causes more air intake than desired and the engine will rev up to balance the air/fuel mix.

I ended up replacing ours recently just because it was old, not because it was broke. its a $30-80 part depending on where you buy (rockauto.com, orielly's, autozone, etc).

I've since spent the past 2 weeks trying to fix the idle/CEL problems I've had after the IAC replacement. BTW, the IAC valve replacement didn't cause these issues, it just didn't resolve them.

Well, come to find out, the engine was running timing at 40+ deg BTDC (Before Top Dead Center). On the 91, this was checked by taking a white or yellow chalk (I used a yellow map pencil) and marking the 10 deg timing line that is etched in to the factory harmonic balancer. Then, with your favorite timing light, look to see were that mark lines up in relationship to the "pointer" on the Timing cover. For me, this "pointer" was just a little sharp jut of metal that came to the rough shape of a point and happened to be pretty close to the timing marks on the balancer.

Even though the engine ran "fine-ish" and I got it to idle around 900-1K Rpms... Once I returned the timing to the 10 deg BTDC that is factory for my motor, it idled GREAT and I stopped throwing codes.

My guess is that the previous owner had a host of issues that they fixed with a piece of black tape over the check engine light and massive timing retard. They basically caused the computer to use factory tables vs sensor input. I fixed the issues by actually diagnosing and correcting the problems.

 

[Lord_Explorer]

OK, Thank you for the tips, Will look for the issues in mentioned areas.
Hope to share my success here soon
Thanks guys!!

 

[awood]

On the 1st gen 4.0 the timing isn't adjustable. The crank sensor down by the dampener pulley provides the necessary signal to the PCM. There isn't any mechanical connection from the engine to the coil pack/distributor assembly - it's all electrical. The only adjustment on the 4.0 that I can think of is the idle screw by the throttle body. It's factory set and (in my opinion) if you have to adjust it, there are other problems somewhere else causing the problem. I've never had to mess with any of mine, so others here may have a different opinion.

There are several common issues with the 4.0, especially now since they are getting up there in years. Vacuum leaks have already been touched on here. The 4.0 is touchy about vacuum leaks (including intake manifold leaks - especially the lower manifold), air intake leaks (after the MAF sensor), dirty throttle body, inoperative IAC, and a host of other possibilities. I even had a Ranger with the 4.0 that had a vacuum leak at the vacuum switch mounted to the brake pedal. This switch is the cut-out for the cruise-control. I've also had vacuum issues with the plugs on the vacuum "tree", vacuum lines under the intake assembly, and just about anywhere where there is a vacuum hose.

To make a long story short, from your first post your engine sounds like it's ok, but some of the parts that control the engine are bad or in poor condition. Just start somewhere, and one at a time eliminate the possibilities. If you determine the intake and vacuum systems are ok, move on to fuel delivery or pressure systems.

If you're considering buying the vehicle, you'll need to be prepared to learn all the different quirks of this engine. 125K miles is pretty good for an engine that old, but if you don't have the time or inclination to baby it, it may be best to walk away.