Hot Engine / Won't Start or Rough Idle

Hi guys.

I originally posted a thread in the 3.0 section with this problem. After spending some time under my hood and actually looking at my engine it turns out I have the 4.0 and not the 3.0. I bought the truck from a used car dealership about 3 weeks ago. It's spent a week in the shop. They were unable to duplicate the issue of it not starting when it's hot.

If I run the truck until it completely warms up and then turn it off for 10 minutes, it either won't start at all or it'll idle really rough until the engine temperature comes down. The temperature light does not indicate that the engine is over heating. It's showing normal.

It had a leak in the intake manifold gasket. I had that repaired and I also had them replace the coil pack. I've read that the coil pack can cause a problem when it gets hot, it causes the engine to no start.

The not starting issue keeps happening (although less frequent, now it's mostly idling rough when its hot). Sometimes though, it'll start and run rough. If I step on the gas it'll eventually get up to speed and as the fan cools the engine compartment, it'll run okay but a little rough until I can start driving the truck normally. The engine compartment cools off and it runs 100% fine.

I cleaned my MAF last night, but I'm still having the problem.

Can anyone suggest what I might look in to next? I need my truck to start and run every time I use it. I don't like wondering "is it going to start yet?". When it won't start, if I let it sit for 45 minutes with the hood open, the temperature drops enough that it'll start and I can drive away.

It's annoying though and I want to fix it.

Thanks in advance!

8/21/09:
RESOLVED!

This entire issue turned out to be a FUEL PUMP that was going bad. It was providing ~20lbs of pressure. Just enough for the engine to run, until it needed fuel "on driver demand". It was fuel starved, as the pump couldn't provide the ~35lbs of pressure that it normally does. It cost me $278 to have a mechanic replace the fuel pump.

The mechanic stated that when you turn on the key and the fuel pump primes, it provides around ~40 lbs of pressure to start the engine. My pump was providing around 20, just enough to start and stay running, but it had a hard time under load but could provide enough fuel to drive it.

That really sounds like the MAF on a 94.

Good luck

When I took it out and cleaned it, it appeared to be in perfect condition. I took a close look at it and it doesn't appear to be damaged in any way.

Should I replace it anyway?

289-tiger- said:

That really sounds like the MAF on a 94.

Good luck

Click to expand...

On my vehicle there was never any damage observed, just mileage. The element on the MAF either accumulates debis or age hardens.

Good luck

Good info, thank you.

In the event that doesn't fix it - what else could it be?

Check the basics. If you think it is the MAF the rebuilds from the the big box stores are no good. Go for a quality replacement.

Good luck

Ugh, ok. The local auto parts store here had one that was a rebuild or something. It was $100.

How much am I looking at for a new OEM MAF?

Don't replace parts just based on suggestions like that. All it will do is cost you money and not solve your problem, unless you get very lucky. Diagnose, then replace. I just responded to your other thread about pulling codes with a paperclip. If anything codes come up, I can look up the troubleshooting info for you.

Your issue might also be as simple as THIS.

sounds exactly like my problem. or former problem.

If it if the same problem. try the fuel pump cycling. or replace the fuel with newer fuel you know doesn't have the butane in it.

Nhaz said:

sounds exactly like my problem. or former problem.

If it if the same problem. try the fuel pump cycling. or replace the fuel with newer fuel you know doesn't have the butane in it.

Click to expand...

Actually this is responing to Nhaz's mercedes quote.

Had a CLK cut me off in 99, same thing, he lost the side of his mercedes and I lost a wheelweight.

To the author as said, check all basics first before replacing parts but when you buy it make sure it is to spec.

Good luck

fastpakr said:

Don't replace parts just based on suggestions like that. All it will do is cost you money and not solve your problem, unless you get very lucky. Diagnose, then replace. I just responded to your other thread about pulling codes with a paperclip. If anything codes come up, I can look up the troubleshooting info for you.

Your issue might also be as simple as THIS.

Click to expand...

Thanks again for the troubleshooting assistance.

I don't think it's a fuel issue. It doesn't get all that cold in Florida, so I don't think they use a fuel mixture like that. Pump gas always reads 'up to 10% ethanol'. I'm not for sure though about a "winter mix" of fuel, I'm just assuming. I've used both Shell and Chevron gasoline. 89 and 87 octane. Now that I know to run 87 octane, I'm sticking with that.

As for pulling my own codes, I've been reading into that. I've purchased a test light to check it out with the KOEO tests. The last time it crapped out on me, the check engine light came on.

It managed to spin back up (although running rough) and in a couple hundred feet it was running fine again.

I've had the rough idle situation twice over my weekend. I just stood on the gas pedal and let the RPMs eventually rise. It cooled the engine compartment and it ran fine again.

Along the line of pulling my own codes...

Does anyone know where I can get a reasonably price, good code reading tool for my 94?

It appears most of the ones on the market are for '96 and later. I'm not looking to dump $400 to get one, but I wouldn't mind spending around $150 for a good reader.

Can anyone offer suggestions please and somewhere that I can buy one?

Thanks again!

You don't need a code reader for any Ranger prior to 1995. There is no difference AT ALL in what it will do for you compared to a paperclip and watching the check engine light. One flashes a light on a plastic box in your hand, the other flashes a light on the dash. Same number of flashes, same everything. I didn't realize you couldn't find them in the auto parts stores anymore, but they were only about $20 a few years ago. All they were was a plastic housing with a couple of switches and an LED light. Worthless on any RBV past around '88 (prior to that, you needed a test light because there was no CEL).

Wow, okay. Great information, thank you!

Would someone be willing to explain to me a little better than the tech library does as to where the plug is that I have to jack in to? I've looked for it, and I think I've found it but I'm not totally sure (it appears to be behind the fuse box under the hood, on the drivers side - but my plug doesn't look like the one in the tech lib picture).

The tech library says to use a test light, but people here are saying a paper clip. Where and how do I attach the paper clip please? Doesn't one end have to be jammed into the socket and the other end to a ground or a positive or something?

fastpakr said:

You don't need a code reader for any Ranger prior to 1995. There is no difference AT ALL in what it will do for you compared to a paperclip and watching the check engine light. One flashes a light on a plastic box in your hand, the other flashes a light on the dash. Same number of flashes, same everything. I didn't realize you couldn't find them in the auto parts stores anymore, but they were only about $20 a few years ago. All they were was a plastic housing with a couple of switches and an LED light. Worthless on any RBV past around '88 (prior to that, you needed a test light because there was no CEL).

Click to expand...

I'm not sure where that tech library article came from. It was obviously copied from some other source, and needs to be rewritten because it causes a lot of confusion. The only EEC-IV equipment that can go further than a simple test light or paperclip that I'm aware of is the Ford STAR tester, but I've never actually seen one - it was a shop tool and certainly not cheap. I'll have to go pop the hood on my Exploder to remind myself where the test connector is. On the Ranger it's on the drivers side fender just to the rear of the fuse box, under a cover that says EEC Test or something resembling that. There are two pieces - the large connector with multiple pins, and a separate single wire connector. You hook the paperclip between the single wire and the SIG RTN terminal of the large connector, as shown in the image below. You can ignore the test light/volt meter portion of the image because your Check Engine Light replaces it.