Something weird happened today..

[Devin Wright]

So, my Explorer has a new fuel assembly and a fresh tune up on it. What it was doing, was it would sometimes start and sometimes wouldn't. Would either do one of three things, either keep cranking and not turn over, start, but idle really low and I'd have to give it gas to keep it going or else it would die, or it would start, idle low and rough and me giving it gas would not do anything, and sometimes during the third thing it would do when I gave it gas it would die. I just put the new fuel assembly in it thinking that was the problem, as when I would hear the fuel pump kick on, 90% of the time so would the car crank up. I even took it to a mechanic for diagnostics, and they said nothing was wrong with it as it wasn't doing its bullcrap at the time. Said possibly my fuel pump could just wearing out. Now, it's started doing it's **** again. I went to leave the store today, and I went to crank it, and it cranked up, idled low and rough, and would die, and me giving it gas done nothing. After about 5 minutes of about wanting to bang my head against the steering wheel, it started right up, and was running like nothing had happened.

So, any ideas?

 

[Mbrooks420]

Idle air control valve?

 

[GTMountain]

IAC or vacuum leak. Perform a smoke test and pull your iac for cleaning.

Quick and easy smoke test (vehicle off):

Buy a vacuum "T", an extra length of hose, and a 2 pack of Swisher Sweets cigars. Remove your intake and cap off your throttle body with a plastic bag and rubber band. T into your vacuum system at the manifold with your extra hose leading to the front of your vehicle. Puff on a cigar and blow the smoke into the line. Place your thumb over the hose end between blows. Keep it up for the whole cigar. If you have a vacuum leak the smoke will come out where the leak is.

Mind you, that air leak may be coming from your injector O rings if you didn't replace them.

Alternatively, a bad connection on (or failing) throttle position sensor can give you the same issues. TPSs can be checked with a multimeter. Tie into the signal wire and ground and see if the value changes as you thumb open the throttle body.

 

[Devin Wright]

Ya know, I've not thought of any kind of air leak. Hmm, interesting. I'll have my friend who is a mechanic look at that today.

 

[ccm2001]

When its dealing with the pump not turning on, Check your Inertia Switch, also the pigtail it self, it usually melts..

 

[J_C]

^ Wouldn't that result in it continuing to fail to start, not work fine again later?

After the fuel sender/pump was done, did you swap the fuel filter since that is a good idea to do at that time? If so I am leaning towards suggestions already made, a vac/intake leak. Is it otherwise in good maintenance, spark plugs and wires not ancient, MAF sensor has been cleaned in the last ten(s) of thousands of miles? That's also a good time to clean the IAC.

Any check engine light on and OBDII trouble codes set?

 

[Devin Wright]

^ Wouldn't that result in it continuing to fail to start, not work fine again later?

After the fuel sender/pump was done, did you swap the fuel filter since that is a good idea to do at that time? If so I am leaning towards suggestions already made, a vac/intake leak. Is it otherwise in good maintenance, spark plugs and wires not ancient, MAF sensor has been cleaned in the last ten(s) of thousands of miles? That's also a good time to clean the IAC.

Any check engine light on and OBDII trouble codes set?

No, I have no check engine lights. I mean, the ABS light is on, but, I have no trouble with my brakes. And I just put a fresh tune up on it not long ago. The car is honestly in good standing as far as everything would go. If It didn't want to give me the middle finger every so often I'd be fine. But, it'll eventually start, I might have to try 2-3 times, it'll start. Sometimes, on a rare occasion (not done this to me in two months) it'll just straight up not start. And I'll come back an hour or so later and it fires right up. Like said, sometimes it'll either not start, or it'll start, but idle low and rough and only will stay on if I give it gas. Or it'll turn on, idle low and rough, and me giving it gas will do nothing, or when I do give it gas it dies. Could they all three be related?

 

[J_C]

They could all 3 be the wrong fuel to air ratio, or some cylinder(s) not firing. You could check fuel rail pressure, and spark at each coil, and/or hook up a scan tool that gives realtime data while running, but I tend to suspect a vac leak. The key is being ready to do a test when having the problem since the mechanic can't reproduce it.

 

[Devin Wright]

They could all 3 be the wrong fuel to air ratio, or some cylinder(s) not firing. You could check fuel rail pressure and spark at each coil, and/or hook up a scan tool that gives realtime data while running, but I tend to suspect a vac leak. The key is being ready to do a test when having the problem since the mechanic can't reproduce it.

Crap man. Ehh, I just been having this problem for a while and it's kinda always unnerving getting into your car and not being 100% certain if it'll crank. The other day, I had a guy offer to trade me a '88 Blazer K5 for my Explorer as he needed a 4-door car since he had a kid on the way. His Blazer had some problems with it but would've still been a good trade for us both, I'm an honest person and a man of my word, and I straight up told him that sometimes it'll start, about 80% of the time it will, but not always. And because of that, it lost me the deal. Couldn't really blame him, I would've killed the deal there too. Just, this car has made such an inconvenience for me at times, and with it only screwing up randomly, it's hard to get a mechanic to look at it.

By the way, I just read back through and saw this, I did not replace the fuel filter. I was planning on doing that here soon though. If that does not fix it, then it's gotta be something in the engine area.