random misfire and no misfire

[julio soto]

hi y'all soto here from houston TX got my hands on a 2000 explore 4.0 truck runs fin then it starts bogging out out wanting to turn off I have the p0171 and 074 lean codes that I now think it cuz of leaking cat but can find the reason for the random misfire really bad to where it almost turns off and sometimes does got a migraine already from looking for the problem starting ti think it ecu also will never start on first try and to crank two of more times to crank on this truck is kicking my behind

 

[J_C]

Most common reason might be a leaking intake manifold gasket. Other things to check are the other vac lines for leaks, check fuel pressure, and clean the MAF sensor.

It is not likely to be a leaking cat, or ECU. It's probably hard to start because it's too lean, too much air to fuel ratio as affected by the above possibilities.

 

[julio soto]

Most common reason might be a leaking intake manifold gasket. Other things to check are the other vac lines for leaks, check fuel pressure, and clean the MAF sensor.

It is not likely to be a leaking cat, or ECU. It's probably hard to start because it's too lean, too much air to fuel ratio as affected by the above possibilities.

Have already changed gaskets and have sprayed countless cans of cleaner around gasket and vacuum lines no leak today the ecu told me it read a c1 misfire then cleared up then it bogged out again and gave me a c4 misfire then cleared up but it bogged out really bad I did fine out the pump don’t turn on when I turn the key till like the second time I turn it and the pump it self don’t hold no pressure but don’t really know if it’s suppose to hold pressure or not I got 20-28psi after the damper on check valve on fuel rial

Ps thanks for reply

 

[J_C]

It would be good to list in your sig or your vehicle info (or both) which 4.0L engine you have, OHV or SOHC? IIRC, year 2000 was the last year both were offered.

The pump is supposed to hold pressure. The moment you turn the key one notch from the start (starter engage) position it (fuel pump) should run, bring your fuel line up to pressure, then if you do not crank the engine it should maintain that pressure until/unless you let some pressure out testing it with a gauge, and take a long time for the pressure to drop much.

If you have a returnless fuel system (pressure regulator in tank, fuel damper on fuel rail) it should be much higher than 20-28PSI, around 65 PSI. I am assuming all year 2000 (including the OHV) had a returnless system and if I'm wrong hopefully some one will correct me. You can see this for yourself by whether there is a second fuel line going back to the tank.

You might pull the vac line off the fuel damper after trying to run it, to make sure it is not sucking fuel through it. If it is not then the damper is probably fine and I'd look at the age of the fuel pump, sending unit, fuel filter, deciding what might need replaced. If it is losing pressure it won't be only the fuel filter, that could reduce steady pressure but shouldn't cause it to drop right away.

 

[Mbrooks420]

As noted above your fuel pressure is too low. Would explain the lean running condition and the hard starting.

 

[julio soto]

It would be good to list in your sig or your vehicle info (or both) which 4.0L engine you have, OHV or SOHC? IIRC, year 2000 was the last year both were offered.

The pump is supposed to hold pressure. The moment you turn the key one notch from the start (starter engage) position it (fuel pump) should run, bring your fuel line up to pressure, then if you do not crank the engine it should maintain that pressure until/unless you let some pressure out testing it with a gauge, and take a long time for the pressure to drop much.

If you have a returnless fuel system (pressure regulator in tank, fuel damper on fuel rail) it should be much higher than 20-38PSI, around 65 PSI. I am assuming all year 2000 (including the OHV) had a returnless system and if I'm wrong hopefully some one will correct me. You can see this for yourself by whether there is a second fuel line going back to the tank.

You might pull the vac line off the fuel damper after trying to run it, to make sure it is not sucking fuel through it. If it is not then the damper is probably fine and I'd look at the age of the fuel pump, sending unit, fuel filter, deciding what might need replaced. If it is losing pressure it won't be only the fuel filter, that could reduce steady pressure but shouldn't cause it to drop right away.

Thanks it’s a sohv I bought the sending unit already just didn’t want to install until I was sure I just drove it back to Houston from McAllen 360 miles all on one tank and no problems but did not turn off at all seems like when it starts off good it stays that way but I have an empty tank now so gonna install the pump and see how that goes still think it’s pretty good for one tank 360 miles 98% of them we’re going 75mph but will install pump and see how that goes and will touch back and no fuel return hose
Thanks again

 

[julio soto]

Ok I have removed the tank found a split hose between pump and what looks like a regulator guess now I know why I have low pressure

 

[tripog]

such a weird hose to split. if you ever have to replace the fuel filler neck hose make sure to buy it at autozone, the spectra replacement hose is known to split like that and autozone is the only store i could find that sells it with a lifetime warranty.

 

[J_C]

I'm surprised it managed to push 20+ PSI still.

 

[tripog]

I'm surprised it managed to push 20+ PSI still.

make sure your fuel pump check valve works once you get the new pump in, mine didn't and i put it off and off until i had a hard time exchanging the fuel pump for a new one. I should of just fixed it immediately.

 

[julio soto]

Didn’t use new pump after all just bought 1’ of hose and new clamps about $4 and now it’s working really nice now I get about 60psi and hello power lol gonna drive a while and see what happens now it’s starts right up
Fuel trims look a lot better and as of that other o2 sensor it’s marking I have no idea why this truck only has 3 and going to see if I can’t get all emissions to turn green once and for all
Thank u all for the help and info and hope this will help someone in the future