Bad Misfire, No codes

[Mojavekid18]

Please help, im at a complete loss and really want my truck back.

1996 Ranger 2.3 2wd 5sp ~200k

About a week ago it devolped a bad misfire on the way home from work. No codes on the dash. Rough idle and almost had to dump the clutch to get it not to stall from stop.

Here is a list of what was already replaced before this happened within the last year that could possibly be related to it

Fuel neck
Fuel filter
Fuel pump
Motorcraft purge assembly-Checked every vac line, all have been replaced or look new
New motorcraft MAF
New accel Coil packs

What i've tried since the issue started/Tests with no avail

New motorcraft wires and msd irdium plugs

Compression is over 160 on every cylinder

IAC and throttle body have been cleaned-Tested IAC at 9.8ohms (normal
range from what i understand)

Pulled it apart today because i expected camshaft sensor or timing. Marks line up on the timing belt just fine

Camshaft sensor tested out at 355 ohms (again what i expect to be normal)

Currently have injectors out and soaking, have not tested them yet but no code was thrown for a lean condition or cylinder misfire and they all looked clean so im not expecting a problem there

What else should i test or look for? Im out of ideas

 

[Spott]

Double check the harness wires and connectors, for a start. If stuff isn't getting a good connection, it doesn't matter how good or new the parts are.

 

[RonD]

Bad gas?

 

[alfacliff]

my 95 did that, I didnt change oil enough, and the filter colapsed bypassing all the gunk into the hydraulic lifters, one stuck causing the valve to not work right on one cylinder. check the compression, or wwatch the exhaust header when the engine warms up, if one is colder than the rest, that might be it. I have also heard that these engines have a problem with cracking the head around the valve seat.

 

[falcon61]

ohm your throttle position sensor and probe for voltage at connector

 

[Mojavekid18]

I put a meter on the TPS and couldent get it to read anything across any terminals. Ill double check it but most likely getting replaced.

Also put a fuel pressure gauge on it and its only reading 30psi while running no matter what rpm your at. Seems low to me

 

[Mojavekid18]

So i checked voltage while running on the TPS. Moved smoothly from .8 to ~4v.

Unplugged the vac line from the fuel pressure regulator and it ran like a dream, and fuel pressure shot up to 40 and held steady. Im think that i have just found the problem!

 

[RonD]

Vacuum is highest at idle and fuel use is lowest, so fuel pressure should be lower at idle, vacuum is opening up fuel pressure regulator(FPR).
As you increase RPM, vacuum goes down, so as fuel use goes up FPR closes more, keeping fuel pressure the same.
Removing vacuum line from FPR should get max fuel pressure, 40-42psi
30psi is not too low, low but that shouldn't be your problem.

You can remove and plug that vacuum line and drive truck that way, to see if it makes a difference.

 

[Mojavekid18]

Vacuum is highest at idle and fuel use is lowest, so fuel pressure should be lower at idle, vacuum is opening up fuel pressure regulator(FPR).
As you increase RPM, vacuum goes down, so as fuel use goes up FPR closes more, keeping fuel pressure the same.
Removing vacuum line from FPR should get max fuel pressure, 40-42psi
30psi is not too low, low but that shouldn't be your problem.

You can remove and plug that vacuum line and drive truck that way, to see if it makes a difference.

Thanks! I couldn't find a straight answer anywhere on what the fuel pressure should be at. My next step was to drive the truck that way but i forgot to get power steering fluid when i removed the pump to test my camshaft sensor.

I did do a vaccum test aswell to make sure the fuel regulator is my problem and i am pulling 16 to 17 in. at idle. Seems about normal for a slightly worn older motor to me

 

[Mojavekid18]

ok so i have been driving it the last 2 days and its running about the same as it was. feels a little better but thats probably only because of the new plugs wires and cleaning of the TB and intake.

Now I have noticed the truck idles really low until its warmed up to full temp (like 600rpm almost dies)

Its low on power in the low RPM range and you have to really caress it if your on a hill and dont want to stall it

It pop/stutters/hiccups in low rpm crusing on the highway (55 and under)

Any other ideas? Would a bad IAC do this is or should i still be looking for fuel issues?

 

[Mojavekid18]

Ok so just and update for anyone who is having similar issues and comes across this thread. About 4 days after my last post i went to start the truck, it revved and then died. I Assumed at this point i should just replace the IAC and get it out of the way. Went to the parts store and on the way home the code for the IAC finally came on. This helped some but still the truck was idleing rough and was getting poor millage aswell on being down on power. Checked everything again and was stumped for a while until i replaced the PCV last night and that had made the biggest improvement so far. Idles smoother, more power, but haven't driven enough to check millage with any accuracy. I belive i need to tinker with the idle speed now because i went with an aftermarket IAC, but thinking the little bit of roughness still at idle should smooth out with a couple adjustments.

 

[AgPete139]

Good catch. Sorry for just now seeing this thread.

Glad you got it worked out, and I'm repping you for coming back and contributing a conclusion to your problem.