99 ford ranger missfire/codes??? - Ranger-Forums - The Ultimate Ford Ranger Resource


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Old 09-15-2016
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99 ford ranger missfire/codes???

So I have a 99 ranger 2.5l 5 speed and im having some issues
it starts fine sounds like its misfiring specially in highers gears and at random times it will stall and die but starts right back up. I also notice when i start it back up the gas gauge drops about half of what it was. on a couple occasions on hotter days like 105f+ it will stall and as soon as i try to accelerate itl die intill i put gas in it then it will go for a couple of miles intill acting up again.

I replaced the fuel filter thinking it was clogged helped alot but still stalls and is under power.

it has 3 check engine codes
Evap code
Egr code
and code p1506 idle air control overspeed error

my real question is can any of these codes cause the misfiring and stalling?

Idle Air Control Overspeed Error

Read more: P1506 FORD Idle Air Control Overspeed Error | AutoCodes
Idle Air Control Overspeed Error

Read more: P1506 FORD Idle Air Control Overspeed Error | AutoCodes
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Old 09-16-2016
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The 1506 code is noting that the engine idle speed is GREATER than that commanded by the computer. The IAC is not responding to what the computer ordered, and is apparently sticking, and making the idle higher than desired.
If the IAC is gummed up, sticky, or dirty, it can keep the idle speed too high. I would remove and clean it, and see if that resolved the problem.
If the EGR is flowing when it should not, the engine will not run smoothly.
The vapor recovery canister, valve, tubing, etc are checked along with the gas cap. Make sure your gas cap is on tight, and the built in check valve working.
tom
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Old 09-16-2016
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Welcome to the forum

What are the EVAP and EGR code numbers

Yes, EGR can cause misfires and stalling.

But so can IAC valve problem.

After engine is warmed up and idling unplug the IAC Valve, idle should drop to 500rpm or engine may even stall, either is good it means no vacuum leaks.
if idle doesn't change then you have a vacuum leak, which can also cause a misfire.

Stuck PCV Valve is a vacuum leak, best to replace PCV valves every two oil changes.

To check IAC valve itself, unbolt it and then plug it's wires back in
Turn on the key/engine off
IAC Valve should now be open all the way
Unplug it's wires, IAC Valve should then close
Plug wires back in, it should open fully again.
Repeat a few times to make sure it is not sticking


EGR valve lets exhaust gases into the intake to slow burning in the cylinders, this lowers the temps inside the cylinders which lowers the NOx emissions.
EGR system is only used when engine is completely warmed up and speeds are above 30mph or when engine is under load, accelerating, going uphill, or pulling a trailer, so any time engine cylinders may heat up.


If EGR valve opens any other time engine will run rough and may be stall.

To test EGR valve you need a vacuum hose that fits EGR valve vacuum port
Remove EGR vacuum hose and put yours on it
Start engine
Suck on the vacuum hose and EGR valve should start to open, engine should start running rough if you hold it open long enough engine should stall.

With engine running check for vacuum on EGR valve's hose, there should be none, put your finger on the end of the hose, if you feel vacuum then EGR modulator/solenoid is leaking and needs to be replaced.

It could be there is carbon build up inside the EGR valve so it isn't closing all the way, hard to determine that without removing the EGR valve and visually inspecting it.

EVAP system problem could effect fuel flow but only after a 30-40 mile drive.
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Old 09-16-2016
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thanks for the replies guys.
The EVAP and EGR codes came up as non complete
Im gonna do the EGR test asap
Forgot to say when I stop at stop signs it does stay at high idle for about 5 seconds then it corrects itself.
I started my truck and disconnected the IAC and there was no idle change
I dont think cleaning it will help because I cleaned it 3 months ago and it didnt fix it so its bad.
anyways ive realized something when it dies if I try to start it from the current key position it wont start but if I bring it back to the off position and let the fuel pump prime again it will start would that have something to do with the fuel pressure? or is that normal
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Old 09-17-2016
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Yes, turning key off and back on could mean fuel pressure related but you are also rebooting computer when you do key off/on.

Usually loss of fuel pressure shows up more on cold start, because fuel pressure has dropped to 0 when truck sits for a few hours.
If you were losing fuel pressure while driving then engine would more likely stall at speed, higher fuel demand, not when stopping, lower demand.

But it is an interesting symptom, good catch.

High idle with a manual trans for 5 seconds can be normal, Ford was adding emissions software that would hold RPMs high for a few seconds during shifting, or when ever clutch pedal was pushed in, this lowers overall emissions because engine has more emissions below 1,000RPMS than above.
But this also means IAC Valve is at least partially working, the only RPM control the computer has is the IAC Valve, adding more fuel can't increase RPMs, only add more air can, so fuel injectors can't raise RPMs only IAC Valve, or Throttle plate can(or vacuum leak, lol)

Non-complete is OK if battery was disconnect recently computer takes it's sweet time in retesting EGR and EVAP systems.

EGR is usually a few days, EVAP a week maybe 10 days
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