Hi guys and gals,

I have done alot of searching but havent found anything exactly like my problem.

So I just picked up a 2000 ranger 2.5 5 speed 2wd.

When driving part throttle it is perfectly fine. However if you go full throttle or put a large load on the motor, like turning a corner in 2nd gear at like 20 mph then trying to accelerate, it sputters and has a hesitation issue. It doesn't throw a misfire code though.

The other problem is if I let the revs fall from say 2500+ the motor will die. If it falls from below 2500 the motor will catch itself.

It idles perfectly fine when it does catch itself around 750 rpms, however the idle stop is all the way out and not touching the throttle blade.

If I pull a vacuum hose off there is no change in the idle, it does throw the ST fuel trims up to like 40-50 if I pull a vacuum line off. It normally bounces between -4% and +5% while idling/cruising. LT is like 1%

Here is what I have tested/replaced.
IAC valve has been replaced
New wires and plugs
new coolant temp sensor
Fuel filter looks brand new, no rust on it still shiny silver
I pulled off the intake manifold and cleaned it out, put new gaskets on.
Injectors ohm tested fine at 14.6 each
FPR doesnt have any fuel in the vac line, and looks like it has been replaced at some point due to the return line being bright blue.
Cleaned the MAF with MAF cleaner, however it looked like it was cleaned by the PO, and I dont know what he used.
TPS reads 15.6% (on my scan tool) when the throttle is closed and 78% when it is wide open. This makes me believe that it is bad and not letting the IAC do its job since the TPS never falls under 15%

PO had a new timing belt put on a month ago.

When I bought the truck it had a #2 misfire code and wouldn't idle at all if cold, but that was a loose #2 plug once I found that the misfire code hasnt come back.

I am not sure what the next step is. MAF? TPS? CAT? Something I havent thought of?

 

Computers for fuel injected vehicles shut off the fuel injectors when you take your foot off the gas pedal, saves fuel, then it should turn injectors back on when RPMs are below 1,500rpms for idle.
(this is why you should leave a manual trans in gear when coasting down a hill, 0 fuel being used, it is also safer)

The stalling part means injectors are not restarting.
First thing to do would be to set the anti-stall screw(the idle stop) on the throttle linkage.
Engine needs to be warmed up and idling.
Unplug the wires on the IAC Valve(IAC Valve will close), RPMs should drop to about 500, barely running but running.
Adjust that screw to make that happen.

I don't know the % you should see on your scanner for the TPS, but if you measure the voltage on the TPS center wire, you should see .7-.9volts closed, and above 4.6volts wide open.
TPS often have slotted holes for adjusting voltage slightly.
If you slowly open and close throttle the TPS voltage should go up and down smoothly no jumping around.
If you get the closed voltage down to under 1 volt, but using gas pedal doesn't get it above 4.5volts, then google: ranger throttle cable mod
Throttle cable stretches so no full throttle
TPS is a Learned parameter, the computer learns closed throttle voltage but not wide open, and you would get a code if closed throttle voltage was bad in most cases.

The hesitation could certainly be the TPS, the TPS gives the computer a "heads up" to add more fuel faster than it can be detected by the MAF sensor via air flow, like the accelerator pump on a carb did, it added extra fuel to compensate for the delay in the main jets catching up to air flow.

MAF sensor issue isn't likely with the symptoms, you would have more issues, but not completely off the table.
Blocked exhaust is noticed first as lack of power at highway speeds, same with low fuel flow(clogged fuel filter) it is first noticed only at high fuel demand.

Unfortunately it looks like the PO was having the same issue, from what you have noticed.

The only OBD II codes seen have been the misfire codes, correct?
Unplug MAF sensor and start the engine, make sure CEL comes on and you can get a MAF code on the scanner, this is just to check computer sanity.

 

Yeah only code was P0302. I will check the MAF when I get back in town over the weekend. I will also measure the TPS with a volt meter. The fuel filter looks brand new but its cheap to throw on a new one just in case.

I was wondering about the exhaust as well but didnt think much since it only has 122k on it, maybe a clogged cat. I will try removing the cat and running an open header to eliminate that. I know I will get other codes due to no cat.

Thanks
Chris

 

You can just remove O2 sensor, it is the same as disconnecting exhaust pipe when testing for blockage

 

Wouldn't I have other issues with the A/R being so far off with it just hanging out in the open or are you talking about the second O2 senor?

Thanks for the ideas, its good to bounce ideas off someone else.

 

Volt tested the TPS and it checks out ok. .5-4.5.

So I also unplugged the maf. When it was still cold it didnt make any difference plugged in or not. Once the motor was warmed up and around 185* when I unplugged it the motor died right away, it threw a MAF circuit fault MOD$06. There was not a Pxxxx code though.

Wondering if it is a clogged exhaust or maybe something else fuel related like a clogged filter.

I tested the EGR valve by putting a vacuum line on it and sucking. The motor started to stumble and when I released the pressure you could hear the valve shut.

 

Talking about removing the O2 sensor so exhaust can get out that hole, you would be testing if exhaust system was partially block, removing the O2 is sometimes easier than removing an exhaust pipe.

I would adjust the TPS for .8 and 4.8, so loosen bolts and turn it slightly.
Unhook battery before doing it and leave battery unhooked for at least 5 minutes.
This will cause computer to reboot and learn new TPS voltage

 

I compression tested the motor today. Was 175-180 for all four cylinders.

I also grabbed a new MAF since I had a coupon to make it cheap. No change.

When I pulled the plugs out all were dry and looked good.

Next step is to unhook the manifold to check and see if the exhaust is blocked. I don't think that is the idle problem but who knows.

Also ohmed tested the coils. 13.3-13.5 all around.

I tried to pull the o2 sensor out but wasn't able to get enough leverage on it to crack it loose. I am going to try again tomorrow.

Another thought, what would the symptoms be if the timing belt was off a tooth or two? Is there a write up on checking the timing marks without taking the fan, fan clutch off?

 

If timing belt was off a tooth the compression would be down in the 120psi area.
At above 170psi your valve timing is good.

 

Changed out the PCV valve, a couple old vacuum lines and the fuel filter. No change

Also pulled out the O2 sensor and it didn't run any different with the o2 out so I am guessing the exhaust is ok.

I am out of ideas at this point.

 

I would do a couple of computer sanity checks.
With engine running unplug the MAF sensor, CEL light should come on fairly quickly.
Plug it back in.
Also do the same with the ECT sensor, CEL should come on.
Loosen gas cap and drive it that way for a day, CEL should also come on after a bit.
If you have an EGR valve unhook the vacuum hose on it and plug the hose with a bolt, drive vehicle, after warm up and when accelerating the CEL should come on.

 

Pulled the MAF while running after 5 mins no cel. Pulled the ECT no cel, even unplugged the o2 and didnt get a cel. Got pending circuit faults.

I decided to take it to a shop, he said he would hook up his scan tool and see what the PCM is trying to do. With the no cel's makes me wonder if the PCM got wet and is messed up.

 

Yup, does read like computer is monitoring things very well.

 

So the shop found the fuel pressure regulator was bad. It was pushing 65-70 psi at idle so it was flooding the motor. The part I guess is a dealer only so it should be here tomorrow to see if that is the only issue.

 

Well that's going to be interesting, 2000 Ranger doesn't have a fuel pressure regulator, so dealer sure won't have that part, or anyone else.

Fuel pressure on 2000 is suppose to be 65-70psi all the time.

I would ask them to be more specific, could just be a misunderstanding.

In the late 1990's Ford switched to a Returnless Fuel system.
This has nothing to do with the engine, 2.5l, 3.0l or 4.0l

Prior to the switch, the fuel system had a return line and at the engine end of this line was the Fuel Pressure regulator(FPR), FPR is controlled by Vacuum.
When engine is idling the vacuum is highest, so FPR was open and sent fuel back to the fuel tank via the Return line because engine didn't need it, as RPMs and engine load increased vacuum decreased so FPR closed to hold fuel pressure at 35-45PSI.

Returnless was chosen because it is cheaper, and less fuel was being circulated, and "warmed up" by flowing past the engine, this kept fuel in the tank cooler and in theory less fuel would be lost in evaporation, even though fuel tank is sealed, lol.
Anyway the correct fuel pressure for returnless is 65-70PSI.

Fuel pump on Returnless or return systems both have Check Valves to prevent pressure loss when key/pump is off, on Returnless system this would be the only Fuel Pressure "regulator", although regulator is a stretch because it doesn't use an external control.

 

Not a regulator, the damper? He ordered something so maybe I misheard him I was talking with him I between talking to clients so I only talked for a min.

 

There is a Pulse Damper at the end of the fuel rail, because of the higher pressure used the injectors opening and closing will cause pressure waves to form which can limit flow in other injectors, the pulse damper is just a rubber diaphragm that absorbs the pressure waves instead of reflecting them back along the rail.
It does have a vacuum hose attached in case of a leak, because of it's location it could leak on hot exhaust system, i.e. start a fire, so vacuum hose is there to suck any leaked fuel into intake.
So yes leaking pulse damper that could cause flooding at idle.
MPG would be way down as well

 

So after talking to him a bit more, the damper was bad but not like I was thinking. It was causing the motor to run rich at idle, replaced the damper and now its reading normal.

It is still dying when revved up.

Our theory is that the valves are sticking open due to a bad relief valve in the oil pump or I have a recessed exhaust valves like the posts below.

2.5 intermittent miss at idle - Page 3 - The Ranger Station Forums

page 3 post #26

https://www.ranger-forums.com/2-3l-2...stalls-102939/

Post 11 has his answer.

'99 Rough idle/Misfire 2.5L - Page 2 - Ford Ranger Forum

Page 2 post 28 and 30

The mechanic is leaning towards a bad pump/relief valve.

BTW Ron I wanted to say thanks for the ideas, you have been a great source of info.

 

Easy enough to throw an oil pressure gauge on the engine.
Gauge on the dash is just a switch, on/off

Drivers side toward the rear of the block above oil filter is the sender, remove it and connect oil pressure gauge, start engine, you will know instantly if there is too much oil pressure.
General rule of thumb is 10psi per 1,000rpms
So idle at 800rpms would be 8psi, 2,000rpms = 20psi, it isn't exactly linear, at higher RPMs pressure should taper off.

Recessed valve seats will show up on a compression test.
And are almost always first seen as a P030X code, i.e. P0303, misfire #3 cylinder.
So if you are not getting a misfire code the valve seat would be off the table

 

I have been getting a P0302. It hasnt popped up in the last couple times I have driven it but has popped up recently. I thought it was a loose #2 plug but maybe that is not the true cause of it.

He has the oil readings but I dont remember what they were off the top of my head.

 

Well update.

Bore scoped the block and it looked really clean, couldn't get a great pic of the valves but from what we could see it looked like the exhaust valves might be messed up.

Pulled the valve covers to see if we could see anything wrong, head was pretty clean for its age, however the exhaust valves were all sorts of messed up. The installed height varied almost 50 thousands from the high to the low. After talking to a machine shop, giving him the symptoms he replied with that he had just repaired a head with the same problems about 2 months ago.

The Cat converter is also plugged up upon further inspection, which would explain the exhaust valves getting too hot.

Ordered a new, remain., head from rock auto as well as a new cat, head bolts, gaskets etc. Should be in middle of next week will let you know how it goes.

 

Got the head off and inspected it. 3 of the 4 exhaust valves were recessed pretty bad.

Hoping to get the new head on and running tomorrow to see if that clears up the issues completely.

 

Thanks for the update

Hopefully you will be back on the road soon.