Hello everyone. My apologies for not reading all the older threads but I finally registered so I could get some other opinions

. First, some history. This is a 2008 4x4 that I bought in 2011 with under 300 miles on it, had never been sold retail. I experienced my problem the day I bought it and every time I have driven it since after the engine cooled off some. I don't believe it has ever gotten any worse, just more annoying since I have not been able to figure it out.

The truck now has 57,000 miles, sets no codes, runs fine when warmed up (I can barely feel it at times when warm but no one else can). This happens under very light throttle pressure, slight load and after the engine rpm has settled down to about 1000 after startup. It is better if you move the truck immediately with the high idle. There is no problem at all if you just stab the throttle until the next stoplight. It starts to diminish as the engine warms up and by 160/170 degrees it will be as good as it's going to get.

The truck has been well maintained and is in excellent condition. Remember, this has been doing this since 300 miles as a new vehicle. I have cleaned the MAF/IAT sensors a couple of times, changed the TPS and checked its voltage(.96) and swept it with both analog and digital volt meters, verified actual IAT and CTS temperatures with a scanner.

The CEL has never been on except for something of my own doing.

Even though there is not supposed to be any EGR input or vacuum to the EGR valve with a cold engine, it can happen. I disconnect the vacuum line to the EGR valve and it is smooth as glass. No hesitation or bucking no matter how light the throttle.

I have all three Ford service manuals and the Emissions manual for the 2008 Ranger. In those manuals I have found specs for the EVR and EGR valves.

The valve spring in the EGR valve is supposed to close the valve at 1.6" HG and lower.

The EVR valve at 0% Duty Cycle has a Minimum value of 0"-HG, a Median value of .38"-HG and a Maximum value of .75"-HG. At 33% Duty Cycle it has a Minimum value of .55"-HG, a Nominal value of 1.3"-HG and a Maximum value of 2.05"-HG. At 90% Duty Cycle it has In-HG values of 5.69, 6.32 and 6.95 respectively. The manual goes on to say the EGR valve is fully open at about 4.5"-HG and since EGR flow requirement varies greatly, providing repair specifications on flow rate is impractical. It also goes on to say "Note that at 0% duty cycle(no electrical signal applied), the EGR vacuum regulator solenoid allows some vacuum to pass, but not enough to open the EGR valve.

I know several things; 1) The EVR and EGR valves are functioning as they were designed and are not setting any PIDs, 2) All other sensors I have checked are within specs and are functioning as designed and also not setting any codes. 3) With the EGR valve vacuum disconnected I have absolutely no problem. 4) with a vacuum gauge connected I have vacuum present at idle and 0% duty cycle. 5) With a cold engine and slight throttle tip-in there is enough vacuum getting to the EGR valve to initiate flow causing the hesitation.

The amount by my gauge at closed throttle is approx. 1.4"-HG and with a vacuum pump connected I can start EGR flow at approx. 1.6"-HG at closed throttle. The vacuum from the EVR valve to the EGR valve will spike some when throttle tip-in occurs.

It is my belief that because of a stack-up of tolerances (like possibly slightly weaker than intended EGR valve spring and higher than normal vacuum through the EVR valve-verified) that I am getting earlier than intended EGR flow at light throttle applications.

I am sure there are things I have left out and there are many more things I could check but I am hoping that someone out there has experienced exactly the same scenario and that you can relate a fix! I really try to define my problem and what will fix it before buying parts!!

I have spent hundreds of hours researching this online, in service manuals, testing etc and I have NEVER found anything online that mirrors my problem exactly so if anyone would have an answer I would be most grateful. (nine years driving this truck with that hesitation is enough!) Thanks for your time!

 

Welcome to the forum

Can't read your post, you need paragraphs, no I am not the grammar police, just would like to be able to help and can't if it's just one long sentence

The part I can read: "4.0L cold engine bucks/hesitates with light throttle"

I would clean MAF sensor first, common symptom, "bucking", on the 4.0l with dirty MAF sensor

 

Post edited with paragraphs. Try rereading now please.

 

Thank you

So it reads like you found the issue for the stumble, exhaust gases being added to intake fouling the air fuel mix


And since its a long term issue then its most likely a computer software glitch, it shouldn't be grounding the EGR solenoid valve at all with temp under 140deg
Computer uses a pulsed ground to open this valve a little or alot depending on engine load

Does your EGR solenoid use intake or vacuum reservoir as the vacuum source?
Reason I ask is because you should get a slight vacuum drop in the intake when you open the throttle a bit, which would offset a slight opening of the EGR solenoid
So if its using Vacuum reservoir source switch it to intake source, not a fix but a work around

The computer doesn't have preset values for the EGR solenoid, its a Learned value
It uses the DPFE sensor to calculate exhaust flow into the intake so it varies the ground pulse to solenoid to get the pressure difference at DPFE it wants for that engine load

But this EGR software should not even be running when engine is still in Choke mode, ECT showing under 140degF
You could check with Ford to see if there is an updated software for your VIN, or ask if they can reload original software, they do charge to reload or update software, I think its $100-$150

 

Hello and thanks for the reply.

The EVR and EGR operate off intake vacuum.

I plan to verify conditions thru pinpoint tests of the EVR, DPFE and signals from the ECM based on your assessment before going to the dealership.

I had also considered using a vacuum delay valve in the EVR to EGR vacuum line. It may also help but I was unsure of how the EGR would react under deceleration with the delay valve inline. What are your thoughts on that?

Also, there appears to be a wide range of vacuum level tolerances thru the EVR valve even without ECM command. Do you think another EVR valve may be better?

I really appreciate your time and thoughts on this issue as it has been bugging me for a looooong time and would love to get it resolved. Thanks much again.

 

EGR should get vacuum to open ONLY during acceleration or cruising, pretty much only when there is a load on the engine

Exhaust gases are added to intake slow the fast/hot burning of the richer air/fuel mix under load, richer mix burns faster/hotter and that causes a spike in toxic NOX gases, so slowing the burn prevents temps for going too hot so less NOX is produced
By product of EGR system is less pinging with Regular gasoline under load as well, 87 octane can pre-ignite as cylinder temps get too high

So I don't see how delaying vacuum would cause an issue, you could even try a PIN HOLE leak in the EGRs vacuum hose, to dissipate the "acceptable leak" from valve

And not sure that the EGR solenoid should leak vacuum and be acceptable, its a valve, like having a dripping faucet and having the plumber say, "oh that's the way its suppose to be"
I understand Ford listed parameters for older vehicles but doesn't make sense if you are having a problem because of that leaky valve, which it seems what this comes down to, a leaky vacuum valve

I test Vacuum valves by blowing thru them, if I can they leak, if I can't they pass, if they click open with 9v battery that is, lol

I love science, but real world and science/engineering can butt heads on quite a few things, "on paper" is not always correct way it works in the real world

 

Hello! Update since my last post.

I have tested out the DPFE, EGR, EGRVR and the supply and ground paths to the PCM. I have used a DVOM, vacuum gauge and a Bluetooth app on my phone with a BlueDriver Pro Scan Tool. (You may be familiar with it) I also used a diagnostic procedure for testing these components from EasyAutoDiagnostics.com. and followed along with the Ford service manual Pinpoint Tests (many of Fords pinpoint tests are looking for solutions to DTCs which I don't have). In conjunction, I test drove the vehicle using the BlueDriver app and verified vacuum actuation of the EGR valve which mirrored the app.

All components tested to be within specs and operating as they were intended. Both coolant and intake air temperatures are correct, the mass airflow sensor is within specs and the TP sensor is working. All inputs associated with the EGR function seem correct. This morning I test drove my truck from a cold start (coolant temp around 90*F) and made several attempts at light throttle applications using the BlueDriver app and the vacuum gauge as verification. The app contains a result for "Commanded EGR vacuum" which was active from the very first test drive and verified with the vacuum gauge. It is clear to me that the EGR vacuum actuation is NOT being blocked by the PCM even though the coolant temperature is well below 160*F.

This brings me to "where do I go now"? I do not know if it is possible to toggle the EGR vacuum delay on and off in the PCM. Would a software update or re-flash of the PCM correct this? (This may be why the truck only had 300 miles on it and never had been sold when I bought it!)

Anyway, any thoughts or suggestions you may have would be very much appreciated. I will come back at a later date with an update on how it came out. Thanks so much for all your help!

 

You could ask Ford dealer to check VIN to see if there is a software update, or if they can reload the original software

 

Update; I took my truck to a Lincoln Dealership to have the ECM checked for an update and re-flashed. I was not able to stay with the vehicle and have not personally spoken to anyone connected with the service since completion. My son works there and he brought me the vehicle last night. He told me that they were able to install a transmission update but the ECM would NOT accept a re-flash as there was no update available. I tried it this morning and was as expected, no improvement!!! I am under the impression that the ECM could be wiped clean and the original program reinstalled. Would I be correct in that? Where should I go now to find a solution? Is this just a situation where the tech just doesn't know how to fully utilize the capabilities of the tool? Thanks again

 

Don't these use a solenoid to open vacuum to the EGR? What happens if you unplug the solenoid? Does the EGR Close?
Could that solenoid be stuck open? And If you disconnect the solenoid wiring, do you get a code?
If you disconnect and plug the vacuum line at the EGR, do you get a code when under load (not at idle)?
I don't know if the solenoid has a specific in and out port for vacuum or even if it matters if the vacuum lines or switched, so maybe check on that.

 

Hello, I will answer your questions one at a time. Yes, it has a solenoid that controls the vacuum but even the Ford service manual states there will be vacuum present at idle, just not enough to activate the EGR valve. If I unplug the solenoid I still have vacuum present. The EGR is closed. It operates as designed, it's just that it also operates when the engine is cold and supposed to be blocked (presumably by the ECM). The solenoid is not stuck open and yes, unplugging it with the switch on sets a code. Yes, with the vacuum plugged at the EGR valve and driving the truck it will set a low flow/no flow code from the DPFE sensor. Yes, the valve has two ports that are specific and, yes, the routing is correct. It is my belief that it is ECM program related since it has been going on since buying the truck as new with under 300 miles on it, never sets a code except something I create and runs fine when warm. Thanks for your response.

 

As I said before I took my truck to a dealership which didn’t work out at all 🤬. They told me there was no update available, they couldn’t get my PCM to accept a reflash and they didn’t even try to wipe/reinstall it. Don’t know if it was just incompetence or lack of interest. Anyway, I bought a $10 vacuum delay valve and installed it inline between the vacuum regulator valve and the EGR valve. The result, light pedal acceleration is smooth as glass both cold and hot. The EGR works as designed and no codes/cel. For the first time since I bought the truck it is a real pleasure to drive. Thanks for the help 👍

 

Good stuff

Thanks for the update and THE FIX

 

Hi Know its been a while but i have the same problem.
can you send me info on what vacuum delay valve you got - i cant seem to find one that is available.
Thanks in advance.
john.
johnkenney@shaw.ca