1994 Ranger (Cali Emissions) - what determines EGR opening strategy?

[snopro879]

Hello everyone. I've been chasing this issue for months, but with the cold temperatures up here in Michigan, my efforts have been somewhat minimal. First off, it's a 1994 Ford Ranger 2.3L four cylinder from California, and yes it's a California Emissions equipped model. Late last autumn my pilot bearing failed, I pulled the trans to replace it and blah blah blah all is well. Except (not sure if this issue was related to pulling the transmission or not, but it's why I mentioned it) shortly after this little adventure, I stated getting a check engine light with very intermittent hesitation. I believe (it's been a couple months since I checked) I had a 332 and 336 code for the EGR, or should I said DPFE, sensor. As an ex Ford mechanic (newer stuff, that's why I'm here asking you guys), I've heard all about these awesome DPFE sensors and how often they needed to be replaced. So I threw one in, and the truck ran like a top again...for two weeks. So back to parts store I go and warranty the sensor. Same problem, same codes, immediately. I put an EVR solenoid on, and that was just a waste of money because it changed nothing. So, after saying screw it and driving with it acting up, this is what I've noticed:

Light throttle, like barely off idle, the truck feels like it's running out of gas. Bucking, jerking, and sputtering until I give it just a little more throttle and it clears right up. 25 mph in 4th gear, forget it. Throw it in 3rd and bring the RPM's up, and it runs fine. But, slow down to like 20 maybe and it'll do the same thing in 3rd. I can't tell if it's throttle or RPM related. Maybe it's load calculated, no clue.

Ok I'm getting off course here. So, if I pull the EGR diaphragm vacuum line, there's no issues. If I pull the EVR solenoid plug, there's no issues. The CEL does pop on for both though, but the truck runs great. Today I went out and revved it up to maybe 2000-2500 in neutral, and it started chugging and sputtering (everything hooked back up again). So, 99% positive the EGR is opening and the engine is eating it's own farts when it shouldn't be.

So what I'm gathering from all this is that the computer is opening the EVR solenoid in effort to open the EGR when this happens. My question is why? What conditions does the PCM look for when it says "alright lets test EGR flow"?? I never would have imagined it would run that flow test at low RPM low speed cruising (25 mph in 4th gear), let alone 2000-2500 RPM's no load? I even have an air/fuel ratio gauge (it was for a college project, no I do not think my ranger is fast by any means), and it becomes a blurry mess when this happens. If anyone has ever dealt with this or know's what Ford's EGR strategy was back then, please chime in. I'm pulling my hair out over this. Thank you thank you thank you!

 

[Mazda]

I never heard of any problems with the DPFE sensors. I have a 94 to with California emissions and have only replaced mine once. I will tell you that after I replaced the clutch the last time I somehow nicked one of the DPFE hoses down by the EGR tube and it game me a CEL light and code like you have. Took me a little while to find the problem with the hose, but replaced both hoses and also put some small fuel line clamps on them and all was fine after that.

Here is a site I used to help me figure out what was wrong. It's very helpful

http://easyautodiagnostics.com/ford/4.6L-5.4L/how-to-test-the-egr-system-1

 

[snopro879]

I did break one of the DPFE hoses from tilting the engine during the transmission removal, but I caught that right away and replaced it. I've also verified the orifice between the two hoses in the EGR tube is open. Thank you for the repose though!

 

[tomw]

I'd be looking at the MAF also. Has it been inspected and cleaned if necessary? It will respond to air flow fluctuation and can cause hesitation if it is reporting improperly.
I have heard of the hoses being swapped, but don't know the symptom. You can test if the EGR is causing the hesitation and surging by plugging the hose with a golf tee. At least narrow it down to the system causing the symptom.
tom

 

[snopro879]

I have cleaned the MAF recently and just cleaned the throttle body last night. I'm not sure what you mean by plugging the EGR hose with a golf tee, but as I mentioned, I'm 99% positive the EGR is the issue. Not the EGR itself, but the fact that the truck is opening it as the wrong time. I could try a good known MAF, but my main question for this thread is what sensors monitor EGR? I guess cause and effect more or less. Could the DPFE just not sense flow, causing the EGR to stay open in an attempt to sense flow? When should the system be trying to sense flow?

 

[kimcrwbr1]

Have you cleaned the MAF? Have you tested the TPS. What are the codes it is sending? When the engine is ideling and you jack the EGR wide open with manifold vacuum the engine should quickly stall. If not here is blockage in the egr or the egr diaphram likely has a hole.

 

[snopro879]

I'll verify the codes when I get off work today. Yes, MAF was removed and cleaned with MAF cleaner when this first started and it made no difference. I've used my vacuum mechanism to modulate the EGR and it does stall the engine if I open it up. I'm almost thinking about warranting that DPFE again but I'd feel horrible if I was wrong. As far as I know that thing should be the sensor that tells the PCM yea hey we have flow, cool.

I'll have the CEL codes verified in a couple hours, thanks everyone.

 

[snopro879]

Recent code is 335 EGR feedback signal is/was out of range - EVR or PFE. Memory codes are 211, 332, 337, and 543. I'll put in the meanings of those later, I'm on my cellphone currently. Note: I'm driving around with my EGR vacuum line off, so that's most likely the cause of the 335 code. I'll plug it in on the drive home and see what other code I get as recent.

 

[snopro879]

Well I chugged and sputtered my way home after disconnecting my battery to clear the old codes, and plugged in the EGR vacuum hose. An hour of traffic, highway, and a little bit of back roads left me with the following KOEO codes:

Currrent:
335 EGR feedback signal is/was out of range – EVR or PFE

Memory:
332 EGR did not open/respond during test or if memory code, did not open intermittantly – EVR or PFE
337 EGR feedback signal is/was was high – EVR

(definitions copied from http://www.troublecodes.net/ford/)

It's acting the same as always, only certain RPM/throttle areas it just falls on it's face. I'm beginning to wonder if that vacuum solenoid is variable, or if the computer is able to use it to compensate? Maybe the EGR diaphragm doesn't have the resistance it used to, and solenoid is opening it too much unintentionally?

Yet, with the KOEO 335 code, it definitely sounds like an electrical issue. I'm going outside (finally almost 50 F out, I can work without freezing my hands off) to trace the three wires from the DPFE. If I find anything I'll surely post it. Again, for those who have commented, and those who plan on commenting, thank you so much!

 

[kimcrwbr1]

Is there a filter on the EVR it is possible the air is not bleeding back into the diaphram to close the egr? 211 and 543 are stored in memory you need to erase the memory before running the codes again. Make sure everything is connected when the engine is running after you erase the memory. PIP and fuel pump don`t seem to be your problem.
http://www.ebay.com/itm/FORD-OEM-EG...Parts_Accessories&hash=item519fc19835&vxp=mtr
Under the grey cap is a filter that cleans the air going back into the EGR diaphram when it closes.

 

[kimcrwbr1]

Sorry didnt see you replaced the EVR solenoid. Maybe put a vacuum guage in the EGR vacuum line from the EVR and see how it responds with different throttle positions.

 

[snopro879]

I may have closed the case on this one, I'll let you all know next week once I get my parts and whatnot. I traced wires from the DPFE to the PCM, less than 0.3 ohms on each wire. Good to go there. Measured 5v ref coming in, but never seemed to see any voltage coming out, ever. I applied vacuum directly to the upstream port on the DPFE (with the vehicle running) and all of a sudden bam, it showed 5 volts (signal return wire). I watched as my vacuum gauge bled off from about 12 inches on down, and the voltage would jump back and forth from 5 to like...1.2, maybe 3 sometimes, down to 0, bam back to 5, basically all over the place. Again, this is as my gauge very smoothly was trickling down to 0 or atmospheric pressure. I have a new set of hoses (kind of buggerd them up removing them and checking them) coming this week, and I'll be back at said parts store for my third warranty DPFE. I'm kind of wishing I would have just bought Motorcraft from the get-go. Lesson learned. I'll post my results later, thanks everyone for your time.