I think I have an"intermittent" EGR system (like twice in the last 5 years,in 15K miles) problem I had (still have?).Background: Conditions-hot 106+ at the bottom of the infamous Baker grade in Calif on I-15 on the way to Vegas. Top of grade maybe 95. Grade is about 6% in places and about 15 miles long. It's along pull from (900 ft to 4750 ft )and everything was fine. I dropped out of overdrive and maintaines about 60-55 mph. The eng temp gauge went up to about a two needle widths past halfway. I figure the temp might have been 215 or so. The vehicle is a class C motorhome on a '93 Ford E-350 chassis with a 7.5l engine. I crested the saddle and eased off the throttle and all of a sudden the engine started missing and loping and eventually died.The check engine light came on. After sitting a bit several minutes, it started up and climbed the rest of grade maybe another 3 miles just fine. A real sense of deja vu. Exactly the same thing happenned 5 years before at the same place and about the same conditions.I suspected that the EGR valve stayed open or was stuck open when it should have been closing with the reduced throttle. I holed up in Vegas(it being the weekend) Meanwhile I pulled codes 172 (HEGO indicates lean condition) and 334(EGR / EVP voltage higher than expected). I recreated the problem by pulling a vacuum on the EGR valve and sure enough the engine stumbled and almost died. I removed the vacuum and the engine smoothed out and ran normal.I also pulled the EGR valve off and did not see any obvious deposits that would cause it to stick. I worked it back and forth and it seemed relatively smoothly. I squirted some WD40 and did not see any significant difference in its action. Took it to a shop on Monday and they said that heat does weird things and didn't think they could do any more than I did.I decided to go back rather than have a nagging thing in the back of my head. Went back early in the morning (temp was only 89) Drove 300 miles without any problems. Is the solenoid a more likely culprit in this situation and is the one that "sticks"? After I got backI removed the solenoid valve and checked the resistance and it was 34 ohms. Manual says it should be greater than 20. The valve is plastic and there is no way to take it apart to check for any blockage or "stickiness". Appears to be nothing wrong with it. Obviously it works fine for 135K miles except maybe the two
incidents I talked about. I also checked the resistance of the EGR position indicator as I applied vacuum to the EGR valve.The readings were 3.4 Kohms at the closed position and 600 ohms at the wide open position. Manual says it should be less than 5.5 Kohms at closed and more than 100 ohms at open. The movement of the valve was smooth. Again everything appears to be normal which is what I expected since I drove back the 300 miles with no problems. So what has caused this weird problem to occur only twice and in the same place? But it didn't happen everytime because I've done that climb other times with comparable ambient temperature conditions. Maybe just a few degrees difference creates the problem. If it does, then the design might be marginal. I wonder if there are TSB's on this. Maybe I need to consider another possibility, even though the symptoms are consistent with a open EGR valve. Again the codes were 172 (HEGO indicates lean) and 334 (EGR EVP closed valve voltage higher than expected). Does the 334 mean that the computer ordered the EGR valve to close by means of cutting off the vacuum to it by closing the solenoid valve and the vacuum wasn't cut off and the EGR remained open with the higher voltage which I assume corresponds to an open valve? TO SUMMARIZE: IT ONLY HAPPENNED TWICE AT HIGH AMBIENT TEMPS AND AFTER EASING OFF ON THE THROTTLE. THE THROTTLE WASN'T FLOORED. ONLY A LITTLE MORE THAN LEVEL CRUISE TO MAINTAIN 60-55 MPH OUT OF OVERDRIVE. Any ideas would be appreciated.

 

This problem is deep!!..was the testing of the ohms are done on a cold motor ??can you emagine the heat of an egr valve after that type of pull..215 at the radiator but probable 400 to 500 just at the valve..you say you have 137 k mikes, maybe just a change out of the solinode and valve is in order..if you think that is the problem at least carry the new part on the motorhome to have incase the old one fails you on the road..
I have a 87 class A that is carbed so it is way different ,but I have an Egr valve on it and it is running fine but by looking at it you can tell it gets super hot..I have climbed that grade a couple of times my self..the heat being generated is tremendous..but getting back to the ohm readings..would the readings be different on a super hot motor then a cold one?

 

Uodate: The measurements were on a cold engine. Did some more checking. Disconnected Solenoid valve connector, applied 12v, applied vacuum with a vacuum pump, and the EGR valve stem moved up like it's supposed to. Removed 12 v and the EGR closed like it's supposed to. So there is nothing wrong now, which is what I expected. The only other thing (EGR system wise) that I could think of is maybe the computer did not command it to close? There is no way for me to check that. But I think that the code 334 tells me that the computer expected the low voltage for a closed valve it commanded, but got a high voltage reading -which means an open valve.I seriously doubt that there is any fuel supply problems. I would not have been able to manage that climb and then drive back 300 miles. I'm thinking of visiting a reputable shop that I know and maybe pay for a half hour's consultation. I don't think they would find anything that I didn't. The only way to test is either to do it again (climb the grade in the same conditions) which I don't want to do-neither does my wife, or if there is a place with a dyno and a way to simulate the ambient temps. I mean factory test lab with probably $$$ thousands an hour. Obviously that is not an option. So....I was definitely leaning toward thermal expansion factors causing it to"stick" because I saw no trace of obvious deposits to cause it to stick open. The fact that it fixed itself lets me think that was the problem.The shaft of the diaphragm part is nice and shinny. The pintle shaft and the cavity and ports have a fairly smooth light tan coating.
So in conclusion: 1)I'll see if the shop wants to consult. 2)I'll stay away from climbing that grade when it's 100+ in Baker. That means early in the morning or late in the evening. 3) I'll slow down to maybe 50-45 and drop into 2nd. 4) I think I'll replace both valves. Cheap insurance?

 

I think that you have diagnosed it properly..the computer forgetting to close it ,I think is wrong, It sent the signal to close and it didn't,Out comes the code..My valve did not shut...Part 4 of your conclusion is the way to go..Change it out and then carry a spare on the motorhome..I keep all sorts of spares on mine..starter,fan clutch,(that went out on me on that hill), coil, radiator hoses, fan belts..and I carry a small tool box that could change out all of these parts..For what it would cost to be towed in to the repair place that is closed for the day,you could have those parts and do it yourself..

 

i had the same issue on my '95 E350 w/ BB. in almost the same place. i had to pull the engine cover and sit for a half an hour. in my case, i finally tracked it to fuel boiling in the lines coming up over the tranny - when it quit the second time that day, i depressed the schrader valve on the test port and got a bunch of foam. remember how hot it really gets under that doghouse...

your mileage may vary
neil in san marcos

 

Thanks for the input Neil 95. I'm all ears. What were the conditions when this happenned to you? What was the temp in Baker? Were you easing off the throttle? Was it at the top of Halloran summit? Did you let it sit at that rest area at the bottom of the saddle? Did it happen again at the top of Mountain Pass? Or did it happen when you were still going up giving it gas? Like to hear more details. What is BB? Where was the second time that same day? Really anxious to hear more.

 

<What were the conditions when this happened to you? >
top of the long uphill climb heading out of Baker towards Vegas. 12 pass extended van pretty much full of people in june or july. HOT day


<What was the temp in Baker? >
over 100 easy


<Were you easing off the throttle? >
yes, rolling off after the long climb

<Was it at the top of Halloran summit? >
top of the hill east of Baker is all i know to say.

<Did you let it sit at that rest area at the bottom of the saddle? >
do you mean where the old gas station used to be? can't remember exactly, but i know i did make it off the highway at an exit

<Did it happen again at the top of Mountain Pass? >
where is Mtn Pass?

<Or did it happen when you were still going up giving it gas? >
no

<Like to hear more details. >
both occurrences were at a slow speed after high speed in high temps, air going max, van h2o temp in the "normal" range, tranny temp (probe in pan) close to 200 deg.

<What is BB?>
Big Block

<Where was the second time that same day?>
outskirts of vegas, some little strip mall. rolled in to park and just lost all power. pulled the cover, opened the doors, 30min later started like a charm. never happened since. i am on my second fuel pump tho'


<Really anxious to hear more.>
that's all i got fer now. ask away if you need more info. i'll do my best to answer.

 

Thanks Neil 95. Wow! This is almost a carbon copy of what happenned to me. Mountain Pass is the top of the grade after you dip down to the rest area. I believe the exit just after the rest area is Cima Rd. Anyways, very interesting. I also suspected "vapor Lock", but couple of things (the physics of it) still bother me. If it was purely heat due to the temp and the climb, why there were no problems climbing? Maybe it's just coincidence that it took that long (maybe 30 minutes) for the fuel to get hot enough to "boil? The fuel line is pressurized to 45 psi?, so that raises the boiling point, but maybe not high enough. The problem surfaces upon easing off on the throttle. The fuel is still pressurized unless the key is turned off. Then the fuel is at whatever atmospheric pressure is and at those temps it could boil. So the question is what does easing off the throttle do to lower fuel pressure? I don't know off hand. The other question is why did I get the 334 code(EGR open when should be closed)? Maybe the vapor lock is the second domino in the chain, after the initial sticking EGR? Did you pull any codes after your incident?
I guess the only answer is DON'T CLIMB THAT GRADE IN THE SUMMER DURING THE DAY! I guess there must be a design issue that pops up only under those conditions. Like I said mine happenned 5 years apart.
I could go on about a problem I had with a '73 Dodge class C w a 360. But that was carburated with a mechanical pump. Long story short. I used to get vapor lock only above 6000-7000 ft AND hot (90+), but not all the time. I could be lower and hotter(Baker grade) or higher 10000+ft but cooler and no problem. Nothing worked, I moved the fuel filter between the pump and carb, etc. It took six years to finally solve it, because the problem would only show up only every other year when I went high and hot (Utah I-70). Anyway, it turned out to be the replacement fuel pump which was not the OEM. I replaced all the auxillaries, fuel pump alt, water pump, etc. when I rebuilt the engine. The preplacement pump flange was a different thickness than the OEM. I installed the OEM brand pump and went 10+ w/o problemsfor 100k+ miles. The different thickness allowed more heat to be transferred and fuel to boil in the pump.
Thanks for your input. Anybody else out there with similar experiences?

 

I don't think that it is a vapor lock problem..in a efi system,the fuel is looped back to the tank so you are constantly getting cool fuel to the injector rails..the egr stuck open will kill the engine as you let off the throttle as you crest the hill..it cooled as it sat on the side of the road,closed and then everything was fine..

 

i don't have a solid answer either altho the only thought i have in favor of the fuel vapor lock possibility is that at full throttle you are consuming more fuel. you are also dumping a lot more heat down under the van possibly heating the already hot fuel/fuel tank. when you let off, you are using minimal fuel but speed decreases and undecar/underhood temps prob climb. the left bank exhaust crosses over under the engine where it bolts to the tranny at the back of the doghouse and the fuel lines travel up over the bellhousing very close to the left head and exhaust pipe.
also note that since that time i have replaced my fuel pump with no repetition of the discussed symptoms...

last comment is that the fuel _was_ foaming out of the test port the one time i checked it... my personal vote is for a fuel issue. just my $0.02 tho'. i have travelled in hotter climates since then w/o issue - north fork feather river and the roads leading to it in 110 degree heat in july heading to quincy.

the egr thought is certainly a valid one.

neil

 

Neil and others.
I think I solved the problem but NOT figured out a fix other than don't drive in 105+ temps. Anyways I decided in mid Aug to redo the trip to Yellowstone. Everything went fine, the climb up the Baker grade, the leg from Las Vegas to Cedar City, where it's considerably cooler. Climbed the Baker grade in the evening (8:30 PM) temp maybe 90 deg, slowed to 50-55 mph, a/c off. Left Vegas 6:30 AM temps around 80. Everything was fine, climbed an 11,000 ft pass(Beartooth) BUT, on the return trip 2 weeks later. Temp in Cedar City was 85. Went down into St. George , Utah where it was 103. Everything fine so far. Stopped in a shopping mall parking lot, wife wanted to get some things. Came out half an hour later, started just fine, AND THEN tried to drive and then same sympthoms (rough running and stalling) came back. After an hour or so (had dinner) it started and ran fine. Decided to stay in St. George( planned on making it to Vegas that afternoon). Next morning left at 4 AM and made it back to So. Cal. by 10:15 AM. with no probs. Temps were 75-88.
IT WAS HOT IN THAT PARKING LOT. The blacktop , it could have been 120 at a couple feet off the ground. So I'm almost a 100% positive it was NOT the EGR, because the problem occured a half an hour after the vehicle sat in that parking lot. I took the engine cover off, and could see the EGR valve was closed. I could feel the fuel lines and they were pretty warm (hot). Curiously, I tried starting, it would start, and then the fuel line would get hotter. and the engine would start to run rough and stall. It took a good hour before everything cooled down enough. SO THE PROBLEM IS DEFINETELY FUEL BOILING IN EXTREME HEAT.
I'm sure Ford is aware of what I would consider a marginal design. Others I'm sure must have had similar problems (Neil). Were there any secret warranties out on this? Is the fuel now more volatile than it was back in the '90s, Maybe the extra volatility (even between batches of fuel) and a few degrees of extra heat push the operating parameters out of the design envelope. What is a reasonable fix? Rerouting fuel lines? That does not seem to be a viable option? Any additional inputs/ideas would be appreciated. Thanks.

 

Your fuel theory is showing how little you know about how and EFI fuel system works.

 

sorry folks, i am going to bow out of this thread. TWICELOW, best of luck working on a solution. if i have any further thoughts i will PM you.

have a dandy
neil

 

http://blog.rv.net/2009/02/rv-doctor...ted-fuel-pump/

I think that this will help..