Removing EGR valve

[BrandonD]

Howdy guys,

Last week I purchased a ‘99 Explorer 4.0 OHV. It had been running lean and giving me the P0174 and P0171. Primary symptoms: long crank times, high and low idles, and lack of power at low idle. When ever I would engage the clutch, rpm’s would drop lower than normal (from what I remember from owning another 99’ 4.0 OHV about 10 years ago). Fuel trims were also running high. Started working down the list of potential issues (Google).

- checked for vacuum leaks (visual)
- cleaned MAF
- confirmed O2 sensors functioning

Started to consider the cause being a fuel delivery problem.
- changed oil and filter
- replaced fuel filter
Immediately noticed an improvement.
- replaced spark plugs
Begin to dissemble the upper manifold (to get to the fuel injectors).
- discovered no gasket at idle air control valve (now replaced)
- discovered no gasket that would normally sit under the upper manifold (ordered, should be here Thursday).
- removed and cleaned throttle body (wasn’t too dirty).
- removed and cleaned fuel injectors

Here’s where I got stupid...
- cleaned lower manifold but had also sprayed some carb cleaner into it. This ended up preventing ignition and flooded the engine. So removed spark plugs, allowed everything to dry out and with spark plugs removed ran a clear out “throttle wide open while starting the vehicle”.

Another big mistake, what I’m suffering through now, is I had noticed the egr tube was filthy during so I sprayed carb cleaner into it without considering the fact that any carbon that may break down would not have anywhere to go. Completely dumb mistakes - lesson learned and it won’t happen again.

I believe the EGR valve is severely clogged now. I can get the engine to turn over but it will immediately die if I do not engage the throttle and keep the rpm’s up. It is a very rough idle with detonations and backfiring. While revving, the engine actually sounds great. I think cleaning the fuel injectors solved a significant portion of the problem (still need to replace missing gasket in a couple days). The detonations have got me concerned. I revved the car long enough for what I would assume was enough to burn up any potential residual carb cleaner.

So, I am on a mission to clean up the EGR valve and tube (assuming I haven’t destroyed it) but can’t get the valve nut to free. I’ve read it is fairly common for the valve nut to be seized up like hell. I’ve been working on it all day, and have hit it several times with PB Blaster (haven’t tried heating it, don’t have a torch but will get one).

Anyone have any further advice on how to get this stupid nut to break? I soaked it with PB blaster and will let it sit overnight.

Also - any idea if I have caused irreparable damage, or if I should watch out for any other potentially damaged systems from my dumbass decision to spray carb cleaner into the egr tube while it was intact.

Thank you in advance!

 

[Turdle]

Your symptoms sound like the same mistake everyone here makes over and over again. Me included.

Recheck your spark plug wire firing order, and do it again. seriously. driver side is the side of coilpack where most of the confusion is

FRONT OF ENGINE

 

[BrandonD]

Good advice - I’ll check and check again in just a few hours when I get the chance. Will report back

 

[Runnin'OnEmpty]

..............So, I am on a mission to clean up the EGR valve and tube (assuming I haven’t destroyed it) but can’t get the valve nut to free. I’ve read it is fairly common for the valve nut to be seized up like hell. I’ve been working on it all day, and have hit it several times with PB Blaster (haven’t tried heating it, don’t have a torch but will get one).

Anyone have any further advice on how to get this stupid nut to break? I soaked it with PB blaster and will let it sit overnight.

Also - any idea if I have caused irreparable damage, or if I should watch out for any other potentially damaged systems from my dumbass decision to spray carb cleaner into the egr tube while it was intact.

Thank you in advance!

It's hard to loosen that nut without damaging/twisting the tube itself. There's a product called "Freeze-off" that you might try in addition to applying heat with a propane torch. Dorman now sells replacement tubes if you find you need one. Good luck.

 

[BrandonD]

Confirmed firing order is fine, I may need to retrace my steps and take it all back apart.

Car turns over, but immediately will stall. Sometimes at turn over, the rpm will surge and then proceed to die. I notice it dips to around 400-500 and hesitated for a split second, like she wants to get back up and go.

Also, white smoke inside of throttle body... oil looks fine.

 

[96eb96]

Count on destroying the tube and spending $50 for a new one. If not get a torch and try your luck.
make a metal blockoff for the EGR opening and tighten it up. If nothing changes the EGR isn't the problem. The only way an EGR can cause these symptoms is if its stuck open. I doubt that, the EGR system is very good at throwing codes. A blocked EGR valve will only throw codes. EGR is blocked at idle anyway. That being said, the EGR valve could be letting air thru and not sealing well.

Also, Monitor EGR DPFE voltage at idle (good scan tool). Should be no more than 1V I think (or.5), but def not more than 1. Has to match the voltage when the engine is off just before starting. If not there is an egr air leak.

Upper manifold should have rubber band gaskets around the ports.

I would like to know the MAF health(baro reading from a scan tool)
Possible Exhaust blockage
Possible fuel problem (did you check fuel pressure?)

 

[BrandonD]

Update:

Got away from the EGR Valve removal (didn’t want to accidentally destroy the pipe - yet).

Tore it all back down today with a buddy of mine and installed the new upper manifold gasket (which was previously MIA)

Confirmed no fuel injectors leaking, all seated correctly.

Found the damn PCV valve was not properly seated AND bad - replaced

After solving these vacuum leaks, engine was able to fire up and maintain itself but with an unstable (but less violent than before) idle. We determined MAF was no bueno - replaced and vehicle starts up and idles perfectly fine when cold.

After it has had the chance to get warm, idle drops to 600-700 and is rough. Let it idle for about 15 minutes and then took it for nice 20 minute cruise. Drives great. Whenever the idles would drop and get rough, I can ease on the throttle just enough to get rpm around 1200’ish and then I can fully back off the throttle - this’ll allow it to idle well as if it was cold, maybe after 30 seconds or so the rpm drops and rough idle will return. Could I possibly still be missing a small vacuum leak somewhere?

Thank you for the help guys, I really appreciate it. Long story short: a solid 8 hours of sleep and 2nd set of eyes may help get it done.


96eb96 - I’ll grab a higher quality scan tool so I can check these. Did not check fuel pressure, I will try to get that done this weekend if I can. Will drive it a bit and see if it will throw any codes. Thanks!

 

[donalds]

656rpm is normal idle

 

[Runnin'OnEmpty]

............

Tore it all back down today with a buddy of mine and installed the new upper manifold gasket (which was previously MIA)
............

This I don't understand. The 99 should have three double O-ring gaskets to fit the upper plenum to the lower manifold, not
a single paper gasket. Earlier models of the OHV did use a single paper gasket. If an earlier gasket is used, it will result in a vacuum leak because of the different shaped plenum. If the upper plenum has grooves in it for O-rings, then that is what should be used, not a single paper gasket....

 

[BrandonD]

Sorry for late update getting back here - Runnin'OnEmpty thanks for the heads up, that did end up being a contributing factor. Removed the single gasket that Advanced Auto had sold me and replaced with three double O-ring gaskets. The idle problem is no longer an issue.

I haven't had much time recently to get back under the hood but hope to be able to do so this weekend. Now, as it has been doing all along - it takes a good 3-5 seconds of cranking before the vehicle will turnover. Just did a quick run through of the forums to search for solutions (will continue searching), one suggestions is was to turn the key and make sure the fuel pump primes before turning over, and I have always done so, and it does. I've already removed and cleaned the fuel injectors, and replaced the fuel filter. Unless the next issue of a possible vacuum leak can cause this, the fuel pump itself may be needing replaced. However, additional to this problem - whenever I hit WOT, or even say 50%+ throttle: I get a loud whooshing coming from the upper intake. When engaging the throttle cable in the engine bay, it sounds like the upper manifold is sucking in air to fill itself up, if this is making any sense? I notice considerable loss of power on the street trying to accelerate under heavier load conditions. Casual drive around the neighborhood I do not notice any issues.

Giving me the P0174 and P0171. Long term fuel trim is around 15% while cruising on the highway, and responds under increased load by dropping to 0% in that moment. Tell-tale signs of still having a vacuum leak somewhere, correct?

Thanks for any guidance you guys may have.

 

[RickOTR]

Just a long shot but what about the fuel pressure regulator in the tank. On 98 and up the FPR is attached to the fuel pump and is known to go bad, but is replaceable without buying a new fuel pump. It's common on this model to go bad.

 

[pol-explor]

If I can:
What is FPR?

 

[donalds]

Fuel pressure regulator

 

[XLTrunner]

FPR = Fuel Pressure Regulator.

'98 must have been a transition year as my '98 XLT still has the regulator on the fuel rail.

 

[pol-explor]

Thank you and excuse me it was well written in your text.

 

[BrandonD]

Dropping in with an update here

Drove the explorer for the first time in 3-4 weeks on Monday. Noticed that it was idling very rough. Took the IAC off to clean it, although it didn’t appear overly dirty (I’m not a mechanic though, just a guy who likes to work with his hands and learn). Nonetheless, cleaned it out with carb cleaner, hooked it back up, reconnected the negative terminal on (had totally drained the power to force a relearn)...... and it idled like absolute dog sh*t. Would not relearn a better idle - I suspect while cleaning I dislodged some carbon and got it stuck deeper into the valve, or I caused the IAC to completely fail somehow. It started throwing IAC codes at that point.

So I replaced the IAC today.... and it idles and runs totally fine! Took it for a short 10 minute drive with no issues. I have previously been chasing possible vacuum leaks for bank 1 & bank 2 lean codes. Previously corrected 2 vacuum leaks, which corrected the fuel trims while under acceleration. Also, I have always had issues with a slow start in the last 9 months I’ve owned the vehicle. Lately I had been suspecting these lean codes as a fuel delivery problem, and was planning on replacing the fuel pump when I get the time. However, she now idles fine nothing yet but I’ll drive her tomorrow throughout the day. At this point I highly suspect the IAC has been faulty all along to some degree, and the vehicle has been relearning an incorrect idle. No more lots of power under load indicative of a vacuum leak (our fuel delivery issue), no more rough idle, fuel trims are sitting well, ECT is reading about 40 degrees higher than what it has ever read previously (and is now strong 175 after my 10 minute drive. Previously it never climbed about 135. Guy at the parts store told me that’s fine, and ok if it was reading cooler than spec. I should have known that was crazy talk, I’m still learning - not sure how the IAC may play into that reading, but it’s reading spec now (I’m happy to listen if anyone has that knowledge on how the IAC can affect that?). In the morning I’m going to try and start it while cold, without cycling the ignition to key on engine off several times before turning it over. Having previously suspected a fuel delivery problem, I was thinking the fuel pressure regulator was going out, located with the pump in the gas tank on these return-less fuel systems. I’ll be beyond thrilled if I don’t need to drop the fuel tank and replace that for a few more years, 2020 has sucked enough for everyone lol.

I’ll return with an update within a day or so! Hoping I’m not in that “excited thinking I fixed the problem only to be let down again” mode. Performed full blown upper and lower gasket replacement about 2-3 months ago, ready to be able to drive her around town with no issues.

 

[410Fortune]

If the lean codes persist:
Did you replace the large green O ring around the EGR tube where it enters the upper intake plenum?
Check FUEL PRESSURE
not once in this thread have I seen you mention checking your fuel pressure?

Glad you are slowly getting this sorted out!