im lost on engine

[poolsexpo]

ok, first off ive searched for hours and days, i cant find what im looking for. i have a 99 explorer 4.0 ohv, 125,000 miles on it. i bought the truck and drove it for about 3 months, during the summer here where it was on average 85 degrees out. about 2 months ago, i got a check engine light, i scanned it, p1405 so i bought a new dpfe sensor. unfortunately, on my way home the old DPFE sensor that was on the truck had blowen a hose, and it blew hot air onto the sensor which then melted and literally torched a penny size hole in my intake (plastic upper) manifold. i limped it home, changed sensor, went and got silicone tubing and changed it, i also sealed the hole by getting a piece of thin metal. i used a epoxy good for high heat and plastics. i layered it on intake, then stuck the metal on it, let it dry, then layered over the whole thing again to give it a extra seal. reset computer by disconnecting battery, all was good for about 3 weeks. then engine light again, this time the so delightful lean codes on bank 1 and bank 2, i think there 1071 and 1074. i cleaned maf, new air filter, checked iac and cleaned it, cleaned pcv valve, changed spark plugs since i thought maybe old plugs sucked. reset computer using same method as before. all was great, for 7 days. low and behold, same codes again. i seafoamed motor, used 3 cans of car cleaner spraying all around motor, didnt notice even the slightest rpm change. i replaced fuel filter and gas cap, still no success. i know there are several things i didnt mention to check for when this occurs, im not done just yet. since the day i bought the truck, i noticed it takes about 5 seconds for it to start when cranking first thing in the morning, after that its good any time of the day, only when it sits for a matter of several hours. so theres suspicion number 1. also, i had drilled 10 1/2" holes around the side and back of airfilter box, the bottom section of the box, not the part maf mounts to. i did this for better air, it helped some but could this cause unmetered air? i thought it would have zero to do with it since its before the maf sensor. then today, when the truck started, it hesitated and sounded like it was dieseling for aout 8 seconds before engine idle went up and smoothed out. if i build a smoke machine, where do i inject smoke on motor?

 

[SoHK_alumni]

Think the first thing I'd do would be to check fuel pressure. Poor/low pressure from a problem with the pump, filter or regulator could easily account for the symptoms.

 

[koda2000]

i think you mean P0171 & P0174. this indicates a good sized vacuum leak which is effecting both sides of your engine. i'd start my verifying your repair isn't leaking. what did you clean your MAF with and how?

 

[chefduane]

I went through the exact same process you are going through. Same codes, same symptoms, rough idle. Turned out to be vacuum leak at the intake manifold gaskets. Replaced both uppers and lowers and now she runs like a top! And with the MAF clean, new PCV...etc.. she really runs great. But not being an experienced auto tech, we tend to start to throw parts at it until a fix is found without actually zeroing in on the actual problem. Upside is that you got a bunch of new/clean parts so she'll breath easier, downside is you spend a bunch of money on unneeded stuff. I tend to fall into the "throw parts at it" crowd myself. But my cash flow is pretty good right now so I figure what the heck. Sometimes I even come here to get ideas on what to do next just because I need a weekend project!

 

[poolsexpo]

yea thanks, 0171 and 0174. ive had roughly 7,000 miles on repaired manifold. ive sprayed nearly a full can of carb cleaner right on and around surrounding areas of the repair i did, no noticeable rpm change was heard. is there a better test? ive heard the propane method, now, ive got one of those blue propane torches for heating up like solder or something, could i fit a length of tubing over its spout and run that around motor? i have cleaned the MAF with MAF cleaner, i sprayed it pretty good let it sit a while, sprayed it again and let it dry. i had a 94 explorer that i use to clean the MAF with carb cleaner, it never threw any code at me. is there a way to see if i need to change both upper and lower gasket sets? is it common for both pairs to go bad, or just uppers. i will do a fuel pressure test in the next couple of days.

 

[koda2000]

i don't know about using carb cleaner on a MAF. there is a cleaner specifically for MAF's. i think electrical contact cleaner might be acceptable, but carb cleaner is pretty potent stuff. i know you're never supposed to touch the MAF's element.

the best way to look for vacuum leaks is with a pressurized smoke test. if you're going to change the upper manifold gaskets/o-rings you'd be foolish not to do the lowers at the same time.

 

[chefduane]

if you're going to change the upper manifold gaskets/o-rings you'd be foolish not to do the lowers at the same time.

+1. Yep, do 'em both. They're cheap at RA and while you have it torn down, might as well do both sets.

 

[poolsexpo]

well, i couldnt get a fuel pressure tester today so i was not able to test the pressure.... accurately, i used a digital tire pressure gauge. it was able to reach far enough into the test port on rail to press in the valve, i also put a tube on the end so it fit tight over test port to TRY and prevent any fuel spray. i did get a reading of 32psi. i checked it 4 times all were the same. not sure how accurate that is, but it helped my hopes. i tryed to use propane to fine any vacuum leaks, even if i stuck the propane hose i used into the intake tube where the oil breather hose goes, i got no change in engine rpm. i tryed wd-40, i chose this last cause i figured if carb and choke cleaner didnt work, why would wd-40. wrong, with wd-40 i think i could hear the rpms change. i said screw it, started disassembling everything i thought needed to come off. im pretty good with general auto mechanics, and from the signs i was getting i figured it had to be gaskets. i had trouble getting the oil dip stick bracket off the stud holding egr bracket, i ended up bending part of it to make it come off. the upper gaskets where done, they didnt protrude past the face of the intake, holy crap, first real sign this could be the issue. looking at the gaskets, still seated on intake, i could see liquid on several of them, in several spots. assuming that was the wd-40 that was sucked in. pulled the fuel rain off, cleaned the crud off, and pulled off the lower intake gasket. surprisingly, it wasnt in bad shape, but like you all said, if your in there go ahead and do it, so i did. i soaked my injectors in a heavy degreaser, then set them in a Tupperware fuel of sea foam ( one of the greatest products for auto anything). hit them with a little brake clean and dryed them off. i put new o-rings on all injectors, vacuumed there seats out on motor to keep crud out, then sprayed a very light layer of wd-40 on top on bottom seats to help o-rings find there home easier. after reinstalling everything, doing a good once over i started it up and made a sound as if there was a socket rattling around in the motor. luckily, it only lasted about 5 seconds. i shut it off after about 2 minutes, started it again and it sounded perfect. what a change just the start up had from new gaskets. did a 10 miles test drive, took it easy but it felt way better, ran smoother, had a wider range of throttle response. thanks for the input on this subject everyone, im glad to finally of found the fix, i hope atleast. ill let you know.

 

[boominXplorer]

Just FYI you should have over 50 psi of fuel pressure. Granted your method of checking wasn't the most accurate but if you have the check engine light come on again I am going to say weak fuel pump.

 

[koda2000]

Just FYI you should have over 50 psi of fuel pressure. Granted your method of checking wasn't the most accurate but if you have the check engine light come on again I am going to say weak fuel pump.

your fuel pressure should be around 67 psi on a '99, of course using a tire pressure gauge is not a very good test. if you use a fuel pressure tester, you may find you need to remove the schrader valve from the fuel rail port to get an accurate reading.