I'm posting this as a new Thread, but it's very closely related to other threads regarding poor idle, flat spots, pinging and stumbling under heavy throttle.

I spent over $1200 last year at a local dealer for a "tune-up". I basically gave them a blank check because my truck had reached the magical 100K, and I hadn't even had the factory brakes replaced. I decided it was time for some pretty major maintenance, and since I had a second car, I'd just leave the truck with them.

The first $400 was for the initial tune-up. For that, I basically got a set of spark plugs, a new distributor cap and rotor, and they MIGHT have read/cleared the codes. They called me up, and said it was ready so I went to pick it up. I didn't get a block from the dealer when I knew it wasn't any better, in fact, it was MUCH worse. I had oscillating idle, stalling out at lights (manual tranny, mind you) and the engine basically behaved like an asthmatic jack-***. So, I turned around and took it right back. I told them make it right. They kept it another week, and then decided to tell me they didn't have or couldn't get a set of Motorcraft wires for it. It was running better at idle, though, and I drove it home. I didn't have to climb any hills or really romp on it, so I didn't know the real problem would rear it's ugly head again. I bought a set of good performance wires and installed them, routing them EXACTLY like the original ones were. I drove it to work the next week, about 100 miles away, and had to go over one of the biggest things we call a mountain in Alabama. The truck started bucking and sputtering so badly, I had to clutch it to calm it down, and dropped all the way to 3rd on a hill I normally screamed over in 5th. During the week, I also noticed exhaust leaks. I checked, yep, busted manifolds between 2 and 3 and 6 and 7. Probably broke them when the engine tried to jump outta the truck. So, back to the dealer I go. Since there was no significant difference in the cost of a set of Ford Racing shorties and OE manifolds, I went with the headers. They kept it a week, and called me to come get it again. The bucking and snorting subsided to a mild sneeze and some pinging, and the dealer's grease monkeys claimed they'd fixed the problem by twisting #7 and #8 wires. Turns out, there is actually an advisory which says DO NOT do this. They made some really pretty knots in my new wires, pinched them in several places and left greasy paw prints all over them, but this is not what really set me off. The bunch of retards used a dremel tool to cut the fender well around a siezed bolt below the battery carrier, tried to pry the vacuum reservoir off the fender with a crow bar(puncturing it in the process), left everything on the right side just hanging in mid air, bent the hell out of the dip stick tube, left the coil support bracket dangling, pinched a vacuum line (red one to reservoir). I pitched a fit in their garage, and when it became clear I would get no satisfaction, I went back home and got out the digital camera. I took photos of all the damage, and sent them to the OWNER of the dealership, and mentioned Ford Consumer Appeals Board in the same e-mail. When I took it back this time, though, I gave them strictest orders to repair ONLY what they messed up, and leave the rest to me.

To make a long story longer, that is when my woes began. Over the past year, the performance has been getting steadily worse, fuel mileage steadily dropping, and me becoming a very unhappy Ford owner after many years of bagging the competition.

I replaced the O2 sensor, no effect.
I replaced the MAP, no effect.
I replaced the ECT, no real effect, slightly poorer mileage. (forgot to reset ECM)
I replaced the ACT (IAT). No effect.
Ran about 10 bottles of injector cleaner through it. No effect, except on my wallet.
Finally, I started the truck in my garage, and turned off the lights. It looked like a KISS Concert under there. So, back to the parts house, and a set of Motorcraft 8 mm OEM wires. Light show solved, idle slightly improved, light to moderate throttle improvement, but still shudder/miss under WOT. Ok, so maybe the Motorcraft plugs installed by the dealer last year were fouled. Pulled #1, and nope, not fouled, but EXTREMELY clean. Too clean. Lean miss was my diagnosis. Ok, next target, fuel filter. Again, very slight improvement on throttle, but still a bit of hack at idle and drop to 6 or 7 cylinders climbing hills. Now I'm getting quite anxious. I got a pretty fancy pressure gage and checked fuel pressure at the schrader valve. Hmm, 40 PSI with fuel pump test, 30 at idle, jumping to about 45 when I popped the throttle. Ok, no problems with pump, filter, or FPR. But, I replaced the FPR anyway, just for good measure, and rechecked to find same results. So, I go get a vac gauge and start doing some deeper diagnostics. Vac was at 18 in Hg. A little weak, but still within spec. Pulled codes, and nothing but ECT and EGR came up, both of which I'd generated by disconnecting to check. So, I came to FTE and started reading. Umm, oh yeah, need to reset ECM after replacing sensors and let it "learn" the new devices again. DOH!!. Wait a minute, I just recently replaced a battery and starter (a whole other story), so that couldn't be it for the O2. But, disconnected the battery and left it off for a couple hours. No real improvement, so I pulled all the plugs and checked gaps. Since I was going through the trouble, I put in a set of Bosch Platinum II's (no gapping necessary). Again, very slight improvement. I know, I know, you're all screaming check the timing by now. Timing was the FIRST thing I checked. Erratic timing was why I tried a MAP. 10 BTDC, on the money, rock solid with spout plug pulled. Bumpy idle, but not rough, but STILL wouldn't pull your hat off at WOT. So, I dig around in FTE again, and probably read 1000 posts regarding cleaning IAC's etc, etc. One piqued my interest about a common problem with plenum gaskets going on higher mileage 5.0's (wish I could quote the source and author, but I've slept at least once since then). Engine would idle just fine with IAC connected, but would immediatly croak when I unplugged it, so needless to say, IAC was working like a champ (too hard as I later found out, thanks to Broken_Wire).

Finally, I bit the bullet today, and pulled the plenum. HOLY CRAP!! The gasket webs were GONE between 3, 4, and 5. Crud was built up around the Torx bolt on the right side of the plenum, and the dirt accumulations were the only thing giving me any vacuum at all. I had pulled EVERY line except the FPR and MAP lines and capped off everything trying to find a leak. EUREKA, I found it. The carbon sludge was built up nearly 1/8 inch thick around the EGR inlet in the plenum, and nearly as bad on the throttle body throats and the backs of the butterflies. While I had the plenum off, I went ahead and pulled the fuel rail and injectors. Cleaned all the injectors with Seafoam, and put new O's on 'em. Slapped a little light grease on them for easy reinstallation and to avoid nicking the new O's. New Felpro plenum gasket set went on with some Permatex Indian Head Gasket shellac. Scraped as much buildup off the throttle body and butterflies as possible. I probably should have replaced the TPS for good measure, but the existing one seems just fine. EGR valve body was clean other than normal ash accumulations, so left it alone. PCV valve just fine, so stuck it back in. After all the scrubbing and cleaning, I set the plenum back on and started bolting everything back on and plugging stuff back up. Knowing now how easy the job really was, this is something I should have checked a long time ago, like before I took it to the dealer. It took longer to clean the TB, Plenum, and Injectors than it did to take them off AND re-install them. The truck is a DIFFERENT truck tonight. I took it for a spin, and still had a slight bump on WOT going up a fairly steep hill in 4th, but my understanding is it takes several miles for the ECM to re-learn after being powered down (Can someone please enlighten me as to how many miles is "several" in Ford's definition?). I drove it about 30 miles, and the farther I went, the better it ran. Near the end of my little test drive, I floored it in 5th on a level road at 40 MPH, and it jumped to 70 pretty quick, and NOT ONCE did it stumble or cough. I won't say it's 100% yet, but it's got 136K on it, and probably still in the re-learning phases. I won't say I have the best crapoline money can buy in the tank either. Fresh tank of BP tomorrow along with a can of Seafoam in the tank, and will repeat for a few tanks to see how it goes.

Thanks to everyone in FTE that's contributed. I can't name the names, and some of you won't even know you did, but still, THANKS!!!!. I got my truck back tonight!! I've included some photos in a gallery to show the mess I found under the plenum. So, for those of you with high mileage 5.0's that wanna buck and snort on the highway, take a peek. Disassembly took about an hour. Reassembly went a little slower, but still took only about 2 hours, because I also ran a pressure test before putting the plenum back on. I'm thinking about contributing an article when I find time to write it. Sorry for the poor photography in some of the photos, but I'm not gonna pull the plenum back off to take the photos again. I'll give the old girl a bath tomorrow and shine her up some so I can put some photos of a good lookin truck on here. Oh, and by the way, I STILL haven't changed the factory pads and shoes on the brakes.

Livin and Learnin ..............

 

Thanks for the post. It is amazing how much junk can accumulate in these areas. Wow ,the gasket really took a beating.How many miles are on the vehicle? Does the vehicle sit and idle a lot,or does it make a lot of short trips and not heat up.Glad the problem is solved, and hope the dealer does something for you.

 

after all of that, I am glad to hear that your truck is running good once again, once everything had started at the dealer, I would have started talking to the service mgr, then the general mgr and then the owner of the dealership, that is crazy that you had to go through all that hell to only end up doing the job yourself. personally I think that you are do some compensation for all your troubles, but the most important thing is that you got your truck running good again.

 

I tune newer mustangs 1994 up and it seems 100miles of light driving is the magical # for the computer to relearn. Expect horrible gas mileage the first time. In one of my manuals is goes threw a relearn test drive takes about 10min and the computer learns everything. Most of it is driving at 35mph flat road for 4 miles then accelerate to 45mph for awhile then pull over and idle for a few minutes. Its been years since i did it but it works.

 

wow, that was a long post. i think you took over the record. hahaha

it was very informative and i bet you are happy to have solved your problem.

 

No, it doesn't idle much at all. Got 136K on it, and it's pretty much all highway, at least 98% of it. Did you see the photos of the gasket? It just crumbled while I was lifting it off the intake. It wasn't stuck at all, just VERY brittle. Needless to say, I'm not real happy with the dealer, especially considering what I've paid at the post Katrina pumps. It really bothers me that the guys with all those patches on their shirts saying how good they are never bothered to use a flashlight and look under the plenum. Then again, they probably didn't want to get their patches dirty.

 

Hmm, ok. Well I didn't quite follow that recipe, but did put about 30 miles on it last night. It was pretty wild listening to it learn how to idle when I first started it up. I drove through about 6 miles of 40 MPH speed limit, another 6 or so at about 55, then jumped on the interstate for a good romp at 75 for about 15, then back down to 35-40 for the next 10 or so. I could feel the truck getting stronger and stronger as I drove it. I hit one flat straight away, and let it slow to 40 then stood on it. I let it accel in OD to 70 mph (very quicklly I might add) before I let up. Drove it again today to fill her up, and drop a can of Seafoam in it to do some more internal cleaning on the weekly 100 mile trek tomorrow. Gonna watch the economy numbers closely to see what happens now.

 

Yes I looked at the gasket photos. On my 88 I have replaced them 2x over the years as part of regular maintainance and they have never been close to the condition of yours.Never had any of the web pieces desintergrate.As far a the computer relearning it normally doesnt take more than a few miles on my model and it is in the idle mode where I see the difference.I do a fair amount of stop and go and short trips.

 

Well, so far, so good. Still got a rare sputter or two, but on cruise, where it was dropping 10 MPH, it dropped 2 this morning, then started speeding back up. Acted like it was doing some more learning, because it bumped a couple times, then smoothed out. Normally, from where I filled up to this end of the trip, it's been eating half a tank. This morning, about 3/8 tank (MUCH BETTER). Taking a SWAG, I'm guessing 18-19 MPG already. Will know at the end of the tank. Expecting some degradation while the Seafoam is doing it's job, and not too anxious about the occasional sputter right now. I attribute that to the crapoline oil companies are selling us at $3/gal as much as any malfunction of the truck. I have noticed a much lower idle, even a little loping while idling, but it doesn't seem to be bothering anything.


My next step, after getting a couple rounds of Seafoam through it, is going to be to bump the timing up to 11 or 12 BTDC. If I get any pinging, I'll back it back down. Should give it a little more zip, and improve economy a smidge too. I would really love it if the old girl gets back up to the 22 mpg it used to get. I won't hold my breath for that number to come back, though.

 

So far, so good. Engine's still feeling much stronger, and there's a definite improvement in economy, even with me driving it a lot harder than I normally do (can't resist the increased power). I still have the little random miss under heavy throttle (3/4 - WOT), and am approaching 200 miles since the gasket replacement. I would think it would have dialed itself in by now. I have the miss when hot or cold, so I don't think the O2 sensor is responsible. The TPS checks just fine. I checked it with key on, and moved the throttle through full range. No erratic readings. .90V at idle, 4.95 at WOT. Can anyone tell me the full effect of the knock sensor? My guess is, it's the one at the back of the block just above the bell housing? That and the TPS are the only two I haven't replaced.

One thing I did notice yesterday when tinkering with it after work in the hotel parking lot, is that disconnecting the IAC doesn't drop the RPM now. The IAC doesn't count after the throttle's open, and besides that, I'm relatively certain it's working. If I snap the throttle open and then let it snap back shut, then the RPM drops a alot quicker and the engine nearly dies if the IAC is disconnected. Connected, the RPM drops a lot slower, and it never drops below normal idle speed. I may have to back the adjustment screw down a little, and then readjust the TPS for appropriate voltage at idle.

New wires, new Bosch Platinum II's, cap and rotor have about 20K on 'em. Cap and rotor look good. TFI has been checked very thoroughly, at least as thorough as it can be by a static machine. It was still quite hot when I had it tested, considering I drove the truck there, pulled it in the parking lot, and took it in to be tested. The heat sink was still quite warm when I put it back in the truck. Inside of the distributor is clean and dry, and the rotor sensor looks all shiny. I know that doesn't mean it's not wonky, but how common are failures on this part that don't kill the engine completely? (been there done that with the old T-Bird.) Replaced the coil at about 90K. Booster vacuum line fell on the coil, and believe it or not, the coil was actually arcing to the rubber hose through the side of the coil.

I'm beginning to wonder if I let the gasket slip when I was putting the plenum back on. Gonna drive it a couple more weeks like it is since it's so much stronger than it was, and see if the little miss goes away. ANYTHING is better than what I had. Like an idiot, I didn't replace the mini filters on the injectors either.
If I don't find what's making it miss in a couple weeks, I'm gonna pull the plenum again and revisit the injectors while I'm in there. This time, I'll write up a full step by step procedure and post it for a tech article. I'll include pics as well. This might save someone a few headaches, and hopefully keep one more Ford truck out of inept hands.

 

Way back in the late analog days, most well equiped shops were equiped with a peice of equipment called a "Sun" machine. A glorified ociliscope that would show the condition of each spark plug. The fire path from coil to electrode on the plug was displayed for each cylinder. If there was a problem with a miss caused by the ignition circuit it would stand out clearly. Has anyone seen something like this used to find this particular problem?

 

Ok, got back home, and got out the trusty propane torch. Fogged all the lines, no difference, so I'm reasonably confident I have no leaking vacuum lines. So, I put the nozzle under the EGR. HEY! Idle smoothed out (from an already greatly improved idle after the plenum gasket job), vacuum went up to 21 inches from 19.5 inches (hot engine idling slow). I also noticed a really high pitched squealing coming from somewhere on the right side of the engine. I took a piece of hose and used it like a stethoscope, and voila! EGR's leaking like a seive, and squealin like a stuck pig. Now, my question is, how the heck is any seal gonna stay in something exposed to hot exhaust gasses? Since the idle improved (EGR closes then, and verified by checking for vacuum on the vacuum line going to the EGR) this means it's pulling air in through that bugger. I think it needs a new finigan pin to go in the wobble hole. Anybody ever disassemble and clean an EGR before? Can the vacuum operator be removed to permit cleaning the spool valve and polishing any rust on the shaft? I'm thinking I may be bypassing enough air through this thing to cause the aforementioned behavior from the IAC, and perhaps too much air when under heavy throttle too. I would think the MAP would compensate based on vacuum, or the O2's due to lean exhaust. Here, I have another question. Is there anything a dealer could have done to disable the O2 sensor in the ECM? This thing acts like it's starving for fuel under heavy load. Got all new o's on the injectors, so no fuel leaks on the top end nor vacuum leaks on the bottom ends. I'd really prefer not to pull the plenum again, but if the only answer I can get is stopped up filters in the injectors, it leaves me little choice. See the opening message in this thread before pointing at sensors. I get NO codes from the beast. It threw a 22 at me (bad MAP) at first, but I think I did that monkeying around with vacuum lines testing last weekend, and forgot to reset the codes. Get a nice 11 11 from it on KOER. Checked mileage on first tank, and still down around 15.5 highway. Dunno what the rear axel is, but know it's a long-legged truck, and quite capable of 20 MPG highway. I've seen it do 22 on long trips for most of it's life. Tire size is original P25570R15. No brakes dragging, nothing mechanically wrong with the drive train. M5OD tranny, new clutch system so nothing slipping. Tested that theory tonite when I accidentally dumped the clutch in the garage with it still in 1st. Damn good thing I had other foot on brake. Still chirped the back tires before it killed the engine at idle. One of those senior moments that cause doctor visits to have upholstery removed from rectum. I may make a blocker plate to see if a new EGR will solve the problem. Those puppies are $76 without sensor from Advance Auto. Gotta get rid of this pinging and poor performance under throttle.

 

EGR blocked off (flattened piece of soup can between gasket and plenum), and STILL, the pinging and missing under heavy throttle. Idle got slightly smoother yet (purrs like a kitten when idling now). But, gouge it under load, and PING PING PING, COUGH, SNORT, BUCK, WHEEZE. No codes, other than in James Brown's famous lyrics, "I Feel Good". (1 11 11 1 11 11) KOEO or KOER. This is REALLY beginning to **** me off. I'm smarter than this truck, but it's kickin my butt.

Now, I have a serious question for someone that KNOWS. Closer scrutiny, and I see my favorite Ford Dealer (see the diatribe above) appears to have adjusted the throttle body screw. They may have put it back pretty close to where it was originally, but the paint spot seal is definitely broken. I've NEVER touched this screw. TPS reading is good, though, at .95 idle, 4.95 WOT, and very smooth in between. Short of putting a brush recorder on it to record the actual signal while I operate the throttle, I really don't believe there's any kind of noise or flaky places in it.

Somewhere, either in here, on FordFuelInjection, or in my Haynes manual, I read the proper adjustment for the Throttle Body butterflies is to run the screw in until it holds the butterflies open, then back it off until they JUST touch. The screw is no more than a mechanical stop to prevent the butterflies from sticking in the bore. That's why we have the cute little hole in each butterfly, as well as the IAC. Then, the TPS should be set to read .90 - 1.00 volts. While cleaning the TB last weekend, I noticed that yes, the butterflies are closing and sealing, but NOT to the point of being jammed. Before replacing the Plenum gasket, unplugging the IAC would most certainly kill the engine. Now, I barely notice any difference when I unplug it, other than recovery when I release the throttle and let it snap shut. W/O the IAC, it'll stumble just a little, but seldom will it die. With it, it just takes a bit longer for the idle to drop, and there is NO stumble.
Ok, so get out the timing light. SPOUT off, 10 deg. BTDC, ON THE MONEY. Trust me, after what I went through on the '86 T-Bird after same dealer replaced the engine, I've LEARNED to check their work. I found it set at 10 deg ATDC. DUUUUUUHHHH. Reconnected the SPOUT, and watching with the light, something doesn't look quite right. When I pop the throttle open, the timing RETARDS first, then advances to something I can't read. (bit of rust on the balancer). It looks like it's retarding to about 0, then advancing. Is this normal? Is it possible that something's gone awry and the ECM has been monkeyed with while I had the plenum leak to modify the timing curve? I have a lot of experience with older mechanical advance systems, and have NEVER seen one retard when punching the throttle, vacuum or weight operated. I really need to fix this, because I'm really worried that I'm doing some serious damage to the engine running it this way. Been there, done that with running one too lean, and the pistons weren't very pretty when I pulled them out.

Before we get into another vacuum leak discussion, I disconnected EVERYTHING except the MAP and FPR lines on the engine while diagnosing the occasional shudder when idling, which is what led to blocking off the EGR at the plenum. I thoroughly gassed both of those lines with Propane, and no change whatsoever, except for the purple elephants I started to see.

Am I looking at a slack timing chain (136K) or WHAT? The slack chain would normally cause rough running at ANY speed. Like I said, tho, idle is now smooth as melted butter. The high cliff is beginning to look like a good solution, unfortunately, we don't have cliffs high enough in Alabama to kill Fords. Maim them, yes, kill them no.