I have a B4000 4x4 6 cyl 5 spd manual with 190K miles. Well kept, engine has always purred and idled great, plenty of power.

About a month ago I began noticing grinding like hitting a spinning flywheel when putting it into reverse. Then I began having trouble going into first gear, and then problems with it popping into neutral from 4th if I hit a bump. The clutch pedal seemed very soft and I figured I needed a clutch. Took it to a shop where I know the owner pretty well and they confirmed I needed a clutch. Paid $650 bucks and went to take my truck home and barely got out of the parking lot. Not only was it still not wanting to go into first, once i got going down the road, at about 50mph and 1500-2000 rpms, the engine was jerking and stumbling. I took it back to them and they said they would look at it.

Supposedly they said they just needed to bleed the clutch again and it fixed it. Went to pick it up, clutch and shifting seem fine, but still engine issues at RPM and stumbling and no power. The odd thing was, if I floored it, it would kick in and go and the power seemed fine, but it was right at about a half a pedal that it jerked and stumbled. Also the engine light came on again.

Took it back and the engine light read bad MAF. They replaced it and it didnt fix it. Then they replaced it with a brand new one instead of a reman one and that didnt fix it either. It sure seemed like a an air flow problem, but wasnt. So then began a series of aimlessly replacing items. Here is list...

MAF (2)
O2 Sensor
TPS
Crank Position Sensor
Fuel Pressure Regulator
Plugs Wires and Dist
Cat Converter

Now, after a month of these guys tinkering with it, the problem seems to have shifted. Now it runs strong and fine at all RPM on level ground, but going uphill loses power big time. No engine light though. And as the car gets warmer and drives longer, it gets progressively worse.

The mechanics are at a loss of what to do next. Supposedluy they have smoked all the vaccum lines, wd40'd all the fuel lines, fuel pressure is good, cylinder pressure is good.

Oh one odd thing, since they replaced the plugs a couple of weeks back, all of the plugs on ONE side of the motor were fouled for some reason. Mechanic said he had never seen that before.

If anyone has any clues, past experience, etc that might help us out itwould be much appreciated. I love my little pos truck and have gotten many miles out of her, and feel like she has plenty more.

Thanks in advance !!
DH

 

What brand of plug did they put in?

 

Im not sure Michigan, why?

Also, I went and drove it this morning, and they are full of it. The truck is runs and idles and reves great and strong. Tranny seems fine, shifts fine. But as you get going down the road, flat or hill, or just doesnt want to go. Like a fuel filter issue, like something is choking it back, jerks and stumbles. Up hill it really loses power and jerks and stumbles. This gets progressively worse as it heats up which seems like a CAT problem, but they bypassed it and it still did it.

Cylinder compression is good. Fuel regulator replaced. Fuel pressure is good. No archingin the wires that we can tell. All of the above has been replacd. What the hell could it be? We are just stumped.........the ECM is the last thing and I dont want to lay out $600 to find out.

Any ideas?

 

Fords must have EO spec spark plugs. The fact that they were gone on one bank tells me that they were not OE spec plugs. What did they replace the plugs with?

One part that affects the way the vehicle runs at temperature is the coolant temp sender. It tells the computer how hot the engine is so that it can adjust. If that sensor goes bad, the truck will run funny.

It could be a fuel pump problem. What diagnostics have been done on this truck, or have you hired a bunch of parts swappers. Every part on this truck can be tested. The idea that it is a cat problem is bogus. If you had a plugged cat, it would be almost immediately obvious after startup, not after it warmed up. Besides, cat problems are the symptoms of other problems anyway.

You mentioned plug wires and distributor? You must MUST use Motorcraft wires in these trucks. And there is no distributor. Factory plugs and wires only, all others will cause problems with your trucks powerful waste spark system.

 

Bear,
Id like to think these guys are not part swappers, but I dont know. Its a reputable shop with a cert mechanic so.........

The problem doesnt start after it heats, up, it runs bad immediately, it just gets worse as it gets hotter. They siad the fuel pump was good and they had tested the pressure and it was fine. They do use OE spec plugs, but werent sure about the wires. They are checking now and going to get back to me. I know we checked the wires for arching and didnt see any.

It does totally act like a fuel pump problem. It wants to go, but feels choked back. But at idle, it revs up great and sounds strong getting plenty of fuel. Id love for it to be the wire set........damn that would be nice if it were that simple.

I also told them about the coolant sensor. Would that not put off a code? They are going to check it.....

Thanks guys....any other ideas or comments are welcome.

 

If this is a NON-sefi system, then the injectors fire one bank then the other bank. Banks would be for cyl 123 and 456, i.e. passenger side front-middle-back squirt all at one time, then the other side squirt.
If you have plugs fouled on one side and not the other, then I'd be looking at the pulse width of the driver circuit. (how long does the computer provide a ground to energize the injectors, measured in milliseconds) If one side has a longer pulse than the other, then something is wrong.
Have they checked the grounds (all of them) on the coil pack? Thinking further, the coils are shared from side to side, not on the same side, so never mind.

I will say this: When they did the clutch, they had to remove the transmission, and they *likely* let the engine sit on its motor mounts, actually tilted down at the back because the crossmember that holds up that end was removed. That could have allowed something on the rear of the engine to cram into the firewall. I know my old 2.3 only has room for my hand flat against the back of the head, to pass from side to side. The 4.0? I have no idea, but the EGR system is likely located on the rear, or smuther stuff... [like my new word?] some other == smuther.

I dunno, but the MAF will cause chugging and driveability if broken, the EGR will cause trailerhitching as will bad plug wires causing misfire. I had that and only found out watching the light show underhood at night as the electricity jumped to the engine rather than jump through the plug. Low fuel pressure will cause a 'lack of power' or inability to accelerate very well or climb hills. Bad plugs will cause noticeable misfire at idle or under heavy load. Timing inaccuracy is hard to accomplish on this system. EDIS, right? Fuel, air, and fire, gotta have all three. Which do you think is lacking, or is there a plethora of fuel or air?
tom

 

It's time to disconnect the battery overnight, hook it back up and drive it for a day or 2 and pull codes. While it might not be anything more than a clogged fuel filter the best way to get a handle on it is to pull codes. For all you know the cel is burned out or disconnected.
Just for the heck of it, disconnect your MAF and drive it for a coupla days. My truck would suddenly lose power, at first just for maybe a quarter second, and then run fine again. Every time it did so the cel would go out for a couple of seconds. Then it would come back on. This problem gradually got worse over time. The code I kept pulling up was the maf sensor. I disconnected it and the engine quit dying on me at highway speeds. Erratic idle at the lights? Mine was the maf. I replaced it, the cel no longer came on and my idle speed when stopped remained constant. After 3 weeks the cel came back on, my idle became erratic again, and my code showed that this maf had failed. Nine months later I still haven't replaced it. $100+ for one of these little jewels every 3 weeks is out of my price range, so I deal with it. But... the problem I had with the sudden power loss is gone.

 

I really appreciate all the responses and detail.

I hate to sounds like one of those "we've done that, we've done that" guys, but thats where we are. Weve replaced the MAF twice, the second time with OEM one. The fuel pressure reg and fuel filter has been replaced and the fuel pump is working great with normal pressure. Vaccum system is sound...not a leak to be found. Its getting plenty of air, its getting plenty of fire, cylinder compression is awesome and the timing seems dead on. We have cleared the codes and havent gotten any since, yet it still lacks power and doesnt want to accelerate for some reason. Im leaning toward it being a sensor of some sort somewhere.....its the only logical explanation at this point. We have a temp coolant sensor on order and will replace that monday to see if it fixes it. After that, all we are left with is the PCM. I mean there just isnt anything much left it could be. The dman thing is going to drive strong and like a new truck once we figure it out I know that. The idle and sound of the engine reving in neutral is the best its ever sounded....very strong and clean sounding. No rattle or engine noise whatsoever. My mechanic has been one for over 20 years and says this the damnedest thing he has ever tried to figure out. And usually when thats the case, its electrical or computer Im thinking...

 

I wouldn't completely rule out the pump. I've had two vehicles, one which shares your engine, and it was a fuel pump on both of them, and some of the symptoms match yours. And both fuel pumps tested good. Yet they were both bad, and replacing them resolved the problems.

Is your MAF getting a good electrical connection? Is it possible that corrosion has gotten into a connector?

The ECT sensor can cause some of the problems you describe. The AIT sensor, or whatever Ford calls it (measures the temperature of the air in the manifold) can also cause some of the problems you describe.

A PCM is possible, but not very likely. A sensor is very likely.

Bad wires or wrong wires may not arc. Most non-OE wires are nearly double the resistance that Ford specifies. Isn't there a clutch pedal sensor? Could that be acting up?

 

Cluth pedal sensor would sure make sense why the engine trouble started immediately after they worked on the clutch. I will have to look into that one. Thanks.

 

Clutch pedal switch is to disable the starter unless the pedal is depressed. Keeps you from starting the engine in gear and possibly running into something/someone. In theory. Same as the brake pedal interlock for automatics. Can't get them into gear unless you have the brake pedal depressed. Some people can't tell the difference between a brake and gas pedal, so this gives the MFG some cover from the legal beagles.
Get the ECT and ACT readings, and compare them with coolant temp and ambient air temp. You noted that it gets worse as it warms up. What if it thinks the engine is hotter than it is, and fiddles with the mix to compensate? Justa thought.
tom

 

I just want to say what a great forum you guys have here. Ive learnd a ton reading these posts and will think hard before sending my truck to the shop next time. Im confident I can do a lot of this myself next time I just never knew a place with such good to help guide me existed.

Just one thing. I keep saying it runs bad. The truth is it starts, idles and revs up like a brand new truck. It even revs high (richer fuel) on cold start and levels out after it heats up, just like its supposed to. During idle you can rev the engine to 2500 rpms and hold it there, and its as steady as it can be for as long as you want, no problem. Not a skip. Its once you get it into gear and going down the road that it starts acting up, stumbling and not wanting to have any power. Im no mechanic but I wonder if the tranny isnt going bad perhaps? They say no at the shop but.....something is keeping power frm geting to the wheels and he engine seems strong as a horse. Man this is aggrevating.

The engine coolant temp sensor is being replaced today (i guess they are parts swappers because apparently you can test these things with a volt meter). Im hoping that this corrects the problem and will post here after I find out. Im looking for a new PCM in junk yards and part out cars just in case.

The telling thing in this case is that it only acts up when in gear and driving, it starts and idles and reves at all RMPs without a glitch like a new truck.

 

As I look back over this entire discussion, I don't recall seeing any mention of replacing the fuel filter. Did I miss something. It could allow enough fuel through it to show that the fuel pump is OK. But once you get on the road and are driving, especiall at faster speeds, the filter may be sufficiently plygged to restrict the flow of fuel to the injectors. Do you have any idea how old the filter is/when it was last replaced? Just a thought.

 

Sorry if I didnt mention it Michigan. Yeah, theyve had it for a month now. they replaced the fuel filter and 02 sensor the first day. DIdnt fix it. As far as fuel system goes, they replaced the fuel filter, fuel pressure regulator and ran it down the road while checking fuel pressure somehow, and siad it stayed steady, even during driving and going up hills, etc.

Somewhere theres a dang sensor throwing things off and Im sure hoping its that ECT.....I need my truck back. A month is a long time to have to share a ride with your wife. No man should be chained to that fate.

 

Did you check the ground wire at the back of the cylinder head? Most FoMoCo's have a bare braided ground wire from the back of the head to the firewall. This provides ground for the body. When they dropped the transmission, as I said, they likely let it hang on the motor mounts. If it sagged, it could have broken this ground strap. I have seen them pulled out of the crimp on fitting, and flapping in the breeze. A cheap fix if that is the problem.
If this truck was running fine, with power, etc when it was driven into the garage, and now runs poorly, the obvious place to look is where stuff was moved and changed. They would also have to have messed with the linkage and associated wires. They would also have to have messed with the speedometer cable or vss and wires, depending on model/year. Look at the places where fiddlin' took place.
tom