Now what should i do?

[DonM]

After so many months of trying to solve my rough running engine i think i might just be getting closer and closer to the fix?

Ive posted about this before and have done a few things since! Two Iac's and a new Maf. My symtoms are as follows... Engine runs rough all ways (Warm or Cold). When coming to a stop, engine feels like it wants to stall, but never does!! Neither Iac's helped, now to the enteresting part. A few days ago i picked up a new Maf and put it in. The engine ran great all day long. I drove about 50 miles that day with no problems. Then i went to work that night, as i was backing into my fav parking spot the engine kept spuddering( trying to stall) but didnt. After work the next morning i drove home, engine running rough just like before. Since then the truck has been running really good one day and really rough the next.

After i put the Maf in and drove it around a bit i came to a stop sign at the end of my street as i waited for traffic to pass i swore my truck stalled out. But it didnt, the engine was running so good i didnt even feel all the vibrations. So now the truck runs good half the time and the other half it runs rough, just like before? This has been driving me crazy for so many months. Just when ya think ya found the fix.

Im clueless as to what i should do now? Can you all give me some advice on what i should look at next?

BTW, all plugs are good, i just had a tuneup not to long ago! All of the obvious is done, what else could it be? Would the FPR cause this? O2 sensers have not been replaced. One shop said they were bad and the other shop said the work fine! Who to believe?

Thanks guys


Don

 

[JDraper]

Have you gone and looked for vacuum leaks or tried torquing down the lower intake manifold?? Both may give you symptoms like you are describing and may vary depending upon engine temp and what vacuum ports are open. You can hunt a vacuum leak with a can of WD-40. With the engine running spray around any areas that might be suspect. If you have a leak, the WD-40 will cause a change in the idle.

Do a search hear for Lower intake manifold. There have been several threads on it and what happens when it is leaking.

 

[DonM]

No, never thought of that! Hell im learning, so i dont know to much about engines.

I will do a search and see what i can come up with.

Thanks


Don

 

[DonM]

Ya know, after the truck sits over night. I come out and start it up and begin to drive. It's only the first few min that the engine wants to cut off when coming to a stop. Before i put the new Maf on the engine ran rough at all times and had the feeling of wanting to stall when coming to a stop.

Today the engine ran good, but this morning when i left work it wanted to stall. Ran good all the way home, it was just the first couple min?

Im no expert, but this seems to be more of a fuel problem dont you think?


Don

 

[JDraper]

Could be the Fuel Pressure Regulator. Seems like quite a few people here have replaced them.

Could be a manifold leak. As the motor warms up, the metal expands. If you have a very small leak when it's cold, it could seal as the motor heats up. Just a thought...

 

[DonM]

Yes i understand what your saying 100%. I dont know why? But i just have a hunch about the fuel thing!

Never less, everything will be checked out. The lower manifold does have me a bit nervous. I dont know what im getting my self into? Maybe i'll just have the shop take a look.

Thanks again


Don

 

[Iggy flywheel]

How long you run with those plugs before changing the MAF? You may fouled the plugs. Another thing is that o2 sensors could be acting up after they heat up they working correctly. When they in open circuit they not working like they should causing rough running.

 

[DonM]

The plugs have been in for 9 months. The Maf was put in last week!

As for the 02 sensors, ive had two shops check them. The first shop said they should be replaced and the second shop said they are fine? I may just replace them anyway, the X has almost 90,000 with orignal 02 sensors. I believe there are two on my truck?


Don

 

[Jarrett088]

Did you reset the computer after installing the new MAF? Just a thought......

Tim

 

[DonM]

Yes i did, infact i did so twice! Once over night.


Don

 

[DonM]

One thing i forgot to mention... engine has a slight knock when running rough. When new Maf went in and every thing smoothed out, the knock goes away!?

I just got home from work and the damn thing was running pretty rough. Seems like every morning i leave work the damn engine wants to cut off, each time the idle goes low a bit(200-300rpm's). After about a min or so of doing this it stops and the engine just runs like $hit!

Im taking it in and have the shop run for codes, all though i highly doubt any will show up. While im there im gonna have the O2 sensors replaced and maybe have them check the FPR? While im at it, i might as well have them check the Lower intake manifold!!!

Don

 

[DonM]

Ok, i replaced both O2 sensors and checked the FPR! FPR is running fine(32). I also checked the Throttle plate. While i was under there i checked the Iac, which is running fine.

The o2 were running a bit slow, so i replaced them! Running faster now. No noticable dif yet, im resetting the computer right now.

I hope the o2 sensors was the problem?


Don

 

[410Fortune]

OKOay these problems can be hard to find.

Check for leaks around the lower intake manifold.

Dont rule out the computer, it has happened before. You can spend months and months and tons of $$$$ trying to fix a lackof power/missing problem like you have, throwing 02 sensors at it, fuel filters, spark plugs, sensors, etc, only to find that the computer itself is bad. Now these baby's are not cheap, and Ford will charge you $250+ just to do a "pin out" on the computer to determine if it is at fault. One thing you CAN do is get a computer from a similar truck (friend, junk yard, must be same year, engine, tranny, etc) and swap them out.

You do know that you must re-set the computer every time you change a sensor right?

 

[camm0n]

I have a 95 as well and it runs rough but not this bad. A very weak reaoning on mine it when the AC is running it will surge due to the power drain of the pump I guess. Anyhow I am pursing this surge issue as well. I just bought mine with 80K on it so new to the issue. I will post what I find.

 

[DonM]

Originally posted by 410Fortune


You do know that you must re-set the computer every time you change a sensor right?

Yup sure do!

I just reset it, took it out for a test drive and seems to run better now. Although the real test will be waiting a few days to see if the problem comes back. Im interested to see if the engine will hesitate in the morning when i leave work?

My next project will be checking for leaks in the manifold, which im nervous about. I dont think there is, but i will look everything over!

Im gonna run out and pick up a torq wrench so i can tighten up the bolts on the Lower intake manifold if the need it?

Thanks

Don

 

[410Fortune]

Oh dude thats a lot of hooey, dont be surprised to find they are loose. Most of the 93-95 OHV's I have seen are loose, finget tight in fact. Mine were loose as a goose, so I just hopped up in the engine bay and tightened them up with my 1/4" drive, wobbly, 6" extension and 10mm socket. I didnt see the need for the torque wrench unless you are going to do the real fix it, which would be to actually replace the lower intake gasket (good idea). Just be careful the intakes are aluminum so it;s pretty easy to overtighten and strip them out.

mine are still tight and I plan to build a new 4.0L this winter so I'm not gonna worry about replacing the intake gaskets....

You can tighten them up for now, but plan to replace the gaskets when you get a free weekend to do the job.....

 

[DonM]

Yeah i dont see me having enough time to do the real fix! Maybe just tighten some bolts up and see if it helps.

You wouldnt happen to know of a thread that has pics of the lower intake manifold, would ya? Im not really sure where it is.

Thanks

Don

 

[DonM]

Well after i put the new o2 sensors in Monday it ran great till this a.m. I was so happy all week long, the engine was running so good! I left work this a.m. and it ran like $hit.

I still think there is a fuel problem? The FPR checked out fine. Maybe the fuel pump? Is there anyway of checking it to see if the it's working ok?


Don

 

[Luv2explorer]

It cant hurt to change your FPR and your fuel filter as well, When I changed mine, the truck ran 10times better.

 

[Opera House]

Fuel pressure regulator

In my 92 Explorer about five years ago the fuel pump started to whine at idle. Also the whine would change in pitch. Since the vehicle had about 160K on it I changed the fuel pump rather than have it fail at an inopportune time on a trip. I should have known no good deed goes unpunished.

I purchased an aftermarket pump for $65 figuring it ought to work for the two more years that I would probably own the car. The pump was installed that evening but, I did not have enough time to replace the fuel filter. The next day was a warm early spring day and the vehicle had hesitation problems on acceleration. Every time I stopped at a stoplight and idled for more than a minute the engine would shutter and die. It was almost undriveable.

I replaced the fuel filter that day and it worked a little better but still had driveability problems. Thought it might be the winter gas formula since this was the time when stations were changing over to the summer formula. Several tanks later still no improvement. After a week of hoping the pump would magically wear in, I decided that my effort to save money had backfired. Figured this pump did not have the moxie. I got a Ford pump for $180 and installed it. It ran worse with this pump than the cheap aftermarket pump. I was getting tired of replacing pumps with all the 1/2 inch anti-armor piercing shields they put around this tank but started to consider installing the original pump back in. After all there never was a problem until I put the new pumps in. I even noticed that the engine would start to die on the same high speed right exit turn every day driving home from work.

I lived with this for problem for a while figuring that which did not kill the car would make it stronger. If it did die and stayed dead it would be easy to figure out. Also, now I considered for sure it was an electrical problem. It did get better at stoplights and didn't die as often. Most of the time the performance was acceptable although it seemed to knock more going up hills than it used to. One time, on vacation towing a trailer, it died in the middle of an intersection. I managed to restart it and pull into a parking lot. There it would run and almost die and then repeat the cycle. I pushed two thin strands of wire into the gas tank electrical connector and measured the pump voltage. When the engine would start to die, the voltage at the pump would actually increase. This no longer seemed to be an electrical problem resulting from a bad connection. I wired an ammeter in place of the pump fuse. The pump would draw about 5-6 amps when everything was normal. When there was going to be a problem you would see the current slowly over a couple of minutes drop to about 2 amps. At 2A the engine would start to shutter and then everything would go back to normal.

Finally it died on a major highway on my way home from work. I could restart the engine but it would barely run and die after going 50 feet. I was almost at an exit and knew if I could make it another 200 feet, the road was then a mile down hill to a parking lot with a pay phone. I coasted down the hill and waited an hour for a friend to show up. When help arrived I tried one last time to start the engine and it worked fine. My friend followed me home without incident.

There was a part I had suspected but it wasn't a stocked item. Desperate, I ordered the fuel pressure regulator. After installing the new one, I cut open the old one to verify the cause of the problem. A flat hardened metal plate covered the valve orifice. The pressure spring on the plate was slightly off center. This caused a 30 degree bevel to be worn on the orifice surface. The new pumps had more pressure than the old one causing the plate to lift up more and occasionally slide to the side on this bevel. This sometimes held the valve open causing very low fuel pressure. When the engine would violently shake just before stopping, the plate would be reset to a normal position and everything would be fine for a while. After replacing the regulator, it ran better but it still wasn't right. 200 miles later, I disconnected the battery and reset the computer. Everything was fine after that.