Hello,

1997 F-150 4.2L
I have been trying to troubleshoot this problem for the past year without much luck, in fact it seems to be getting worse.

Recent mechanical history:
Hydrolocked, coolant in #1 and lower intake gasket replaced last year. Coolant temp sensor, idle air control IAC and intake temp sensor changed. Fuel filter changed. I also tested the throttle position sensor, coolant temp sensor and intake temp sensor with a multimeter and they were all in the normal range. I also replace one of the vac hoses on the intake manifold and inspected the others and they seem fine.

I swapped the coil pack for a new one and it made zero difference. I though I might have a problem with the EGR system so I spent a while troubleshooting that and everything seems to be working perfectly. I checked vacuum pressure at the intake manifold and I am getting a pretty steady 18.5-19.5 in. of pressure which is what a healthy engine should get and this hopefully also means that there aren't any vacuum leaks. I also cleaned the MAF with special CRC electronics cleaner and no difference. New spark plugs and wires. Finally I pulled the vacuum hose off the fuel pressure regulator and no change in how the engine was idling, does this mean the regulator could be bad? Its vacuum line is getting pretty good suction.

SYMPTOMS:
-The old autolight platinum plugs were pretty carboned up but the engine doesn't consume any oil so it must be running rich?
-No check engine light
-Rough idle (seems to be when warm, engine vibration almost seems like an occasional miss)
-about 1 out of every ten times I start it, it shakes violently and stalls after about 5 seconds. If you press the gas it usually will not stall.
-Poor gas mileage?

Any ideas? This is driving me crazy, I can't figure it out! Thanks

 

You sure the hydrolock didn't bend a rod?

 

My truck has the same thing, but only if I havent started it for a few days it sometimes shakes bad, like its stuggling to turn over, then after a few seconds it runs normal, its only stalled on me once. As far as I know this engine has never hydrolocked and I had the bad gaskets replaced last month. I have no idea what it is, I've changed plugs/wires, PCV (both elbows), no vaccuum leaks, I'm stumped too.

 

You might have a severe carbon build up... try some of that BG44 or some Seafoam.

 

Well I had the intakes and TB cleaned last month when they had my motor apart to replace the intake gaskets and its still doing it. I've been thinking of the seafoam thing but I just had an oil change so maybe next month I'll put some in and try it.

 

[QUOTE=jeffceo]Hello,

1997 F-150 4.2L
I have been trying to troubleshoot this problem for the past year without much luck, in fact it seems to be getting worse.

Jeff, Whats the fuel pressure reading @ idle and then dead head pressure. If you install a fuel pressure gage @ the fuel rail, (You may have to remove the shrader valve) turn the vehicle to run but not start. Take that reading down. Then start the vehicle, check that reading, it should be primairly the same, then find the fuel return line to the fuel tank (rubber) and crimp it. Your readings usually double but you'll need to ask ford or a tech here @ this site. Ive seen 80psi on some vehicles it may be the same or close. 1.) What may be happening is your fuel pump is not meeting the demand for the engine @ idle. 2.) Or your IAC is playing and not allowing enought air to pass to keep engine @ idle? 3.) Possiable broke plug wire. #'s of thing right now, hard to say without seeing, but keep plugging @ it.

 

UPDATE: Hey Everyone, thanks for the help so far. I don't think I have a bent rod from the hydrolock because the engine never fired or turned over, I was lucky.

I tested the fuel pressure at the rail: 38-40 psi with key on engine off. 32 at idle (should be 30-45) and 42 at idle with vacuum line off fuel pressure regulator (should be 40-50 according to haynes manual). It increases slightly when you rev the engine.

Even though I cleaned and tested the MAF several times I figured I would try a new one since it seems this sensor causes a lot of trouble. Zero difference.

One key symptom I am wondering about here and I hope someone can help is that the plugs were in my opinion very dirty after approx 12K miles. here is a picture of them: http://picasaweb.google.com/jeffceo2...65817055358610
The plugs closest seemed slightly dirtier and are from the drivers side. Most people may say it is burning oil with 89,000 on it but it does not burn any noticeable amount after 3k mi. The exhaust pipe opening also seems excessively carboned up.

Along with the symptom of poor gas mileage, this leads me to the conclusion that it is running rich. Now why, and how do we fix it?!?!?! I am wondering if the injectors are so clogged that each cylinder is getting a stream of gas that doesn't burn very well/cleanly/evenly instead of an atomized stream and that is why I am getting a rough idle/ miss because the fuel/air mix can't ignite consistently????

 

When I had my troubles...with the hydrolock and all. the engine never fired up after I tried to start it and it just locked. I thought i could just replace the gaskets and be good to go...Wrong, bent rod was found...i would of never thought you could bend the rod without the truck actually starting up...

 

Im gonna go with manualF150 on this one.

Dump a can of Seafoam in the oil tank and try to get it up in the vaccume lines.

Look into NGK or Bosch plugs... do not use iridium plugs Another trick is to disconnect the ECU of the truck for about 30 minutes to reset it.

 

What is Seafoam in the *OIL* going to do for you besides dilute the oil?

See my comment on your spark plug choice in the other thread you posted the same thing in.

You also do not have to disconnect the ECU to "reset" it - you pull the battery cables or you pull a specific fuse. The only reason to reset it would be to clear trouble codes and see if they come back, or to wipe out all the adaptive driving parameters and start fresh.

 

^ I have found that if you want to get junk out of the motor that Seafoam can clean the head by dumping it in the oil. Seafoam through the gas tank works but I feel its less effective. It doesn't necessarily dilute the oil. Its a combustible material and *technically* your vehicle could run off it.

I also mentioned the tip on resetting the Ecu because sometimes it can error from an old problem. Its like a desktop PC, for some reason it runs slow or not properly once in awhile. Rebooting it is typically the quick fix and works.

Now Im not here to start a pissing match with you because its not the best way to make friends as a new member. But I just want to make sure you know I'm not spouting off random things without reason.

 

If you have sludge, etc. in the oil system, I'd rather trust cleaning to an engine flush designed for that purpose. Example:

http://www.amsoil.com/StoreFront/aef.aspx

Rebooting the ECU is fine when indicated - but you don't do it in our trucks by disconnecting it. You do it by pulling a specific fuse or by disconnecting the battery.

 

Gotcha. Im still learning a lot about my new truck so thanks for the info for future references.

 

Just my $0.02 but I'd stay away from Bosch plugs. Our engines dont seem to like them. I put in a set and the truck ran rough, almost stalling at idle. I even gapped the plugs to the proper gap 0.054" I think, made no difference, still rough. I changed to a set ot Autolite Dbl. Plats, now it runs smooth. For some reason our particular motors only like Motorcraft or Autolites.

 

Hello all: I know this is an old thread but my 1997 4.2 XL does the same more so in the winter time. It does not want to start when cold on first go and stalls ou. Then I start it again and it fires right up. After warm up it runs fine. I often drive long distance and every time I plan on driving over a 100 or so miles one way, I add Techron Concentrate Plus in the tank and it does run fine for a few months. I use Amsoil in all my vehicles and I will use the engine flush.

Did you guys found the solution for the problem?

Thanks