My apologies if this sort of question has been answered here, but I could'nt find anything with a search of this forum. Also, up front, want to say thanks for any help you guys may be able to provide me.
Now, my problem: I have a 1988 F150 2WD with the 300 I-Six/5 speed. This truck is my daily driver, and gets about 150 to 200 miles a week put on it. It will start and run at idle with no problems, but sometimes, at highway speeds, when I let off the accelerator it will hesitate, almost to the point of stalling, as though it is out of fuel. The "check engine" light comes on for a second, as well. It never dies, only hesitates, since I usually manage to depress the clutch and give the throttle a tap before it can die. It will also do this when starting up from a stop sign or red light in first gear, and sometimes continue through all the gears. It does'nt happen everytime I let off the throttle, but has been increasing this behaviour of late. I'd say I first noticed it about 4 to 6 weeks ago. At the time I put it down to the colder weather and possibly some water in the gas. Pursuing that line of reasoning I ran both gas tanks to nearly empty, then filled them up and added a can of HEET to each of them. No change.
What I've done so far is to replace the spark plugs, plug wires, fuel filter, air filter, and distributor cap. The battery is not too old and holds a charge well enough to jump start my tractor with in a pinch. I run ethanol in it exclusively (10% alcohol). The fuel pumps all seem to be in good working order, too, which leaves me thinking it is not a fuel related thing. Being my daily driver (and my only truck at the moment!), I am very consious of routine maintenance with this truck. It has a lot of miles, but I'm not ready just yet to put it out to pasture, since I think the old boy has a lot of life left. As I said above, the truck does'nt behave this way all the time, but it is becoming more and more often, and I'd like to get it corrected before it does leave me stranded.
What I'm looking for is anything else I might have overlooked and can do to fix the problem myself. I'm a pretty decent shade-tree mechanic, but I do have my limits. Just thought I'd pick the brains of my fellow FTE'er's before taking the truck in to have a pro look at it.
Once again, my thanks for any help anyone can provide me on this.
__________________ The American Farmer Feeds The World
You need to pull the code. Many years ago I purchased a Equus code reader. I think it was less than $40.00. OBD1 code readers are real cheap now.
It plugs into the diagnostic connector mounted on the driverside fenderwell under the hood.
Makes it easier than counting the blinking light.
Autozone will also pull codes for free.
You can monitor fuel pressure problems by attaching a fuel pressure gage to the schrader valve on the fuel rail. Tape the gage to the windshield.
You can also unscrew the IAC valve (on the side of the throttle body) and with fuel injection cleaner, clean the carbon from the bore of the throttle body and the tip of the IAC valve. Also manually open the throttle body and spray the fuel injection cleaner in the throttle body .
The IAC (Idle air control) acts like the dashpot used in the old carburator engines. Keeps the engine from stalling when you quickly let off the gas pedal.
If the problem is ignition related, the TFI module (bolted on the side of the distributor) or the pickup coil inside the distributor could be bad.
You have an EFI engine correct? First guess would be an ignition problem, specifically the stator module in the distributor. Have seen plenty of "phantom" ignition problems due to these guys going bad from age and use. They tend to start misbehaving before they die, causing random sputters and stumbles as they give out delayed or missing signals to the ignition module. The TFI module is the other potential cause in the distributor, but they fail less often than the stator and usually "just die" rather than protesting first. You can test the stator with an ohm meter: Pull it from the distributor and read between the two contacts, you should see 800-950 ohms. If it's in that range then it should be OK, but if it reads higher or lower it's shot. If the stator tests fine then the TFI module is suspect.
Second guess would be a dying fuel pump. My GF's truck did the same hit-or-miss stalling for several weeks before the pump finally went. Since most EFI Fords have dual pumps [LP feeder pump in the tank, HP on the frame rails] it can be tricky to figure out which of the two is misbehaving. FYI you can replace in-tank pump only, don't have to buy the whole assembly. Bare pump w/ strainer is about $50, assembly is over $100. Rail mounted pump is $80 or more. Could also be something as simple as a clogged strainer in the tank... you just have to drop the tank top check it though.
Second guess would be a dying fuel pump. My GF's truck did the same hit-or-miss stalling for several weeks before the pump finally went. Since most EFI Fords have dual pumps.....
My husband's 83 E150 302 was acting the same way for a few months before it finally died in town. Hesitating while driving, cutting out, hard starting, trying to die at stops and all. He and a mechanic friend when through testing the carb, filter, fuel filter and all. Thought it was the ignition module. Everything except the last obvious culprit.....the fuel pump that was progressively dying and finally did. Although the mechanic mentioned this might be the case, my husband thought not as he replaced it only a year ago. But it was.
My own 81 E100 300 was just starting become abit harder to start in the last few weeks. Had to pump it more before turning the key. Finally it really acted badly this last Monday while in town. It was hot that day (over 104) and it did die while pulling into a parking space. First thought....Fuel pump....just like my husbands last year. It even hesitated while driving down a back street and was able to keep it going with a couple of quick foot pumps.
It finally died and would not start AFTER driving back from a mechanic friend (who helped out before)....this a few yards from his shop. Waited abit and it started up again for me to drive it back to the shop. He checked everything. Filter, carb and even the line. Even tested the fuel pump pressure. This because the pump SEEMED ok otherwise. And this was more sudden than what we went through with my husband's van. But then the diaphram might have weakened enough over time to start acting up sooner. So, I bought a new fuel pump.
I got the van in late 2004 and did not know how long the old one had been on there. The friends replaced a number of things before I got it (starter, new plugs/wires, gaskets) but not the pump. Just glad it died not far from the mechanic's and not along a very long, rural and lonely state highway going home.
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