jdl2430

Hello, I have a 1988 f150 with the 351w. I am going to start off with a little history. When I first bought the truck 2 years ago, it ran fine but every once in a while it would hiccup while idling, it would slow down almost die but pick back up again. Last year about this time I installed a new timing chain, chain cover, water pump, fan clutch. Also I replaced the sending unit for the front tank with the small fuel pump. I only use the front tank because the rear one leaks. Everything still ran fine but the hiccup would still happen. This past summer i was back in the woods and I got caught on some tree limbs and I was able to get through, but at the expense of my exhaust. It cracked the pipe going into the 2-to-1 cat. I cut off the exhaust right before the cat. I had to drive it like that for a couple weeks, but just around town.

This when it started really getting bad. At first it would start up and idle but there was a really bad surge. I don't have a tach so I don't know exact rpm but it sounded like it was at normal idle then dip down to almost dieing, then pick back up to normal. Gas mileage was terrible and it would die at stop signs. I bought a commuter car soon after this started happening to commute to college. So i am no longer dailying the truck.

So now, when I start the truck it immediately dies unless you give it gas. Even when you give it enough gas to get a high idle you can still hear a surge. I don't have a lot of money to go buy a whole bunch of parts for them not to work so i've been doing a lot of testing.

This is what I've done so far to address this problem. I've tested the TPS, it had the correct range and had no gaps. I cleaned out the IAC and even bought a used one from pull a part. I don't have a multimeter that measures hertz, so i grabbed 2 MAP sensors from PAP as well. I've replaced the PCV valve. I've replaced the fuel filter and spliced in some new wire for the fuel pump that was frayed. I even checked the temperature sensor and that tested good.

I'm getting frustrated with this, and any help would be appreciated. Also if you have any questions I'll try to answer.

Chris_1

iTrader: (1)

Test your fuel pressure with a gauge.
Check your O2 sensor - it should be right on the y-pipe right where you cut it; that could cause a problem.

jdl2430

Thank you. I forgot to mention that I did patch up the exaust. I did it with flex pipe and it leaks, but I was worried there wasn't enough back pressure or constant flow on the o2 sensor. When I fixed it, it had no effect but I didn't check the sensor. I have class all this week, but I have time this weekend. I was trying to get a list of things that I can do this weekend.

Chris_1

iTrader: (1)

Maybe try and do a little better job on that leak too. Exhaust that leaks before the cats has carbon monoxide (bad for you). After the cats it will be carbon dioxide (much better). That's what they do, basically.

mahi's 1989

My 1989 6 cylinder / automatic is not going into gear. 65 degree weather, I let it warm up completely... go to put it in D and it won't go. have to push down alittle on accelerator and rev up the engine and then it will go into D. Then run around town... no issues. Thoughts?

Chris_1

iTrader: (1)

You should really start your own post for your problem; but I'd suspect a dirty trans filter or low fluid. The place to start anyway.

jdl2430

Ok, I just got back in from working on the truck. I sprayed the o2 sensor with pb blaster a few hours ago. I could not get it turn for the life of me. Ill have to wait untill next weekend to borrow a torch to heat it. Since I couldn't get it out I just unplugged it then I unhooked the battery then hooked up back up again. I tried to start it but it still wont idle on its own.

Thoroughbred

I had a what I would call a surging problem. it would sputter if i didn't jam on the gas, but when i did, it was fine.

turned out to be a fuel pump with lower than recommended psi. supposed to be 90 i think, but the one they had on there was pushing out around 35 max (mechanic checked it for 20 bucks).

the issue existed because the "master mechanic" who replaced the pump couldn't tell the difference between the 50psi fuel pump and the 100psi ... because the two were exactly the same as far as the label and packaging when they ordered and installed it. only upon testing psi was it possible to tell the difference, and that the part that was on there was below specifications.

no wonder it couldn't push the juice it was weak

so there's something to maybe think about

jdl2430

sorry for not replying sooner, but I did some more work on my truck. I rented a fuel pressure gauge from autozone. I hate autozone soooo much, I didnt realize the relief valve on the gauge was broken untill I hooked up to the shrader valve on the fuel rail and ended up spraying gas everywhere. I was able to put my thumb on the valve and stop it so the readings may be a little off. I also used that one plug to ground out the fuel pump with a wire and i got 38psi with the pump running and it drops down to 34 when it shuts off.

I was reading online about taking the vaccum line off of the regulator and that the pressure should increase, but it was the same 38psi on, 34psi off. I also read something about if the vacuum line smells like gas that the regulator is bad. I hooked the line back on and started the pump, turned it off, then i smelles the hose and it smelt like gas. I dont really know what this means but just putting it out there.

i was really hoping my problem was the fuel pump, but i think this just about ruled it out. Also this was the first time that my truck wouldnt start, even if i gave it gas while starting. I didnt want my night to be wasted so i went and pulled codes by counting the check engine light blips. I got 21, 24, 33, 41, 51, 63, 87, 95. I believe 21,24, and 51 can be ruled out because the engine was cold. 33 is EGR not closing. I dont know what 41 means by "HO2S" switching detected. 63 says that the TPS circuit is below minimum voltage, but when i tested it, it was fine? Also i dont get 87 and 95 because it says that the fuel pump circuit is failed and open. It also says "PCM to motor ground"

Thank you to everyone that has responded, and again sorry for the delayed update.

Chris_1

iTrader: (1)

If the regulator vacuum hose smells like gas that would indicate that the diaphragm inside the regulator is leaking gas (and pressure) into the vacuum line.
Usually the way to check that is pull the hose off the regulator and see if it smells like gas inside. If so, replace the regulator.
Engine needs to be warmed up to test for codes as the system won't go into closed loop until the ect indicates that the engine is at operating temperature.
Clear the codes and test it again with the engine hot.