dissum ol' bull sh**

Ok, for some time now i've been gone from the site on the count i haven't had to bask in the knowlege of my fellow ford gurus. But here's the sh** kicker....

I have a '90 F150 351 EFI (i know, not a bronc, but oh well....) The truck has major balls, enough to spin 35x12.50's at the drop of a hat completely through 1st and into 2nd, thanks to a 270 crane cam and a set of heddman shortys through a 2.5 true dual.

The problem is fairly recent. Yesterday, the truck started fine in the morning, drove great, went on break at 10am, hauled major 4ss, went to lunch, drove the same, filled up, went back to work, all driving like normal. Come time to go home, it started running like crap. No power, acts like there's no fuel, smell gas, sputters, dies, backfires, etc. At night, after adjusting the timing (the old man thinks that is always the problem, so i just shut him up) the damn thing overheated and spewed all my new fluid all over the ground.

Now the truck has had a 160 thermo put in about 3 days ago, but it was running better than ever. The 02 is out of my old bronco 2 (i miss my 86....) that had to be wired in due to ****** wiring. Here in this part of texas, all the old ford trucks have a hot wire to the fuel pump for the ignition, so pulling codes doesn't reveal anything but "circuit open fuel relay".

I'm out of ideas, the TPS and MAP have been replaced, there's no EGR, no cat, new plugs, blaster coil, "new" wires (slightly used bosch 8mm), and it pulls this crap. IT ONLY DOES IT WHEN IT WARMS UP. Fuel pressure is 30-40 psi.

Turn that thing on at night and pop your hood. Sounds like you may have a bad plug that's getting warm and "expanding" but I may be thinking weird?

bidibronco said:

Turn that thing on at night and pop your hood. Sounds like you may have a bad plug that's getting warm and "expanding" but I may be thinking weird?

Click to expand...

Or if you still have a cat on the exhaust then it's clogged. If not check the pcm itself. I had a similar problem a few years back and it turned out to be the pcm.

Doesn't have cats, plugs are new bosch plat 2's.

May be a shot in the dark...But the last time i tried to run bosch anything in a ford it ran like crap...I stick mainly to autolite plats..or motorcraft plats.... B) ...Just my 2 pennies worth..... >-

It's been running on the bosch equipment for some time, has a new Accel cap and rotor, a brand new borg warner module, a "new" bosch 02 sensor (although it's possibly a contributing factor). I know for sure the plugs are not part of the problem, all my fords run Bosch Plat 2 plugs. Like I said earlier, the fuel pressure is plenty and it does increase upon throttle, the TPS is brand new, the MAP is replaced, new 160 thermostat (has to be inspected, overheated last night), there's no cats, no EGR valve, the PCV is working fine, and yet for some reason it acts like it either doesn't have enough gas or too much gas.

Here's something interesting:

If I pop it in neutral and turn it off while driving (when it acts up) and turn it back on, it runs normally for like 30 seconds and then craps out again, it idles REALLY low and "chugs" and jerks when driving (when symptoms are present).

Just throwing things out there.....Fuel filter, carb built up in throttle body, did you gap the plugs properly, spark plug wires, rat's nest in air filter (had that once in a Jeep, caused same symptoms), try running premium gas for a while....idk. My dad's 98 F-250 also had similar symptoms and running premium gas through it seemed to help, it ended up being the spark plugs. Hope this is helpful.

Does the engine have an actual miss? Is the exhaust black and carbed up?

fuel filter was supposedly just replaced by my old man, TB is squeaky clean (dremel), plat 2's don't need to be gapped, open design, plug wires are good, no air filter clog, has always hated premium gas, exhaust not unusually black (all fords run rich), and it's hard to tell if there's a miss on the count of my bump stick throwing valves every which way, but when it starts acting up it seems like it.

Was it low on coolent?

Temp sensor is important.

But most likely a vacuum leak.

Checking for vacuum leaks.

Some of the sensors and some of the actuators either read the amount of vacuum, or use vacuum to move controls, therefore it is important to the proper functioning of the engine that your vacuum system is fully intact. Otherwise one may get codes falsely indicating that there is a problem with a controller/actuator, or a sensor when in reality it is caused by a lack of vacuum.

Look at your rubber vacuum hoses (they are about 1/4 - 3/8 inches in diameter, if they are dry rotted or cracked, replace them. IF they slip on/off of their connectors too easily, they may have stretched out a little bit, cut the ends off, and put them back on.

You may listen for a leak. Sometimes using a cut off piece of garden hose is a good aid to listen with. Sometimes a cardboard tube (like from gift wrapping paper) is helpful. Just remember that whenever you stick your head inside a running engine compartment, that you are not wearing any loose clothing or jewelry that can get caught.

Another suggestion is to use a spray can of carb cleaner and spray around the bottom of the intake manifold, and the base of the throttle body assembly. IF there is a leak, you should hear a change in your engine.

Keep a fire extinguisher handy, or use water instead of carb cleaner (it works, but not as well.) Be aware that if you use water and the wires get wet and it runs worse... your wires may be bad, and the water is allowing them to arc instead of jump the gap of the spark plug.

You might want to individually check each cylinder for spark to rule out a miss. Have you checked your distributor?

DUHHHH! My elevator went to the top floor finally. If it is only doing this when it warms up it may be due to a cracked distributor cap. I had that problem on an old 429. It had pleanty of power and ran like a scalded dog until it warmed up, then it felt like someone moved my distributor about 10 degrees. Turned out to be a crack in the cap that I didn't notice. May not be the cause in your case but just another thought. --Vince

distributor is brand new (old oil pump crapped out and shat on the pump gear, so a new dizzy was put in), and the cap and rotor are still shiny brand new accel units. there's no miss that's unusual (it misses at idle due to cam, no problem there). motor was just rebuilt not too long ago, so a vacuum line is most likely not the case, considering my old man took his sweet time fixing all the lines when he had the truck.

we did however just change the coil back to the one it came with, which is a factory unit, but most likely not the original piece. so far, it's not crapping out, but more testing is needed. we'll find out soon enough.

as to the overheating, the thermostat is coming out tomorrow and we'll see about that problem. it may be new, but it could still be defective, and considering i know almost all the managers at the local autozone, i may be able to exchange it.

is there a mass air meter on the truck? if so make sure its pluged in or clean it out with a q- tip!

my mass air on my mustang came unpluged and it ran just like that....

but , like i said im not sure if there is a mass air meter on the truck

yusuebronko2_86 said:

went on break at 10am, hauled major 4ss, went to lunch, drove the same, filled up, went back to work, all driving like normal. Come time to go home, it started running like crap. No power, acts like there's no fuel, smell gas, sputters, dies, backfires, etc. I'm out of ideas, the TPS and MAP have been replaced, there's no EGR, no cat, new plugs, blaster coil, "new" wires (slightly used bosch 8mm), and it pulls this crap. IT ONLY DOES IT WHEN IT WARMS UP. Fuel pressure is 30-40 psi.

Click to expand...

Instead of tearing apart your engine, maybe when you filled up, you got some bad gas. I would try a bottle of dry gas and a new fuel filter and see what that does for you first.

hey had this same problem with my ford check the actual temperature. take the temp of your truck at the exhaust manifold. i think it should be right around 180-195 degrees. if the same thing is happening my truck was runig raund 135 so the truck was dumping gas in trying to warm it up so i would change the o2 sensor the plugs and the thermostat.

the one thing i hate about ford the most is they all rust like ****

but they run for ever

something about that ford steel hey? Ive never understood how someone could past a judgement on a vehicle saying they are crap cause they rust. every vehicle rusts.

Not saying you said they are crap but I hear this all the time. If you dont take care of the body sorry man it will rust

A few things.

I dont' know what the timeline was with all of the parts that you replaced, when is started runny ******* and when it overheated etc. So I don't know how much of this is relevant.

I commented on both the fact that you need to look for vacuum leaks, and I don't beleive that you replied on that topic.

BOTH olDTIMER and I commented on temperature being important.

Now I took another look at this thread, and noticed that you changed from the OEM temp of 192 degrees to 160 degrees. I don't know when you made that change, but like oldtimer stated you may be running too cool.

I know just about nothing about cams, but I do know that Blade262US had commented a number of times that changing the cam typically causes more problems than not in an EFI, unless the engine is a MAF system (I think). I am certainly unclear of the details.

I also don't know when you changed your ignition module to an after market one, but could it be that it does not work well with the cam?