F-100 barely runs

[imakedacookies]

Im going to apologize now for a long post but I want to give a full timeline of whats happening hoping for some good answers. I have a 78 F-100 with a 302 and 3 speed auto, I need it fixed as my girlfriend now drives my nice truck. So I bought the truck about 6 months ago and it ran fine, used it as a daily driver for fun. Then about 3 months ago it started to stall if the gas pedal was pushed to hard and ran really rough. I cleaned out the carburetor the best I could which helped it run smoother but it still had a slight stalling issue. I changed the idle and adjusted some of the mixture screws and that seemed to help a lot. Then one day I was driving down the road just fine and when I got where I was going I shut it off, then less than an hour later I went to start it and it was running rougher than ever. I couldn't even take my foot off the gas or it would die. I did a quick one over and found that ALL the oil had leaked out. I had just checked the oil a day or two earlier so I thought that was really random. I put some oil stop leak in there and ran it, was able to limp it home. Did another oil change just to clean it out and now it seems to be holding oil. Now heres the current issue. I went to start it for the first time in about 10 days, it wont run without me giving it a little gas, and shakes like hell, the idle screw doesn't seem to do anything if I turn it either way, and when I shut it off to do a once over there was a decent amount of smoke coming from the headers. It wasn't enough to see with the hood closed though. I checked the oil and coolant and everything seems to be good. I just cant figure out the exact problem. Im hoping its just a simple idle issue and bad valve cover gasket or something like that but I cant even get the idle to adjust. Any help would be awesome, I need this truck to get back to work because carpooling with my girlfriend who works the opposite shift is tough.

[imakedacookies]

Major update. after about 4 hours trial and error adjusting mixtures on the carb and redneck rigging the idle it seems to be a lot better. I still have a question though. It will run just fine when in park or neutral, but when I put it in a driving gear the idle drops a lot. it runs rough in a drive gear, it will drive but when stopped or braking the engine sounds like its bogging down, stays running ish. After I come to a stop the idle will come back up a little. I thought it could be a vacuum leak in the going to the brake booster or something but holding the brake in a drive gear doesnt effect anything. Just while stopping.

[yekrats]

The difference in how it runs when idling in neutral and in gear is typical of a vacuum leak so I was thinking about that but it sounds like it's able to get to (suck some up) the oil so now I'm wondering about the intake manifold gaskets or even the manifold itself. I'd put a vacuum gauge on it and see what it says at idle. Should read around 15-18 lbs and needle be fairly steady. Triple check all vacuum ports and hoses, check (carb?) gasket and check PCV and hose too. If the valve covers are leaking, change the gaskets. See if any of that helps. Good luck

[imakedacookies]

I did a little more adjusting on the carb and cleaned it out again. Also replaced the pcv valve , I noticed it was almost broke in half. . I feel stupid for asking this but could it be the speed sensor? I noticed that it bogs down the worst while slowing, especially if I have to brake hard. and I dont think its anything to do with the actual brakes because once im stopped I can put the brake pedal all the way down with no new symptoms. It also bogs down on sharp turns, it gets worse the slower I go. I checked the vacuum and it is steady in the fact that the needle doesnt bounce quickly, but when the engine stumbles the vacuum does change with the rpm change. I thought it could be the brake booster but all of the tests I did on it seemed to pass. Im beginning to think that it is still a carb issue, like the change in motion while stopping or turning is somehow effecting it?

[yekrats]

Originally Posted by imakedacookies

I did a little more adjusting on the carb and cleaned it out again. Also replaced the pcv valve , I noticed it was almost broke in half. . I feel stupid for asking this but could it be the speed sensor? I noticed that it bogs down the worst while slowing, especially if I have to brake hard. and I dont think its anything to do with the actual brakes because once im stopped I can put the brake pedal all the way down with no new symptoms. It also bogs down on sharp turns, it gets worse the slower I go. I checked the vacuum and it is steady in the fact that the needle doesnt bounce quickly, but when the engine stumbles the vacuum does change with the rpm change. I thought it could be the brake booster but all of the tests I did on it seemed to pass. Im beginning to think that it is still a carb issue, like the change in motion while stopping or turning is somehow effecting it?

There's no such thing as stupid people. You did a very smart thing. You asked for help. And besides, cars is hard. Anyhoo, it could be anything that gets vacuum. Oh and the vacuum drops when the engine stumbles because it's not running as fast. (not sucking in air as hard) Perfectly normal. Did you replace the vacuum hose to the PCV valve too? Sounds like the PCV was bad but the vac hose could be too. Could it be the carb, sure. Bogging when it turns or stops or whatever could be a sign the float is out of adjustment or just plain old sunk. Either of those conditions can allow the carb bowl to over fill when turning, stopping (maybe even going up or down steep hills) which in turn floods the motor. (making it bog down or die) You'll have to take the top off the carb to check that. Not too hard usually. Um, 2 bbl or 4 bbl by the way? One last thing, you might already do this but you can check vacuum lines easily by squeezing them (with engine running of course) with a pair of pliers closest to where they hook to the manifold or carburetor. When you pinch them, if it runs better you have isolated the problem. Then you just have to figure out where it's leaking. Usually the vac line is bad but could also be disconnected or whatever it's hooked to is bad.
Aren't cars fun!

[imakedacookies]

I actually hate working on cars, but seem to buy ones with hidden problems so I end up doing a lot of work, so no cars arnt fun ha. It is a 2bbl, and thanks for the tip about squeezing the vacuum lines, im gonna try that my next day off. Im still thinking that it is the carb seeing how that's the only thing that has consistently caused problems for the past couple months. I had to drive it to work today and while coming to a stop I had to keep my foot on the gas to keep the idle up a little and that seemed to do the trick to keeping it running. Unfortunately that means I have to brake with my left foot, takes some talent, and its drinking gas more than usual.

[yekrats]

Originally Posted by imakedacookies

I actually hate working on cars, but seem to buy ones with hidden problems so I end up doing a lot of work, so no cars arnt fun ha. It is a 2bbl, and thanks for the tip about squeezing the vacuum lines, im gonna try that my next day off. Im still thinking that it is the carb seeing how that's the only thing that has consistently caused problems for the past couple months. I had to drive it to work today and while coming to a stop I had to keep my foot on the gas to keep the idle up a little and that seemed to do the trick to keeping it running. Unfortunately that means I have to brake with my left foot, takes some talent, and its drinking gas more than usual.

Sorry to hear it's drinking gas. I've got an F-150 so I know trucks aren't gas misers to begin with. I feel for you man. Good news it's a 2 bbl. Those are easy and I'm sure you'll have no trouble. Top of the carb comes off easy so you can check out that float. Hope it's something simple like that. Even more so that it's a vacuum leak.

Good luck

edit: Just remembered something from way back and did some research. Ford had a tremendous problem with their egr valve setup on v-8's in the 70's. I don't know what kind you have but if the egr bolts onto the carb spacer plate (plate that sits underneath the carb) that may be your problem.

note: these pics may not be exactly like yours but hope they give you the idea.



They eventually discontinued this and the egr bolted directly onto the intake manifold.


Heck it could be the egr no matter where it's at so check it out either way. Anyhow, the carb spacer plate was made from aluminum and it would slowly disintegrate from the hot exhaust when the egr opened. Cars/trucks wouldn't idle, ran crappy, etc. Sure sounds like it fits your bill. Same goes for a bad egr valve. They can really foul things up. Sorry it took so long for me to remember this but what can I say!?! I'm spoiled these days. All I gotta do now is ask the computer what's wrong. Oh and actually I agree. Cars are not always fun.

Hope this helps. Thank you Auto Zone

Before attempting to troubleshoot or repair a suspected exhaust gas recirculation (EGR) system on a vehicle, the following conditions should be checked and be within specifications.

• Engine is mechanically sound.
• Injection system is operating properly.
• Mechanical-vacuum advance is properly adjusted or the electronic advance system is operating properly.

If one or more of these conditions is faulty or operating incorrectly, perform the necessary tests and services to correct the problem before servicing the EGR system.

Typical EGR valve. Courtesy of Chevrolet Motor Division-GMC.Before attempting any tests of the EGR system, visually inspect the condition of all vacuum hoses for kinks, bends, cracks, and flexibility. Replace defective hoses as required. Check vacuum hose routing. (See the underhood decal or the manufacturer's service manual for correct routing.) Correct any misrouted hoses. If the emissions system if fitted with an exhaust-gas-recirculation valve position (EVP) sensor, the wires routed to it should also be checked.
If the EGR valve remains open at idle and low engine speed, the idle operation is rough and surging occurs at low speeds. When this problem is present, the engine may hesitate on low-speed acceleration or stall after deceleration or after a cold start. If the EGR valve does not open, engine detonation occurs. When a defect occurs in the EGR system, a diagnostic trouble code (DTC) is usually set in the powertrain control module (PCM) memory.

Typical computer-controlled EGR system. Reprinted with permission of Ford Motor Company.In many EGR systems, the PCM uses imputs from the engine coolant temperature (ECT) sensor, throttle position sensor (TPS), and manifold absolute pressure (MAP) sensors to operate the EGR valve. Improper EGR operation may be caused by a defect in one of these sensors. A scan tester may be connected to the data link connector (DLC) to check for an EGR DTC or a DTC from another sensor which may affect EGR operation. The cause of any DTCs should be corrected before any further EGR diagnosis.

[imakedacookies]

Im almost positive that the egr valve is the main issue. Problem is I cant seem to find it. I cant figure out how to post a freaking picture on here without a url address, but I would be more than happy to send you pictures and maybe you can help me find it? It would be much appreciated. From what I can see there is no egr valve behind the carburetor or anywhere else bolted to the intake manifold. Heck Im so confused at this point Im not even sure its the right engine for the truck.

[yekrats]

Originally Posted by imakedacookies

...Heck Im so confused at this point Im not even sure its the right engine for the truck.

Hey, that's entirely possible. Hmmm, it's possible the spacer plate and EGR have already been removed and that's why you can't find them.

Here's a pic of what it would look like/resemble. This is off the engine of course. The silver thing with two holes in teh middle is the spacer plate that sits under the carb and the thing that hangs off the side is the EGR valve. (ERG is gold colored)


Can't seem to find a pic of one on an engine. All joking aside it is possible it's already been removed. As I said, they were a lot of trouble. Have you tried spraying carburetor cleaner around the base of the carburetor with the engine running? (and anyplace else it could leak too) If there's a vacuum leak the motor will speed up immediately. This is a very good way to find leaks.

Here's a pic of an EGR mounted on the intake. Yours may resemble this if you have one on the manifold.


Typical EGR valve


Hope this helps some. Hang in there!!!

[imakedacookies]

Sorry I havnt been able to update this thread in a while, been working too much to work on the truck. Anyway the egr has been removed and bypassed like you said may be the case. Now Im stuck wondering what the problem is. Im going to put a new carb on it hoping itll help. If not then I just don't know. Should have the new carb next week or early the following week so ill let you know if that works. Thank you again for the help.

[imakedacookies]

Thanks for all your help vekrats! I still dont have the carb yet, but Ill let you know how it goes when I get a new one on there. Also if you know anything about wiring or anyone else that knows about wiring check out my other thread, I need help with a tailight issue. This truck is driving me insane Thanks in advance

[imakedacookies]

I'm still waiting on the carburetor and my truck is getting rapidly worse. I have to drive 4 miles to work and it died at least 3 times coming home this morning. I'm almost positive it's the carburetor because while coming to a stop I put it in neutral and it still tried to die so yes i know there is a vacuum leaknow but in neutral it shouldn't die from that so it's gotta be fuel not getting through the carb. Anyway, I got home and my engine was hot, I could feel the heat in the cab, temp gauge stopped working this morning and when I opened the hood the engine may have well been on fire, could of got a tan off it, and the radiator was cool. Opened the cap just fine no steam or anything. That a bad water pump or coolant temp sensor? Only reason I won't get rid of the truck is because I need something and it's old enough it doesn't need to be inspected and my girlfriends car won't pass so it's in the process of being parted out. Therefore it's drive the pile or have my girlfriend drop me off with the good truck a few hours early before she works

[yekrats]

Sounds like there was almost no coolant left in the engine. That's why the temp gauge didn't work. No coolant in it to heat the sensor/make the gauge work. You must have a leak somewhere. Fill it up with coolant, start it and warm it up. Check for any leaks. Yes the water pump could be bad. Leaking around the input shaft (shaft that sticks out the front of pump and the fan belt pulley bolts on) is not uncommon when a pump gets old. Could be anywhere though. Radiator, hoses, freeze plugs... You might want to change the thermostat too. Could also be the reason there's no coolant. Maybe it got hot and blew all the coolant out? Anyway, hope your engine survived the heat. Good luck.

[imakedacookies]

The coolant was topped off, ando I ran it today to check for leaks, nothing seems to be leaking so I have to assume there's just no coolant pumping through the engine. I just want to make sure I understand before I buy some parts. It could be because of the temp sensor because that would make it not pump coolant? Or the pump itself therefore nothing can cycle through causing the temp sensor not to get any coolant?

[yekrats]

Originally Posted by imakedacookies

The coolant was topped off, ando I ran it today to check for leaks, nothing seems to be leaking so I have to assume there's just no coolant pumping through the engine. I just want to make sure I understand before I buy some parts. It could be because of the temp sensor because that would make it not pump coolant? Or the pump itself therefore nothing can cycle through causing the temp sensor not to get any coolant?

Sorry, I thought there was no coolant in the radiator for some reason. Still possible the radiator's full but there's a big air buble in the top of the engine. This is supported by the fact that the temp gauge (the sender) isn't working. No water to the sender, (a bubble will do this) no temp reading on the gauge. You can check this by pulling one of the heater hoses off and seing if water flows out. If there's a bubble it will be dry there. Suppose it's also possible the temp sender has just gone bad and the water pump is bad inside. Inside being the impeller has broken off, rusted out, whatever. Doesn't happen too often but... Sorry you're having all this trouble, sounds like the PO didn't do too well.