Help me diagnose
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Elder User
Joined: Sep 2005
Posts: 647
Likes: 3
From: Brumley, MO
Help me diagnose
My truck just started acting up. I have to keep giving it gas to keep it running otherwise it will idle down greatly and die. When it idles down it sounds choppy, and the whole truck shakes like crazy, and then it sputters out and dies. It also will die even after it is warm I can be driving along and go just a few seconds without touching the gas and all of a sudden the truck is dead. After starting it I can leave the choke out and it will not die Now just recently the truck has started surging while driving(constantly). It will just surge going down the road as long as you are giving it gas.
I know there are like a billion things that could be the problem. I will be taking it to a mechanic eventually, but I just want to be prepared for what he might say.
I know there are like a billion things that could be the problem. I will be taking it to a mechanic eventually, but I just want to be prepared for what he might say.
Lead Driver
Joined: Jul 2009
Posts: 6,477
Likes: 19
From: Sheffield, AL
dwrestle,
It might not have to be too big of a leak to give you drivability issues. First, open the hood and just look for loose vacuum hoses and with the engine running [if possible; be careful!] stand in front and listen for hissing sounds. Spray carburetor cleaner or WD40 at the carburetor base and intake manifold to engine connection. Be careful if the exhaust is hot [fire]. If the idle speed changes while spraying, you have found the leak. Check the PCV valve and brake booster and hoses. If automatic, check vacuum lines to modulator if so equipped.
Our wonderful 4.9L engines have many ports on the intake manifold and on the firewall where leaks can occur. Any leak will show up as poor performance.
Has any recent work been done in the engine compartment where a line might have been cut or dislodged?
Check the mounting bolts at the base of the carburetor as they are known to vibrate loose.
It might not have to be too big of a leak to give you drivability issues. First, open the hood and just look for loose vacuum hoses and with the engine running [if possible; be careful!] stand in front and listen for hissing sounds. Spray carburetor cleaner or WD40 at the carburetor base and intake manifold to engine connection. Be careful if the exhaust is hot [fire]. If the idle speed changes while spraying, you have found the leak. Check the PCV valve and brake booster and hoses. If automatic, check vacuum lines to modulator if so equipped.
Our wonderful 4.9L engines have many ports on the intake manifold and on the firewall where leaks can occur. Any leak will show up as poor performance.
Has any recent work been done in the engine compartment where a line might have been cut or dislodged?
Check the mounting bolts at the base of the carburetor as they are known to vibrate loose.
Moderator
Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
This sounds like what mine was like before I replaced all of the vacuum lines. It was particularly worse in the colder months since the colder air has a greater effect on a warm engine.
I also didn't have a big open leak, just lots of old vacuum lines.
It got to be a lot of fun having to keep a foot on the brake, a foot on the clutch, and a foot on the gas pedal to keep it from dying at stop lights.
I also didn't have a big open leak, just lots of old vacuum lines.
It got to be a lot of fun having to keep a foot on the brake, a foot on the clutch, and a foot on the gas pedal to keep it from dying at stop lights.
Thread Starter
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Elder User
Joined: Sep 2005
Posts: 647
Likes: 3
From: Brumley, MO
I stay away from stoplights as much as possible, but when I am coming up at a stop I throw it in nuetral so I only have to worry about the brake and gas. When it turns green I just rev the engine high in nuetral and put it in first and let off the clutch till it starts to pull then I let off the brake and gas it.
I might need to check all the vac lines because it has always had it's issues. It is a pain in the butt to try and take off unless it's in granny gear.
I might need to check all the vac lines because it has always had it's issues. It is a pain in the butt to try and take off unless it's in granny gear.
Posting Guru
Joined: Jun 2004
Posts: 1,092
Likes: 2
From: Casa Grande
This sounds like what mine was like before I replaced all of the vacuum lines. It was particularly worse in the colder months since the colder air has a greater effect on a warm engine.
I also didn't have a big open leak, just lots of old vacuum lines.
It got to be a lot of fun having to keep a foot on the brake, a foot on the clutch, and a foot on the gas pedal to keep it from dying at stop lights.
I also didn't have a big open leak, just lots of old vacuum lines.
It got to be a lot of fun having to keep a foot on the brake, a foot on the clutch, and a foot on the gas pedal to keep it from dying at stop lights.
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Moderator
Joined: Dec 2007
Posts: 7,987
Likes: 104
From: Boise, Idaho
When I did mine, I simply re-created the whole setup using standard rubber vacuum lines mixed with vacuum T's. It wasn't too hard.
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Posting Guru
Joined: Jun 2004
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From: Casa Grande
Kind of had that feeling, sure haven't been able to find them. Oh well, rubber should last longer than the plastic ones anyway.
Senior User
Joined: Aug 2011
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They are discontinued. Not sure but i had that issue with my truck at stop lights. Was not vacuum lines. I ended up replacing the alternator and battery and it fixed my problem. Had a bad voltage regulator. Do you notice your voltage meter spiking at all? If thats the case than try vacuum lines as thats the cheapest. Go to autozone and find a size hose that fits the fittings and just run them yourself. VERY EASY!!! If that doesnt fix your problem than maybe what i did to mine might help. Also check you fuel pressure to make sure your getting enough fuel, might be a weak fuel pump if u need to keep it gassed up. Also how long has it been since a tune up? could be bad spark, or could even be a clogged fuel filter and need to keep the gas flow so it keeps the pressure up in the lines. A lot can be going on. But overall to make a motor work you need fuel, air, and spark... once you check those, if you still have a problem, than you might have a bigger issue.
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Elder User
Joined: Sep 2005
Posts: 647
Likes: 3
From: Brumley, MO
No I haven't figured it out yet. As far as I know the volt meter stays the same. I was kind of thinking fuel pump myself, but I am not sure yet. I just hope it's something simple and cheap. If it helps diagnose the problem I have noticed sometimes I can smell gas pretty bad in the cab which is something it has only done when the old Q-Jet was on there running real rich(I have a 2100 off of a 390 now).
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Elder User
Joined: Sep 2005
Posts: 647
Likes: 3
From: Brumley, MO
Well guys I got the brunt of the problem solved. My PCV valve hose was disconnected from the hose that goes to the carb(T fitting thing). Anyway it idles pretty decent, and doesn't die anymore. It still has a shutter that shakes the truck here and there while sitting at idle, and it still has kind of a surging while accelerating, but not nearly as bad as it was. It makes me wonder if I don't have another smaller leak somewhere. It almost feels like I could have a loose mount somewhere(motor trans or somewhere else).
Postmaster
Joined: Dec 2006
Posts: 3,603
Likes: 10
From: Spokane, WA
Check for a 1. plugged/worn-out Cat 2. Burned-out EGR valve and 3. If you are smelling gas but don't see a leak it could quite possible be the fuel pump. They go kapoot internally sometimes and pump gas into the crankcase...NOT GOOD!
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