Engine Miss...
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Freshman User
Joined: May 2003
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From: KCMO
Engine Miss...
Last weekend the truck developed a miss. At the same time (or close to it) the brake booster started to fail....I think I posted about it.
Anyhow, replaced the booster, replaced the hose, New plugs, rotor, cap, coil; wires were replaced about 3 months ago, and I still have a miss...It acts as if it's a vacume leak, but I can't find it?
Does anyone have any ideas how to locate the culprit?
Could my timing chain have jumped? The dist. is cranked down tight, doesn't move to lose time.... Could the dist. be failing? How can I tell?
The truck idles smoothly, but it stutters under a load, and talk about bad gas milage...I thought it was bad getting 6-8 MPG, this weekend I was lucky to get 2-3mpg...It took $5.00 to drive 10 miles...and no more.....outa gas....
I need help!! And so does the truck!!
Any ideas appreciated!!
Thankyou
Darrell
Anyhow, replaced the booster, replaced the hose, New plugs, rotor, cap, coil; wires were replaced about 3 months ago, and I still have a miss...It acts as if it's a vacume leak, but I can't find it?
Does anyone have any ideas how to locate the culprit?
Could my timing chain have jumped? The dist. is cranked down tight, doesn't move to lose time.... Could the dist. be failing? How can I tell?
The truck idles smoothly, but it stutters under a load, and talk about bad gas milage...I thought it was bad getting 6-8 MPG, this weekend I was lucky to get 2-3mpg...It took $5.00 to drive 10 miles...and no more.....outa gas....
I need help!! And so does the truck!!
Any ideas appreciated!!
Thankyou
Darrell
Senior User
Joined: Jan 2003
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From: West Kentucky
Engine Miss...
What about your carb????? What kind and how old is it? Maybe you have developed a vacume leak around it? Is it tightened down good to manifold? Do you smell gas or does it seam to be running rich? When you said your gas mileage went way down but was still driveable, reminded me of a similar instance I had on a motorcraft 2V carb on a windsor years ago. Turned out there that the main throttle body was worn out allowing a massive vacume leak. Replaced the carb and was fixed. Maybe your carb just needs a rebuild kit. Just an idea!!!!! Good Luck!!!!!!!
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From: KCMO
Engine Miss...
Good question....I don't know how old the carb is...it was on the truck when I bought it a year ago. It's a 650 holley.
Yes, sometimes it seems to run rich, even after adjusting it.
Hmmm. I'll have it checked out...I don't know alot about carbs.
I did check the bolts...it's tight...
How hard would it be for a first time "rebuilder" to rebuild the carb???
Thanks!
Yes, sometimes it seems to run rich, even after adjusting it.
Hmmm. I'll have it checked out...I don't know alot about carbs.
I did check the bolts...it's tight...
How hard would it be for a first time "rebuilder" to rebuild the carb???
Thanks!
Post Fiend
Joined: Nov 2001
Posts: 6,748
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From: Tallassee, ALabama
Engine Miss...
First off, this is not an approved method by OSHA....lol.....but a good shade tree mechanic's way to find an air leak. Extenguish all smoking materials while doing this....
Start the engine. Take a propane torch and open the valve sightly so you have a small amount of propane coming out the nozzle, but do NOT light the torch. Move the UN-LIT torch around the engine, manifold, carb (efi) and any vacuum hose. When the engine speed picks up, you have found the area where the air leak is located. Might require a bit of searching in that area to find the actually leak.
Start the engine. Take a propane torch and open the valve sightly so you have a small amount of propane coming out the nozzle, but do NOT light the torch. Move the UN-LIT torch around the engine, manifold, carb (efi) and any vacuum hose. When the engine speed picks up, you have found the area where the air leak is located. Might require a bit of searching in that area to find the actually leak.
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From: KCMO
Engine Miss...
Ahhh...I take it that's another method like the "ether"......I'm gonna try that tonight...I don't have propane, but I just bought a can of ether yesterday evening....
Just a little leary about it...lol
Thanks guys
Just a little leary about it...lol
Thanks guys
New User
Joined: Apr 2003
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Engine Miss...
another way to find out the miss is to check temp. at each exaust outlet. the lower temp is the cylinder that is not firing. usually a large difference like 500 deg. to 200 degr. if you dont have anything to measure, you can put a wad of spit, yes spit, on your finger and swipe it across the header at the exaust, a good running cylinder will burn quickly where the one with the miss will burn very slowly. you can then start your investigating on that cylinder, [plug, wire, cap, compression etc.]
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From: KCMO
Engine Miss...
Well.......
I tried the propane/ether trick last night.....
Nothing....It didn't rev at all, it didn't do anything. I traced all the hoses, I traced the intake seals, and the base of the carb, everything I could think of. At least now it's cleaner than it was
Now, out of nowhere it's getting worse. It's got a bad stutter to it now.
How can I check the valves?? I'm worried this might be it, but not sure. How much does it usually cost for a valve job? Can I do it myself?
I'll try to get a temp. on the exaust tonight...tell ya what I find.
thanx
here trucky, trucky trucky.....
I tried the propane/ether trick last night.....
Nothing....It didn't rev at all, it didn't do anything. I traced all the hoses, I traced the intake seals, and the base of the carb, everything I could think of. At least now it's cleaner than it was
Now, out of nowhere it's getting worse. It's got a bad stutter to it now.
How can I check the valves?? I'm worried this might be it, but not sure. How much does it usually cost for a valve job? Can I do it myself?
I'll try to get a temp. on the exaust tonight...tell ya what I find.
thanx
here trucky, trucky trucky.....
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Joined: Jun 2003
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From: AK. OH.
Engine Miss...
Another way to find a vacum leak on a carburated engine is to cup your hand over the top of the carb inlet and slowly close off the air going into it. If at any time the idle comes up and/or smooths out, you know you have a leak.
Also when yuor booster was replaced. Did you also replace the check valve?
Also when yuor booster was replaced. Did you also replace the check valve?
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From: KCMO
Engine Miss...
I'm not sure what it is.....
I don't have any vac. leaks that can be found.
I've replaced everything in the ignition syst.
What else should I check??
The miss has gotten considerably worse, I've lost lots of power....To the point I'm not driving it anymore until I can fix it. The truck couldn't even get out of its own way if it had too.
I think it may be time to tear it down and rebuild....At least then I'll know what is done to it.
Thanks for all the help guys!!
I don't have any vac. leaks that can be found.
I've replaced everything in the ignition syst.
What else should I check??
The miss has gotten considerably worse, I've lost lots of power....To the point I'm not driving it anymore until I can fix it. The truck couldn't even get out of its own way if it had too.
I think it may be time to tear it down and rebuild....At least then I'll know what is done to it.
Thanks for all the help guys!!
New User
Joined: Jun 2003
Posts: 4
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From: AK. OH.
Engine Miss...
You could perform a compression test on the engine.
If you can get your hands on a compression guage. It goes like this.
First pull all the plugs and it is best to disable the coil. start on cyl. 1, screw the guage into the spark plug hole, crank the engine several revolutions, check and record the readings. Follow the same procedure with the remaining cyl's. If you find a cyl. with considerably different readings you've probably found the culprit. You can then perform a (WET TEST). Put a shot of motor oil in each cyl. as you repeat the test. If that cyl. now has a much better reading the problem would point toward rings as the oil would help to seal them. therefor making the compression go up. Hope this helps.
If you can get your hands on a compression guage. It goes like this.
First pull all the plugs and it is best to disable the coil. start on cyl. 1, screw the guage into the spark plug hole, crank the engine several revolutions, check and record the readings. Follow the same procedure with the remaining cyl's. If you find a cyl. with considerably different readings you've probably found the culprit. You can then perform a (WET TEST). Put a shot of motor oil in each cyl. as you repeat the test. If that cyl. now has a much better reading the problem would point toward rings as the oil would help to seal them. therefor making the compression go up. Hope this helps.
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From: KCMO
Engine Miss...
Thanks....I'll try that next...as soon as I get a comp. tester. Is there a certain style or brand tester I should find/get??
She doesn't smoke except 1 puff during start up.
Is there a possibility it could be valves? or burnt seats??
How could I check that???
She doesn't smoke except 1 puff during start up.
Is there a possibility it could be valves? or burnt seats??
How could I check that???
New User
Joined: Jun 2003
Posts: 4
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From: AK. OH.
Engine Miss...
Any engine comp. tester should work. The smoke at startup will be valve stem seals. Probably smokes if you really get into the throttle too. valves seals can be installed without removing the engine or cyl. heads. You have to use compressed air to hold the valve up while you remove the valve spring and replace the seal. As far as the burnt valves, you will get some indication of them when you do the comp test. Let us here your test results. There is also something called a leakdown test but not many people have the equipment. Check your compression so you know what it is. It's probably something else but at least you'll know.
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From: KCMO
Engine Miss...
I haven't got the chance yet to do a compression test, but I did pick up a "professional compression tester" Didn't look much different than the regular comp tester they had, but it does have a few attachements for different size plugs....
My heads are the: D3ve-a2a heads...Are these good...can I go to a higher comp. head?
I've been checking on valve jobs around here...the best quote I have so far is aprox. $350 to grind, 3angle cut, guides, seats for both... Is this a good price?? He said he could have em done in about a week. Does that seem timely?
Doing the comp. test tonight..soon as I get home from work...
It doesn't really smoke bad when on the throttle...Just smell real rich....no matter how many times we've adjusted the carb to lean it out...still thinkin' valve seals?
Thanks for everyones input. I really appreciate everything!
Didn't look much different than the regular comp tester they had, but it does have a few attachements for different size plugs....My heads are the: D3ve-a2a heads...Are these good...can I go to a higher comp. head?
I've been checking on valve jobs around here...the best quote I have so far is aprox. $350 to grind, 3angle cut, guides, seats for both... Is this a good price?? He said he could have em done in about a week. Does that seem timely?
Doing the comp. test tonight..soon as I get home from work...
. The smoke at startup will be valve stem seals. Probably smokes if you really get into the throttle too.
Thanks for everyones input. I really appreciate everything!
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From: KCMO
Engine Miss...
OK, I did a Comp. test on the truck this weekend......Not too good
All the cylinders read between 135psi-140psi, except #3...0psi, didn't even try to register
So, I've been talking to people about what they think it is, or what I should do.
About 3 people said it could be a stuck valve, the rest say a burnt piston....Either way is not good, but I'm hoping for the valves...I can fix that soon and relativly fast. I don't have the money for a rebuild
I found my engine code, but left it at home, If I post it tomorrow could someone help me decode it? ie. How old my block is, ect.
So what do ya'll think I should do? The truck sits on the side of my street, I don't have a driveway, the closest driveway/shelter I have to use is only 35 miles away
All the cylinders read between 135psi-140psi, except #3...0psi, didn't even try to register
So, I've been talking to people about what they think it is, or what I should do.
About 3 people said it could be a stuck valve, the rest say a burnt piston....Either way is not good, but I'm hoping for the valves...I can fix that soon and relativly fast. I don't have the money for a rebuild
I found my engine code, but left it at home, If I post it tomorrow could someone help me decode it? ie. How old my block is, ect.
So what do ya'll think I should do? The truck sits on the side of my street, I don't have a driveway, the closest driveway/shelter I have to use is only 35 miles away
