OK so here we go. I was told by several garages that my 73 Chrysler 400 engine had a potential wrist pin problem in one of the cylinders and the engine should be rebuilt. It exhibited low speed engine knock and would not idle properly when cold or warm. The engine always sounded like it was grasping for air and the exhaust sounded tinny and smelled rich. I did not want to ruin this engine since it is original to the car and had only 64000 original miles on it. So I found the best shop with great references in the area to do the job over the winter. Was quoted a price between 4500 to 5000 to do the complete job. Well now I have 8300 into the engine and it runs no better than when I took it in. The knock is gone but it still idles rough when cold It will quit once in a while and if run for a period of time have a tough time restarting. Replaced the carb,distributor, coil, voltage regulator, ballist resistor, just about everything you could think of and the car still runs terrible. I am at the end of my rope with this and broke to boot. I thought this would solve my problem and it has only added to it. The carb has been tweeked and adjusted and am told it is working properly by the shop. We are at an end to finding a solution. Do any of you have suggestions as to what it might be? Any help would be greatly appreciated.Also the exhaust still sounds tinny but the rich smell is gone. It has a new nos muffler on it and sounded fine before this problem started. Help!
engine idle problems
- Thread starter chry73luv
- Start date
727
New Member
If you look down into your carb bores with the engine idling. Do you see any large droplets of fuel falling onto the carb flappers? This would indicate you carb float valves leaking by, Or improperly adjusted floats and will give a rough idle.
A torque converter with a low stall will make the idle seem rough while in gear.
Does your engine have electronic ignition?
Have you run a compression check?
Also how much vacuum are you pulling at idle?
Make sure you have the correct firing order on your plug wires.
A torque converter with a low stall will make the idle seem rough while in gear.
Does your engine have electronic ignition?
Have you run a compression check?
Also how much vacuum are you pulling at idle?
Make sure you have the correct firing order on your plug wires.
In addition to 727 suggestions:
1.) If you have an EGR valve, it could be carboned up and leaking. Go down to your local auto parts and buy a block off plate and see if that helps (about $10). EGR valves function poorly with oxygenated fuels and it is only a matter of time until it starts leaking if it is not already leaking.
2.) Remove the hose to the power brake booster and block off the port. If the idle improves markedly, you have a bad brake booster. Don't try to drive the car this way.
3.) Check the heat riser to be sure it is not stuck shut.
4.) Check the distributor for excessive shaft play. Do this by removing the dist. cap. Next, try to move the shaft side to side, if you feel movement, the shaft bearings are shot and the dist. needs to be rebuilt. This was a common failure on older Mopars and the loose shaft causes erratic dwell issues and engine misfire. Also check the lobes on the dist shaft for excessive wear as this will cause the same problems. I know its new, a lot of today's rebuilds are crap. (Cardone)
5.) You could also have a clogged pick up screen on the tank sending unit that is starving the engine for fuel.
$8300 is a lot of money for a standard rebuild. Did you have any performance work done or what exactly cost so much? Wrist pin failures on the 400 are extremely rare unless there has been a head gasket leaking or a dropped valve. Your shop does not sound like they are very good at diagnostics. Should have hooked the car up to an infrared exhaust analyzer first thing after the rebuild as an aid to find the misfire. This would have told them if the car was missing, running to rich, too lean etc. Hooking up to a shop scope would check for distributor issues etc. I think you may have been dealing with parts changers rather the trained tech personnel. Common problem these days on older cars.
Dave
1.) If you have an EGR valve, it could be carboned up and leaking. Go down to your local auto parts and buy a block off plate and see if that helps (about $10). EGR valves function poorly with oxygenated fuels and it is only a matter of time until it starts leaking if it is not already leaking.
2.) Remove the hose to the power brake booster and block off the port. If the idle improves markedly, you have a bad brake booster. Don't try to drive the car this way.
3.) Check the heat riser to be sure it is not stuck shut.
4.) Check the distributor for excessive shaft play. Do this by removing the dist. cap. Next, try to move the shaft side to side, if you feel movement, the shaft bearings are shot and the dist. needs to be rebuilt. This was a common failure on older Mopars and the loose shaft causes erratic dwell issues and engine misfire. Also check the lobes on the dist shaft for excessive wear as this will cause the same problems. I know its new, a lot of today's rebuilds are crap. (Cardone)
5.) You could also have a clogged pick up screen on the tank sending unit that is starving the engine for fuel.
$8300 is a lot of money for a standard rebuild. Did you have any performance work done or what exactly cost so much? Wrist pin failures on the 400 are extremely rare unless there has been a head gasket leaking or a dropped valve. Your shop does not sound like they are very good at diagnostics. Should have hooked the car up to an infrared exhaust analyzer first thing after the rebuild as an aid to find the misfire. This would have told them if the car was missing, running to rich, too lean etc. Hooking up to a shop scope would check for distributor issues etc. I think you may have been dealing with parts changers rather the trained tech personnel. Common problem these days on older cars.
Dave
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Another rare and difficult to diagnose problem could be a cracked intake manifold. Some times when a heat riser sticks shut, the manifold super heats and a crack can develop between the heat riser passage and one of the center line intake runners. This will result in the cylinders effected not getting enough fuel and a significant misfire is the result. A crack of this type will usually be directly under the carb in one of the intake ports and if you get lucky you can see a bright discolored spot where exhaust is intruding into the intake part of the manifold.
Dave
Dave
PontiacJim
Member
Dave's last paragraph says it all. Could not agree more.
KInd of sounds like the issue that was there before the engine work is still there (relating to the engine's performance at idle/low speed). There might be many things, but to me, most of those things aren't usually operative in an original 64K mile B/RB motor. Presuming it's had a "normal" life of normal uses and maintenance.
By observation, distributor shaft wear is not a real issue with the Chrysler electronic ignition distributor. The shaft spins with a balanced (side to side) rotor and NO sideloads from a set of ignition points. What might be an issue is the air gap between the shaft's trigger wheel and what it works with. Seems like there was a brass feeler gauge that was used to measure that gap, earlier on?
I would hope that when the engine was being done, a verification of the TDC mark on the crankshaft balancer was done. With time and age, the outer ring (with the timing mark) can move. Sometimes, too, how the keyway in the crankshaft nose is cut might be a few degrees "off", which will affect how the timing on the motor is done.
One thing that keeps coming up in my mind is "fuel with too much ethanol in it", far exceeding the normal 10% range. What happened to me once in the 1990s. I was in my '77 Camaro and stopped at a private-name-brand station for fuel. All was good, but the longer I drove it, I noticed the exhaust had a hollow sound to it. I also had to manually throttle into the carb at red lights to keep the engine from idling very low and rougher. But it still ran good on the highway. It was a little harder to start, but did. Figuring I had some "bad gas", I drove that tank of fuel down enough to put some better stuff in it, diluting the flaky stuff I'd put in it. As the fuel became more normal, the problem went away. This was WAY before the E10 fuels happened, but after the RFG fuels were in place.
So, just curious how long the "tinny" sound and poor idling had been going on? Next time the car is on an overhead lift, take a wrench and tap on the exhaust pipes, front to rear. Note any difference in the sound you get from the "taps". That should also include the muffler, too.
ALSO curious of what the actual determination of where the knock was coming from when th engine work was done? What was done to correct that?
Just some thoughts,
CBODY67
By observation, distributor shaft wear is not a real issue with the Chrysler electronic ignition distributor. The shaft spins with a balanced (side to side) rotor and NO sideloads from a set of ignition points. What might be an issue is the air gap between the shaft's trigger wheel and what it works with. Seems like there was a brass feeler gauge that was used to measure that gap, earlier on?
I would hope that when the engine was being done, a verification of the TDC mark on the crankshaft balancer was done. With time and age, the outer ring (with the timing mark) can move. Sometimes, too, how the keyway in the crankshaft nose is cut might be a few degrees "off", which will affect how the timing on the motor is done.
One thing that keeps coming up in my mind is "fuel with too much ethanol in it", far exceeding the normal 10% range. What happened to me once in the 1990s. I was in my '77 Camaro and stopped at a private-name-brand station for fuel. All was good, but the longer I drove it, I noticed the exhaust had a hollow sound to it. I also had to manually throttle into the carb at red lights to keep the engine from idling very low and rougher. But it still ran good on the highway. It was a little harder to start, but did. Figuring I had some "bad gas", I drove that tank of fuel down enough to put some better stuff in it, diluting the flaky stuff I'd put in it. As the fuel became more normal, the problem went away. This was WAY before the E10 fuels happened, but after the RFG fuels were in place.
So, just curious how long the "tinny" sound and poor idling had been going on? Next time the car is on an overhead lift, take a wrench and tap on the exhaust pipes, front to rear. Note any difference in the sound you get from the "taps". That should also include the muffler, too.
ALSO curious of what the actual determination of where the knock was coming from when th engine work was done? What was done to correct that?
Just some thoughts,
CBODY67
Another possibility, is a defective or poorly grounded electronic control unit. Most of the time if the car is still running the unit is probably still good. There was a problem with the pins for the harness on the electronic control unit getting corroded. It is also very important that the case of the electronic control unit have a good ground. Good chassis and engine grounds are also important as are clean battery cables.
Dave
The Holley 2 bbl carburetors on those 1973 engines was notorious for running badly because over time the upward tension of the air cleaner wing nut pulling up on the stud mounted to the air horn of the carburetor warps the airhorn upward and causes a vacuum leak that results in poor idle and off idle poor driveability. Just rebuilding it will not fix it unless the rebuilder is aware of the problem and has a way of machining the air horn flat again on the bottom side or perhaps another technique for fixing this. The only reliable rebuilder of those Holley 2 bbls in my experience is Autoline, which is available from Rock Auto. They are well aware of the problem and fix each one properly. I would personally start there, as your symptoms sound just like that issue has surfaced. It is a ***** to find unless you are aware of the issue too and know how to remedy it. If you get an Autoline carburetor, forever after, do not tighten the air cleaner wing nut any more than absolutely necessary to prevent the problem again in the future.
AUTOLINE C7107 {Click Info Button for Alternate/OEM Part Numbers} Rochester 2 Barrel; Reman Info
2BBL; H2-2210
By the way, the listing says it is a Rochester carburetor, but that is incorrect, as it is a Holley 2210 model, but the Autoline rebuild is the one to get. The photo shown is definitely the Holley 2210, not a Rochester. Just FYI
I worked for Chrysler in the fuel systems laboratory as a permanent assignment and there was also a field fix issued to prevent the warpage, but few ever got the fix, which was a brace to hold the airhorn down so it would not warp. Better to just not tighten the wing nut very much in the future.
One addidtional thought, I found out the hard way on my 73 Monaco with the 400-2 bbl engine that the front exhaust pipe was dual wall (for better noise control), and that within about 40K miles, the inner wall would collapse, causing really poor exhaust flow and might be the source of the tinny sound and might also contribute to the poor idle, but mainly it affects acceleration performance as I recall. If you take the pipe off and look inside it, you will see the inner wall collapsed near the outlet. The fix is to replace it from the exhaust manifolds to the downstream pipe (i.e. the junction is just below the front of the passenger door on the underbody).
Good luck and let us know how it turns out. This was a beautiful car but it kicked my *** until I found these two problems (I don't give up easily!). After that, it was sweet!
AUTOLINE C7107 {Click Info Button for Alternate/OEM Part Numbers} Rochester 2 Barrel; Reman Info
2BBL; H2-2210
By the way, the listing says it is a Rochester carburetor, but that is incorrect, as it is a Holley 2210 model, but the Autoline rebuild is the one to get. The photo shown is definitely the Holley 2210, not a Rochester. Just FYI
I worked for Chrysler in the fuel systems laboratory as a permanent assignment and there was also a field fix issued to prevent the warpage, but few ever got the fix, which was a brace to hold the airhorn down so it would not warp. Better to just not tighten the wing nut very much in the future.
One addidtional thought, I found out the hard way on my 73 Monaco with the 400-2 bbl engine that the front exhaust pipe was dual wall (for better noise control), and that within about 40K miles, the inner wall would collapse, causing really poor exhaust flow and might be the source of the tinny sound and might also contribute to the poor idle, but mainly it affects acceleration performance as I recall. If you take the pipe off and look inside it, you will see the inner wall collapsed near the outlet. The fix is to replace it from the exhaust manifolds to the downstream pipe (i.e. the junction is just below the front of the passenger door on the underbody).
Good luck and let us know how it turns out. This was a beautiful car but it kicked my *** until I found these two problems (I don't give up easily!). After that, it was sweet!
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Check you coil pick up in the distributor sometimes they fail when they get hot then cool down and work fine. One of the checks I do when rebuilding them is hit them with a heat gun.
THE BRIDGE KIT! Been there, done that. It works!Only thing is that the prior Stromberg WWC-3 carbs had the same issue! No "factory fix" for those, other than (as our old-line Chrysler dealer service manager said he used to do) filing them flat, using a piece of plate glass for the flatness reference. Carter BBDs didn't have this issue due to the way their air cleaner stud was held to the carb airhorn.
On our '66 Chrysler 383 Stromberg, after the carb rebuild it would not get more than 12mpg, as the raised/warped air horn compromised the seal between the carb body and the air horn, which took away the vacuum from the power valve actuator and left the power valve "working" all of the time. I successfully made some "spacer gaskets" using two air horn gaskets and a thinner layer of silicone between them in the middle area to keep the power valve working. That took a few to get right, but when they did work good, they'd stay until the fuel degraded the silicone. Then, whenever the choke was on, it'd suck fuel from the float bowl into the venture, making it run very rich.
My fix for that was a 1970-spec OEM Holley 2210 2bbl. Bolt-in replacement, just needed the factory thick base gasket rather than the "cardboard" one supplied with the new carb (which cost all of about $35.00 NEW, in 1973).
Did the Bridge Kit fix on our '72 Newport. Worked well.
Glad to see some mention of that kit and the 2bbl carb/air cleaner wingnut torque issue! I suspect it happened with other carbs, too, but never did hear of it. Back when there was an air cleaner base and an air cleaner top, with the filter inside. Common practice to "torque it down" so the top sealed against the filter "real good", back then.
CBODY67
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I want to thank everyone who responded to my problem. All are great suggestions and I am taking them all to my shop to test out. Hopefully this will find a solution. It is a beautiful car and deserves to be enjoyed for years to come. Again your help on this website is valued highly and this is the place to come for answers.
frito dave
New Member
Ballast resistor can cause poor idle. Btw seen loose wrist pins once but it can't affect idle. I've owned an automotive machine shop most of my life
Reviving this thread in the hope of hearing more about the eventual solution.
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