If I'd have to guess, I'd suspect the distributor pickup (Hall-Effect pickup) inside the distributor on the base plate. I've had a couple of those mysteriously go bad over the years and so have a lot of other people. With an intermittant failure the computer will not likely throw a code and because these often fail hot there is no really good way of testing without a scope connected when the problem occurs. Another possibility is a failing injector. We saw one of those fail a couple of months ago, according to another poster on this board. If you have a pick and pull salvage yard with those ,and can get them very cheap, it might help with the diagnoses without spending a lot of money on new parts.
wierd issue.. stumbling and bucking after 15 min
I have been fighting this issue for a little bit now. If I run the car for more then 15 min I start to get a stumble and she feels like she is missing a cylinder. If I reset the computer for 5 min, i get another 15 min of good running and we are back to the same issue after 15 min. Happens hot or cold.
some stats on the car.
89 chrysler lebaron 2.5 l 4 cylinder.
a413 3 speed
I have changed the following:
plugs twice. 1 set were autolites and when I pulled them last night they were sooty and black. (running rich)
new set of wires
new cap
new rotor
o2 sensor is denso unit and seems to work fine
map sensor was changed last year
coolant sensor reads 13,000 ohms at cold so I dont think it is that
tps fine.
ground straps tested ok last night .
I am totally at a loss. I get no codes from the computer so this is making this really hard to troubleshoot.
Could the computer be the problem? I know it was replaced by the previous mechanic to me it seems like an air/fuel issue and it seems like it gets too much fuel. I have had it in my driveway with cardboard under the tail pipe and I get black soot when it stumbles...
some stats on the car.
89 chrysler lebaron 2.5 l 4 cylinder.
a413 3 speed
I have changed the following:
plugs twice. 1 set were autolites and when I pulled them last night they were sooty and black. (running rich)
new set of wires
new cap
new rotor
o2 sensor is denso unit and seems to work fine
map sensor was changed last year
coolant sensor reads 13,000 ohms at cold so I dont think it is that
tps fine.
ground straps tested ok last night .
I am totally at a loss. I get no codes from the computer so this is making this really hard to troubleshoot.
Could the computer be the problem? I know it was replaced by the previous mechanic to me it seems like an air/fuel issue and it seems like it gets too much fuel. I have had it in my driveway with cardboard under the tail pipe and I get black soot when it stumbles...
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John.. thank you for replying so quickly.. the hall-effect is the only thing I have not changed on the ignition side. I will see if I can pick one up at the parts store. I wish I had a spare that I can check with. Will that cause a rich condition too? or is the computer compensating for the fault by adding fuel
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878 Posts
No, not necessarily. The Hall effect tells the engine where the crankshaft is. If the Hall is flaky, the computer gets a bad signal and fires the injectors and the spark plugs at the wrong time. Of course, the valves are not controlled by the computer, so you might get injector firing for a closed valve, spark plugs firing very early or late, or other things of that nature. This can give you a lot of unburned hydrocarbons coming out of the tailpipe due to the bad timing, which can look like rich running. Depending on what the Hall is telling the computer, any number of things could be going on. Replacement pickups are about $35. A poster in another thread noted getting one which had frayed insulation right out of the box, so make sure the new pickup is good if that's the route you decide to go.
wow.. I Really never thought that could be the issue.. I will definately put a new one in and see if that could be the problem... it makes sense that it would get a missfire and no code... I will see if I can get one tonight after work and put it in the car.
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12,316 Posts
When you say "ground straps tested OK", does that mean you measured them with a multimeter? Did you remove and clean the connections? Did you check the braided strap at the firewall, the ground from battery to left fenderwell, and the ring tongue terminal from the harness behind the valve cover to the driver's rear corner of the block? All must be intact.
I measured each ground strap with a multi meter and I cleaned all the connections. The ring tougue terminal I cleaned and refitted to the block. I did not check the ground from the battery to the left fender well.. I will check that one tonight.. along with the hall effect
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12,316 Posts
How about the braided strap from intake manifold to passenger side firewall? They often fray or break, and will cause poor operation.
The ring tongue wire is often a little short and stretched. Make sure the strands aren't breaking off at the crimp. I had an intermittent problem there, had to rewire it.
The ring tongue wire is often a little short and stretched. Make sure the strands aren't breaking off at the crimp. I had an intermittent problem there, had to rewire it.
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12,316 Posts
Sometimes you get codes when the ring tongue ground breaks, but not always with the braided strap.
Check the primary coil resistance when cold and immediately after it acts up, shut down and check it again. Sometimes there is a thermal expansion issue with them.
Check the primary coil resistance when cold and immediately after it acts up, shut down and check it again. Sometimes there is a thermal expansion issue with them.
ok.. now I know the grounds are good. I removed each one that bob mentioned and the car died each and every time. I cant seem to find a hall effect sensor anywhere so I guess I will order it on line.
It is just soo wierd... I had it idling for over 15 min and it was reving up fine ... then it did its studder step and was back to loping and stumbling... forget about putting it in gear because then it just shakes..
it just does not make any sense to me....
It is just soo wierd... I had it idling for over 15 min and it was reving up fine ... then it did its studder step and was back to loping and stumbling... forget about putting it in gear because then it just shakes..
it just does not make any sense to me....
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12,316 Posts
Is it doing this mostly at idle? How is it when cruising warm at highway speed?
I'm wondering now if the EGR is sticking open. The engine runs rich enough to overcome the EGR when cold, but when hot and running leaner, adding some EGR gases at idle or under load can make it stumble.
To test, at idle, grab the EGR valve stem (pintle) with needlenose pliers and gently lift it. If it was stuck open already, there will be little or no change to the idle. If it is fine, it will cause a stumble or stall.
I'm wondering now if the EGR is sticking open. The engine runs rich enough to overcome the EGR when cold, but when hot and running leaner, adding some EGR gases at idle or under load can make it stumble.
To test, at idle, grab the EGR valve stem (pintle) with needlenose pliers and gently lift it. If it was stuck open already, there will be little or no change to the idle. If it is fine, it will cause a stumble or stall.
Bob.. it preforms fine for about 10 to 15 min .. then it starts shaking and loping at idle.. and when you are crusing with little pressure on the gas it starts to buck and stumble. The only way to get rid of the stumbling if you are driving is to literally floor it and then it takes off.
When it is like this.. if you put it in neutral and rev the engine it seems like it misses all the way up and then finally after about 3000 rpm it sounds fine .. let it go down and it will repeat the process
if you let it sit for about an hour and restart it .. it is fine .. again for another 10 to 15 min..
I am wondering about the egr valve too. It looks origional to me. I will play with it tomorriow as it is dark out here in the New York.
When it is like this.. if you put it in neutral and rev the engine it seems like it misses all the way up and then finally after about 3000 rpm it sounds fine .. let it go down and it will repeat the process
if you let it sit for about an hour and restart it .. it is fine .. again for another 10 to 15 min..
I am wondering about the egr valve too. It looks origional to me. I will play with it tomorriow as it is dark out here in the New York.
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12,316 Posts
Could easily be the EGR. And it might not trip any codes, since a code 32 means 'no change to air/fuel mix when EGR is activated'. It could be stuck open a little and then when actuated, opens a little more.
bob.. I think you are right with the egr valve. I took it off today after work and it was caked in carbon deposits .. I freed it up somewhat but then took off the vac so it will not activate. the car was pretty stable. I did not have any carb cleaner to clean the valve.
what would be a good top end cleaner for this car
what would be a good top end cleaner for this car
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12,316 Posts
You can use Gumout EFI cleaner or CRC, or some similar brand to loosen it. Sometimes the crud is so solid that you have to get a fine drill bit and drill it out.
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