AE102 Misfire Issues - Won't Go Away!!!

XsV

XsV

d[O_O]b
#1
#1
So here is my problem. I recently purchased my 93 ae102 (1.8L manual) and have been loving it. However it seems like it's idle is pretty rough as it shakes the car, like it wants to die. I figured it was a misfire so I went to check the plugs. While keeping the car running, I removed each boot to see if any, when removed, didn't change the idle. Cylinder 2, with the spark plug boot removed, let's the car run the same (around 600-700rpm).

So I replaced the plugs, wires, cap and rotor, and it's still doing it. When I pulled out the boot again, you can see the spark arking to the plug tube wall so it's definitely getting spark from the distributor. Where do I go from here? Fuel issue? Compression?
 
Scott O'Kashan

Scott O'Kashan

Super Moderator
#4
#4
If it were a fuel injector issue the condition/color of the spark plugs will provide huge clues.

Did you look at each of the old spark plugs when you removed them? Do you still have them?
 
XsV

XsV

d[O_O]b
#5
#5
Scott O'Kashan said:
If it were a fuel injector issue the condition/color of the spark plugs will provide huge clues.

Did you look at each of the old spark plugs when you removed them? Do you still have them?
Click to expand...
I do yes. Some have a little bit of black around the threads. Nothing major on any of them.
 
Donabed Kopoian

Donabed Kopoian

6 Speed Master
#6
#6
If you are certain that the issue is from Cylinder #2, put a multimeter on the fuel injector connection and verify that it is getting voltage, then do a resistance check on the fuel injector terminals and verify that there is proper resistance. If all of that checks out, then I would pull it out and look for obstructions or contamination around the sprayer.

If the spark plug looked normal, that tells me that the injector isn't firing at all and the cylinder is firing a dry charge, so definitely check the connections and the resistance of the injector first.
 
XsV

XsV

d[O_O]b
#7
#7
Donabed Kopoian said:
If you are certain that the issue is from Cylinder #2, put a multimeter on the fuel injector connection and verify that it is getting voltage, then do a resistance check on the fuel injector terminals and verify that there is proper resistance. If all of that checks out, then I would pull it out and look for obstructions or contamination around the sprayer.

If the spark plug looked normal, that tells me that the injector isn't firing at all and the cylinder is firing a dry charge, so definitely check the connections and the resistance of the injector first.
Click to expand...
So since I don't have a working multimeter (I'll pick one up tomorrow), I just unplugged the obd2 connector from the injector and the idle didn't change. I'm thinking I should just order an injector.
 
Donabed Kopoian

Donabed Kopoian

6 Speed Master
#8
#8
Don't do that until you get a multimeter on it. If you buy the injector and it still doesn't work, that is going to be an expensive way to find out that there is no voltage at the connector.
 
XsV

XsV

d[O_O]b
#9
#9
Donabed Kopoian said:
Don't do that until you get a multimeter on it. If you buy the injector and it still doesn't work, that is going to be an expensive way to find out that there is no voltage at the connector.
Click to expand...
In all honesty though, what is the likelihood that just the one of the four connectors is bad? I'm trying it tonight so I'll keep you all posted.
 
Scott O'Kashan

Scott O'Kashan

Super Moderator
#10
#10
XsV said:
I do yes. Some have a little bit of black around the threads. Nothing major on any of them.
Click to expand...
The important issue is that they all look the same, especially from the cylinder that is having the suspected misfire problem.

The color of the threads is not important. What you want to look at is the electrode, where the spark occurs.

This video will help you out. The old spark plugs will provide you valuable clues -

 
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XsV

XsV

d[O_O]b
#11
#11
So I checked both the connector for proper voltage as well as the injector for proper resistance. Connector has over 14 volts and the injector's resistance is different than the rest so I'm assuming it's just a bad injector.

The plugs all looked the same because the previous owner said they were recently replaced but I don't want Champions in my ae. No sir-ry Bob! :thumbsup:
 
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Donabed Kopoian

Donabed Kopoian

6 Speed Master
#13
#13
Scott, sounds like the plugs had too few miles on them to get any type of warning signs.

Plus, that one injector having different resistance than the rest definitely isn't good.
 
Donabed Kopoian

Donabed Kopoian

6 Speed Master
#15
#15
Even if the injector is completely shot? I know a poor spray pattern will show carbon build-up, but usually, if it completely dies out, nothing shows up on the plugs.
 
IFMJohn

IFMJohn

New Member
#16
#16
Donabed Kopoian said:
Even if the injector is completely shot? I know a poor spray pattern will show carbon build-up, but usually, if it completely dies out, nothing shows up on the plugs.
Click to expand...
If the injector will not open then nothing will show on the plugs.

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Scott O'Kashan

Scott O'Kashan

Super Moderator
#17
#17
Donabed Kopoian said:
Even if the injector is completely shot? I know a poor spray pattern will show carbon build-up, but usually, if it completely dies out, nothing shows up on the plugs.
Click to expand...
If one cylinder is misfiring, (for whatever reason), then the spark plug from that one cylinder will have a different appearance than the spark plugs from the other cylinders.
 
XsV

XsV

d[O_O]b
#18
#18
Ok well regardless here is the update.

New injector is in (Beck/Arnley) and functioning properly and there are no leaks. However the issue still remains.

Injector is spewing fuel, spark is bright and vivid, and compression is solid.

So now where the heck do I go from here?

** Just in case anyone hasn't read the original post, here is what is going on:
It's idle is pretty rough as it shakes the car, like it wants to die. I figured it was a misfire so I went to check the plugs. While keeping the car running, I removed each boot to see if any, when removed, didn't change the idle. Cylinder 2, with the spark plug boot removed, let's the car run the same (around 600-700rpm).

So I replaced the plugs, wires, cap and rotor, and it's still doing it. When I pulled out the boot again, you can see the spark arking to the plug tube wall so it's definitely getting spark from the distributor.**
 
XsV

XsV

d[O_O]b
#19
#19
Should I pull the valve cover off and check the spark plug tube seals and see if there is any oil in there? Would that prevent combustion?
 
Donabed Kopoian

Donabed Kopoian

6 Speed Master
#20
#20
If you have fuel, spark, and compression, it should be firing. A severe oil leak would show up on the plugs quick...

Give me a while to mule over it ... that's definitely bizarre.
 
Scott O'Kashan

Scott O'Kashan

Super Moderator
#21
#21
More parts replacing and the problem still persists. So expensive. :(

With replacing so many parts, this opens a Pandora's box of other potential problems like, were the parts installed correctly? Are the new parts functioning correctly and so on. This factor makes the original problem even harder to diagnose.
 
Scott O'Kashan

Scott O'Kashan

Super Moderator
#23
#23
How many miles are on the car?

Does the engine running rough change at all when it is put into gear? As the car is accelerating and maintaining speed, does the engine still run rough?
 
Donabed Kopoian

Donabed Kopoian

6 Speed Master
#24
#24
He said that disconnecting the spark plug and the fuel injector from cylinder #3 didn't change the idle (so I'm assuming that doing the same thing on #1, #2, and #4 DID change the idle).

I would say mechanical damage, but he says he has compression.

So that eliminates:

Ignition issues (plugs have spark)
Fuel issues (fuel injector with abnormal resistance was replaced)
Valve issues (compression is good)
Head gasket (again, compression is good)
Damaged piston (yup, again, compression is good)

Scott, be easy on him. If I saw a fuel injector with resistance way off from the other three, I would have replaced it as well. He checked it before replacing it ... he didn't replace it right away.

Even with a severe vacuum leak, disconnecting the plugs should still make a change in idle since the computer can compensate for them. But electronics can get goofy ... so I suppose the only thing that is left, is to get a spray bottle with water, and spray around the injector on cylinder #3 (just to verify that the O-Rings didn't rip or deform when they were being installed), and on the intake manifold gasket on the intake runner for cylinder #3.

If all of that checks out and there is no loss of vacuum, then I am not sure what else could be off.

Also, for future reference, never disconnect ANY electronics while the vehicle is running. You can cause an arc that can damage the electronics by doing so. If I am checking for a misfire that doesn't throw a code, I disconnect #1, fire it up, note any changes, kill the engine, reconnect #1, disconnect #2, repeat.
 
Donabed Kopoian

Donabed Kopoian

6 Speed Master
#25
#25
Back in the days of points ignition where no electronic modules existed, this was alright to do, but nowadays, this can destroy PCMs, and they aren't cheap and are a pain to diagnose.
 
XsV

XsV

d[O_O]b
#26
#26
Donabed Kopoian said:
Back in the days of points ignition where no electronic modules existed, this was alright to do, but nowadays, this can destroy PCMs, and they aren't cheap and are a pain to diagnose.
Click to expand...
Ok good to know. Yeah I have been working on cars for a long time and I know everything is installed correctly. I'll check for vacuum issues but the likelihood that it's only affecting one cylinder is small but it's worth a shot.

Is there anyway there could be issues with the block itself?
 
Scott O'Kashan

Scott O'Kashan

Super Moderator
#27
#27
Some of these engines are noted for vacuum leaks. The easiest way to diagnose this is with a smoke test.

No the engine block is fine.

 
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XsV

XsV

d[O_O]b
#28
#28
Scott O'Kashan said:
Some of these engines are noted for vacuum leaks. The easiest way to diagnose this is with a smoke test.

No the engine block is fine.
Click to expand...
Okay I'll give that a shot. I know there is vacuum pressure in the valve cover, could the valve cover gasket be pulling a two-fer (vacuum leak and oil leak into the spark plug tube)?
 
Donabed Kopoian

Donabed Kopoian

6 Speed Master
#29
#29
Oil leaking into the spark plug tube is a possibility and if bad enough, could cause the misfire (but you wouldn't miss that when you went to get the plugs).

My '96 Mustang GT had the crap plastic intake manifold that would crack at the heater core return line and leak coolant all over spark plug #4 and caused a gnarly misfire, but it was so obvious that the boot was soaked in coolant, you would have been blind to miss it.
 
XsV

XsV

d[O_O]b
#30
#30
Hmmm. Okay. Well I'm still trying to figure it out. No noticeable vacuum leaks, but the chances that it would only be messing with once cylinder is beyond slim.

A local mechanic that I used to strongly trust seems to think that it's the MAF. But I now think he's an idiot because the 7th gens don't have MAF's, only air charge sensors right?

So compression, spark, and fuel, all there. But still misfiring on cylinder 2... :mad:
 
IFMJohn

IFMJohn

New Member
#31
#31
A coolant leak into a cylinder would be obvious on a spark plug. Your plug would literally look like someone steam cleaned it.

When you checked compression, did you have all the spark plugs out? Or did you remove cyl 1 spark plug and check compression, reinstall cyl 1 plug and remove cyl 2 plug, etc?

Independent AMSOIL Dealer, Contact me to get the world's best oil for prices lower than brands like Mobil1 and Royal Purple!

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XsV

XsV

d[O_O]b
#33
#33
Yes I removed one plug at a time to check compression in each cylinder.

And yes I had the college do a smoke test and the only vacuum leak we found was the hose going to the valve cover. I replaced it but obviously not the problem.
 
IFMJohn

IFMJohn

New Member
#34
#34
XsV said:
Yes I removed one plug at a time to check compression in each cylinder.

And yes I had the college do a smoke test and the only vacuum leak we found was the hose going to the valve cover. I replaced it but obviously not the problem.
Click to expand...
This could be an issue. If you have a head gasket leak between cylinders it wouldn't show up in the test you did. The proper way to test compression is to remove all plugs at once and check each cylinder with no plugs in any cylinder.

Independent AMSOIL Dealer, Contact me to get the world's best oil for prices lower than brands like Mobil1 and Royal Purple!

GoldMedalSyntheticOils.com
 
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