Stevens
Jeeper
2008 Mud Pit Master
Posts: 3,240
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Post by Stevens on Feb 17, 2010 17:40:37 GMT -4
It would be helpful if we had some sensor data from the sensors so we could see what they are indicating......also the snap shot (freeze frame) of the data from when the code was set would help. Watching the misfire data would help too, a 98 should have a misfire counter for each cylinder as well, which would be great to narrow down the problem. There may be some pending codes in the ECM too that could help diagnosis.
I guess the first step is to determine if the missfire is the result or the cause of the lean condition.
A misfire is going to cause a lean condition, the o2 sensors are going to read more oxygen in the exhaust than there should be and the ECM will then try to compensate by enrichening the fuel trim. So what can cause a misfire, obviously a bad plug, wire, or coil, a clogged or inoperative fuel injector, low fuel pressure, bad gas, bad wiring to the injectors, faulty injector driver in the ECM. etc, etc
Also, unmetered air in the engine will cause a lean condition.....exhaust leak before the o2 sensors, intake manifold leaks, vacumn lines, cracked air intake tube downstream of the MAF sensor, leaking TB gasket and leaking brake booster diaphragm, etc, etc.
And obviously any sensor that is not reading correctly will cause the engine to run improperly.....like a faulty ECT or IAT.
Good luck
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Dewie
Jeeper
Junk Lord
Yeah thats right - I drive a Lada :P
Posts: 1,249
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Post by Dewie on Feb 18, 2010 9:15:49 GMT -4
I have it in the city with me today - worked on from FallRiver on... lol
There has been nothing really out of range with anything that we can see - the miss-fire detector was counting primarily cylinders 1 and... uh.. the other front one on the opposite bank. (My father was monitoring stuff one day on a trip to the city and back while I drove)
The efficiency code hasn't come back so I can't even tell you what it is.
Picked up a new rotor button and distributor cap yesterday - in looking at it I can tell the one on the truck is obviously worn.
The truck has a fairly new exhaust on it - went on at the same time as the O2 sensors about 2 years ago.
Next is the distributor cap - and then I start digging into it more.
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Hawkes
Hardcore
Lurker
Posts: 5,404
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Post by Hawkes on Feb 18, 2010 9:24:13 GMT -4
Your post prompted me to check my dist cap, it wasn't in great shape, time for a new one.
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bill richards
Jeeper
Millwood Marauder
mud re-freshener
Posts: 4,169
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Post by bill richards on Feb 18, 2010 9:38:02 GMT -4
It would be helpful if we had some sensor data from the sensors so we could see what they are indicating......also the snap shot (freeze frame) of the data from when the code was set would help. Watching the misfire data would help too, a 98 should have a misfire counter for each cylinder as well, which would be great to narrow down the problem. There may be some pending codes in the ECM too that could help diagnosis. I guess the first step is to determine if the missfire is the result or the cause of the lean condition. A misfire is going to cause a lean condition, the o2 sensors are going to read more oxygen in the exhaust than there should be and the ECM will then try to compensate by enrichening the fuel trim. So what can cause a misfire, obviously a bad plug, wire, or coil, a clogged or inoperative fuel injector, low fuel pressure, bad gas, bad wiring to the injectors, faulty injector driver in the ECM. etc, etc Also, unmetered air in the engine will cause a lean condition.....exhaust leak before the o2 sensors, intake manifold leaks, vacumn lines, cracked air intake tube downstream of the MAF sensor, leaking TB gasket and leaking brake booster diaphragm, etc, etc. And obviously any sensor that is not reading correctly will cause the engine to run improperly.....like a faulty ECT or IAT. Good luck Get back to studying bookworm! The internet is gonna fix this problem! Bill
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Dewie
Jeeper
Junk Lord
Yeah thats right - I drive a Lada :P
Posts: 1,249
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Post by Dewie on Feb 18, 2010 9:41:05 GMT -4
A misfire is going to cause a lean condition, the o2 sensors are going to read more oxygen in the exhaust than there should be and the ECM will then try to compensate by enrichening the fuel trim. So what can cause a misfire, obviously a bad plug, wire, or coil, a clogged or inoperative fuel injector, low fuel pressure, bad gas, bad wiring to the injectors, faulty injector driver in the ECM. etc, etc Wouldn't a misfire lead to a rich condition due to unburnt fuel?
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chevystroker
Jeeper
NEVER CONFUSE HAVING A CAREER WITH HAVING A LIFE ! ! ! ! ! !
Posts: 896
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Post by chevystroker on Feb 18, 2010 9:58:09 GMT -4
LOL. I thought the same thing, and PM'd Stevens in case I was wrong, and didn't want to confuse the thread. His reply: "An oxygen sensor measures oxygen, not fuel. Yes, there is more fuel in the exhaust, but the o2 sensor reads lean because it only senses the extra oxygen in the exhaust that shouldn't be there. Then the ECM will enrichen the fuel trim to counteract the percieved lean condition." Extra O2 because it didn't combine with the fuel and disappear. I keep forgetting it IS an OXYGEN sensor, not fuel sensor. Hope that helps.
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Dewie
Jeeper
Junk Lord
Yeah thats right - I drive a Lada :P
Posts: 1,249
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Post by Dewie on Feb 18, 2010 10:07:48 GMT -4
Thanks for the input. I need to look at the engine again, but I don't think this is MPFI... I don't recall seeing any fuel rails... so singling out one cylinder due to fueling is going to be tough, unless the intake is filthy.
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Stevens
Jeeper
2008 Mud Pit Master
Posts: 3,240
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Post by Stevens on Feb 18, 2010 18:21:35 GMT -4
It would be helpful if we had some sensor data from the sensors so we could see what they are indicating......also the snap shot (freeze frame) of the data from when the code was set would help. Watching the misfire data would help too, a 98 should have a misfire counter for each cylinder as well, which would be great to narrow down the problem. There may be some pending codes in the ECM too that could help diagnosis. I guess the first step is to determine if the missfire is the result or the cause of the lean condition. A misfire is going to cause a lean condition, the o2 sensors are going to read more oxygen in the exhaust than there should be and the ECM will then try to compensate by enrichening the fuel trim. So what can cause a misfire, obviously a bad plug, wire, or coil, a clogged or inoperative fuel injector, low fuel pressure, bad gas, bad wiring to the injectors, faulty injector driver in the ECM. etc, etc Also, unmetered air in the engine will cause a lean condition.....exhaust leak before the o2 sensors, intake manifold leaks, vacumn lines, cracked air intake tube downstream of the MAF sensor, leaking TB gasket and leaking brake booster diaphragm, etc, etc. And obviously any sensor that is not reading correctly will cause the engine to run improperly.....like a faulty ECT or IAT. Good luck Get back to studying bookworm! The internet is gonna fix this problem! Bill hahaha, I am studying! Studying Automatic trannys for the next 2 weeks! Did they still have tbi's in 98?? lol
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Dewie
Jeeper
Junk Lord
Yeah thats right - I drive a Lada :P
Posts: 1,249
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Post by Dewie on Feb 18, 2010 20:09:48 GMT -4
Did they still have tbi's in 98?? lol I don't know, did they?
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Stevens
Jeeper
2008 Mud Pit Master
Posts: 3,240
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Post by Stevens on Feb 18, 2010 20:23:41 GMT -4
Did they still have tbi's in 98?? lol I don't know, did they? I think you should find out what fuel delivery system your truck has.....kinda hard to help diagnose without knowing.
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Creepy
Administrator
Dartmouth
Posts: 18,718
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Post by Creepy on Feb 18, 2010 22:07:37 GMT -4
Let's run thru the CT checklist and see how far we get!
1.year 2.make 3.model 4. engine 5. is it 4x4?
only #4. uh-oh! You have failed the CT parts counter test.
Return to top of list and start again.
heeheehee
I'm watching with interest......i'll do what you did to fix mine too.
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Dewie
Jeeper
Junk Lord
Yeah thats right - I drive a Lada :P
Posts: 1,249
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Post by Dewie on Feb 19, 2010 8:22:54 GMT -4
The engine is a 4.3L V6. I know what the engine is, I just haven't had to mess with it enough yet to know how it is fueled. I recall looking back when we first got the truck (it isn't even technically mine, I just maintain and drive it) and thought it odd that I wasn't seeing fuel rails and injectors but it has been long enough I can't quite picture it in my head. I wasn't feeling great lastnight so I did SFA. Will put the dist. cap etc on this weekend - and will maybe even take pictures for you of the fueling system
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▲▲▲▲
Jeeper
Twister of the Panties
Posts: 565
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Post by ▲▲▲▲ on Feb 19, 2010 9:11:16 GMT -4
C O I L
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Dewie
Jeeper
Junk Lord
Yeah thats right - I drive a Lada :P
Posts: 1,249
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Post by Dewie on Feb 19, 2010 9:38:34 GMT -4
Will be trying the cap first. Looking at the new one the poles are perfectly round, the old one, iirc, had flat areas.
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Dewie
Jeeper
Junk Lord
Yeah thats right - I drive a Lada :P
Posts: 1,249
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Post by Dewie on Feb 20, 2010 19:24:18 GMT -4
Well I found a very likely cause of my issues... the rotor button. I have a receipt here from the previous owners saying the distributor cap and rotor button were changed, but I doubt the button was... The cap wasn't too bad, but I replaced it anyways: Also - here is the only place I could find anything fuel related - it disappears into the intake... but I see no individual fuel injectors at all:
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