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I have info regarding my misfire issues in multiple threads and its time to consolidate it in one place so some sense can be made.
The vehicle in question is a 1999 Dodge Ram 1500, 5.2L V8 4×4 Automatic, with 260,000 miles.
In November I had the plenum gasket replaced with a Hughes plenum kit. This ended about 6 months of misfiring, extreme oil usage, and bad mileage. I got 18 mpg after the fix as opposed to 16 before the gasket went bad, and 11 directly before the repair.
A few weeks later it began performing poorly again. It would knock at idle and flash the CEL under heavy load. I discovered that the wires, cap, and rotor were in need of replacing and this fixed it.
Roughly a month ago, the idle knocking returned. It got progressively worse, to the point of shaking the vehicle in park. I replaced the spark plugs, and this time it got worse instead of better. About a week after, I got a constant CEL with misfire codes for 6 out of 8 cylinders. It almost wants to stall when idling in drive or reverse. The RPM drops from 600 to 400 and there’s an audible “tick” and pronounced shake when it happens, which is every few seconds.
Realizing that the coil was the last old part of the ignition system, I tested it, and it’s within spec. We know this doesn’t mean much though, so I went to the U-Pull-It and got one off an 01 V6 Dakota with 2013 inspection stickers that wasn’t wrecked. (not sure why it was even there) It was the only one out of all the Rams, Durangos, Dakotas, and Magnum-engine Grand Cherokees that I was able to remove. (they all share a coil)
I have not seen a noticeable improvement with the “new” coil. I can’t remove the old coil because the screw heads are stripped, so until I can get a screw extractor, I won’t know how it handles actually being driven with the replacement coil. But at idle, I noticed no improvement.
To clarify, All of my symptoms:
1. Somewhat poor mileage (14 mpg)
2. Knocking at idle in park/neutral, felt in steering wheel especially
3. Shaking at idle in any gear
4. Almost stalling in drive/reverse, with a “tick” sound (like a relay) when it misses and the RPM falls by 200 accompanied by a shake
5. Noticeable exhaust smell inside and out when idling
6. Noticeable dead misses in exhaust note at idle
7. Jolting when TCC is locked up (normal for misfire, as it happened before when plenum was bad)
8. If you spray carb cleaner in the TB, it will run absolutely perfect for a few minutes
9. CEL with misfire codes P0300-307, but not 08. No other codes, and most are pending.Relative compression test sounds good (aka clear flood crank). I have fuel pressure. Coil does not appear to be the issue, but I will know more about that next week. I am not burning excessive oil. (but at 260k without a rebuild, I am burning some, no doubt)
I really am at my wits end here, and I need to get this thing running right. The 4 mpg I’m losing is enough to hurt the wallet, and it isn’t very enjoyable to drive since every time I stop, it shakes enough to drive me crazy and every time I get up to speed it kicks me in the rear.
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PS. I assume you’ve already checked the trans fluid for level & condition. If it needs changed, don’t forget to change the filter also. Also, now we both know why Chrysler has us check the 42/46/47RE transmissions in neutral, not park.
Eric mentioned in anther thread that what I’m hearing is just normal intake noise. He said that vacuum decreases with throttle, so you shouldn’t HEAR a vacuum leak the way I am.
I’ve checked for leaks a few times, and sprayed carb cleaner on the joints of all the vacuum hoses I can reach and was quite surprised not to find any leaks.
I will be able to post more hard data (fuel trims, etc) when I get a live scanner, which should be early next month. These should be interesting to see because the ignition system is nailed down and I can smell the unburned fuel in the exhaust so a lack of fuel misfire wouldn’t fit either. Thanks for the trans info too!
[quote=”LJ11194″ post=47535]Eric mentioned in anther thread that what I’m hearing is just normal intake noise. He said that vacuum decreases with throttle, so you shouldn’t HEAR a vacuum leak the way I am.
I’ve checked for leaks a few times, and sprayed carb cleaner on the joints of all the vacuum hoses I can reach and was quite surprised not to find any leaks.
I will be able to post more hard data (fuel trims, etc) when I get a live scanner, which should be early next month. These should be interesting to see because the ignition system is nailed down and I can smell the unburned fuel in the exhaust so a lack of fuel misfire wouldn’t fit either. Thanks for the trans info too![/quote]
Sounds good, let me know how it goes. I’m fairly sure it’s trying to run too rich (Symptoms 1 & 6). Lots of causes for that. Look at the O2 sensors and fuel trims. I really can’t disagree with Eric on this one either. 😉
Can running too rich really cause it to act up in all these strange ways? As in, there’s too much fuel in the cylinder for it to burn so it ends up just pumping it out?
[quote=”LJ11194″ post=47537]Can running too rich really cause it to act up in all these strange ways? As in, there’s too much fuel in the cylinder for it to burn so it ends up just pumping it out?[/quote]
Sure can. Here’s a link to one of the best explanations of fuel trim I’ve ever seen http://realfixesrealfast.com/realfixesrealfast.com/Interactive_%26_Webinar/Pages/Webinar_01_Understanding_fuel_trim.html
The ‘balance’ point he talks about is 14.7:1 (14.7 parts air to 1 part fuel, called stoichiometric or stoich) for gasoline. If this balance is too far off to either side, the engine will run poorly or even not run at all! The only way the PCM has to ‘adjust the balance’ is to add or subtract fuel. For example, if the PCM thinks there is too much O2 in the exhaust for whatever reason (it thinks the engine is running lean, although it isn’t), it will just keep adding fuel to the point it can’t add any more (engine is actually running rich if it runs at all).
I just had a thought. As simple as it is you can check the PCV valve. Doesn’t explain all the problems but just take out the valve and jam a bolt in the hose as a test. Take it for a drive. It is a test that costs nothing. PCV can cause any of the problems I am seeing here at idle.
I pulled the PCV valve when I changed the plugs just in case, but it rattled like it should. Can the part inside not be jammed and the valve still be bad?
I think the fuel trim theory is good considering that when you floor it and the PCM abandons stoichiometric, it has plenty of power and usually doesn’t miss. Only under a heavy load (like up a hill at highway speed) I get a flashing CEL SOMETIMES.
At the moment, the codes I have are P0301 and a pending P0305.
Do oxygen sensors go bad without a lean/rich code?
yes a PCV can rattle and be bad, if it doesn’t close then it creates a vacume leak at idle. Not common but have seen it happen, and for what it takes to test it then why not.
yes, just leave it in the valve cover. you dont want to leave it disconnected as it is part of the polution system as well as removing moisture and stray gasses from the crankcase. but driving around for a couple hours wont hurt anything and you shouldnt even need that long to tell if it works.
I’ll try. The weather is terrible today, so I will test that out and make the video I promised tomorrow.
I just had a thought that could narrow things down. Can a misfire on one cylinder eventually cause others to miss also?
Reading over the thread, I realized I didn’t mention something: It is EXTREMELY difficult to stop this engine from starting when attempting a clear flood crank. I had to try more than 5 times to be able to crank without it turning over instantly. I hopped in my Contour, put the pedal down, key on, and it cranked as long as I wanted without even trying to fire on the first attempt. If you see my thought process here… could I have a stuck injector causing the rich condition?
[quote=”LJ11194″ post=47732]I just had a thought that could narrow things down. Can a misfire on one cylinder eventually cause others to miss also?
Reading over the thread, I realized I didn’t mention something: It is EXTREMELY difficult to stop this engine from starting when attempting a clear flood crank. I had to try more than 5 times to be able to crank without it turning over instantly. I hopped in my Contour, put the pedal down, key on, and it cranked as long as I wanted without even trying to fire on the first attempt. If you see my thought process here… could I have a stuck injector causing the rich condition?[/quote]
This does sound as if fuel is supplied when it shouldn’t be. In ‘clear flood’ usually spark is supplied, but fuel isn’t. So lets look at the injectors. If you have or can get one, use a noid light to check that the PCM isn’t telling an injector to fire constantly, but does pulse them on/off when cranking/running. Next, check for an injector that isn’t ‘ticking’ or sounds weak compared to the others. Like this: http://realfixesrealfast.com/realfixesrealfast.com/Diagnostic_1./Pages/RAV_4_Misfire.html The section you’re interested in is from 8:20 to 11:00. In your case, you’ll want to check all of the injectors.
In my experience, an ignition misfire on one cylinder won’t cause misfires on others. A stuck injector may cause a misfire on multiple cylinders if it is flooding the intake manifold, in extreme cases it will cause a hydraulic lock.
BTW, another sign the engine is rich is no misfire on cyl. #8 while the others are. Because of the design, a carbed or TBI V8 engine usually is leanest on that cylinder. So although the other seven are running rich, #8 isn’t, therefore no code.
Thanks again. I’ll keep watching for the P0308 but as of now I still haven’t got it yet. I’ll stop clearing the misfire codes and let them accumulate, see if it ever shows up. (I don’t like driving with the CEL on, its distracting)
I may have asked this before, but can you have bad 02 sensors without a lean/rich code? The sensors (and the cat for that matter) had probably 15,000+ miles worth of extreme oil burning sent across them so I am expecting to find out they are the problem. But I’m done shooting parts at it, don’t worry 🙂
I don’t think a multipoint injection system can flood the entire manifold, can it?
I know this probably ISN’T the problem, but I read the whole thread and it put me in mind of a dodge van that a friend had back in 2006 it had very high mileage and started doing a lot of the stuff you’re describing. We went over it with a few other shade-tree mechanics and many suggestions were thrown around, finally It was decided that maybe a module inside the distributor might be the problem.
So, we get this module and replace it, and Wallah when we start it, it runs perfect… “I told you suckers” says Duane, who suggested that it was this module, so we take it for a test drive and after about a mile it starts to misfire worse than ever. We limp it back to the garage and I take off the distributor cap to see if the module was not tightened down correctly, and when I’m messing with it I notice there is a huge amount of play in the shaft itself. To sum it up the distributor shaft bearings were GONE and the resulting slop in its movement was the cause of all his woes.
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