- This topic has 96 replies, 11 voices, and was last updated 11 years, 9 months ago by
.
-
Topic
-
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.
-
Replies
-
Interesting, thanks for the info. I wish this distributor was easier to get to. I’ll keep that on the list if the easier stuff to check doesn’t go anywhere.
One of the things that really made me remember that story was the “whirring or grinding” noise that seemed to be coming from the trans… because this distributor is at the rear of the engine tucked down under the curve in the firewall it could make it seem like it’s coming from there.
[quote=”LJ11194″ post=47832]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?[/quote]
Yes, a bad O2 sensor might not set a code, most often on OBDI rarely on OBDII (96 and later). That’s why I’m not looking at them YET.
A multipoint injection system can flood the entire manifold if one injector is stuck open. Fuel injected at the end of the intake runner goes into the cylinder on the intake stroke. It has to go somewhere on the other three strokes. Into the intake manifold is often easiest for it. At that point the intake system acts as if the engine had a carb or TBI.
I agree that the distributor has a lot of miles, and is probably worn, maybe could use replacing soon. But, a jumping or worn distributor misfire would probably be across all eight cylinders. To check before replacing, the engine cylinder spark/burn time would need to be checked on a lab scope. Or the distributor will have to be pulled, eyeballed for wear/wobble and tested on a dedicated tester. Let’s wait on that as we check/test one system at a time. Don’t know about you, but too much jumping around and I lose track of what I’m doing! 🙁
Just brainstorming until I have the means to provide real data. I’m probably spending in fuel what it would cost to have my local shop do a diagnosis. 14 mpg was probably an over statement. Looks more like 10 right now.
[quote=”moparfan7008″ post=47846]
A multipoint injection system can flood the entire manifold if one injector is stuck open. Fuel injected at the end of the intake runner goes into the cylinder on the intake stroke. It has to go somewhere on the other three strokes. Into the intake manifold is often easiest for it. At that point the intake system acts as if the engine had a carb or TBI.[/quote]I should mention that this is most likely on a V type engine (like yours), unlikely on modern inline 4’s and 6’s.
Did the PCV valve test, nothing changed. Did another brake torque and it didn’t break the wheels lose this time (maybe I wasn’t on the brake hard enough before), and I got it up to 3 grand before the sounds it was making scared me enough that I stopped. I’ve never heard a knock that loud and it’s never made a sound like that while driving. I still am unable to clear flood crank it.
On a side note, my rear tires were down to only 16 PSI!!! Glad I checked them!
You may be having a couple of different problems here. First thing I would try to check is fuel injector leakdown. A leaking injector will cause runability/fuel mpg problems. To do this you need to hook up a fuel pressure tester, bump the key on to pressurize the system then pinch off the fuel return line and monitor the pressure leakdown. You shouldnt have more than 10psi in 30 min.
Another thing that comes to mind is your torque converter. You mentioned that at cruising speed you would get a shudder/vibration. If the torque converter clutch was locking up or partially locking up at idle it could cause noise and most definately make the engine want to stall. A failing torque converter/clutch will cause an MPG drop too.
Last but no least you may be having engine mechanical issues. Have you been able to do a compression or leak down test yet? (I know your weather sucks)
The shaking when the TCC locks up is a direct result of the misfire. I’ve been down this road before, the last time I had misfire issues, so I’m confident the TCC is fine. At the time, I had thought the TCC was slipping but it never was.
I don’t have the tools to do those tests. I really would like to do that test for a leaking injector, so I will buy a fuel pressure gauge when I get more money, but I’ve just spent it all on a live data scanner…
Ok can you give us the readings with your data scanner? Such as engine coolant temp,intake air temp, fuel trims on both bank 1 and 2 and o2 sensor readings for bank 1 and 2? Idle and loaded would be helpful.
Cool, you may want to check with the local auto parts store about renting a fuel pressure tester too, they are generally cheap to rent. Just try to do some research on what types of fittings you will need to tap into the fuel line.
I believe the fuel rail has a Schroeder valve to tap in to. (I think that’s a Chrysler standard thing)
Ok that will make things easy as long as you can locate the fuel return line (if there is one) so you can effectively check the injectors for leakage
My FSM says this:
Testing for fuel injector or fuel rail leakage:
Clamp off the rubber hose portion of Adaptor
Tool between the fuel rail and the test port “T” on
Adapter Tool. If pressure now holds at or above 30
psi, a fuel injector or the fuel rail is leaking.I don’t really know what that means. However I have confirmed there is a Schroeder valve on the rail.
Yes, there will be a test port & valve on the fuel rail. To check pressure you’ll need to get a 0-60 psi test gauge. Your local parts place may have a ‘loan a tool’ program. Hook it up like this:
For your truck, you want about 30psi with the engine off, 44-54 psi at idle.
Hook up the gauge, unplug the electrical connection to the injector, then do this:The gauge likely hooks up to the rail at the orange circle.
Look for hoses connected to the fuel rail at the green and red circles. The connection should look like this:If you have a ‘returnless’ system, you’ll only find one. If you find hoses in the red and green circles, you have a ‘return’ system. (I don’t recall which you’ll have). If you find a hose in the red circle, clamp it off, and charge the fuel system (key on about five seconds, don’t start the truck). Watch the pressure, a leaking injector will start dropping pressure immediately. If the pressure doesn’t fall, you don’t have a mechanical leak, connect the electrical connectors one at a time and retest. If the pressure still doesn’t drop with all eight connectors on, you’re fine. If the pressure doesn’t drop with all connectors off, but does when one is connected, it’s being told to fire. (and testing elsewhere is needed.)
If the pressure falls, charge the system, then clamp the connecting hose at the light blue circle, leaving the red circle hose clamped. If the pressure falls again, one of the injectors on the rail with the gauge is leaking. If it doesn’t fall, look at the injectors on the other rail. Once you find the rail with a leaking injector, it’s just a matter of swapping injector pairs across the rails one pair at a time, then retesting. When the problem moves, the injector you just moved from the leaking rail is likely bad and should be replaced.
- You must be logged in to reply to this topic.