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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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That is some great info mopar fan. If all goes well with the leakdown test then the next easy thing to try would be propane enrichment. You said it ran better with a bit of carb clean in the intake (you may have had too much the 2nd time) If propane enrichment makes it run better then that would tell me you have a non firing injector(or more) or a fuel psi issue.
Propane enrichment is as easy as disconnecting the intake air boot and using a propane bottle w/nozzle to “leak” propane into the engine. Please be careful as a backfire could cause a fire/explosion!
You are awesome, moparfan. I’ll look into getting a tester and keep you updated.
So what if I don’t have a return line? Also I got a P0301 and 05 first (at the same time) so I fully expect it to be on the driver side rail. Also a test I could do right now is unplug the suspect injector and see if then it will clear flood crank.
[quote=”LJ11194″ post=48317]….So what if I don’t have a return line? Also I got a P0301 and 05 first (at the same time) so I fully expect it to be on the driver side rail. Also a test I could do right now is unplug the suspect injector and see if then it will clear flood crank.[/quote]
The main difference is when and where fuel hoses are clamped. 😆If you have a ‘returnless’ system, connect the gauge to the fuel rail, disconnect the electrical connections 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, and the pressure is 30 or more psi, 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, and the fuel line comes into the rail the gauge is connected to, clamp the connecting hose at the light blue circle, then charge the system. 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 (which rail is losing pressure) moves, the injector you just moved from the leaking rail is likely leaking and should be cleaned or replaced.
If the pressure falls, and the fuel line doesn’t come into the rail the gauge is connected to, charge the system, then clamp the connecting hose at the light blue circle. And continue as above.
The odd cylinder bank codes may be a hint. But remember that if an injector has a mechanical leak, it will put fuel into the engine even if it’s electrical is disconnected. Taking an injector out of the rail and then charging the rail will send fuel everywhere. We’re trying to avoid taking anything apart until needed.
I wasn’t going to remove the injector, just unplug it lol. And that would be a quick way to gather some evidence without any tools. I may do that tomorrow. I could just have a stubborn computer that doesn’t want to recognize clear flood mode (see: Eric and Scannerdanner solve a misfire)
If the fuel pressure and injector test check out.
pull out the o2 sensor closest to the engine.see
if its all black or sooty looking.On top of the engine and possible transmission issues, First my (new) blower motor resistor goes out and now I have no heat anyway! I swear this truck doesn’t want to be fixed. Since I’ve been hearing abnormal amounts of “air intake noise” I’m sure there’s a leak letting air into the cooling system somewhere. Just a general update.
[quote=”LJ11194″ post=48377]On top of the engine and possible transmission issues, First my (new) blower motor resistor goes out and now I have no heat anyway! I swear this truck doesn’t want to be fixed. Since I’ve been hearing abnormal amounts of “air intake noise” I’m sure there’s a leak letting air into the cooling system somewhere. Just a general update.[/quote]
Yes, when replacing a blower motor resistor you’ll need to ensure the cowl vent boxes are cleaned out also. They provide cooling airflow for the resistor. You’d be surprised about the amount of debris they collect. I’ve found that adding a fine mesh screen similar to window screen at the main cowl screen helps. Also check/change the blower motor and clean the heater box if you can.
What’s going on with the heat? Do you mean no air movement, or cold air moving? They troubleshoot differently.
[quote=”college man” post=48337]If the fuel pressure and injector test check out.
pull out the o2 sensor closest to the engine.see
if its all black or sooty looking.[/quote]Yep, that’s where I planned on going next.
Not to throw too many topics into one thread but yeah, no heat. I need to get one of those spill free funnels and bleed the system. Thanks for the info on the blower motor resistor, how would I go about cleaning the cowl vent boxes?
[quote=”LJ11194″ post=48407]Not to throw too many topics into one thread but yeah, no heat. I need to get one of those spill free funnels and bleed the system. Thanks for the info on the blower motor resistor, how would I go about cleaning the cowl vent boxes?[/quote]
Pull the blower resistor, and vacuum the area behind it. MAKE SURE the blower motor isn’t pulling too much current, or you’ll be replacing resistors a lot.
Yes, bleeding the cooling system is mandatory. Pressure testing the system and the cap is also a very good idea.
Alright… have some data:
The vehicle IS going into closed loop.
02 sensor is switching with a max voltage of 1 and a min of 0, but it is landing in-between sometimes.
STFT is stabilized at 2.34, but sometimes drops to -.78
LTFT is between -2 and 10. It was all over the place and never really settled down.And something ELSE has gone wrong because my seat belt light will not go away.
[quote=”LJ11194″ post=48888]Alright… have some data:
The vehicle IS going into closed loop.
02 sensor is switching with a max voltage of 1 and a min of 0, but it is landing in-between sometimes.
STFT is stabilized at 2.34, but sometimes drops to -.78
LTFT is between -2 and 10. It was all over the place and never really settled down.And something ELSE has gone wrong because my seat belt light will not go away.[/quote]
Now that we have some data:
Going into closed loop – Good
O2 sensor switching 0v to 1v – Good
STFT is 2.34 to -.78 – Good, 5 to -5 is considered normal.
LTFT is between -2 and 10. It was all over the place and never really settled down. Is this switching faster than STFT?Also, does your reader give STFT and LTFT numbers for each bank?
E.G. STFT Bank 1=2.0, STFT Bank 2=1.20 If it does, what are the STFT & LTFT for each bank. What are the O2 sensor readings for each bank?Next, are the misfires occuring in open loop, closed loop or both?
The STFT and LTFTs were switching at the same speed (fairly rapidly) until the STFT settled down around 2.34. It only reads fuel trims for bank 1. I don’t have a separate O2 sensor for each bank as far as I know, I only know of 1 forward of the cat (on the y-pipe) and one after it. I don’t notice any difference in how it runs between open and closed loop.
The surprisingly confusing part is that according to my ultra-gauge, I’m getting very good mileage for this vehicle. Steady 25 mpg at highway speed. I never get a chance to run the tank empty so I can’t test against a hand calculated number, but after 3 days of commuting it says I average 14 which isn’t too bad considering all the hills here.
[quote=”LJ11194″ post=49128]….The surprisingly confusing part is that according to my ultra-gauge, I’m getting very good mileage for this vehicle. Steady 25 mpg at highway speed. I never get a chance to run the tank empty so I can’t test against a hand calculated number, but after 3 days of commuting it says I average 14 which isn’t too bad considering all the hills here.[/quote]
That’s extremely high mileage on the highway for that vehicle. Combined 14 mpg is good. From http://www.fueleconomy.gov/feg/bymodel/1999_Dodge_Ram_1500_Pickup.shtml:
1999 Dodge Ram 1500 Pickup 4WD 8 cyl, 5.2 L, Automatic 4-spd, Regular Gasoline
City 11
Combined 13
Highway 15
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