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Trevor
Dodge Dakota
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12/26/2006
18:04:51
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 Subject: Backfire and Power loss
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OK, first off it's a 1999 Dodge Dakota with a 3.9 V6, 3.92 limited slip diff, 4x4 with 202000kms on it. All factory but it has a V8 throttle body on it.
A couple days ago, it revved up till about 2000 rpm, then almost died a couple times, after starting it up after it sat for 6 days. So i put some methyl hydrate in the gas, thinking it could be ice....it hasn't done this since.
Next, after starting it up again, driving it would loose power, and would backfire loudly through the intake, the best way to describe this would be loud popcorn popping. It would do this even after starting it up after is sat for a while (half an hour maybe). After it's gone through it's 'fit' it runs perfectly fine, till the next time you shut it off and run it again
I brought it in the shop at home and took a look, and found a vacuum plug that had come off, that is right behind where the PCV valve goes into the intake manifold. Putting this plug back on didn't help the problem.
I had my brother run codes on it, and everything appears fine, all the values are in the proper limits....one thing we noticed was that the air conditioning compressor doesn't turn on when the switch is turned on...don't know if this is related or not.
I sure hope you guys can help me out, I'm at a complete loss.
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GraphiteDak
GenIII
 
12/27/2006
00:59:29
| RE: Backfire and Power loss
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Sounds like it is leaning out, or something like your spark plug wires are cross firing.
I have had the cross firing before on what appeared to be ok wires. It will randomly cause a problem similar to that noise and a loss of power. Simple tune up of replacing plugs, wires, cap and rotor are never a bad idea.
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Trevor
Dodge Dakota
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12/28/2006
17:42:22
| RE: Backfire and Power loss
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If this was the case, why would it only do it after its just started, doesn't matter if it's warm or not?
I replaced the plugs not too long ago, didn't replace the wires 1-they're not cheap 2-we've had vehicles run for a long long time on the original set
I'll look at replacing the wires, caps and rotor i guess, unless someone can think of something else it could be.
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little jer
Dodge Dakota
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12/28/2006
23:58:43
| RE: Backfire and Power loss
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my vehicle did that when it was low on gas. Gauge showed 1/4 full, but I think it was probably a lot of water instead or the gauge was bad. It popped and jerked and died when I went around a corner. When I stopped on a grade and it died it wouldn't restart until I backed down the hill to a level spot. Just one possible cause.
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Bob Lincoln
Dodge Dakota
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12/29/2006
08:23:50
| RE: Backfire and Power loss
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"didn't replace the wires 1-they're not cheap"
www.napaonline.com has Belden PN 700107 for $35.99. Not bad for custom fit.
"2-we've had vehicles run for a long long time on the original set"
You have 202Km or 120K miles on the truck. WTF do you expect out of them? Change 'em!
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Trevor
Dodge Dakota
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12/29/2006
11:52:08
| RE: Backfire and Power loss
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Yea, I know they need changing, but I'm not one to chuck parts at something when there's nothing wrong (up here, they're closer to $100CAD)...example: o2 sensors...still original ones too, water pump...everyone said to change it when i did the timing chain, but it's working fine
little jer - that's exactly what we thought it was too. It's below freezing so i put some methyl hydrate in the tank to help it thaw, then filled it up with gas, and I'm at about a half tank now. In the last two tanks of fuel, I've been taking it from our bulk tank at home, but my dad runs the fuel from it in his ram just fine...could my truck be more susceptible to water in the gas?
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little jer
Dodge Dakota
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12/29/2006
21:21:29
| RE: Backfire and Power loss
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well, if it runs fine on a full tank ( gas floats on water ) but crummy when it gets low than it is probably water in the tank. If it runs that way on a full tank then the problem is not water in the tank. lol
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Trevor
Dodge Dakota
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12/29/2006
23:14:38
| RE: Backfire and Power loss
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Well, i don't think the level of the gas matters all that much, because the water always goes to the bottom...gas is lighter than water.
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OBIO3
Dodge Dakota
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12/29/2006
23:47:57
| RE: Backfire and Power loss
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You need to understand something. As a rule, plug wires only act up when cold or damp. As they deteriorate, they will act up warm too. You don't need to change them to know there bad. Get a friend to start your truck as you look at the wires on a cold engine in total darkness.High humidity really helps here. You should see them arcing between each other causing backfire. If you see no arcing, run your finger tips over the wires slowly. If there leaking, your fingers will glow. Long as the plugs are hooked up, you will not get a jolt.
So many problems .... So little time
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Dooooh
Dodge Dakota
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12/30/2006
00:27:49
|  RE: Backfire and Power loss
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"run your finger tips over the wires slowly. If there leaking, your fingers will glow."
you forgot to mention works even better while standing in a puddle of water
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Trevor
Dodge Dakota
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12/30/2006
00:55:56
| RE: Backfire and Power loss
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Would a code reader not pick up a miss fire? Like arcing of the wires?
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OBIO3
Dodge Dakota
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12/30/2006
02:04:13
| RE: Backfire and Power loss
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Mine does yes . Can't speak for others.
You stand in a puddle and report your findings . I've stood in snow doing this with no jolts. Long as the wires are hooked to the plugs, You should get no shock. At the most you might feel a tingle and that is as much as I ever felt. Can't tell you how many times I did this over the years. Guess there is always a first time.
So many problems .... So little time
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Trevor
Dodge Dakota
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12/30/2006
12:12:28
| RE: Backfire and Power loss
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Um...I'm not really up for being the guinea pig......haha
The code reader was a snap-on one, i would imagine it would pick up almost everything...
I'm gonna take a good look at her today.
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Dan M
Dodge Dakota
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12/30/2006
12:35:47
| RE: Backfire and Power loss
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Ok, I'm a little confused here. When does the truck have power loss and backfire? When it's low on fuel? When it's cold?
When the vehicle is first started, it's in open loop mode and using things like MAP, ECT, etc to calculate fuel delivery. Once the vehicle warms up then it uses the 02 sensors in closed loop mode.
hook the scanner back up when the truck is cold and watch MAP pressure, IAT, ECT and if the vehicle is in open or closed loop.
It could also be a fuel pump, if it does it all the time when the fuel level gets to a certain point and below.
Also, if you have the truck running, run it at WOT and see if it misses out. in WOT it should be running open loop mode.
If it misses out only at WOT or when cold then check the sensors on the TB.
- Dan M
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Trevor
Dodge Dakota
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12/30/2006
20:04:15
| RE: Backfire and Power loss
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Ok, Dan M I'll try to explain it...it's hard to explain, so i can easily see why you guys could be confused...I'll give you exactly what it did today:
Ok, so it's sat in a shed for a week, no running at all. I start it up to bring it into the shop to check it out. I start it up, gets proper oil pressure, i walk around it, looking for flats...every thing's good.
I pull out of the shed, and head over to the shop, and keep my foot off the gas, it goes along on it's own, slowly...it feels like it accelerates a bit, then not, then accelerates, then not...so i keep driving it see if i could get the power loss/popping sound.
I go around our yard and out on the road, and start accelerating and then i get the power loss/popping sound from the front of the truck.
I bring it into the shop, and my dad and i went over it, checking everything we could think of...and take it for a spin, it has sat for a couple hours in a heated shop. I get out on the road and it does the power loss/popping sound again. After it's done it's 'fit', i shut it off, then start it up, a minute later, just to see if i could get it to loose power again, but it didn't do it.
Fuel level doesn't matter, temp of the coolent doesn't seem to matter, it can sit for a week, or 15 minutes and it will do it. We were talking about fuel, just because of possible water in the fuel.
It has it's power loss, shortly after starting it, and driving.
When the code reader was hooked up, my brother said everything was fine.
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Trevor
Dodge Dakota
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12/30/2006
20:07:43
| RE: Backfire and Power loss
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Forgot to mention, one thing we noticed today, was that there was a lot of corrosion where the coil wire plugged into the distributor.
We tested the resistance in the wires...anybody know what they're supposed to be around?
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GraphiteDak
GenIII
12/30/2006
21:09:14
| RE: Backfire and Power loss
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The first car I bought for myself I got cheap.
It ran great except randomly it would do that backfire/powerloss but not always.
Of course this was before Fuel Injection so the only thing electronic was the distributor. No sensors to look for like we do now.
Anyway the wires looked ok to me. It was the last thing I changed but it was the problem. It's strange how one wire can arch to another and fire the plug on the other wire! But it can happen!
It could be something else, but changing the wires is considered a normal TUNE UP so you have nothing to loose if they are original.
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Dan M
Dodge Dakota
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12/30/2006
23:37:15
| RE: Backfire and Power loss
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corrosion on the cap? how long has it been since the cap was replaced? did you try to clean the corosion off?
you said:
"I go around our yard and out on the road, and start accelerating and then i get the power loss/popping sound from the front of the truck."
you also said
"After it's done it's 'fit', i shut it off, then start it up, a minute later, just to see if i could get it to loose power again, but it didn't do it."
you said it's "after it's done it's fit" does this mean the symptoms will stop if you keep driving it? you never said it will do this everytime you start it up after it's sitting and the engine is cold (ambient temperature)
you never said at what point in time it's done or after how long you drive the truck.
if it only does this when it's cold, it could be a problem with open loop. If it does it when the truck is hot (normal operating temp) then it's not anything with open loop mode.
what kind of wires do you have stock? did they all test the same? any loose boots? wires are easily damaged from taking them off the plugs.
- Dan M
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Trevor
Dodge Dakota
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12/31/2006
01:22:35
| RE: Backfire and Power loss
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Man, this is a bitch, i bought a Dodge to avoid this hahaha
Ok, the corrosion was on the 'male' part of the cap that the coil wire goes on....we cleaned it up and put some dielectric grease on it, problem still happens. I've only had this truck for 2 years, maybe 40,000kms. I would imagine that the cap is probably original too.
It will do it after it has sat for more than 15 minutes I'm guessing...i haven't tested it down to that time. It will do it EVERY TIME it has sat that long. 'after it's fit' is after it's done it's popping/power loss...it lasts for maybe 30 seconds, then almost instantly, I've got power back right away, and the popping sound stops. The truck will run beautifully, until i shut it off and run it again, 15 minutes later. For example, I was in the city shopping when this problem first started, so i ran my truck down to the shop my brother works at...he looked at it for maybe 20minutes. I pulled out of the shop onto the street and it did it's popping/power loss right in front of the shop...people on the streets were looking to see where the sound was coming from hahaha
More info, the popping doesnt seem to have a rhythm to it, it's random like popcorn.
The time it takes it to do it varies...sometimes it happens when I'm at 80km/h, other times it's when I'm probably at 40km/h
All the wires are the stock mopars....the coil wire tested about 14ohms, (don't know what cyl. number it is) but the front passenger side was about 10, front driver was 8, next one back on the driver was 7. All the boots look fine.
Thanks alot for your help....I really appreciate it
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Dan M
Dodge Dakota
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12/31/2006
02:29:21
| RE: Backfire and Power loss
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so it happens only when you first start the truck? Then it stops after you warm it a while? Does it do it a WOT (wide open throttle) as well?
if it only does it at start up for a few seconds and does it at WOT, that sounds like a sensor on the TB - open loop mode.
The PCM is feeding the fuel based on sensor input (engine coolant, map, etc) then once a preset set of conditions are met (o2 sensor is warm, coolant level reaches certain temp,etc) then it switches to closed loop mode and uses input from the o2 sensors). At wide open throttle it uses open loop mode so it can feed fuel at higer rate than what can be done looking at o2 sensor.
If you don't have this while driving normally (highway speeds for example) then it's not pointing to be ignition system issue.
hook the scanner back up and watch the short term fuel trim, map, coolant temp and open loop/closed loop mode condition. specifically keep an eye on open/closed loop. if the backfiring stops once it hits closed loop, you have better info to diagnose what's wrong.
- Dan M
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Trevor
Dodge Dakota
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12/31/2006
10:28:01
| RE: Backfire and Power loss
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It happens in a range of 3 minutes after start up to probably 10 minutes...it happens while driving from between a slow speed, and at 80km/h
can you explain the best way to get WOT, just put it to the boards while driving?
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