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Dan M
Dodge Dakota
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11/14/2005
11:39:06
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 Subject: backfire while accelerating
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So on to my latest issue with my 95 3.9L auto 4x4.
It occasionally backfires while accelerating from a stop. The backfire is in the front part of the exhause (I can feel/hear it under the cab). It only happens at low speed, has not happened on the highway yet.
When I am accelerating, I can feel a lack of power.. ie the pedal is down but the truck is not accelerating. I at first was thinking it might be an issue with the fuel pump, but the backfiring indicates that fuel is present. Could it be the pressure regulator?
It was really bad this morning. I recently changed the cap and rotor and that did not fix the issue. I also checked the routing of the wires and verified they were all snug. I have yet to check the plugs. I do have an inline spart tester I will check the plugs tonight. If that does not show me anything, i'll pull the plugs and check them out.
The other thing I can think to check is the headers, they are the original ones. I don't think it's this since the truck does not backfire all of the time and if there was a leak, I would think it would be occurring all the time. Perhaps someone can correct me if my logic is off here.
- Dan M
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Dan M
Dodge Dakota
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11/15/2005
05:26:34
| RE: backfire while accelerating
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I got around to testing the spark plugs/wires with my in-line tester last night. After 3 successful wires the 4th plug wire boot connector broke taking it off the plug (metal connector pulled right out of the boot). Needless to say I replaced the plug wires under warranty (ltd lifetime). The friendly folks down at advance suggested a cam or crank sensor as possible source for backfire.
So far in the short time driven since replacing the wires, I have not had any backfires (about 30 miles driven so far).
- Dan M
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zzark
Dodge Dakota
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11/15/2005
09:01:56
| RE: backfire while accelerating
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Hey Dan M,
Did you solve the dieing issue?
Or is this part of it?
I've never had any backfire problems, so I can't offer any ideas.
zzark
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Dan M
Dodge Dakota
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11/15/2005
14:35:04
| RE: backfire while accelerating
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The issue i had with the truck dying was solved by the ole #115 splice.
Now, to solve the backfiring issue. I went to lunch today and it backfired several times.
- Dan M
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zzark
Dodge Dakota
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11/15/2005
18:47:49
| RE: backfire while accelerating
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Email to Dan M. !
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Adam
Dodge Dakota
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11/15/2005
18:49:58
| RE: backfire while accelerating
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I had a problem kinda like that..almost felt like it was comming out my intake. I change my cap and rotor and it went away for a little while then came back...after that I change wires and coil and haven't had a problem since then..(knock on wood). Dunno if that helps any.
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schmidtmike
Dodge Dakota
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11/15/2005
18:59:37
| RE: backfire while accelerating
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I would check all of your connections with the engine running (shake em), and check the ground wires especially. Then try hooking up a vacuum gauge and get the truck to repeat the conditions. I'm guessing vacuum leak.
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Dan M
Dodge Dakota
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11/15/2005
22:03:49
| RE: backfire while accelerating
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I tested the plugs/wires with my in-line tester again tonight. I found one plug (passenger side) that was inconsistent. I pulled the plug and it had carbon build up on it. According to haynes this is caused by running rich/no burn. I replaced the plug, tested and it tested good. I went shopping with the wife tonight and she was in the truck when it backfired. She said it sounded like it came from the passenger side of the engine bay. This would support the fouled plug on the passenger side.
I am now thinking I need to replace the intake manifold gasket.
- Dan M
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Dan M
Dodge Dakota
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11/16/2005
22:38:28
| RE: backfire while accelerating
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I'm not so sure it's a vaccuum leak or the intake gasket. If it were either of these, I would expect the backfire to occurr more often than it does. Some days it wont backfire at all, some days it does it every trip (every time I drive it). Other days it does it sometimes. It's not consitant at all.
I mentioned this before, but not on this post. Sometimes at highway speeds I will have a hesitation - ie, the rpms drop quickly and then recover. When it recovers the truck bucks. The backfireing is only at low speeds. I was thinking this bucking may be a quick lockup in the torque converter but am not positive.
Could it be the fuel pressure regulator causing both the backfiring and bucking? Maybe a intermittent back injector? I replaced the fuel pump, but used the original (1995) pressure regulator. I tested all plug wires again tonight with the in-line tester, all tested fine. This is a tester with a light inside, as it sparks, the light comes on. All plugs/wires light consistantly.
Tomorrow I am going to pull all 6 plugs and inspect and check the gap. I did replace 1 last night that had carbon build up. This weekend I am going to try to get my hands on a pressure tester to test the fuel pressure.
schmidtmike - I have not been able to duplicate the backfire while the truck is parked (tried reveing the engine using the throttle lever, but nothing).
- Dan M
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schmidtmike
Dodge Dakota
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11/18/2005
14:47:52
| RE: backfire while accelerating
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so it only occurs under load, interesting.
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Dan M
Dodge Dakota
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11/18/2005
19:13:39
| RE: backfire while accelerating
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More interesting information.
The truck did not backfire at all yesterday, but did today. Another thing, the truck has died twice, both times driving down a slight incline slowing down. 1st time to make a turn and 2nd time stopping for traffic in front of me to turn on a side road.
Tonight I picked up a fuel pressure tester and tested the fuel pressure at the test port. It was a steady 38 psi (manual says 35-45 psi is normal). I let the engine run for several minutes with the pressure guage attached and the pressure did not fluctuate.
During the test, the truck started to idle rough. I could hear what sounded like a sucking sound and I could smell gasoline. I could not see any gas coming out of the test port. I accelerated using the throttle lever and the sound stopped while reving the engine. When the rpm level returned back to idle, the sound was gone, about a minnute later, it was back. Reved the engine again and it stopped. I ended the test on that note.
I have not pulled the plugs yet, will do that tomorrow. I'm also going to pick up a compression test kit and test the compression in all cylinders. I am also going to check the EGR and IAC.
I think the advance here has a vacuum tester for their loan-a-tool program. I will inquire about that and possibly check vacuum as well.
- Dan M
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cuzindoug
GenIII
11/18/2005
20:27:58
| RE: backfire while accelerating
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With that last post, it sounds like the next things you are checking, EGR and IAC, or maybe a combo of the 2.
If it ain't broke, fix it til it is.
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Dan M
Dodge Dakota
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11/19/2005
14:30:57
| RE: backfire while accelerating
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I think I found the culprit. The control valve assembly of the EGR. It looks like it sit on something hot and melted and it has a couple of "holes", vacuum leak...
Pictures will come later after i install my camera software to download the pictures.
- Dan M
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Dan M
Dodge Dakota
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11/20/2005
13:08:07
| RE: backfire while accelerating
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I replaced the EGR. The truck still backfires and idles rough. Next step is to clean the IAC. I am going to pull the throttle body and replace the gasket when I clean the IAC.
I guess the next step would be to replace the IAC and MAP sensors.
What has been done so far:
new cap
new rotor
new plug wires
inspect plugs (about 12k miles on them)
check spark to plugs/wires using inline tester
check fuel pressure at test port
replace EGR
check for vacuum leaks using vac guage/tester
use seafoam at every oil change.
Anyone have any other thoughts?
- Dan M
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zzark
Dodge Dakota
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11/20/2005
15:54:04
| RE: backfire while accelerating
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Dan,
Did the PDFs give any good clues?
zzark
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Dan M
Dodge Dakota
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11/21/2005
10:19:09
| RE: backfire while accelerating
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I have tested most of the stuff listed.
There are a few items that I'm not sure what they refer too and am doing some research on.
I do have an alldata subscription that I've been reading alot lately as well as haynes manual.
If I can't figure anything out this week, I'm going to see about taking it to a shop that I use on occasion. The Owner and Manager are good people to work with. The Manager used to work for Chrysler.
any shop that is on the jasper engines preferred installer list is a good shop in my opinion.
- Dan M
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CrackDak98
Dodge Dakota
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11/21/2005
19:00:17
| RE: backfire while accelerating
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hey Dan M. i am having the same problem so please as soon as you get it fixed post what the problem was please so i know what to fix becuase im low on cash i need this thing to run right for a change...damn i miss the old carburated days...i know fuel milage sucked back then but hell motors were cheaper to fix though....less electronics the better we are is how im starting to feel...
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Mopar1
Dodge Dakota
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11/21/2005
20:09:48
| RE: backfire while accelerating
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Boy, I know how the lack of money feels. I think we all do. I went through roughly 1,000 bucks before I found out it was the distributor gear and bushing. Good luck.
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Dan M
Dodge Dakota
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11/21/2005
20:57:31
| RE: backfire while accelerating
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Ok, an update. I drove the truck to and from work with no issues today. The wife and I went to pick up a few things from the store. Pulling out of the parking lot at a light and accelerating, the engine did what would normally lead to a backfire- hesitation, lack of power. However it did not backfire. After a few seconds of now power, it kicked in and drove fine the rest of the way home.
Definately the EGR was bad, that was an easy test using a vacuum guage. After pulling it off and inspecting it, it was evident it was bad.
Cleaning the IAC also helped. I did reset the PCM after cleaning the IAC. I think I may just go ahead and replace that and the MAP sensor. Why not? The are not that expensive and they both are the original parts from when the truck was manufactured in 1995.
- Dan M
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CrackDak98
Dodge Dakota
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11/22/2005
00:49:36
| RE: backfire while accelerating
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so then the best suggestion would be check the egr valve right....where is it located at?
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Dan M
Dodge Dakota
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11/22/2005
04:17:19
| RE: backfire while accelerating
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On my 1995, it is at the Back of the engine, next to the distributor cap. It's a 2 part piece connected with a small (few inches) of vacuum tubing.
Also, check for other vacuum leaks and clean the IAC. Pepboys may have vacuum tester in their loan a tool program. I actually picked mine up at harbor on sale for $16.99.
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=92474
What is your email address? I'll send some instructions on testing it.
- Dan M
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