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Luke
Dodge Dakota
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9/26/2004
11:29:19
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 Subject: RE: '93 3.9 running bad and getting worse
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Did you only check the fuel pressure at idle? You should check it while driving also. It should maintain pressure while driving and if the pressure falls a lot, it could be a bad fuel pump.
I wouldn't recommend using a 160 thermostat. Go with a 180. My 93 3.9 stays in the very bottom of the normal range with the 180.
Have you noticed any slow loss of coolant when it hasn't overheated? Mine was losing coolant very slowly. I added about a quart of coolant every 1-2 weeks. Well, the coolant was getting sucked into the combustion chambers because of bad intake gaskets. I found that out when I pulled the manifold to replace the belly pan gasket. If coolant is being burned, that could kill your o2 sensors which could cause the rough running and loss of power.
Good luck and let us know what you find out.
Luke
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Nathan Howard
Dodge Dakota
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9/26/2004
23:15:33
|  RE: '93 3.9 running bad and getting worse
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Ok, I've sent a few sparatic messages and I need to update this thread.
----------------------------------------------------
1. My fuel pressure is 32 at engine idle, 35/36 key on engine off.
2. I did a compression check and performed up to 4 rounds of 4 cycle checks on some questionable cylinders. This is what I found:
# Cylinder | 1st round | 2nd round | 3rd | 4th
---------------------------------------------
1 Cylinder | 120-170 | 120-170 | 120-170 | |
2 Cylinder | 120-170 | 120-170 | 120-170 | |
3 Cylinder | 120-170 | 120-170 | 120-170 | |
4 Cylinder | 90-170 | 90-170 | 90-170 | 120-170 |
5 Cylinder | 90-170 | 90-170 | 120-170 | 90-170 |
6 Cylinder | 80-170 | 80-170 | 120-170 | 120-170 |
Though 4,5,6 had at least one check starting at 120, the other 2 or 3 checks started at 80/90. While the other cylinders 1,2,3 always started at 120. All cylinders maxed at 170, every single one of them.
3. My truck overheated yesterday, BEFORE I performed the compression check. Today, I installed a new 180 degree thermostat thinking the thermostat might be stuck open. The old one seemed fine when I pulled it out though.
4. While performing the compression check I noticed the plugs were pretty darn white.
At this point I'm trying to decide what to do. Should I spend $100 to get yet another diagnosis that might not tell me anything (already taken it 3 places so far)... or should I just start tearing the top end off looking for a blown head gasket or a broken pleneum belly gasket? Some of you say the fuel pump or regulator might be bad, but I see no indication according to the manual and my tests.
Again, I've already replaced the following parts (after repair shop advice, yet no change in engine behavior other than a quieter drive chain):
--------------------------------------------
Plugs, Wires, Cap, Rotor
Fuel Filter
EGR Valve and Sensor
Fuel Injectors (5.0 Motorsports)
Timing Chain and Tensioner
Water Pump
K&N Air Filter
Valve Cover Breathers
and now a 180 degree thermostat
Nathan
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Verde SAR Dog
Dodge Dakota
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9/27/2004
00:25:18
| RE: '93 3.9 running bad and getting worse
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Message:
Your compression looks good, Are you losing coolant through your heads or intake manifold ??? So why think a blown head gasket??? Your fuel pressure is low, significantly lower when only idling so I would really suspect the filter/regulator, have you tried a flow test??? Are you getting 1 liter/min? Your truck is over ten years old has it ever had a new fuel filter??? I always try the simlpest most economical thing first.
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93Dak
Dodge Dakota
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9/27/2004
09:02:26
| RE: '93 3.9 running bad and getting worse
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Message:
His fuel pressure is fine for a 93. My 93 shows the same as his does. The Haynes manual says that 32 psi is fine.
Sounds like compression is fine too. On my 93, I get 120 psi out of all but one cylinder. The last one on my truck only gets up to about 90 psi.
The overheating thing should be investigated. Were you low on coolant when it overheated? (Is that why it overheated?)
I would not go with less than a 180 degree thermostat. They came with a 195.
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Bob Lincoln
Dodge Dakota
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9/27/2004
09:04:54
| RE: '93 3.9 running bad and getting worse
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Message:
"My truck overheated yesterday, BEFORE I performed the compression check. Today, I installed a new 180 degree thermostat thinking the thermostat might be stuck open."
Overheating would mean that the thermostat stuck CLOSED, not open.
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Nathan Howard
Dodge Dakota
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9/27/2004
12:32:55
|  RE: '93 3.9 running bad and getting worse
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Message:
Checked my old thermostat, and it was indeed stuck CLOSED... which is why it overheated. I have no idea how long it's been running too hot, as I hadn't been checking my heat gauge for some time now. HOpefully didn't cause too much damage.
The new 180 degree thermostat makes my engine run cooler than it ever has though! Awesome.
I still need to figure out why it's running rough though... and I'm at my wits end.
Nathan
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93Dak
Dodge Dakota
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9/27/2004
15:05:29
| RE: '93 3.9 running bad and getting worse
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Message:
How long does your fuel pressure hold after you turn the engine off? They are supposed to hold for a couple hours. I think that is wishful thinking honestly, but it should hold for quite a while.
I think that I mentioned before that the fiveomotorsport injectors are a little shorter than your stock injectors on a 93. When I installed them on my 93, they would leak fuel around the o-rings. It wasn't enough for me to see, but the fuel pressure would bleed off rather quickly. I bought all new o-rings for my old injectors, installed them, and then the fuel pressure stayed high much longer after I turned the engine off.
Another thing to consider is if you have an intake manifold or belly pan gasket leak. I'm sure that you've read that you can pull the throttle body and look down in the intake manifold to see if it is really oily. If it is, your belly pan gasket is leaking.
As far as I know, intake manifold gaskets don't leak often on these engines, but I replaced mine seperately from doing the belly pan gasket, and it made mine run much better.
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93 Dak
Dodge Dakota
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9/27/2004
20:42:29
|  RE: '93 3.9 running bad and getting worse
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Message:
Nathan, you asked:
"Any clues?
Symptoms:
Lumpy idle and hard starts after engine sits for a while (when engine is cold).
Poor acceleration.
Bad MPG
"Feels" like it's "missing" mostly when it's cold.
Backfires or Pops when decelerating and post-rev. "
Did all those symptoms happen before or after you changed the timing chain?
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Nathan Howard
Dodge Dakota
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9/27/2004
23:17:52
| RE: '93 3.9 running bad and getting worse
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93Dak, before _and_ after. As I said, all the modifications I have done to this date have done nothing to improve my symptoms.
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93Dak
Dodge Dakota
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9/28/2004
08:14:40
| RE: '93 3.9 running bad and getting worse
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Message:
I was just wondering if something you have done caused those symptoms.
I had a lot of trouble with the Bosch injectors from fiveomotorsports. At first, they seemed great, but after a week of driving, the truck would miss and light up the check engine light.
Have you checked the EGR valve?
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?
Dodge Dakota
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9/28/2004
13:54:45
| RE: '93 3.9 running bad and getting worse
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I didn't see anything re cat - Has it ever been changed ?
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brenda reed
Dodge Dakota
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2/20/2008
21:25:05
|  RE: '93 3.9 running bad and getting worse
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Message:
i think that it is your fuel pump.my truck was doing the same thing a month ago going over 65 for more tha 10 miles sounds think popcorn and dies down cool off for 10 min then fin e for 10 more miles. no acceleration .. try fuel pump
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dakota49
Dodge Dakota
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2/21/2008
01:20:26
| RE: '93 3.9 running bad and getting worse
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Message:
brenda, did you realize you were replying to a 3 year old post?
Good Luck
Dakota49
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