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Dan Wallace
Dodge Dakota
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7/25/2006
15:11:14
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 Subject: 5.2 Missing at Idle
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I have a '92 dak and I have a problem with it missing at low rpm. It has been doing it since I had a new engine put in. I've taken it to 3 different shops and they tell me I have a low end spark problem that is heat induced. The truck runs cool just like it should, but the engine bay gets very hot thanks to Gibson headers. I have tried to get rid of that heat by wrapping headers, 180 degree thermostat, and I even removed the hood to see if that made a difference. Nope still does it. Runs perfect until it warms up to operating temp. then, if I am sitting at a stoplight idling it starts to miss and sometimes stalls. At high rpms or cruising down the highway, it runs fine. It has been getting worse the farther into summer we get. The ignition system is all MSD, that checked out fine. I've changed plug wires, distributer cap, and heat wrapped all wiring that is close to the exhaust. Anyone have any ideas? No one else does.
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zzark
*GenII*
7/25/2006
20:45:32
| RE: 5.2 Missing at Idle
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Do you have the stock clutch fan?
How about installing a high performance electric fan? (after removing the clutch fan)
What do you call the hoods with the vents at the windshield? That will help. But they are expensive.
zzark
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zzark
*GenII*
7/25/2006
20:49:04
| RE: 5.2 Missing at Idle
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And the routing of the plug wires is very important.
There is a TSB about it. But I just did mine so they were not near each other and not near metal or other cables. My cables are a little longer than stock OEM, so it was better and easier to route them than the official TSB.
zzark
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Dan Wallace
Dodge Dakota
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7/26/2006
11:18:02
| RE: 5.2 Missing at Idle
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I did test the clutch fan, just to make sure. It turns on when it supposed to. I don't believe it is the plug wires because I'm missing on all cylinders, not just one or too. Had that happen before. I've changed wires a few times. I have MSD helicore 8.5mm on now---with heat wraps. Routed best I can. I have a hood on order---looks like the one on the new Challenger. Has a heat extractor on it with ram air up front. I doubt this will make a difference because my truck was doing the exact same thing described with the hood off completely. Not sure what else to check---I'm DOOMED.
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Mikey
Dodge Dakota
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7/26/2006
15:14:33
| RE: 5.2 Missing at Idle
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Check your timing, You could have moved the distributor alittle bit while you were installing the new cap and rotor.
Check your distributor hold down bracket to see if it is loose, maybe you are combusting out your exhaust stroke and its making things a little hot, and making you miss.
Or maybe it wasn't timed properly when it was installed
Just a thought!
Let me know if it works.
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Dan Wallace
Dodge Dakota
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7/26/2006
17:41:25
| RE: 5.2 Missing at Idle
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Timing is set by the computer. I can put the cap in any position--doesn't matter. Cap and bracket are tight though.
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zzark
*GenII*
7/26/2006
20:18:33
| RE: 5.2 Missing at Idle
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It could be the O2 sensor.
It is only monitored after the engine is warm, in closed loop.
You can get a NGK O2 for about $40 at ngk.com
While you are there, get some NGK v-power plugs.
Both are recommended by J&J Auto Larry.
I think I have a driveability problem caused by my Bosch O2. I have a new NGK, just haven't installed it yet.
zzark
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Dan Wallace
Dodge Dakota
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7/26/2006
22:22:51
| RE: 5.2 Missing at Idle
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I replaced the O2 sensor about 2 years ago before I had the engine built. It's worth a shot I guess. I remember awhile back when I was trying to troubleshoot the missing problem I had a diagnostic reader thing hooked up to it. It read the O2 sensor constantly fluctuating between rich and lean---like every 1/2 second. I talked to a ASE guy about it and he said thats normal.
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clint
Dodge Dakota
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7/26/2006
23:16:43
| RE: 5.2 Missing at Idle
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check spark plug gap. one plug on my jeep was messed up and at idle you could really hear it was missin. but as soon as i started drivin it was fine.
just a thought.
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Dan Wallace
Dodge Dakota
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7/27/2006
11:42:34
| RE: 5.2 Missing at Idle
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Ok, checked all plugs--all are good on gap--no kind of discoloration. I hooked up my diagnostic tool again.. Idles well until the Charge Temp. gets to 177 F(I think coolant temp at that time was right at 200 F). Starts to idle erratically around this area--but it is only minor, not enough to stall it. I let it idle some more, about another 15 minutes with ac on. As the temperatures climb, the idle problem gets worse. I have to keep the rpm's up at 1000 to keep it from stalling. I shut er down when coolant temp got to 233.8 F and charge temp was around 207 F. Coolant gauge was reading about 3/4 to max. Not sure why it's overheating. Engine temp was up there before with this same problem and I replaced thermostat and put in a 180. I know it's working, upper hose is hot and has pressure. The clutch fan works--I think. I hear it come on when I'm driving sometimes. Only time I heard it come on when I did this test is when I lift the rpm's over 1000. Water pump is also new and fluid is full. About 3 years on the radiator. Could this be the reason for the missing at idle? Particularly the Charge Temp? All other sensor readouts were normal. Went to Checker awile back to get a new fan clutch---installed it and it was always engaged. WTF? Took it back and installed old one. Sorry this is so long--just wanted to get all the facts out. Thanks for the help.
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zzark
*GenII*
7/27/2006
19:06:02
| RE: 5.2 Missing at Idle
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Yeah, you're running hot.
Think about getting an electric fan!
Also, get a Prestone flush kit and some cleaning chemicals. Do a good flush. Make sure you do a back flush. Remove lower rad hose and flush.
I also recommend using Redline water wetter.
Oh, and get a new radiator cap. They're cheap enough.
And where does it measure the charge temp??
I don't know.
zzark
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Dan Wallace
Dodge Dakota
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7/27/2006
22:59:36
| RE: 5.2 Missing at Idle
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Not sure where the charge temp is read. Somewhere on the throttle body I'd imagine.
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Dan
Dodge Dakota
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7/28/2006
13:51:08
|  RE: 5.2 Missing at Idle
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Well, today I had the radiator flushed--didnt make a difference. Barely made it home, it was stumbling so bad. Temperature gauge was reading a little over half way.
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Dan Wallace
Dodge Dakota
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7/28/2006
17:46:18
| RE: 5.2 Missing at Idle
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New Update!! Replaced fan clutch. I notice it engage alot sooner than the old one. Still, didn't make any difference. Still stumbling. The more heat, the more it stumbles. And it also seems like the worse the stumbles get, the hotter it gets also. Oh man....any engineers in here?
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clint
Dodge Dakota
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7/29/2006
01:31:11
| RE: 5.2 Missing at Idle
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well dont get an electric fan cuz that wont solve anything. if it comes from the factory runnin 200 that means it will run 200 with stock parts. sounds to me that mabey an injector is goin wacky.
now im not exactly sure how this works but it might be runnin it real rich. and thats why it wont idle. it isnt burning all the fuel. and when you start runnin it at higher rpms and dumpin a tons of fuel...it gets hot.
i really dont know but if i had to guess thats what id say. if ALL eles fails return some parts back to stock. cuz stock ALWAYS works.
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shatto
Dodge Dakota
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7/29/2006
02:08:11
| RE: 5.2 Missing at Idle
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Some random thoughts;
1. Did you stick a thermometer inside to check? I shot my 3.9 (with Gibson headers) with an infrared and it was only 150 degrees! Shocking.
Remember, the temperature gauge in the insturment panel is mostly for show. It can read normal when the dry engine is just about ready to sieze.
2. My 3.9 was showing missing and the check engine light stayed on. Ultimately it was bad valves and cracks between valves.
3. Bypass the MSD. What does it do with the stock coil.
My truck began missing extremely badly as my Jacobs died.
4. You said the distributor position doesn't matter for the ignition. Right. Injection timing will be off though.
On the other hand, if you don't have injection you have a percolation problem or the float level is too high or a plunger seal is shot or something is sticking. Carb pro's are worth the money.
5. Jacobs makes ceramic booted racing wires. I've always used standard Jacobs wires with no problems.
6. Pop the hood and drive around. There will be a bit more air flow through the engine compartment. While you are at it, pull the rubber seal for the back of the hood. That'll let smelly engine air directly into the cab, and allow better air flow through.
7. Have a radiator shop pressure test for leaks, and for exhaust gas in the system. They can also accurately assess the condition of the radiator and cooling system. You cannot tell if your radiator is partly plugged, with a garden hose.
It wasn't until I felt the back if the radiator, and found it was 2/3 cold, that I had any idea mine was shot. (800radiators)
8. New engine, eh? Possibly not assembled properly?
I bought new factory heads. They needed re-planing and most of the valve seats needed to be re-cut, the factory, as in Dodge, did such a poor manufacturing job. The valves would never have seated with just grinding compound.
I'm out of randoms for now.
Nite.
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zzark
*GenII*
7/29/2006
10:17:30
| RE: 5.2 Missing at Idle
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Clogged cat ! ??
zzark
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zzark
*GenII*
7/29/2006
10:21:27
| RE: 5.2 Missing at Idle
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What size was the old engine?
If it was a 3.9, did you upgrade the radiator with the 5.2?
zzark
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Dan
Dodge Dakota
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7/29/2006
11:29:29
| RE: 5.2 Missing at Idle
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Nope it's a 5.2. As for a clogged cat---did it just happen to get clogged when I installed the rebuilt engine? The engine builder knows what he's doing--he's done it for 30 years, so I dont think it is something he did. Already bypassed the MSD, no change. Temperature gauge is accurate since I compare what the gauge is showing and what the scope is showing in realtime. As for the injection timing, I thought that was regulated by the computer regardless of distributer position? It is MPI injection by the way. The plug wires are brand new MSD helicore-8.5mm with heat wraps on all. I've already driven around with the hood completely off---no difference. Took the truck to the shop to have the cooling system flushed/cleaned. Replaced radiator cap. As for it running rich--see prior post. I tend to think it has something to do with the air/fuel mixture--but why would that make it run hot at idle? Also, would a clogged cat trip a code?
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daddio
Dodge Dakota
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7/29/2006
12:55:33
| RE: 5.2 Missing at Idle
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"I can put the cap in any position--doesn't matter."
something is not right there. turning the distributor changes the injector sync. and if you get it too far off it will not run. have you checked that?
you are running too hot though. have you pressue checked the cooling system? even the new cap could not be holding enough pressure. and maybe try a plug 1 heat range colder than what's in there now.
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clint
Dodge Dakota
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7/29/2006
16:28:09
| RE: 5.2 Missing at Idle
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if a injector goes wacky it will mess with the air fuel mixture. thats exatly what i was sayin. but after readin the last couple posts i think it would have to do with the cap postion.
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