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00:46:56 - 12/20/2024
V8 Dakotas
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318DAK
Dodge Dakota
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10/08/2003
21:24:09
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 Subject: Mopar PCM vs custom flash
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ok- I have a 99 318 5 speed with a nasty cam, head work, and M1 intake- just to list the major mods. The truck has an inconsistent miss through the rpm range and wants to die at stops because I'm only pulling 9 lbs of vacuum at idle. Will a Mopar PCM get this thing running right, or do I have to get it custom flashed? If I need the custom flash, who do I contact? Thanks!
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graphiteRT
R/T
 
10/27/2003
22:23:09
| RE: Mopar PCM vs custom flash
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Custom flash is not likely to fix your problem. Once you get below 12 in. vacuum you start getting into problems with the factory controller and anything as low as 9" is just a nightmare. Stand alone is probably your best bet with a setup that wild.
Bob
'01 Graphite CC R/T, MP headers, Magnaflow muffler into 'Cuda style exhaust, M1 2bbl, ported 2.02 R/T heads, custom grind cam, Crower SS rockers, Paxton Novi2000, Boyd's 20s w/Dunlop SP9000s, Featured in April '03 Sport Truck, Viper 4 wheel discs
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Fast92
Dodge Dakota
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10/28/2003
23:50:19
| RE: Mopar PCM vs custom flash
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Dak318,
I'm having the same "problem" with my '92. I've just recently installed a complete "Lightning Killer" long block form KRC, and I too have the inconsistent miss, along with the dying at a stop. In fact the miss seems similar to a "stutter box" on a bracket racer, were as the dying reminds me of an "old-school" carburated engine that's setting to rich.
The cam is a KRC220, which Marty recommends a Mopar PCM, and the heads are 2.02 R/T...are you running something bigger as far as a cam???? That's about as big as you can get with the Mopar PCM, anything bigger (as Graphite mentioned), will need a stand alone system. Well, let me rethink that, I'm almost sure you can go with a slightly bigger cam, but only a few thousandths on the lift side, and a few degrees on the duration side...not much more.
I'm currently running uncapped Hooker Super Comps with my 02 setting about 2-1/2 inches away from open air, in a "02 friendly" collector, so my next step is to build the exhaust (get a little back-pressure), relocate my MAP vacuum, change out my nasty fouled plugs, and blank the computer. Hopefully, this will remedy my problem, or it's back to the drawing board.
Which all of this is a real shame, for when I originally fired the engine...WOW! It had response like a solid-lift cammed engine. It would literally SNAP from idle to 1,300-1,500RPM in a split-second...then right back to idle.
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318Dak
Dodge Dakota
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10/29/2003
15:39:18
| RE: Mopar PCM vs custom flash
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my cam is slightly bigger, but I really think the custom flash is gonna fix it. Vacuum shouldn't affect performance and I can deal with it wanting to die at stops.
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RT
Dodge Dakota
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10/29/2003
23:05:21
| RE: Mopar PCM vs custom flash
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My RT usually sits at about 20lb vacuum when I am at a stop. Lately though, if I am stopped for more than a minute or so, my vacuum goes to like 10 or less and my truck wants to die. Any ideas what this could be?
thanks
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b1llyw
GenII
10/30/2003
06:13:24
| RE: Mopar PCM vs custom flash
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318Dak, it's a moot point. You need the custom flash for your setup, IMHO, and there is no Mopar PCM for a '99 5 speed. Mike Leach or BG can do that for you.
Bill White
'95 CC 4x2, SLT - under construction
'03 Ram 1500 QC 4x4 Hemi Off-Road
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318Dak
Dodge Dakota
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10/30/2003
19:39:41
| RE: Mopar PCM vs custom flash
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got it and it runs a HELL of alot better! But it seems like it's trying to adjust even more cuz as I drove it felt better. BUT- my check engine light came back on. It stayed off until I killed the truck and started it back again. I don't know what the deal is with that- I guess the vacuum. I'm gonna try some resistors to fool the pcm.
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graphiteRT
R/T
10/31/2003
00:12:56
| RE: Mopar PCM vs custom flash
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Resistors to fool the PCM??? Messing with the MAP signal is not a good idea. Outside of the O2 sensor, the MAP is the most important sensor to a speed density computer. You don't want to indiscriminantly tweak that signal. Both fuel and spark are calculated from that.
The reality is a factory computer just doesn't like that sort of low vacuum. Custom flashes can only tweak the fuel and spark tables, they can't alter the base logic and that's where the problem lies. The low signal is tripping the code more than likely.
Bob
'01 Graphite CC R/T, MP headers, Magnaflow muffler into 'Cuda style exhaust, M1 2bbl, ported 2.02 R/T heads, custom grind cam, Crower SS rockers, Paxton Novi2000, Boyd's 20s w/Dunlop SP9000s, Featured in April '03 Sport Truck, Viper 4 wheel discs
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MJB
Dodge Dakota
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12/11/2003
18:22:54
|  Anyone know who does custom flashes
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I replaced a 319 with a 360 and its a 1997 4x4. I need a custom flash to run it right
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mondtster
Dodge Dakota
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12/15/2003
10:31:08
| RE: Mopar PCM vs custom flash
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Guys, there are ways to get around needing custom flashed ecus to a point. From the import world you could get something like the Apexi S-AFC which intercepts the map sensors signal and feeds the ecu a new one based off what the map sensor is giving the AFC. They are actually pretty crude in their operation, but I have used them in the past on other projects and they work very well.
With that said, why doesn't someone learn how to tune the rom that is in their ECU? I don't know anything about the newer Dak's OBD2 ecu's, but my '93 has all the instructions on an external eprom which could be desoldered and replaced with a custom flashed one. All that it would take is someone with some smarts about Assembly programming language to do it. Unfortunately, I can't seem to understand it no matter how hard I try. Check out the DIY EFI website for more details on the subject. They mostly are interested in GM ecu's, but there is still some good information none the less.
As for the true problem with these trucks with large cams, it is the fact that the map sensor is not seeing enough vacuum and it is trying to dump too much fuel. The location of the vacuum source for the map sensor will make a difference too. Honestly I really feel that standalone would not completely remove the problem either due to the fact that it still has very low vacuum. Standalone would help, but not be even close to worth buying just in order to cure this problem.
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