PCM / Engine swap questions 98 dodge truck

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rod7515

rod7515

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I need some help with making some decisions on a 98 Dodge truck That I bought a few months ago. I guess I have many options. First a little history that I know of the truck as of today. It starts and runs but I have never driven it. I am pretty sure it has the plenum leak that needs a gasket kit. It misses at idle but goes away when I rev it past 2000 rpms. I have replaced the plugs, cap, wires, and ignition pickup. Did a cyl compression test and all are at 140-150, also a leakdown test and they vary from 15% to 30%. Still functioned the same after the parts replacements. I plan on using this truck for towing my car trailer if I ever get the Dart completed.
Its a 1998, 5.2L, Automatic, 4wd 1500 sport. Has AC, PW, PB, cruise and 3:55 gearing.
So here is the bad news, I have a slight coolant leak that is coming from the back of the motor. I see no external leak. Its dripping from inside the trans converter shield which leaves me to believe its going to be a rear freeze out plug. I wasnt planning on this as it didnt leak until this week when I pulled it inside for the first time. So now I know either the trans is going to need to come out or the motor comes out to verify and replace rear plugs. I was originally just going to replace the plenum gasket and drive it for a while but now I think this changes things.
After thinking about this I am leaning towards pulling the motor out. That leads me to some other questions. Since Im going to be using this truck to tow do I change direction and look for a 5.9L instead of spending money on the smaller engine. If so what will happen using the original PCM or will I have to change that as well and if so what do I get? Now should I go with the smaller 5.2 and maybe go with a slightly different cam to add some additional power and how will the PCM react to that and what changes would that require. Im in no hurry as I wont need this truck until late summer at the earliest.
One person told me that since I replaced the ignition module, I messed up the fuel sync and I would need to have a dealer reprogram that. What if any reprogramming issues am I going to run into. When I worked at the garage years ago I have replaced the ignition modules and I never had to have them reprogrammed so Im not sure what he was referring too.
So what are your thoughts on what i would need to do? And what issues will I run into? Please ask any questions that I may not have covered to help get ideas.
Thanks for your thoughts in advance!
Thanks Rod
 
with engine running, pull breather and pcv valve from rocker covers, hold thumbs on grommets, if suction is felt bottom plenum gasket is sucked in. if not, its ok. should verify with a vac gauge.rough/high idle,oil consumption etc: is symptom. exhaust valve leakage/pitting/bad spot is a idle miss/roughness symptom that goes away on accell. seen this many times, esp. with bad plenum gaskets that were left go too long, but your comp. test results don't appear that way. make sure. 5.9 should be used with its pcm. what do you mean by ignition module? ing.coil? as long as you didn't rotate dist. you didn't change fuel sync. there wasn't a real huge difference between 5.2 and 5.9 power wise in 98.
 
ignition module would be the round flat electronic part that goes under the rotor. I called them the pickup but the replacement box from napa called it the ignition module. I did not touch the distributor at all except to remove the cap rotor and module just below the rotor.
Thanks Rod
 
I towed with my 2000 ram 5.2. Ehhhh. Not as torquey as the 5.9 but it did fine. Just had to be more patient with it. Not a problem though. If you do go to a 5.9 you'll have to reprog the pcm. I thought about doing the same at one point. There was some hiccup about swapping pcm's from a truck with theft control vs non theft contol that I can't remember, but one of the programmer guys told me that flashing the original pcm was no prob. Best!
 
Mechanicmark or any one that can answer the questions i did a vacuum test while checking the other things and vacuum was around 16-18. As for oil usage i cant answer that since i havent had the truck on the road yet. I will do your grommet check. As for power i understand the 5.2 wasnt loaded but i think i can make do as i will only tow 3-4 a year at most and its only about a 45 mile haul to drags.
A few things i forgot to mention, the truck sat for about 7-8 years without being run and no battery. What memory lose will that cause in the pcm if any and also how would the pcm know about distributor being moved if it had no power all that time. I ask this because if i pull the motor to replace the rear plug i may have to pull dist and i may add an rv performance cam, re-ring, bearings and valve job. How do i re program pcm without going to dealer for a programming? How will truck act without the reprogram?
Thanks Rod
 
If I'm not mistaken, there is a TSB out there about the leak issue.
It's in my craw that it has to do with a intake gasket replacement. So you probably won't have to replace the motor. I guess you're calling the cam sensor the ignition module. For the most part, you shouldn't have to flash the PCM, but I have had them where you have to. Mostly when you replace both the cam and crank sensors. I have also seen a high rate of failure with aftermarket sensors.
To answer your question about the PCM, the truck won't run properly (if at all) with the 5.9L motor and 5.2L PCM. The PCM controls your timing, fuel injection pulse and other functions. You would have to find a PCM that is for a 5.9L with your transmission set up. There also may be the issue of the VIN being burned into the PCM and a communication issue with the BCM/TCM. Flagship One is an economical source for PCM's.
If you go this route, you will definitely need to have the PCM flashed.
Flagship sells a "plug-n-play" PCM.
You shouldn't have to go to a dealer to have the flash done. There are plenty of aftermarket sources that private garages use. But I have found that the dealers run about the same in price, and you get a more recent version of the flash software. As for not flashing, well if the changes are that dramatic, the truck may not run or run very poorly.
 
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engine will take up to two hours to ''relearn'' after extended batt. disconnect. also clean throttle body. with pcv valve removed from rocker cover there should be no vacuum at grommet [other side also plugged] not talking throttle body vacuum here. i have only flashed modules with a drb, but mac/snap on etc; can also do it if shop has purchased this ability. and as noted above, don't get theft mixed between modules, they ''learn'' each other on can bus. i did this one time with a used pcm, total nightmare. as far as perf. cams, perhaps sct tuners,or others work? never used one, maybe somebody can chime in. if you pull dist., just mark base to block, hope this helps.
 
Heres an update on the truck. After doing all the testing I finally broke down and pulled the intake and timing cover off motor. Replaced chain and gears with a double roller chain, found no definite leak on the plenum but saw some rust deposits on the #8 injector while the intake was turned over and cleaning gaskets. It was midnight on saturday night when I saw this so I cleaned up gaskets replaced the old gaskets and put everything back together. Started it up and still had a slight miss at idle. Pulled the injector wire from #8 and no change. So tonight I replaced the injector. Found a ton of garbage in the old injector, replaced with a new one and the truck now runs great. Now I need to go get tags and insurance so I can go more than a mile at a time! Thanks for all the help!!
Rod
 
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