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4.2 tbi upgraded, but now i have issues. HELP!

13K views 218 replies 13 participants last post by  motormike24 
#1 ·
hey guys. i've used this forum exclusively to do the complete GM tbi upgrade to my friend's 4.2 wrangler. it had the usual motorcraft carb swap already due to the crap carter carb that it came with smoked the old motor.

heres a brief rundown of what i've done til this point:

he had a rebuilt engine shipped to a shop that did his motor swap. drove it 200 miles or less with the motocraft carb. and burned up a piston in cyl 6. wasnt happy. called me cuz he was sick of the bs with the shop, and nobody would honor any warranty. I overnighted another engine kit, it has .060 over pistons in it, new rings, bearings, etc. then got it fired up, only to find the head musta been warped too. basically he got a junk rebuilt motor. so i swapped the head with a freshly machined head.

then he decided that since we could NOT get that damn ford carb to run worth a crap so he wanted to go FI. i researched options vs costs, again, from this wonderful site ;) and opted for the GM 4.3 tbi swap. i took the computer, MAP sensor, TPS, IAC, TBI unit, and temp sensor from a 92 chevy blazer 4.3. had a machine shop custom make me an adapter plate for the TBI.... but it wouldnt fire. found i had no injector spray. so i goosed it with some starting fluid, it fired, and like magic i suddenly had injectors! ran like a champ after some minor distributor adjustments. after we ran it around town we discovered it would lurch and pop and sputter at lower rpms, such as when driving 25-30mph in town in 3rd gear. but it ran perfect anything above 2500 rpms. never had a problem starting it again.

THEN, a few months later he decided he wanted to upgrade the distributor. i read about the HEI upgrade, and tried to do that. but could not obtain the proper distributor gear to run that set up within the time frame i had to work on his jeep. so we bought a brand new stock distributor, but got the ford distributor adapter and the ford 300 c.i. inline 6 distributor cap (because of it being bigger and farther spacing between posts). also ran with the TFI coil for better spark. went to fire it up, and no go. again, no injectors. so once again i goosed it with some spray, and it fired right up, and had great injectors as soon as it fired! kinda confused me, but figured it happened the first time, so no biggie. got the distributor timed properly, let it run a bit, then shut it off. i fired it up a few times, it was GREAT. i literally put a glass of water on the valve cover and it didnt move. went inside, drank some beers, and 4 hrs later came back to start it, no injectors. no matter how long it cranked. so i sprayed it AGAIN, and fired up and drove fine. shut it off, and it fired right back up. after lots of playing with it, i've discovered it will give injector signal every time to start it as long as its at least remotely warm. as soon as this winter weather cools it down, it loses its initial pulse signal to get it started. i dont understand. at all. ive changed the temp sensor with a new one, no change. the old distributor was JUNK i found out as it had many floppy parts and the magnetic deal that reads the star wheel under the rotor was constantly touching. but now that its got a good distributor it does this ****. HELP. im only here in town to help him out for a few days. im going the yard tomorrow to get a different computer in hopes maybe it was a freak coincidence that it went bad the same time i swapped the distributor, but i doubt it. please help me!

thanks, mike
 
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#202 ·
Okay, I'm just starting the learning process on reprogramming chips, but from what I have found, that ECM (1228062) with that prom ID (981) should be BCC ASSB. Which came in a 1991 S-truck 2.8 TBI HO with a 5 speed manual tranny. Not a particular ECM I would run on a 4.2 6 cylinder
 
#203 ·
I wonder if the pinouts are the same on this ECM as the 1227747. I bet they aren't, so we may have given bad wire locations in this thread.

I gotta give it to you Mike, you're a helluva friend for going through this much trouble for someone elses vehicle. :thumbsup:
 
#205 ·
jeepardy said:
Okay, I'm just starting the learning process on reprogramming chips, but from what I have found, that ECM (1228062) with that prom ID (981) should be BCC ASSB. Which came in a 1991 S-truck 2.8 TBI HO with a 5 speed manual tranny. Not a particular ECM I would run on a 4.2 6 cylinder
So, does he have a PCM for a 2.8 or one for a 4.3?
 
#206 ·
for one its a guy, LOL. but hes my best friend. and it blew all its coolant out the tailpipe today on its first test drive. so. im saying its gotta be a junk block. its had 3 different reman heads, and all new pistons/rings/bearings every time. but less than 3 miles and its blowing coolant out the exhaust (in smoke form) and throwing it up out the coolant overflow when not on the throttle. we are DONE with this inline 6. he now swears he will never own another inline 6, of any make or model, carb or injected. sooo... since he still has mad love for the jeep, we are going with what im intimately familiar with... the chevy 350. ive got a line on all the parts. a friend has a rebuildable core motor for 150, and another buddy has the pre-made motor mounts for it, as well as the adapter plate to go from the turbo 350 trans to the stock jeep transfer case. and i already have the tbi wiring set up, just gotta swap computers and tbi units (and maybe a couple wires gotta get switched around), and we are rockin! i really appreciate the help you guys, but after over 100 man hours into this piece of **** and to have it blow up in my face... im done with the 4.2. and the bit*h of it is, right be4 i realized how bad it was puffing smoke out the tailpipe, i finally got the distributor set in a spot where i could idle it at 700 rpm all the time, not die after smashing the gas, AND not pop and sputter anymore. fml. but again, thanks to you all. soon to start the 350 swap after i get started at my new job. thanks.

mike
 
#209 ·
it was another shops mess they created originally, when they got fed up with the mexicans (sry, not trying to be racist, but thats their nationality) that run that shop not knowing what they were doing, they called me across the state because of (like i mentioned before) my reputation for building bad *** motors. and this is the most cluster-fu**ed nightmare i've ever dealt with. ever. and ive been in some serious messes before. and yea, he makes about as much as most government officials, so yea he had the money but none of us are pleased by any means with the outcome. but yea, the 350 is my bit** so it will be a walk in the park and an amazingly powerful lightweight machine! thanks!
 
#215 ·
So, in a nut shell, the AMC 258 was more confusing than all the those "high performance drag racing engines" that you build.

OK....

Good luck with the new build.

Matt
:
PopCorn::popCorn::popCorn: this thread has entertained me without a doubt!. Mike if your buddy has cash convince him to go with a "turn key" carburated crate motor. it is time for him to have a jeep that runs. :cheers2:
 
#211 ·
Matt, why are you so emotionally invested in this thread? Trying to stick it to him at every post?
 
#213 ·
I miss the non angry, forgiving Matt that I saw in the greasy pig build.
 
#216 ·
Matt you are a large presence on this forum now. Maybe try to be a large positive one.
 
#217 ·
I gotta admit, my BS meter has gone off a few times in this thread. Who rebuilds an engine without checking the deck for flatness? The devil is in the details and this TBI swap (and apparently the engine build) is missing a LOT of details.

It's certainly not a valid reflection on the swap-ability of TBI.
 
#218 ·
I gotta admit, my BS meter has gone off a few times in this thread. Who rebuilds an engine without checking the deck for flatness? The devil is in the details and this TBI swap (and apparently the engine build) is missing a LOT of details.

It's certainly not a valid reflection on the swap-ability of TBI.
:thumbsup: #2
This certainly has been an up and down build thread.
Kind of like eating a whole can of jalapenos in one setting. Exciting on the front, but heartburn the next morning... God bless.
Jon In Tucson
 
#219 ·
never said more confusing. its still just pistons and bolts... just sick of once i fix one broken part, the next breaks, then the cycle repeats. so we are scrapping that project and moving on with a much more proven engine. and ya yea i know your so partial to that motor so you can save your breath on the lecture that im just too stupid or something. you dont have to believe me about my career, because i have had so many people witness my builds that i really dont care what you think. out of over 150 engines i've built, this is the ONLY one that has had these kinds of headaches. again, thank you to the rest of you guys for all your awesome help. thanks and pce.

mike
 
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