back to old setup. truck still dont run right

[whitelightnin92]

ok i originally had a 700r4 and a 7747 ecm in my truck and it ran awesome, i loved it. great throttle response and really quick for a heavy truck. i tuned it myself. mods were vortec heads, performer rpm intake, XE256 cam, open element, headers, and all that good stuff. anyway. i decided to swap in a 7427 pcm(because it was so much better supposedly) and a 4l60E transmission. ever since the swap i never seemed to be able to get the truck to run right(poor throttle response and lack of HP) and i was constantly burning the 3-4 clutch. i finally got tired of all this and reinstalled the 7747 ecm and rebuilt my 700R4. i expected the truck to run just like it used to....WRONG! it runs with alot of the same problems ive been having. poor throttle response and lack of HP. it acts as if its running rich(smelly) but the ecm says otherwise. ecm says its alittle lean.. i havnt pulled the plugs, but i can say i havnt made any changes to anything since the swap. so it should run the same. the plugs, wires, coil, cap and rotor are like a year old, and the distributor is like 2 years old. im wondering what could do this. valve not seating? lobe missing on the cam? low compression on one cylinder? i have no idea and im really getting PISSED. any ideas appreciated. oh yeah almost forgot. im getting runaway knock counts in certain RPM/MAP cells but timing it set the same as its always been. whats even more wierd is the truck runs better with more timing! only thing i can think of with the knock counts is i have an idler pulley making some noise

[whitelightnin92]

also got a couple snaps out the tbi when the throttle was cracked at an idle. im not going to touch the tune untill i figure this out becase it aint the tune. im wondering if ive got a valve screwed up or missing a lobe on the cam.

another thing thats funny is it idles at just 42 kpa. lol

[whitelightnin92]

im tempted to pull the whole motor out and go thru it. i just dont want the truck off the road two more months again. thinking back tho im wondering if i have a ground issue because the starter sounds weak and also i had a fairly new altenator go up not long ago and the new one is whining alittle. so MABE its a ground problem. im going to put new ground straps on it this week i think

[whitelightnin92]

think i found the problem thats been haunting me for quite some time. i pulled the serp belt off today and started the truck thinking my squeling would go away but, it didnt. still squeling. cant pinpoint it but the stethescope picks it up more around #1 cylinder. so i may have a cam going out. its definately valvetrain related i think

[1997chevydriver]

my friend had a 6.2L diesel in his truck and the #1 and #2 rod bearings burnt up and it started as a very light squeel then got louder very fast then motor just locked up........dont know if this might help or not just an fyi.

[whitelightnin92]

doesnt sound like a rod bearing. rod bearings have their own distinct sound. and it wouldve spun by now with all the times i turn it 6k + lol. could possibly be the mains but i tink its cam related. im going to buy another motor to build. im going to goahed and build that stroker ive been wanting. 383 or 377 w/hotcam and 9.7-10.0 comp topped off wit a single plane to replace the dual plane.

[1997chevydriver]

ok well then in that case you should build it then send it to me at no cost lol jk. i think im going to try to find a 350 tbi motor this summer and rebuild it and put it in my 243,000 mile 1994. ive got some plans for that truck this summer......big list.....not alot of time when i get back to work....

[whitelightnin92]

yeah it just blows because its been off the road for two months while i was building a trans for it and now i find this. im going to keep driving it while i build the motor and swap it on a weekend. luckily ive got another truck to drive. toys dont make a good DD. im going to try and further diagnose it this week but im pretty shure what it is

[1997chevydriver]

not to derail your thread but since you seem to be quite knowledgeable......
would i see any worthwhile gains in putting lt headers and 2.5" true duals with an h pipe? instead on my stock manifolds true duals (no crossover) and its either 2 inch or 2.25 ich pipe (i tink its 2.25. (no cats)

the reason im asking is ive been contemplating redoing my exhaust since my over-the-axel tubes are rusting....(not stainlesslike the rest.....)

[Eagle-Mark]

Do a thorough compression test before you make any decisions on rebuilding the engine. This will narrow it down, would even help in the rebuild if you knew you had an issue somewhere.

[whitelightnin92]

yeah i was going to do a compression test today but didnt get to it. im going to try and do it thursday. we shall see. also i put the ground strap on. didnt really make any difference but atleast i have it

[whitelightnin92]

the most restrictive part of the stock exhaust is the y-pipe. if you trash that and run 2.5" all the way back you will gain a good bit. LTs are even better

[Eagle-Mark]

yeah i was going to do a compression test today but didnt get to it. im going to try and do it thursday. we shall see. also i put the ground strap on. didnt really make any difference but atleast i have it

Just to be sure I would clear codes and try again. Good Clean Grounds are very important in EFI.

the most restrictive part of the stock exhaust is the y-pipe. if you trash that and run 2.5" all the way back you will gain a good bit. LTs are even better

Please excuse my ignorance but what is an LTs

[1.721afr]

Unfortunately compression or intake vacuum tests can't reveal a bad cam bearing.

Please excuse my ignorance but what is an LTs

Long tube headers.

[whitelightnin92]

well got more bad news to go on top of my already bad news. ive been wondering why my datalogs look all stupid. i figured it out tonight when i left work in limp mode and the truck was bucking and popping all the way home. checked the chip, it was corrupted. made a new one and still no good. time to get another ecm

[1997chevydriver]

ouch......is it possible chip was problem all along???

[whitelightnin92]

wasnt really the chip. these ecms are 20 years old and they go bad. ive had them go bad before but never really like this one did. ive had problems with the G2 chip adapters going bad in the past. im not shure if thats what happened to this one or not

[Fast305]

ok i originally had a 700r4 and a 7747 ecm in my truck and it ran awesome, i loved it. great throttle response and really quick for a heavy truck. i tuned it myself. mods were vortec heads, performer rpm intake, XE256 cam, open element, headers, and all that good stuff. anyway. i decided to swap in a 7427 pcm(because it was so much better supposedly) and a 4l60E transmission. ever since the swap i never seemed to be able to get the truck to run right(poor throttle response and lack of HP) and i was constantly burning the 3-4 clutch. i finally got tired of all this and reinstalled the 7747 ecm and rebuilt my 700R4. i expected the truck to run just like it used to....WRONG! it runs with alot of the same problems ive been having. poor throttle response and lack of HP. it acts as if its running rich(smelly) but the ecm says otherwise. ecm says its alittle lean.. i havnt pulled the plugs, but i can say i havnt made any changes to anything since the swap. so it should run the same. the plugs, wires, coil, cap and rotor are like a year old, and the distributor is like 2 years old. im wondering what could do this. valve not seating? lobe missing on the cam? low compression on one cylinder? i have no idea and im really getting PISSED. any ideas appreciated. oh yeah almost forgot. im getting runaway knock counts in certain RPM/MAP cells but timing it set the same as its always been. whats even more wierd is the truck runs better with more timing! only thing i can think of with the knock counts is i have an idler pulley making some noise

Run-away false knock counts can make for a sluggish running turd of an engine. I have seen engines make goofy sounds and run weirdly having a blown headgasket. You can have a head gasket blow between the cylinders and never leak a drop of coolant.

[whitelightnin92]

Run-away false knock counts can make for a sluggish running turd of an engine. I have seen engines make goofy sounds and run weirdly having a blown headgasket. You can have a head gasket blow between the cylinders and never leak a drop of coolant.

yeah the when i took the swirl ports off of it and put vortecs on both banks had blown out between the cylinders 3-5 and 4-6. its possible. we will see when i put in another ecm. when i get it running again i will do a compression test on it..... actually i could do it right where she sits i guess. either way the motor will be rebuilt or i will build a replacement for it. thanks fast

[whitelightnin92]

well put another computer in the truck last night with my chip and drove it a bit. it ran much better but i could tell something wasnt right because it just acted like it wanted to die. it idled smoothe but had that sound like if i turned the headlights on or put a load on the power steering i knew it would kill it. well some buddies envited me to a mud hole and i couldnt resist so i went. my very first run in the pit i got halfway thru and the truck died. cranked it over a few times and it started but was breaking up bad. went through the next bigger pit and the same thing happend other than the truck didnt start at all. i knew it was weak ignition but didnt know what got wet. just for the heck of it i hooked jumpers up to it and it actually fired right up. had to keep it revved up to about 2k for 5 minutes or so and it cleared up. but it still has the same problem its been having and im thinking its all related. my question it what the heck is it!!!! ive got it narrowed down to ignition. i know the plugs and wires, cap and rotor are good. delco plugs gapped at .045(im thinking of closing it to .035) taylor wires and a good napa cap and rotor with brass terminals. the dizzy is a cheap autozone one. a few months ago i took the module off and replaced it with another GM 369 module just to see and it didnt make a difference.. oh yea and it has a good delco coil on it