Jonathan Ellender

Hey all, going to try this again I really need help before taking this to the shop for super high diagnosis charge.

I have a 1998 K1500 5.7 L Vortec. When I got the truck It ran (sputter) like it needed a tune up, so that's what I did first, Denso 7MM wires, Autolite copper plugs (never failed me before) cap rotor (blue one) I think it's a united engine brand.. I also replaced coild with a Delphi just to do it.

I do remember some play in rotor like you could turn from 12 o'clock to maybe 12:02 I don't remmeber but I can get a video if that would help.

So tune up didn't do much, did seem to help some. There was another problem with stobing lights I fixed by new alt, while there put idler, tensioner belt on. Problem solved there.

so next after reading through forums and stuff I replaced with AC Delco spider injector with the upgraded version. Cleaned all the gunk in there, replaced thermostat with 195, did timing chain also though it looks like it was done before I got the truck but did it anyways.

replaced collant temp also as that seems one big issue with these trucks.

replaced seals all new on top end ( plastic intake all on that one.)

I did NOT pull entire intake or distributor.

Lower end looked good while I had the engine hoisted and did the oil pan gasket. Cleaned map and maf sensors.

.......so this is basically what's going on.

Ever since I got the truck it has a sputter like it needs new plugs or wires.. listening to exaust you can hear the putter by ear.. put pit here and there and feel the miss like a jerk when driving. Sometimes it's smooth random put sometimes it feels like it's puttering on all cyl.

Engine starts every time no issues. No dyeing at all. From what I can tell it mainly does it when it's very very light throttle or when your cruising at constant speed like feathering the accelerator. Makes you wanna keep your foot in it as it seems like it sputters less or non at all..

it gets better!!! Unplugging EGR . Seems to make the symptom "less intense" with or with out egr sometimes it runs smooth as glass other times its putting it's butt off, when this happens I do read a P0300 (multiple miss fire)

truck runs like it's got some power.. so I'm sure it's not clogged cats... and I have seen water vapor and dripping out meaning they work.

engine does smell a little rich but since doing the upgrade ot the multiport it's no where near as bad.

Keep in mind no check engine lights come on except when I pull EGR plug obviously. The P0300 you would not know about with out reading with scanner.

Only other thing I can tell you is number 4 cyl valve guide seal is leaking I have a non fouler on as it had ash built up when I did tune up. After that I had a little oil on tip of plug before putting non fouler on. But this should not cause multiple cyl missfire.

Last thing I count 4 shifts but no TC lockup cruising at 70 I'm seeiing 2100 or 2200 rpm. I think I've felt it. Lockup a few times in past but I don't remember

I have not done any compression tets or checking of timing as I don't have the tools needed so at this point this is what I'm thinking..

TPS sensor?

MAP sensor - due to all the gunk in the intake?

Distributor worn or the pickup?

Long shot as no codes but faulty 02 sensors?


so needless to say I'm trying to consider what to do next with out troubleshooting by part replacement since I was about sure the spider inkectors was my issue.

any help advise or troubleshooting steps I can do would be great.

I have standard test light digital multimeter at my disposal.

Jonathan Ellender

Really discouraged over 150+ read this post but no one responded at all... I've noticed these year model Chevy/GM forums are DEAD!

But I was able to figure this one out on my own,..... after reading a ton of forums here and else where my problem didnt match but one other thread (On this forums) but no fix on it yet..

OK guys; here is the deal; another post; I will update as well but i have 1998 K1500 - 5.7 "R" engine code.

Had a miss sometimes it was smooth as glass other times (Randomly or even somethings constantly) under light or constant acceleration it would putter.. putt putt here there ... like yall said before it made you wanna put your foot into it to keep it from missing.

I already did the MFI upgrade , full tune up; including doing new timing chain (Which was already previously replaced) i started thinking it was the dist too but then i got to thinking......... acceleration is key.. even though sometimes it still putters it seems when i give it gas it clears up..

TPS sends voltage readings back to ECM to know where the butterfly is.. if that thing which acts like a tensiometer (Spelling?) is acting up there is no telling what it will do. I pulled mine off, first thing the part that turns should be spring loaded.. you could turn it and it stayed in place. it was also loose as all get up like i could wiggle it.

Went to O'Riely's their BWD (lifetime warranty) i got them to comp autozone's house brand also lifetime warranty at 36.00 plus tax. Slapped it on and now its running like a new truck.

There is a putter once in a random while, but its so light and hardly noticeable and does not happen anything like before and does not affect drivability what so ever.. Power is also restored and OD kicks in even at 70mph where before it did not (But would down at 40 under light acceleration)....

So My problem was fixed by TPS. If you have a miss random... P0300 and putting your foot in it seems to be the only thing that seems to help even if its still kinda studdering try a TPS.. I will say though it was just a matter of time I would had injector issues anyways if i didnt already and just not noticed it.. so i would for sure suggest doing it if you plan on keeping your truck and also if its never done do the timing chain as PM.

kevinkpk

Sometimes you already have the answer, and when you don't get a response, usually it means people don't know the answer. TPS is a common issue on GM, it's nothing more than an over priced reostat the ECM reads a 0-5 volt reference signal, that tell's it electrically where the throttle position is in reference to the other "stuff". My suggestion would have been to do a compression test as to check for a burnt valve, and with that you didn't post even that you had a check engine light.
Opps i do read where you had a general misfire PO300, sorry

Jonathan Ellender

Just an observation; this is not the only GM product based forums that seems a bit on the 'dead side'...

But yeah like the EGR was magnifying the issue; unplugging it simply eliminated it as culprit, and then after really sitting thinking about what was going on hardcore i came to that conclusion, instead of just doing some ohm I just pulled that off and seen the spring didn't even work and figured if that didn't the rest of the insides were prob shot to hell to so it was causing a big issue.

Like i said there is still a very small hardly noticeable burp here and there.. still smells like it's running a touch rich even with new MFI upgrade in it, I took the truck out testing it up at 60 - 75 mph it does for sure run better.... now and then you might get a little burp again hardly noticeable.. since i know this truck was rode hard put up wet before I got it; I'm going to go ahead as Preventive maintenance / restorative replacing the sensors one by one... and prob. even the dist. as well just to do it..

I know i do have valve guide seal leaking on cyl. 4 so that's also in the works. I've yet to plug my EGR back in; actually i have plans for that i gotta replace it anyways because i cracked one of the wings on it so i cant bolt it; I also have code for RPM higher than expected due to slight air leak there But for now; I'm at least happy the truck is running better I can focus on other things.

Jonathan Ellender

So this morning temps dropped went out; started perfectly normally did not give time to warm up because i had to get to pop's as he just had some medical issues. the hardly noticble burp was a little more but no where near what it was..

After it warmed up fully it was back to hardly noticeable. So the TPS was def. issue magnifying root cause. I also poped a MAP sensor code; so with all the crud that was in my top in i planned on replacing the MAP anyways but this just confirmed the MAP sensor issue.

Jonathan Ellender

Another thread (Different forum) someone mentioned that this was sign of leaking intake; I have yet to replace yet; just been driving it as-is after TPS and also a MAP sensor; truck drives so much better; still has random putter; normally cold outside; getting down the free way at almost closed throttle it seems to do it more often but its more tolerable; still gotta get to the lower intake manifold; wish i would had done it while i was half way there... but thought for sure it was the spider injectors.

easttexasredneck

I have a 1996 k1500 with the 5.7. Reman engine less then 2000 miles. Twice rebuilt transmission less than 200 miles. New distributor with new cap, rotor, and cam sensor. New crank sensor. New fuel filter and pump. New throttle position sensor. All plugs and wires firing. E.G.R. passes all tests. Cats are clear. Have tried two different mass air flow sensors. Spider injector was replaced with a cleaned and tested unit as I don't really have money for new one or the upgraded one. Truck will idle fine anytime you start it up. Will run smooth until you get to about thirty the first time. Then it bogs down and starts missing on what seems like multiple cylinders You can get in the throttle good and when it downshifts it runs smooth until you start letting off throttle then it goes back to crap. pull up to park throw it in park and about 5-10 seconds later it'll return to smooth idle. Didn't start doing this till shop rebuilt and installed transmission. Any help from anybody would be greatly appreciated. Thanks in advance.