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454 random ignition cut/misfire
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Post 454 random ignition cut/misfire 
long time guys - hope everyone is well...

here is a short story to describe my issue....

i have a 1998 CCDRW 454/4l80E, less than 100k miles, bone stock when i bought it - had a few little issues, nothing major - mostly from sitting in the AZ desert region ....

one day, while passing a vehicle, it acted just like a dying fuel pump - started bucking and chugging, but let off and still went down the road.... every time i tried to apply power did the same thing, so first thing i thought of was fuel pump.... i have several sitting at home at all times along with a bunch of other parts due to my growing GM collection, lol - but thats another story....

new pump, new filter, new regulator - ran good for a while (keep in mind i still OTR driving truck, so i dont get to drive it every day)

one day it did it again, but this time involved some tailpipe popping.... naturally i though of the distributor gear being knifed....

i had some spare time so instead of trying to fix the issue, i dropped in my 45k mile 454 i had been saving away from the rolled suburban.... so - out with the old, in with the new(ish)..
while i had the motor out, i replaced all the ground straps, battery cables - all ungraded to 1/0 cables.... swapped in the nice aluminum distributor for the stocker and did a fresh water pump and 250amp ALT. with a brand new (bolt together) A/C compressor, forget the name of it.....

anyways, did a lot of other odds and ends and things i just let go by the wayside and got it all back together and buttoned up, running beautifully.... more so than my cousins powerchoke Ford (which he now has a dirtymax) - and back OTR i went....

well - the issue has some how shown up again, like that relative you simply cant seem to ignore...or wont take a hint....

its not as bad as it was before, its a bit different.... seems mostly there when cold, and hard to duplicate when warm....
its always more than 1/2 throttle and always backfires through the pipes, but is still able to accelerate - sounds like a shitty carb tune....
does it both with MAF plugged and unplugged....

im pretty convinced its a sensor, but i get no codes - NONE....

open for thoughts or direction, i got plenty of parts to swap out, but im just ready to actually get it fixed, plus im planning on selling the truck soon, so i dont wanna hand off an intermittent issue to someone else...

TIA guys

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Did you change out the fuel pump this time around (since the engine install)?

Also, do you have a way to read your fuel pressure under acceleration?

Back in the day, I had a similar problem and had an old mechanical fuel pressure gauge. I hooked it up to a line and taped it to the outside of the windshield (in the lower corner, of course) in case the gauge gave out. It wasn't the fuel pump - turned out to be a fuel filter issue. Of course, with the in tank unit and the "sock", it's not a perfect way to check it out, but it helped a lot.

Does your truck have an in-line filter from the tank to the injectors anywhere (as an aftermarket install - for extra protection)?

Last shot, maybe rust in the tank and it's breaking loose and somehow getting past the sock?

Tailpipe popping sounds like a "richness" issue. At least it's not leaning out and popping through the intake. So I agree with you on the sensors maybe being an issue. Do you have any codes for bank one or bank two?

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If I'm not mistaken, those have two temp senders, one for the engine and one for the computer. If the computer temp sensor is bad, it may not necessarily show a code, but make the computer think it's warm when it isn't. A scanner that can read the temp from the computer would reveal this. No idea if you used the same senders or not.

The 90s model trucks/SUVs also had faulty fuel pump connectors, and usually come with replacement kits. If it's never been replaced you may be getting voltage problems, if it has one of the spliced connectors may be going partial open. Not sure how you'd go about checking this, but replacing the connectors would solve it if this is the problem. When I do this I normally ditch the supplied splice and use my own, and cover them with heavy duty hear shrink. Some of the stuff I have has a temp sensitive glue inside that completely seals the connector, rather than just depending upon friction.

I wouldn't discount the possibility of this being two problems, either. You may have an issue causing the cold performance problems, and another causing the hot performance problems. Bad O2s can cause a rich condition without setting a code.

Hope some of this helps.

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Do you have any fuel pressure and volume measurements? Also have you been able to access any fuel trim info?

Since you have mentioned that new fuel pump and filter fixed similar symptoms in the past, that is where I would suspect the issue first too. Also the connector issue as mentioned by Speeder.

However, I have doubt your issue is due to the one of the temperature sensors, because the ECM will check for correct sensor values before engine start. The way this works the ECM keeps track of elapsed time since the last engine off. If sufficient time has elapsed between engine off and re-start attempt, briefly before re-start, the ECM checks all temperature voltages and compares them with each other. If there is a discrepancy, a check engine light will be illuminated and code set. This info is from my GM factory manual and is for my 5.7 Vortec, but to my best knowledge it is part of standard OBDII protocol.

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fuel pressure is good, not sure about volume though, i dont really have a way to check that...

when i did the pump/filter i also upgraded the connectors and wires and checked the harness for any broken wires, cuz i thought that may be an issue in the dry desert air....

i have not checked any programming - its completely stock ( maybe i will drag out my tuner cat )

thinking about getting a data logger to see if maybe i can find something that way....

im also wondering if its not the computer itself, maybe a cold solder or something - i really dont know, just spitballing....

it also does it with the MAF unplugged - which is my go to for most trouble shooting, lol, as that way it bypasses most of the tricky sensors and just relies on the basic core sensors....

gonna be a while before i have any time to look into it any more....

the thing that gets me is no codes, if its a sensor - the computer will throw a code, hell - i have had correlation codes thrown without even noticing anything wrong.... so im starting to think there is some sort of mechanical break (if you will) with the electrical or ignition system.... like someone dicking around with a light switch turning it on and off...

might just have to check every connection for corrosion and fitment, maybe somewhere there is just enough gap to create a problem, then when it warms up, it expands enough to fix itself??

or maybe i have a broken wire inside the main harness - i never pulled that apart, but it might be worth a look....

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How old is the exhaust? It occurs to me that a rusted muffler might have a piece of metal broken off inside that is intermittently blocking exhaust flow. This would be unlikely if you have duals.

The other thing, did you change the coil when you changed the distributor? I had a coil start going bad on my 96 Tahoe, and it showed by not being able to keep up with high RPM operation. As the coil grew worse, the RPM where the problem started showing itself became lower and lower. A new coil solved the problem.

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Speeder wrote:
How old is the exhaust? It occurs to me that a rusted muffler might have a piece of metal broken off inside that is intermittently blocking exhaust flow. This would be unlikely if you have duals.

The other thing, did you change the coil when you changed the distributor? I had a coil start going bad on my 96 Tahoe, and it showed by not being able to keep up with high RPM operation. As the coil grew worse, the RPM where the problem started showing itself became lower and lower. A new coil solved the problem.


i used the stock dual cats and dual mufflers - also the coil and module is stock, didn't think about the coil - got a few i can swap around whenever i get home....

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