sputtering at cruising speeds

[ProjectXC]

have you run a diagnostic on it? I have been working on my 99' k1500 the past 2 days because mine is sputtering and mine is because my 3 and 7 arent firing I dont know whats wrong yet but ill let you know if i figure anything out

[wally91vhevrolet]

i'm carrying the truck to my friends shop within the next few days to hook it up to his cpu to monitor the injectors and determin wether the injector is bad, or the computer is bad, ill update once i figure this out... i might add tho the injectors are both new, so i dont think its an injector problem but if it is a cpu prob, if i have to get a new one does anyone know what this might cost me?

[ProjectXC]

i would say check aftermarket magazines and not magazines for exhaust and intake, a true engine magazine rather than going to a dealer and paying out the rear for the same thing you might find a better deal for an aftermarket that could make some more power and probably cheaper, I dont know for sure never done it but a friend back home did it...

[wally91vhevrolet]

ill have to check into that if it comes down to having to get a new cpu, ill post again as soon as i find whats wrong

[wally91vhevrolet]

well checked 2 see if the cpu was bad... its good sending the right signal to both injectors... replaced the "dripping" injector cause it was still under waranty... no more dripping but im still gettin the miss after the motor warms up.... im goin back 2 my friends shop 2moro and were gonna test the plugs, plug wires, n all that stuff 2 see if that might be the problem, ill update as soon as we figure it out

[2000CAYukon]

Take a look at this: http://www.mightyautoparts.com/pdf/articles/tt71.pdf

The pickup coil fixed my miss when warm.

//2000CAYukon

[wally91vhevrolet]

thanks for your help man but on that article its talkin about the chevy 5.0's and 5.7's and mines a 4.3 V6, im gonna carry my truck back to my friends shop and if it comes down to it we will pull the dist. and replace the pick-up coil.. who knows that could be it... ill update later when i figre it out

[2000CAYukon]

Originally Posted by wally91vhevrolet

thanks for your help man but on that article its talkin about the chevy 5.0's and 5.7's and mines a 4.3 V6, im gonna carry my truck back to my friends shop and if it comes down to it we will pull the dist. and replace the pick-up coil.. who knows that could be it... ill update later when i figre it out

True that the article was for the 5.0/5.7 but the dist and pickup coil work the same way for the v6.

At least try to get a reading of from the pickup coil. In my case, I decided to pull the dist looking for wear. The plastic on the pickup coil has cracked and the coil was pretty rusty. Cost was only $20 at my local AC Delco parts store.

Also, if you do pull the dist, make sure the magnet and the shaft look good. If the magnet can move on the shaft, you will need a new shaft.

Also, if your dist is original, the pickup coil is 14 years old!

Good luck and let us know how is goes.

//2000CAYukon

[wally91vhevrolet]

i talked 2 my friend today about takin my truck to his shop, im gonna take it tomorrow n hes gonna test the pick-up coil and the ignition control module, also last time this happened it ended up being a blown head gasket.. i HIGHLY doubt this will be the case again but for everyone else reading this if you've checked EVERYTHING, be sure you check compression on all cylinders one at a time with ALL spark plugs out, last time i checked it i left the other plugs in and found no prob but when the mechanic did it and pulled the plug next to the one he was checkin the pressure dropped, but i really doubt this will be the case again both heads have been rebuilt and brand new head gaskets but then again who knows? ill update again tomorrow after i figure out what the problem really is..

[wally91vhevrolet]

well after having a huge problem with advanced autos giving me a second new injector cause the other one started dripping and then them giving me the wrong one... i put my old stock ones back in (even tho a few months back they werent even spraying) i figured id give it a shot, and they spray like new now and the truck isnt missin nemore, so it was the injector, if you EVER buy injectors dont go to advanced autos, my friend told me if i ever got new ones get performance ones with a waranty or get AC Delco's so itll be like stock new, it was only 6 or 7 months and the ones i had from advanced went bad, and now i put in some that are 14 years old and they work? hmm.. well the prob seems to be fixxed for now.. if i find out its not ill let yall know but i believe it is

[wally91vhevrolet]

well spoke to soon, STILL having the SAME problem, and NEITHER injector is dripping, problem ONLY occurs when cruising normally and about the time the shift light comes on, during acceleration its real smooth and deceleration is smooth too, its when the speed levels out and im about to shift.. whats goin to be crazy is when it IS the pick-up coil like 2000CA said, i'll let yall know when i get this figured out

[2000CAYukon]

Originally Posted by wally91vhevrolet

well spoke to soon, STILL having the SAME problem, and NEITHER injector is dripping, problem ONLY occurs when cruising normally and about the time the shift light comes on, during acceleration its real smooth and deceleration is smooth too, its when the speed levels out and im about to shift.. whats goin to be crazy is when it IS the pick-up coil like 2000CA said, i'll let yall know when i get this figured out

I am now wondering if you have a Torque Converter Clutch (TCC) lock up problem. When the problem is happening, tap the brake pedal. Just tap it since that should unlock the TCC. Does it always happen at the same engine RPM? If so, put the tranny is 2nd and get the engine to the same RPM and see if the problem occurs.

Normally, the TCC locks up after 40 MPH depending on throttle position. You could also drive the truck in D instead of OD to see if you can still recreate the problem. I am pretty sure that the TCC does not lockup in D (but not 100% sure).

If the pickup coil was giving you problem, it would surely show up at idle and lower RPM.

//2000CAYukon

[wally91vhevrolet]

i got a manual trans, and at idle there is somewhat of a miss, and sometimes at lower RPM's but when im driving and about to shift its very notacable

[2000CAYukon]

Originally Posted by wally91vhevrolet

i got a manual trans, and at idle there is somewhat of a miss, and sometimes at lower RPM's but when im driving and about to shift its very notacable

OK. That rules out the TCC

Pickup coil is still a possibility. I also wonder if the fuel pressure regulator is bad causing the fuel pressure to change while you are cruising.

//2000CAYukon

[wally91vhevrolet]

yea i also wondered about the pressure regulator.. ill check all this out