1989 Silverado K1500 4X4
 

1989 Silverado K1500 4X4 with 350 TBI and automatic transmission, I have searched thru hundreds of post for a fix. Last friday while leaving from work, truck started to miss. I had just filled up with gas from a chevron station that was getting a face lift. so i thought maybe i got some trash in tank or something. Went to parts house bought new fuel filter. didnt help. Have now replaced, plugs, wires, therm,cap,rotor, pickup coil, pvc, can of seafoam all over throttle body, can of seafoam in tank. took to firestone to have put on computer. nothing was found. they replaced pickup coil as a guess. still misses and gets worse the longer its driven. the only thing not replaced is coil, egr valve, map sensor, tps. timing has been set twice just to make sure. injectors seem to be spraying in good pattern. sprayed for intake leaks and hoses. Cant afford to keep throwing parts at it. Most post that have this problem never followed up with a fix or solution. Please any ideas?

When you set the timing did you unplug the wire for the computer? Checked for vacuum leaks? Checked fuel pressure? If all that checks out I would do a compression test to see if all cylinders are close. Good luck!

Spray some ether or starting fluid around your TBI and your whole intake to see if there is a vacum leak. Intake bolts might be loose or TBI may need new gasket or something with the intake.

wanted to update on this, i replaced coil, o2, rotor button,dist cap and plugs again, unplugged the black and tan wire. after replacing all those parts it ran fine again. stayed running well until a week ago. Now same symptoms are back. So for almost 2 months it ran fine. a week or so before that when it was first started it seemed to idle rough for about 45 secs then clean up and run fine.
one day it will run fine to work,(sitting for hours overnight) leave for lunch symptoms return,(sitting 4 hours) hour later may run fine or may not. I have used different type of gas,W/W/O ethenal, leave the gas station and it would run great. Think must have been gas. stop for a min get back in. symptoms return. I sometimes pull over take the black and tan loose take the pwr from the battery let it set for a min. hook it all back up. runs fine. next day do same thing. doesnt help at all. No pattern to it at all. sometimes it will run bad then 5 miles down road it will completly clear up. Like i said before, sprayed for leaks, timing is set etc. Watched tbi spray pattern and it looks good. never seems to be a lack of fuel. Could it be the ECM going bad?

Gotta be something restricting flow of fuel. I had similar problem years ago on 78 Bronco.

Piece of elec. tape in tank. Floating around it would run ok. Get sucked up to fuel pick up and would die or run like crap. Depending on the amount of blockage.

Good luck!

I seen some of these same symptoms on another forum and they said it was the PCM grounding that was weak. Might look into something like that. When it does run sluggish, try to hook up a fuel guage and see if the pressure is fluctuating.

With all the things that have been replaced and all the hands that have been on it I would check ALL grounds and wiring. RUFFNECK4LYFE is on the right track and I was thinking the same thing before I read his post....the problems are consistant with a ground or wiring problem

PCM grounding? Is that the same as ECM/ECU? I have retightened the ground from Ground on term housing,added #8 to another part of intake, battery to block,block to frame grounding strip. Added a #8 wire from block to Frame. Anywhere im missing?

Thanks for helping with this, im lost at what to look at next.

Have drove truck 6 times today, going to work this morning, would barely get going, stuttering so bad. I have 5 miles intown 40 MPH, then 8 miles on highway 70 MPH, back to 55 MPH, then 30 MPH and finally 45 MPH. Reverse back home, it gets alot of different speeds, stop lights and stop signs, idleing for a few mins here and there. acts up all the way. Lunch same thing, back to work, and back home. Missed around with it, looking at plug wires etc. Crank it up, still runs like crap. Run it down road a few miles, still acting up went home, closed it up, shut hood. dazed and confused again.
Left to run to store, idles like crap, hesitates, stutters bad a few miles, stop at store let it idle while inside, start down road, clears up again. keep driving for 20 mins. still running good, stop, turn it off and on 4 times, drive another 10 mins, still running good, floor it going 50 it kicks down runs good, do that five to ten more times. it stutted one time for a millisecond while in it, for good 5 secs. kept on going. Nothing is ever the same, could do this exact same thing tomorrow and it will never clear up. or it may run fine in morning and start running like crap at lunch or anywhere between. When its acting up, it smells to me like its running lean, not a bad gassy smell, but the fumes are pretty rough. Im just throwing things out there so any one that reads this will know whole story. I have never seen such a ghost problem before.

The fuel pressure was check at firestone before, i have no tools to recheck, the 298 dollars for the computer code check and fuel pressure check was to much to throw away again.

I went to Oreilys where a guy works there that was a mechanic at a GMC dealership for 30 years. thru the years this truck would have been new to 10 or so years old. Went thru all the things i have bought from there new for the truck, some items twice. He said the only thing that would be a last resort would be to swap the ECM out. I looked around on ebay etc, i found my 1228747 but not the 4 letters that follow. Does that matter if i went down that road? Any more ideas? I will take any idea. Thanks for the help thrown at it so far.

Changed the ignition control module, didnt change anything.
Put another coil on, just to be sure.
New ITEMS:
Plugs
wires
Coil
Pickup Coil
dist cap
rotor button
ignition module
egr
pvc
o2
timing set
fuel filter

Oh yeah I remember on these trucks when the coolant sensor went bad it would make the trucks run rough. Might look into that. Shamrock knows more about it.

Thanks, I will pick up a new sensor and try that.

Which coolant sensor? The temp sending unit or the one by the therm inlet?

It would be the one by the therm housing.

I unplugged the temp sensor and noticed no difference. Of course, I don't know what that would do anyway. Probably just easier to replace it.

Do you guys think that this could be a fuel pump problem? The fact that I can get it to run smooth and rev in park kind of kept me awayy from the pump but not so sure of anything now. I need to get a couple of fitting to adapt my fuel pressure gauge the truck. Should it just go inline at the fuel filter area? If so, do you turn on the key and see what it pressures up to or should I tee te line so it can be read while running? I do LS1's and not too familiar with these engines.

Last, when you turn the key on after the truck has sat for a day or so, how long should the fuel pump run to pressure up the line??

Thank you guys very much.

Thanks RUFFNECK4LYFE for the suggestion, but the temp sensor didnt do the trick. I thought at first it did, it seemed to run better after the swap.

All the things listed i have tried at the start of this post, they all seem to change the way it misses. But nothing takes it away. I dont know anything else to change other than the ECM.

I would guess the fuel pump. I just read your 4th post and it describes what my brothers truck was doing to the "T". Actually his is an 89 also. I guess sometimes the pump was providing enough psi and other times not. We thought it was bad gas b/c we ran all the gas out and went and filled up and it started running good again. Then all of a sudden ran bad again until it just quit one day. Luckily it was in his driveway. I helped him pull the bed and replace the pump and it has ran like a champ for the last 8 months. You need an adapter that goes in place of the fuel filter to check the fuel pressure on the TBI trucks. I would definitely check that first. Even a few pounds low can throw these truck for a loop. If you decide to go that route I have all the test procedures and PSI ratings. Good Luck!