Suggestions for 89 K1500

[Kyle C]

I have 124K miles on the truck. Since I bought it (89K) it has always had a slight surging issue at highway speed. It has recently started a severe surging at anything above idle. It only does the severe surging once in a while but is undriveable when it does. When this is happening it idles fine but if I give it any gas it will accelerate for ~1 second then shutdown for ~1 second it never completely shuts off. I tried moderate gas pedal to holding it on the floor it does the same thing, pretty violent when holding to the floor. I don't think it is the ignition cutting out because I'ld expect some significant back firing when it kicks back in. I have replaced fuel filter, egr valve, and had the injectors cleaned. I think I'll just start replacing parts, any suggestion on what to replace first would be appreciated.

[snoman]

I have 124K miles on the truck.  Since I bought it (89K) it has always had a slight surging issue at highway speed.  It has recently started a severe surging at anything above idle.  It only does the severe surging once in a while but is undriveable when it does.  When this is happening it idles fine but if I give it any gas it will accelerate for ~1 second then shutdown for ~1 second it never completely shuts off.  I tried moderate gas pedal to holding it on the floor it does the same thing, pretty violent when holding to the floor.  I don't think it is the ignition cutting out because I'ld expect some significant back firing when it kicks back in.  I have replaced fuel filter, egr valve, and had the injectors cleaned.  I think I'll just start replacing parts, any suggestion on what to replace first would be appreciated.

 

<{POST_SNAPBACK}>

 

 

 

 

For starter have you replaced the spark plugs and the wires recently? Years ago I have a surging problem in my 89 that turned out to be that even though it may not be the case here, process of elimination.

[Kyle C]

I did replace the plugs, wires, O2 sensor, cap and rotor about 10k ago in hopes of getting rid of the slight highway speed surge. It had no effect on the surge and I just decided to live with it. This new off idle surge is a show stopper when it happens

[Wingnut]

When is the last time you gave your TB a good cleaning? Gummed up parts around there could easily cause these problems.

 

Heck, just spraying a bunch of B12 in there could help a ton.

[snoman]

When is the last time you gave your TB a good cleaning? Gummed up parts around there could easily cause these problems.

 

Heck, just spraying a bunch of B12 in there could help a ton.

 

<{POST_SNAPBACK}>

 

 

 

 

Good starting point and you might want to check for water in fuel too as he may have a big slug of it rolling around in tank that is getting picked up from time to time and it is a definate show stopped when it hits the injectors. Check fuel filter too.

[Kyle C]

I've had the TB cleaned, changed the fuel filter a couple of times. I've also run 2 or 3 bottles of seafoam through the thing. The randum nature of the problem makes me doubt it is water in the tank.

[snoman]

I've had the TB cleaned, changed the fuel filter a couple of times.  I've also run 2 or 3 bottles of seafoam through the thing.  The randum nature of the problem makes me doubt it is water in the tank.

 

<{POST_SNAPBACK}>

 

 

 

Water can be very random indeed as it will stay a slug in the botom of tank shifting around with motion. Try throughing in 2 or 3 bottles of dry gas in tank and run it near dry to get out all of old fuel mix and then see if it helps. Back in the 70's I have a 4x4 burb that gave me fits with a problem simular to yours for weeks on end on and off. It turned out to be water in the tank from a bad batch of fuel after much frustration.

[Shawn T]

Check all of your vacuum lines. It is hard to say if one is pinched because it happens randomly. I had this happen on my 88. It had a leaky line and when it was bent in a certain fashion the truck surged. On idle, acceleration, you name it. It was a bitch troubleshooting. I did the same thing that your doing, plugs, wires, filter, dist, etc.. I even drained the tank. You could go that route. Then you would know for sure if it was bad gas. It sounds like a fuel supply issue. If you were getting blowby it would probably throw a code.

[lowflyer]

Just throwing ideas around here, but check out the throttle blades and throttle shaft play. Sometimes the harder shaft material eats away at the alum. TB housing. The resulting air leak causes the IAC to start reacting weirdly.

 

Also when you have it apart, check the little screen on the injectors themselves.

 

Other than that, it would be best to take it to a shop and have them put it on a scanner and Fuel Gauge when it starts to surge. Good luck

[OUMike]

Vaccum can have a lot to do with this. I had similar problem, that was not quite fixed but made A LOT better after just re-attaching that line. Apparently the last time I had the AC checked out they musta been fooling around or soemthing and disconnected it How many vaccum lines are there usually? I only know of the one directly on the motor that runs to the TB.

 

Is it hard to replace injectors?

[snoman]

Vaccum can have a lot to do with this.  I had similar problem, that was not quite fixed but made A LOT better after just re-attaching that line.  Apparently the last time I had the AC checked out they musta been fooling around or soemthing and disconnected it    How many vaccum lines are there usually?  I only know of the one directly on the motor that runs to the TB.

 

Is it hard to replace injectors?

 

<{POST_SNAPBACK}>

 

 

 

 

Injectors on TBI are easy to change but I still think you have a fuel problem.