My newest problem w/ '88 K5

[bammax]

Recently my truck developed a problem with the engine. When I accelerate the engine stumbles and the truck shakes like mad. Now for the info:

1. It's an '88 350 TBI engine with auto
2. It only happens when the truck is warmed up and at about 25% throttle. If I get on the gas harder then I can power through the rough spot and the truck takes off fine.
3. I already replaced the fuel filter and lines, changed the oil and filter.
4. I watched the injectors while the truck was running and they seemed to be firing perfectly.
5. I'm guessing it's not vacuum issues since it is fine at idle and since it was a problem that came on suddenly and hasn't gotten better or worse with time.

Now I just need you guys to vote on ignition problems (distributor, coil, plugs, wires), Throttle Position Sensor or fuel pump so that I know what to replace with the little money I have.

 

[Jonny-K5]

if no one can pinpoint it on here it wouldnt be a bad idea to take it to a local garage and ask them how much to diagnose the problem.usually they'll do it for an hr's worth of labor.its alot easier for a mechanic to figure out whats wrong when the trucks infront of him than just by a description. much better than just throwing parts at it hoping it fixes it.

 

[89GMCSuburban]

Did you check to make sure your spark plug wires aren't arcing somewhere? I had the same problem, ended up needing a tune up.

 

[bablazer73]

A real common problem with the T.B.I. system is carbon build up in the vacuum ports. The carbon restricts or blocks the vacuum to the MAP sensor and can give you several running issues. Base gaskets are cheap and most the time can be cleaned out with a GOOD carb cleaner. I did have one I actually had to drill the crap out of!!

 

[blackblazer717]

Just Fixed That Problem

i JUST fixed this exact same problem not three days ago on my 88 k-5 with 350 TBI
i replaced the Fuel Pressure Regulator or (fuel modulator valve) 24.99 at Auto Zone it fixed her right up, comes with everything you need new gaskets too. what its doing is off idle the plugs are loading up... and causing it to buck like that.

LUKE

 

[dyeager535]

Being able to "power through" the dead spot would lead me away from fuel delivery...any restriction/issues that cause loss of power should be worse when fuel demand is higher.

Autozone supposedly will scan your vehicle (for free) if you have one close by, a scanner will let you watch your TPS, which will show if there is any problem with the way it reads through it's travel.

 

[bammax]

Well the problem seems to be fixed now. I replaced a bad vacuum line and the plugs, wires, cap, rotor and it hasn't acted up since. I did run into a small problem when one of the old plugs broke off in the head, but it got fixed and the truck is running strong. Thanks for the help guys.

 

[93h22cvc]

i just had a similar problem. i took the vacuum line off the egr and it ran fine. obviously need a new egr. just my 2cents