1990 k5 stumble

[Justin Fleming]

So I am finally getting this turd rolling down the road. In the initial test run today I notice that if you are just barely giving it a little gas like in bumper to bumper traffic it has a horrible stumble. I can repeat this consistantly and I can get it to almost stall out as it is spitting and sputtering. Other than this it seems really response, drives smooth at speed no codes or eninge lights. If you are to take off normal it powers through the stuble and you would hardly know that it was there unless you were really looking for it.

Whats your thoughts....

 

[SouthernYank]

I would go through and check ignition/fuel system. Could be caused by incorrect timing, what all have you replaced and checked already? Fuel filter could have trash inside as well.

 

[Justin Fleming]

I would go through and check ignition/fuel system. Could be caused by incorrect timing, what all have you replaced and checked already? Fuel filter could have trash inside as well.

new fuel pump, new fuel line, timing set correct,

 

[snowdriver]

I would replace the ignition control module,and if you haven't already replace the cap and rotor while you are at it,

 

[SouthernYank]

new fuel pump, new fuel line, timing set correct,

So you didn't change the filter when you put the pump in? For the little they cost I'd recommend changing it out when putting a pump in.

it's one of the two fuel/fire....

 

[gone huntin]

My '90 Suburban would stumble at the same stop sign every day, but no where else. I know that sounds stupid, but it is truth. It turned out to be the pickup coil in the dist.

 

[Justin Fleming]

No I did change the fuel filter. so new cap rotor igniton module etc and the stumble is still there. I can mimick this while in park and looking into the throtle bores.... It appear to be spraying fuel in with out a problem. If anything it looks like a little much in my opinion..

 

[Justin Fleming]

Anyone have any other ideas on this one? I did check the TPS sensor and it appears to have the correct voltage signal through the sweep

 

[SouthernYank]

EGR Valve or IAC Valve?

 

[Justin Fleming]

EGR Valve or IAC Valve?

No codes present.... But I will investigate, I do know for some reason when I got the truck the EGR vaccum line was pulled and blocked off. In all the mess of work that I have been doing I did reconnect the egr but was expecting a code if something was wrong.....

 

[Justin Fleming]

So tonight I unplugged the vaccum line going to the egr valve and capped off the vaccum line. The stumble went away. This was a temporary test, so it would appear to seem as the EGR if faulty and I should replace. Do you agree?

 

[SouthernYank]

If you capped it off and the stumble went away then the truck thinks the valve is closed. EGR could have trash or debris keeping the stem to seat, could be a bad diaphram in there as well. If it were me, I would replace it.