What should I do next about my rough idle?
 

I've been having trouble for awhile now with the very common vortec rough idle. The exhaust smells rich to me as well. I think I've read most of the applicable posts in this forum about this idle problem, so at least I know I'm not alone. My Jimmy has 140K miles on it. So, I cracked open the upper plenum to see what I could see and to at least clean or replace the EGR and inspect the IAC. I was surprised about how clean the passenger side of the intake was compared to the driver' side. There was maybe a teaspoon of gas in the passenger side as well. The EGR valve has probably been stuck open for a long time now. Maybe that is why the driver side is so dirty. Or maybe the passenger side looks about normal, but something is wrong with my driver side cylinders. I don't know. So, my questions....

Is the fact that the passenger side is relatively clean mean there is a fuel leak on that side? If there is, I can't really tell where it's coming from. The driver's side is more than just carbon, it's sludgy.

I'm going to replace the EGR (with screened gasket) and the IAC valves (already have the parts). I already scrubbed the EGR passageway very thoroughly. Should I replace the fuel injector assembly and nut kit while I'm in there? (I don't want to unless it's absolutely necessary becuase of the $$$).

What's the best way to apply this miracle Seafoam stuff? Funnel it into the PCV while the engine is running?

I'm going to replace the cap, rotor, plugs and wires as well, while everything is taken apart.

I took this picture right after the upper plenum came off. Please let me know what you would do. I've learned more about my truck reading this forum the past couple days than in the past 11 years I've owned it. It's been a pretty good vehicle for me, and I thought I'd be getting rid of it soon, but if I can kick this rough idle, i'll hang onto it for awhile. I look forward to hearing your advice.

I'm not a super mechanic, but I did stay at a Holiday Inn Express last night....


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RE: What should I do next about my rough idle?
 

Sorry, I forgot to say that my truck is a 1995 Jimmy SLS 4.3L Vortec "W" CPI 4X4.

RE: What should I do next about my rough idle?
 

Fuel pressure regulator with that much washing of the passenger side. And when you replace it don't forget to check the fuel lines and their connections at the spyder so that you don't have to tear into it again. Might as well put in new "kit" at the same time...make it all new.

RE: What should I do next about my rough idle?
 

with sea foam just put into the gas tank and let it do its thing. but once you put it in it will make it run real rough until the stuff passes. but i always change the fuel filter after i use it. thats how i used it the last time mine ran rough and now it runs great.

jimmyboy

RE: What should I do next about my rough idle?
 

i wouldnt do all that stuff until you let it run the seafoam threw it. but i would change the fuel filter.

RE: What should I do next about my rough idle?
 

I had the same problem. I had to replace the entire spider unit and put in a new EGR valve. I bought a rebuild kit from Lindertech. Cost about $400 for everything by the time I was done. I agree though, before you go that route you ay want to try some Seafoam. I have a feeling that you'll be changing out that CPI unit though.

RE: What should I do next about my rough idle?
 

Well I took a closer look at your photo and from what I see I am confident that the fuel pressure regulator is the problem. There is a small amount of what you call black goo but that would appear to be coming from the fuel pressure regulator stradling the center of the manifold with the majority of the fuel washing the passenger side of the manifold. You should be able to get by with just the fuel regulator and related seals.

RE: What should I do next about my rough idle?
 

Update.....
I ended up buying a new spider assembly and a nut kit. I'll be installing them, along with a new EGR valve tomorrow. I'll keep you posted. By the way, I accidently broke off one of the poppet valve "handles" when I was trying to pull it out, so be careful if you're removing your own spider assembly with plans to use it again. I also found out today that a 4M x 16 pitch .7 metric socket head cap bolt will perfectly replace the little T15 Torx bolt that holds the IAC onto the upper plenum in case you ever accidently strip the Torx bolt. :)

RE: What should I do next about my rough idle?
 

That is a carbon copy ( no pun intended ) of what the inside of my 95 looked like when I removed the plenum a few weeks ago. I was told my spider injector was bad because of very rough idle. I replaced the pressure regulator only, but I now know that there was nothing wrong with it. My plug wires were corroded where they connect to the distributor cap. What threw me for a few weeks was that I had just had the cap, rotor, plugs and wires all replaced last January or February, but they got corroded in just 8 months. Gets damn pricey trying to figure out what's wrong huh? After everything I went through, I believe it was definitely the spark plug wires. Runs like new now with 322,000 miles. Also check the connector wires on the electrical plug to your spider injector, one of mine was broken and I replaced the "injector harness" ( so it is called ) while I was in the plenum, $101.55 minus 10% cash discount = $91.00 dealer item. It never ends. $$$$$$$ and a little more $

RE: What should I do next about my rough idle?
 

Final update.....
Well, I got it all cleaned up, got all the parts (spider, nut kit, EGR, IAC, cap and rotor) in there and buttoned it all up and it runs like a champ now. Better than it has in years. I'm gonna hold off on the plugs and wires for a week or so until the seafoam has a chance to work its magic. Thanks for all the advice! I never would have attempted to fix this problem by myself without the info from this forum.