Question for the gurus

[cypher_2001]

I recently got an 87 s10 2.8 tbi with 166k. It has had a rough idle, and stumbles on acceleration since I have had it. It isn't throwing any codes.

So far, I have changed the cap and rotor, plugs with a .45 gap, air filter, fuel filter, removed the throttle body and sprayed the hell out of it with a couple cans of carb cleaner, ran a bottle of Lucas fuel injector cleaner, and sea foamed it this weekend. I actually sea foamed it properly, with a third of the can being sucked in the vacuum line from the brake master cylinder instead of the guy at Autozone telling me to just pour it into the throttlebody....

At this point I'm going to try a new TPS for the acceleration at part throttle then it falls flat. Other than that, I'm out of ideas as to what to try next.... And sorry for the book!

[bszopi]

Have you checked timing on it? Sounds like a no-brainer, but you didn't mention it, so figured I'd ask...

[robertisaar]

stumbling and rough idle could also point to a vacuum leak...

[cypher_2001]

Have you checked timing on it? Sounds like a no-brainer, but you didn't mention it, so figured I'd ask...

Haha! I haven't yet, lost my timing light in my last move. I had also thought about vacuum leaks. I saw something about using a propane torch and moving it slowly around while the truck is running to make the a/f mixture richer and makes it idle faster when the propane gets sucked into the area that is leaking to help diagnose where the leak is. Think this works?

[pocket-rocket]

I've used carb cleaner to do the same, so I imagine it would work with propane. I've never injected propane to know how a gas engine would react, but I know some of the performance diesel guys use propane injection.

[geldartb]

i used the propane and it worked awesome.
i had a vac leak on my upper intake and within a minute i found it.

i bought one of those cheap torches you get at home depot for like $15 and aside from using it start the firepit at my friends house and to find the leak i havent used it for anything else.

if you do have a leak the moment you hit that area with the propane the idle should spike.

[SofaKingWeToddDid]

how many vacuum lines are there on that motor? its kinda old, replacing them all couldnt hurt!

[neo71665]

First thing I had to do when I got my 87 was fix all the old vac lines. I'm a firm believer in silicone lines over rubber.

[geoffinbc]

Check timing and check for vacuum leaks. Then check the fuel pressure. If pressure is low then get a full rebuild kit for the whole TBI unit and it will have the diaphragm for the regulator. Check the injector spray pattern and make sure it is a nice cone shape with no drips then shut the engine off and check for drips after the engine is off. If there are drips you need new injectors. Check the EGR system check for chunks in the valve holding it open. Check that the valve operate freely by hand with no hangups.

If these don't fix anything let us know.

[SofaKingWeToddDid]

where is a good place to buy a roll of silicone vac line? can you pick the colour?

[robertisaar]

i imagine summit racing might have it for a decent price... and in any color you might want.

[neo71665]

I started out with orange I got from a buddy that is made by purosol but soon after decided I didn't like it and went with black.

The black came from http://www.hosetechniques.com/

[cypher_2001]

Sorry it has taken so long for me to get back to you guys. Had a hotrod buddy stop by and he diagnosed it within about 30 seconds....

I was wondering if anyone had a diagram for the vacuum lines for the egr routing? 2.8 S10 TBI.

[robertisaar]

need more than this?

[cypher_2001]

I think that should do it! I just need to wait for a non-rainy day to get out and figure it out. Thanks again for all the help guys!