1988 S15 Jimmy tuneup?

Just picked it up. Recently had a fresh O2 sensor and coolant temp sensor thrown on it. Has 300,000 KM on it, original engine.
Starts reasonably well - spits when its very cold outside. But when fully
warmed, the in-gear idle is pretty rough and the truck exhibits an off-idle hesitaton thats not always there. At higher cruising speeds, punching it yeilds no hesitation - its always off idle/off the line, and not all the time.
I don't wanna spend a lot on what amounts to a beater, but if a few bucks in parts can get me a few MPG and better running, i'm all for it! According to 2 tanks of fuel now, its averaging about 15 mpg (2wd, 2.8L V6). Its winter and there's lots of remote starting in there too - but it seems it should be a lot better??
Any ideas would be appreciated.
b
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A TBI rebuild kit is only like $30 - might be worth a shot! Anything else to look at for the symptoms below? I"m tempted to pull the EGR and disconnect it honestly....
b
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On mine the vacuum port going to the PCV valve was carboned shut so the PCV wouldn't open. Not only did it make it idle rough, but it caused it to leak oil too. The only parts I used were the TBI and EGR gaskets and 2 cans of carb cleaner.

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I'm not sure if the 2.8 TBI is like my 4.3 TBI, but I've found that the gasket between the ring the TBI unit sits on/in often gets brittle and allows air to leak in. On mine there are two identical gaskets, one on top of the TBI unit between it and the air cleaner housing, and one below the unit that seals between the ring and the TBI unit. If your's is like mine, you'll see what I mean if this doesn't make sense. Those gaskets come two to a box, and run $6-7 US dollars last I checked. Check the plugs, wires, cap and rotor, and as others mentioned the EGR valve. It's also probably worth it to put a fuel filter in when it gets warmer.
Big Chris
Chuck wrote:

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What I wonder is what effect eliminating the EGR completely will have on the motor. Will this make it run 'open loop'? Occasionally, either the EGR valve or the EGR soleniod are sticking and I can't figure out which is doing it.

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In article < snipped-for-privacy@wbar100.chi-4.29.138.73.chi1.dsl-verizon.n et>,

No, it will not cause it to run open loop. What will happen is; The engine will knock, the knocking will be detected by the knock sensor which sends a signal to the ESC module, the ESC module will retard the timing resulting in a drastic loss of power. The knocking will also cause mechanical damage internal to the engine, hammered rod bearings, collapsed piston ring lands, hammered fire rings in the head gaskets. The there are the increased emissions...
Good plan to use extra fuel and destroy an engine you got there.
The EGR solenoid is easy enough to check, a vacuum supply, a vacuum gauge and two jumper wires, if it's sticking (doubtful) you should be able to duplicate it. More likely to be the EGR valve that is sticking.
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It only sticks about once a month, so I doubt could duplicate the problem. I think it is the EGR, but I don't feel like putting a $50 part on that only occasionally sticks (or occasionally makes the computer spit out the EGR code).
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Interesting - on my old 1991 K1500 it was recommended by countless people here to disconnect the EGR alltogether - which is what I did. There were no adverse effects, reduced fule mileage or power, or knocking or damage. It /occaisionally/ threw the egr code, and I mean like once every 5 months.
I'm thinking that cleaning the TBI and fresh fuel filter is all I'm gonna spend on her... :)
b
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Update!
The truck began to run particularly rough today so I pulled it in the garage to pull the air cleaner off and have a look. I found
- a VERY DIRTY throttle body assembly (dirty isn't the word for it) - vaccuum line from small electronic module on side of air cleaner to intake broken in half (this was the source of bad running) - at least one other rubber fitting on the vaccuum side of the intake thats cracked - vast amounts of oil from a fat breather line that goes the aircleaner (from the valvecover to under the filter)
It was amazing how one little vaccuum line broken could cause the truck to run so badly! Any ideas what that small module does (out of curiosity) ? I'm going to have a TBI rebuild kit thrown into it sometime soon (fresh gaskets, o-rings, fpr bladder, etc) and have the mechanic thoroughly clean the unit and its parts.
I've also got a leaking waterneck (not sure if the hose is split or the waterneck itself is leaking) but thats gonna get tweaked too. I have to assume that this clean up will make some difference to the engines smoothness. Also - the breather line from the valve cover to the air cleaner housing- should it spitting clean oil into the engine????
I'm tempted to remove it and put a filter breather on it - it doesn't seem right that the engine is drawing liquid oil into the tbi - when running without the airfilter inside, you can see a steady stream of vapour flowing from the port into the tbi...is this normal?
any other suggestions?
b

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On Wed, 16 Mar 2005 21:05:16 GMT, "Hamilton Audio"

the little electronic module most likely was your MAP sensor, which is the single most important sensor on a TBI vehicle. it tells the ECU engine load by how much vacuum is or isn't there and adjusts fuel accordingly.
hth, Bret
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What an interesting place to put it! So it makes sense then when it came undone that it didn't run so well :) I know vaccuum leaks are an issue that I need to work on too....
one thing at a time!
b
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