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
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.
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.
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.
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.
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.
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).
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... :)
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
- 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
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
any other suggestions?
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
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!
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