Check temp.control switch,should be located on the intake. computer uses info from it to set many other parameters.
Joking they all do/ really,! but yours is outside normal.
the OBD2 DTC codes clear, no P0300s at all, or the like?
cold misfire.
new spark plugs , using OEM type plugs and gapped to factory spec. not to Autozoned spec. they lie.
misfire can be many reasons
even a leaking EGR main valve.
1: low compression any cylinder. (compression gauge)
2: bad spark (look for OBD2 pending P030x)
3: bad fueling, (injector balance tests)
there are tests for each , all are simple.
injector clogged or leaking?
is the fuel old?
try techron fuel additive, (i hate additives) but this one is just
more benzine that is already in all chevron fuel. so is 100% safe.
run that, read bottle for rates.
the misfire is real, it can be found.
the first question, is it all 8 cylinders or just 1.
we can do a spark shunt test to find cylinders that are dead
during the misfire.
SOURCE: transmission
hello, your truck will not shift from second to third . If it wont shift to third it is going to need new clutchs or seals installed in the transmission that is a common problem with the 4L60e transmission.
SOURCE: misfire code, rough idle, full tune up complete,
The black soot on the plugs means that you are running extremely rich. The fuel injectors ma test good electricly, but they are notorious for leaks. The spider-looking thing sandwiched between the plastic intake plenum and the intake manifold gets cracks in it's "legs" and leaks fuel ito the plenum area. The fuel pressure regulator is also housed in this same assembly. if the diaphram in the regulator gets a pinhole in it, it also leaks fuel into the plenum area, causing all kinds of erratic idleing, black smoke from the exhaust, and will cause your fuel trims to drop into the negative 20s.
There is a technical service bulletin covering this subject. This procedure outlines the steps required to replace the existing Central SFI Fuel System with a new MFI (Multiport Flexible Injection) Fuel System.
It is removing the injectors which are all housed in the center body of the injector assembly and replacing them with a new version where the injectors are located where the ols "poppets" used to be in the intake manifold ports. The picture below is for a V-8 engine that is covered by the same TSB.
The poppets and the pressure regulator are available individually to fix your existing fuel injection system, but I gave up on that after replacing several poppets only to have them come back in a few months with another popet line broken. I recommend replacing the whole assembly with the new and improved version. My customers have told me after doing this that the engine never ran that smooth when it was new.
The GM part number for the new injector assembly for your V-6 engine is 12568332 it is also now available at several aftermarket parts outlets.
As for the timing chain solution posted by doodieman200, all I have to say is that I have enough fingers on one hand to count all of the failed timing chains I have replaced on these engines. If you don't have a cam/crank sync code, the timing chain has definitely not slipped a tooth.
Testimonial: "thank for tech update. due to working in a fleet bus shop i no longer get regular tech bulletins"
SOURCE: 1993 Chevy Silverado will not shift in to 2nd 3rd
Are you sure its stuck in first gear, Its probably in second.. It sounds like a stuck or open shift solenoid in the tranny (4L60E hydra-matic). Depending on the year and type of tranny this was a default setting to either only second or only third gear, should some electrical or transmission hydraulic fault occur. Another common problem for that year is a faulty ignition switch at the key cylinder. It will fail and not send power to the tranny (thus not powering up the shift solenoids). The default (or limp home mode) is when both solenoids are commanded off. They will be both commanded off in second gear (even when the tranny is operating normally).
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