hi,
'90 4x4 pickup. 22re, fresh head/gaskets all around, everything cleaned up, etc etc.
Truck was barely running when it came to me - we thought it had a blown headgasket, but it turned out the head was corroded to the point that the water jackets were leaking into the combustion chambers on the surface of the head. needless to say, we had to take care of any extra issues as we found them, once the truck was running with the new head.
anyway, the engine that was in it was cobbled together with parts from at least 1 other engine (possibly the original?).
got the truck running, and it seemed to be running great. no over-heating, no missing, seems to run like it should. failed smog (california) the first time due to a stumble @ ~2500 that we didn't notice before.
assumed it was a bad TPS, because the ohms jumped all over the place when we tested it per 4crawler's site.
changed out the TPS with a new unit (borg warner), and adjusted it incorrectly (~2,200 ohms).
note: the first TPS we picked up, specifying it was for a '90, didn't fit. the tabs that are supposed to line up with the tabs in the TB were 90 degrees off. got one for an '87, and the tabs were in line with the adjustment/mounting holes in the TPS - this is what the correct one for our throttle body looks like:
. could there be an incompatibility between our TPS and the ECU?
anyway, idle emissions were ~4x higher than legal limit, but 2500rpm emissions were super clean. sounds like it was dumping fuel @ idle.
re-adjusted TPS to 200 ohms per 4crawler's website (using '85-'88 specs), and the stumble/dead spot @ ~2500rpm came back. gradually moved it up to 800 ohms, and the dead spot got smaller/moved in the powerband the whole way up, but it was still there/noticable. barely moved the TPS up to 820 ohms, and the dead spot disappeared completely. truck still seems to run great. idle is still set to 5° BTDC with the diagnostic port jumpered.
any ideas as to what's causing the dead spot? there aren't any vacuum leaks. new fuel filter. timed correctly. we need it to pass smog soon, and i would assume we need the TPS adjusted between 200-800 ohms to do that
thanks.