humboldtcorrado

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.

humboldtcorrado

bump...

humboldtcorrado

bump...

Gamefreakgc

I've had poor experiences with aftermarket TPS's. Bout a Beck-Arnley and it broke in 3 days. Bought a DENSO (OEM) and it's worked fine for years.

A dead spot could mean either a fuel, air, sensor, or ECU issue. If you adjust the TPS out of spec you're not going to pass the idle test, since it will be operating in closed loop at idle instead of open, which means it'll pour on more gas and air than necessary. Since you've got your ohmeter out, check the VAFM to make sure eveything is ok. Also check your fuel lines and make sure you're not smelling any fuel vapor or see any leaks.

The other culprit that might cause a flat spot could possibly be your ECT (engine coolant temp sensor). It's not likely but that sensor will cause a host of different issues as it starts to fail.

kornhuskerwizard

That tps you have in the pic is for 89 and up with 22re i beleive. I had issues with compatibility on tps sensors and they have different ones for different years of 22re. I also think the oe sensors are better than the aftermarkets.

humboldtcorrado

thank you both very much for your replies. checked the TPS again before i got them, and adjusted per 4crawler's site again. checked the AFM per 4crawler's static specs. everything was perfect and in-spec, except E2-VS, which was ~1500 (20-400 is spec).

Dynamic Test #2 (E2-VS) then failed, because everything seemed way out of whack. looks like that's next on the list to address, and once the AFM is reading correctly, we can worry about the TPS. makes sense that we'd have that stumble at partial throttle if the AFM was providing 4x the max specified resistance @ idle and then jumped around.