Hesitation w/o SES codes. Temp sensors?

Bought this used a few months ago - I think is sat a few years before that. 1991 S-10 4.3L TBI has new O2, TPI sensors. Had a "tune-up": plugs, wires, EGR cleaned
Vac is good (dealer checked) Timing light looks good (about 10BTDC and advances fine). Gas tank was improperly installed (fixed) - seems likely new fule pump.
passed inspection, has no codes set, but runs like crap. It isn't missing, but... It hesitates badly, lacks power and chuggles a little when cruising.
Known problem: Temp sensors (could that do it?) Also: I belive it sat for a long long time before I bought it. The water was very rusty and had to be flushed >10x to get it to stay green (still rusty too). This is why I haven't yet replaced the temp sensors. The cat-conv. is also very old (but doesn't backfire, etc).
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Top Post!!!!!!!! Just woundering...You said you think it sat for a while? And all your fluids look lile crap....Ok did you replace the fuel when you Reinstalled the tank?How about looking at the fuel filter ? Get a fuel pressure reading......Before you start slapping sensors in it...Could be just a guess of course Weak fuel pump,Clogged fuel filter,leaking fuelpressure regulator,Didnt 91s have distributor caps?Obviously they ha a fuel problem before you got it So lets start here..IEven though you passed an emissions inspection we would still like to know what pressure you are running.. Steve C Hesitation w/o SES codes. Temp sensors? Group: alt.autos.4x4.chevy-trucks Date: Sun, Aug 15, 2004, 9:25am (CDT-2) From: snipped-for-privacy@comcast.net (Elliott) Bought this used a few months ago - I think is sat a few years before that. 1991 S-10 4.3L TBI has new O2, TPI sensors. Had a "tune-up": plugs, wires, EGR cleaned Vac is good (dealer checked) Timing light looks good (about 10BTDC and advances fine). Gas tank was improperly installed (fixed) - seems likely new fule pump. passed inspection, has no codes set, but runs like crap. It isn't missing, but... It hesitates badly, lacks power and chuggles a little when cruising. Known problem: Temp sensors (could that do it?) Also: I belive it sat for a long long time before I bought it. The water was very rusty and had to be flushed >10x to get it to stay green (still rusty too). This is why I haven't yet replaced the temp sensors. The cat-conv. is also very old (but doesn't backfire, etc).
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Thanks for a reply... progress but not done... Answ. to your questions: I didn't replace the fuel or filter. I didn't 'reinstall' the tank but simply tightened the hose-clamps on the filler-spout and vent hose (so it didn't leak when filled), and tightened up the rear strap that was looose. I 'slapped' in TPS & 02 sensors because they were amazingly cheep (<$30 @AZ each). The filter looks like the original filter. Is TBI more sensitive to fuel blockage/pressure than carborators (ie: no resevour but pressure/flow dependent?)? I don't have a fuel-gage. Progress: I did see another thread on a 4.3L drivability that Doc said he thought was an EGR and I tried his test... Disabling the vac into the EGR. It does run alot better (smother) but is still lacking power. It isn't heasitating/stumbling like it did before I disabled the EGR. I didn't expect that since the shop who passed it for inspection said they cleaned the EGR with the tune-up. Then again, spend enough $ around here on BS parts replacements and anything will pass (just don't get sukered into anything big like the Cat-conv). So I'm guessing the EGR is a primary part of the problem. Doc mentioned a screened gasket. I'd guess that either they didn't use a screened gasket or they didn't even clean the EGR like they said they did. Still for a $250 sticker I can't complain. Beyond the EGR?: The rest of the powerless-ness still seems a mistery of too many unknowns to know - and the dealer had a shot at it (that was a big waste of $). I'm rather amazed at how insensitive the computer is to setting SES codes on this truck. The 02 senser seemed to help and the old one was darker than any I've seen. The EGR is disabled and still no codes. It has yet to set a code with any test, etc - and the light does work (key on not running). Before it passed inspection I was more agressive going after it's issues - and now am very casual about it - if there's another easy test to do or point of information on a cheeps sensor I haven't replaced (temp sensors???) - ideas welcome. Thanks.
snipped-for-privacy@webtv.net (Steve Cook) wrote in message (Elliott)

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I'm going to top post this as there is too much to read through. I have similar problems (my thread is 'the vacuum monster'). Like you I disconnected the EGR vale and had some improvement.
Today I gave up and stopped by an old mechanic's place I know of. As luck would have he wasn't all that busy and anyway it would only take 15 minutes to fix. No parts to buy. Told me to come back after lunch. I did and twenty minutes later I had gained 100 horsepower.
The poor old trucks butt was plugged up. Air and fuel in but not much coming out, - sorta like you eating lunch and then not being able to getrid of it. The Cat was plugged. He said they can do a pressure test on the tail pipe but didn't bother as he could tell from the sound of the engine revving up.
Dave
(Elliott)

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