OK IÆve pretty much got my 3.4 swap done in my 91 for the 2.8 but IÆm having problems with the idle. I know there are plenty of posts out there about this, but every time I search with what I think are good key words I get hundreds of matches but they donÆt seem to help with my problem. I have a completely rebuilt TBI off a 4.3 on it now but it seems like its running way too rich, looks like itÆs dumping way to much fuel in there, way to much black smoke too. It runs terrible at first but eventually the check engine light comes on and it gets a little better, although not much. I had two experienced mechanics working on this so I know all the vacuum lines are correct, we actually worked on them quite a while and the vacuum diagram on the hood is in like new condition. I would almost say this is like the lean/surge problem some have experienced, but I thought that was due to the 2.8 injectors and since I have the 4.3 TBI IÆm kind of confused, I sort of remember something about a fuel pressure regulator issue. If anyone has any answers I would greatly appreciate them. On another note, I have the starter relocation drilling jig I would sell to anyone who wants it for $50.00 which includes shipping to the continental United States. Thanks, Bill

billw, i'm curious, why did you use the 4.3tbi on the 3.4?

also, i'm assuming you installed a 3400, and if so, lemme steer you to a site that will be of much help: v6z24.com. i used to own a cavalier, and the 3x00 swap is very popular in those cars. they can give you a lot of help on the motor

F.Y.I. to Crazz, a 3.4 when swapped into a 2.8 Trooper will lean-surge badly until warmed unless you jack up the fuel pressure regulator on the 2.8 TBI, or use a larger TBI such as GM's 4.3 TBI (commonly used in S-10's for one) or Holley Big-Bore meant as a performance option for the 2.8. The larger injectors in either of these TBI's takes care of the lean-surge problem. The Holley is mounted with a special base gasket which allows the larger-bored TBI to sit proper on a stock 2.8 TBI intake; however, the popular mod is to bore out the 2.8 TBI to match the larger holes. This increases performance markedly over a non-bored intake. As an aside, if you were to install 4.3 injectors in a stock 2.8 TBI, they'd be rich enough to run a 3.4 but the top end would be quite limited due to more restrictive breathing. Even the little 2.8 benefits from airflow improvements (at both intake and exhaust), and the 3.4 wants a lot more!

Now, on to Bill's rich running problem; if you haven't replaced the O2 sensor, probably a good idea. Especially if the old motor blew a head gasket, antifreeze will kill the sensor.

Check the injector spray pattern while idling, if not properly atomized it'll mess with your mixture.

Given that the 4.3 TBI was rebuilt, the fuel pressure might be too high; something to check, anyway. Here's some info on dealing with GM TBI fuel-pressure issues:

http://www.aces.edu/~parmega/efi/tbi_adjust.htm

http://s-series.org/component/option,com_tech_article/Itemid,/item,21/task,item/

BTW the Holley unit comes with an ajustable regulator (Sweet!).

The ECM does take a hundred miles or so to learn but I didn't experience any excessive rich probls following my 3.4 swap, so that's just a possibility, not real likely.

I'm assuming you bored out the intake to match the larger TBI, otherwise you'd have less airflow and run richer.

If your muffler or cat is plugged up it'll cause rich running; you can have a muffler shop check for excessive backpressure ahead of the cat.

Last but not least, very important to re-adjust the minimum idle air/speed settings & T.P.S voltage; after you make major changes (such as the 3.4 swap, that's major!), this has to be readjusted or it'll run real funny.

Here's some links for that, if you have a volt/ohm meter, some small Torx bits and a bit of patience, it's pretty easy:

http://www.4x4wire.com/forums/showflat.php?Cat=&Number=445449

http://www.s-series.org/htm/how2/tpsadjust.htm

http://www.wellsmfgcorp.com/pdf/Counterpoint2_1.pdf

General info from the above site, a fantastic collection of articles:

http://www.wellsmfgcorp.com/counterpoint.html

http://s10planet.com/forum/showthread.php?t=951

A few more random thoughts, bump your base timing up to around 13-14 deg BTDC, it'll run better. Don't forget to disconnect the ESC (Electronic Spark Control) wire located in the center console when you check/adjust timing. Otherwise, you'll never get an accurate adjustment. It's the only wire in there with a quick-disconnect type of coupler.

Did you connect to ground the big bundle of wires on the pssgr's side, which all terminate into one montrous lug? This is amongst other things, ground for the ECM and it'll really really run funny if left disconnected. The 2.8 block has flat pad, tapped for a bolt to secure this bundle, but the 3.4 does not. I bolted mine to the block, using the screw which holds the (now useless and only filling a hole) cam position sensor (under the exhaust man on pssgr side and best accessed in the vehicle by going thru the pssgr's wheelwell).

HTH, keep us posted.............ed

Well I stand corrected, I found one big mistake with the vac lines, when I tee'd off one of the lines to make up for the missing one on the 4.3 TBI I hooked the MAP up to the one I split and that one only had vacuum when the throttle was open and MAP needs constant vacuum. It runs a lot better but I havn't had a chance to put any miles on it because I have an exhaust leak which I need to fix first. Has anyone had the exterior oil cooler hoses leak? They have special fittings and new hoses are only available from the dealer and the are like over $150 each?

For finding different fittings , try going to a local hydraulic hose place.Take a fitting in with you and there is a chance they can match it or make something else work for it.

A quick example was a ford truck I had for work , the power steering hose went , ford wanted 260 for the 2 hoses , a hydraulic place made new hoses and fittings for 96 total cost.

So , if you look around you might just find what you need without forking out the large cost.

WOULD A 185.00 FOR BOTH HOSES SOUND LIKE A BETTER DEAL. WITH THE SEAL. HOW MANY DO YOU NEED JERRY

Thanks guys, I went to like 3 different hydraulic hose places when I started this project none of them had the banjo fitting and none did repairs. That was like 3 or 4 months ago. I spent all day looking today and finally the 4th place I went to actually did repairs. They cut the old collars off and crimped new ones with new hoses on the old fittings, all for $60. Thanks again for all the input.