Emissions mystery - complete loss of power

[sdsshawn]

Hey Everybody!
Hoping someone can give me a little direction in solving this mystery. I inhereted my Mother's Gran Sport 1989 with 76k on V6 - it sat in my driveway for a few years and then I went to smog to get registered and it failed as gross polluter. I took it to my mechanic that does stuff I don't have the skill or tools to do. Anyway, he replaced oxygen sensor, catalitic convertor, and three fuel injectors the it started to run on only about half power - I could get it up to about 40mph. He declined to charge me anything $1,300 parts and labor which was the ONLY good thing to happen. I'm wondering if any of you genious mechanics have any clues ideas or solutions for me to follow from here? I don't want to take the chance of taking it to another mechanic who is not as honest as Leo and end up paying a bunch of money for no solutions. Leo thought it might be the Cam gear (made of fiber?). Also, I'm thinking that sitting so long the injectors clogged and I need to replace the other three - problem with that is having to lossen motor mounts and move engine to get to them. At this point it is a huge mystery as the car never had any problems until it sat for all those years and I want to sale it but can't unless I can smog. Any suggestions????? Thanks for any help in advance - I am always amazed at the wealth of knowledge and genorosity of members of this forum. Thanks again.
Shawn

 

[92sub]

You need to check fuel pressure and quality.
After that you'd probably have to consider paying someone to look at it who actually knows what their doing. There's lots of parts you can throw at it but unless you find another benefactor like Leo it will get expensive.

 

[user1238]

To replace injectors you have to remove the intake manifold. Rotating the engine is easy to do since the torque links r upfront. U put in in neutral, undo bolts, rotate the engine by putting a tire wrench or any metal bar in the right bracket, pull it forward, reinstall left-side bolt throught the service hole on the torque link.

Did he replace all the spark plugs and wires? It is quite mandatory. Although if the plugs/wires/coils are misfiring u'd have obvious exhaust explosions (pops).
How about the fuel filter? Unless the car was stored with a full tank, it will have a lot of varnish and crud accumulated through the system.

Those early injectors are crap. Modern fuel dissolves the insulation on them, they short out & misfire. (especially if any fuel sys cleaner was added since the end of hibernation) This results in simple dead cylinders, no exhaust explosions, no stink, no power.

You could grab injectors from a '90+ 3.1L at the junkyard but it's a tough job to get to them and u'd be doing twice as much to install them. They don't have to be exact same ones as your mechanic used, but have to match on each bank. This MPFI is bank-fired and the computer can adjust for front/rear bank differences. If u are rich I recommend buying new ones.
While u have the intake apart u can verify that the new ones have consistent resistance of 10.5~12Ω, and work off of a 9V battery. Put the rails over a pan, plug in the fuel prime connector, and check the spray patterns with a 9V battery. Injectors that don't open under pressure from 9V are bad. Aftermarket injectors must be checked in this fashion before packing them in.

All of that of course after checking compression and all the mundane stuff (fuel pressure, etc.)

In fact u can access #1 and #6 injector connectors without removing the manifold. Check the resistance with a multimeter - less than 10Ω is bad. Plug in 9V battery momentarily - there should be a faint but sharp-sounding click.

U can check resistances on each bank by unplugging D connector on the computer and probing between D3 and corresponding INJ/PFI 10Amp fuse and then D9 and corresponding INJ/PFI fuse. Approximate bank resistance is 3.6~4Ω. This test would only tell u about totally shorted or open injector coils. (less resistance = shorted, more = open)

A GM guru would charge $500-1000 to make it perfect. These cars are a B to debug. It should take 2-3 days. Easy-peasy when u'r not busy.