Engine management--Running like junk--Please help

[oldsguard]

Have an 02 Alero with engine trouble. Issue first started with a miss that would manifest itself randomly. Under steady throttle position (roughly 15%) for cruising speeds the car was fine, but if there was a demand for some more throttle either through gentle acceleration or incline grade the engine would occasionally begin to miss and the MIL would begin to flash. The issue could be alleviated either by releasing throttle and reintroducing it, or by tromping on it and kicking it down and opening it up. The MIL would go out immediately and wouldn't store a code. This went on for a while, but before I found some time to research it and work on it, it really started acting up. It now hesitates and lugs under normal acceleration with no MIL, you can reach highway speed, but it is weak and takes about three times as long as normal. Under hard acceleration she'll still lug and run with an anchor in its pants, but at around 2700 RPM she'll open up and pull like a dragster. Again no MIL or code. The gas mileage has also dropped from the normal 30 to 32 highway to about 23. I ran it with the handheld diagnostic tool and all I could see as a potential issue is one O2 sensor was all over the place with its number and the other was steady. But then again I’m not a drivability mechanic, and certainly not an expert on reading the tool. I’ve thought of many potential causes myself, but thought I could plug in to the collective wisdom of all you guys before I just started throwing parts and money at it. I’d appreciate any help or thoughts any of you had. Thanks everyone!

[Olds64]

If there is no diagnostic trouble light and the ECM hasn't stored any codes I would check for a vacuum leak.

[OLDSRALLYE350]

How many miles on the car ? Has it ever had plugs and wires replaced?

[joe_padavano]

Could be a plugged or leaking injector. This won't show as a code since there is no direct measurement. At a minimum, have the injectors cleaned using one of the products that us flushed though the fuel system while the engine is running. Also check ignition as suggested above. Temporarily install a fuel pressure gauge and check that while driving (I tape the gauge to the windshield while driving). Have you changed the fuel filter recently?

Also, have the DTCs read with a full-function machine like an OTC Genysis. The inexpensive units don't read all the codes. You can even drive with the Genysis connected, allowing you to see what is happening real-time and to record the data stream when an intermittent problem occurs.

[csstrux]

Joe...is the Genysis available for private purchase? or is that special equipment? Assuming it can be purchased OTC where would one be found and roughly how much?

[Olds64]

Chad the Genysis is an expensive scan tool. I recall when I was in college that one of the professors spent about 5 months writing a proposal for the college to buy a Genysis scan tool. The college finally bought one and man is it cool!

I assume it would be available for private purchase, but why would you want one? Unless you have your own auto shop you probably couldn't justify spending the money to buy one. Of course, if you are independently wealthy then maybe it would be a cool toy.

[csstrux]

That is about what I expected...Oh well.

[Redog]

Sounds like a clogged cat, could need new plugs and/or wires

Which engine do you have? the 3400 or 2.2 Ecotec? The 3400 needs the correct plug. If it doesn't get the plug it wants, it will miss (Trust me I know)

Clogged fuel filter? Clogged injector, but not likely.

Could be a TPS also

[oldsguard]

Thanks for the suggestions everyone. I had a lot of the same thoughts, but wanted to know if there was some giant gremlin out there that I had no idea existed, and that it would kick my butt--and my wallet.

It's the 3400 with about 150,000 on it. I put plugs/wires in it at around 100 K so maybe that's it, enough time to go bad if they wanted to.

I guess start at the simple and move up the chain and utilize occams razor.

It's just that I've already dealt with repairing the ubiquitous gasket issue and a major PCM issue that still irks me 4 years later. The wife over-paid for the car in the first place and loved it so much I just kept putting time and money in it when I would have personally ditched it....hell even for another one...but this one was lemon/money-pit city. **Kicking my own ass**

So in a way it was almost a question of again attempting to fix it and run it or cut losses and use what's left of its worth to put towards a project or something else.

Again thanks for the assistance. I'll get to some of those and keep my fingers crossed. I really don't want to try and hunt a vacuum leak...

[Olds64]

You could always use ether to search for a vacuum leak. It is hillbilly but it works.

[joe_padavano]

Originally Posted by csstrux

Joe...is the Genysis available for private purchase? or is that special equipment? Assuming it can be purchased OTC where would one be found and roughly how much?

I bought mine used on Ebay for about $600. I later bought software upgrades for about $200 each.

[csstrux]

THX. Joe