Running rich? Temp sensor maybe?

[3X00-Modified]

Most of the time it's the O2 if the car has over 80k. I really don't know for sure man.
But it's an 89, so my guess the O2 is overdue anyway.

Sorry I had to laugh at that comment. lol

Only because I still have the original O2 sensor on the Z. Along with every other sensor on the engine. I wasn't aware of a life expectancy...
/offtopic

Sounds like you guys have this one pinned down though. Temp or O2 sensor would be my guess as well unless something is really screwed up like injectors or similar.

It's right on WIKI we are not making it up.

Sensor failures

Normally, the lifetime of an unheated sensor is about 30,000 to 50,000 miles (50,000 to 80,000 km). Heated sensor lifetime is typically 100,000 miles (160,000 km). Failure of an unheated sensor is usually caused by the buildup of soot on the ceramic element, which lengthens its response time and may cause total loss of ability to sense oxygen. For heated sensors, normal deposits are burned off during operation and failure occurs due to catalyst depletion. The probe then tends to report lean mixture, the ECU enriches the mixture, the exhaust gets rich with carbon monoxide and hydrocarbons, and the fuel economy worsens.

Leaded gasoline contaminates the oxygen sensors and catalytic converters. Most oxygen sensors are rated for some service life in the presence of leaded gasoline but sensor life will be shortened to as little as 15,000 miles depending on the lead concentration. Lead-damaged sensors typically have their tips discolored light rusty.

Another common cause of premature failure of lambda probes is contamination of fuel with silicones (used in some sealings and greases) or silicates (used as corrosion inhibitors in some antifreezes). In this case, the deposits on the sensor are colored between shiny white and grainy light gray.

Leaks of oil into the engine may cover the probe tip with an oily black deposit, with associated loss of response.

An overly rich mixture causes buildup of black powdery deposit on the probe. This may be caused by failure of the probe itself, or by a problem elsewhere in the fuel rationing system.

Applying an external voltage to the zirconia sensors, e.g. by checking them with some types of ohmmeter, may damage them.

Some sensors have an air inlet to the sensor in the lead, so contamination from the lead caused by water or oil leaks can be sucked into the sensor and cause failure.[4]

Symptoms of a failing oxygen sensor includes:
Sensor Light on dash indicates problem
Increased tailpipe emissions
Increased fuel consumption
Hesitation on acceleration
Stalling
Rough idling

Note the bold lifetime, He has an unheated O2 sensor.

Well, as stated before, I already changed the temp/coolant sensor. So its o2 or injector cleaning/replacement?

Yes, and I would start with the cheaper/easier of the two, and I think that would be O2 for you. Denso #2341001 89 2.8L, $10.88 from Rock Auto.

[ifixalot]

My thoughts, What do your plugs look like? See if they are uniform in color.
That era, fuel injectors had a habit of the coil going bad. Once that goes bad, that cylinder leans out, the o2 sensor tries to richen the mixture making the others rich. Looking at the plugs, one will be lighter than the others, the others will be soot black. If you have an ohm meter, check each injector. It should be about 11-12 ohms. If one has something like 4-6 ohms, that is the bad injector. Of course you can check the ohms on the injectors first whichever is easier to do. But looking at the plugs will also tell you if one cylinder isn't firing and the plug is black and or wet with gas. Or if one is black and dry indicating an injector that isn't shutting off and is leaking fuel into that cylinder.

[GTU89]

Should I go for a universal Denso for 14.99 or Denso direct fit for 19.99?

[Money pit Beretta]

Just get the direct fit.

[3X00-Modified]

agreed... Universal means you need to splice wires to the pigtail... One more connection to fail in the future.

[GTU89]

Should i go with denso premium plugs instead of bosch as well? the denso's are like 3 bucks cheaper a pop.

If not, then what brand?

[scd88ga]

Standard OE AC Delco's

[GTU89]

Okay, sounds easy. Does the sunroof make it alot more difficult or not really?

[scd88ga]

Okay, sounds easy. Does the sunroof make it alot more difficult or not really?

No, I don't think having a sunroof would make spark plugs more difficult to change...

[Money pit Beretta]

Standard OE AC Delco's

AC anything, if you want to spend the big money so you don't have to change the pulgs for a long time go for it(platinum, they should out last the engine). There is another trusted brand though. I just don't remember the brand or the number to use.

Sunroof? You have one on your hood? Just kidding, not sure where you are going with that.

[GTU89]

Sorry, was in a hurry and posted in the wrong thread lol

Now, back to the right thread lol.

They (Advance Auto) also have Autolite copper spark plugs on sale for $1.49 a piece, they'd last, what at least year or two? not bad for 8 bucks and some change. I'm guessing they're probably crap though.

Oh yeah, and the strange idle that makes the car wanna stall comes back when the car is warm on occasion.