My car feels generally sluggish, such as throttle response, transmission shifting, etc. I get 10 mpg with city driving, and on 18ish with highway driving, which seems rather poor (I've heard I should be expecting 25-30 with highway?).

The car is bone stock. I've replaced the distributor cap and rotor, plug wires, plugs, air filter, fuel filter, and adjusted the timing. There are no trouble codes in the ECU. A friend of mine says it is running rich (he said he can tell from the exhaust).

I'm a novice at this and trying to learn. What should I be looking for? The fuel system? What can I check myself? I'm a little hesitant to take it to a garage and pay a wad of cash for them to tell me nothing is wrong.

I've only had the car for a couple months, so I don't know how the car should be running. But compared to a 1982 Trans Am (carburated 305) I owned, it is rather unimpressive for a newer 350...

 

How old is your O2 censor?

Does your exhaust smell alright? Maybe a plugged cat?

 

I've only had the car a couple months so I have no idea when the O2 sensor was replaced last. I'm going to replace it, but when no trouble codes came up in the computer, I started wondering if something else could be it. Can you have a bad O2 sensor and not have it throw a trouble code?

And the exhaust doesn't have any abnormal odor that I can tell. No rotten egg smell that I've heard accompanies a bad cat...

 

Check the fuel pressure for bleeding off, your injectors may be leaking or possibly grounded, dumping fuel. Any hard starting or smoke on startup?

You're right in looking to the fuel system since you've pretty much replaced most ignition components. You could try advancing the timing a little, though.

 

On occaision it will stall right after starting. This only happens in the morning. This has only happend a handful of times. Also, when i start it in the morning there's a puff of blue smoke, and then nothing the rest of the day. I understand that the smoke is probably blow by from bad piston rings and not something that requires immediate attention?

 

Stalling after starting..does it set a code? Has the coolant temp sensor ever been replaced? If the engine is cold your ecm will add in fuel until the cts shows a certain temp...like the cold start injector did in earlier cars. A bad sensor could cause it to stall, and/or make you run rich. I would look into replacing that.

The blue smoke is most likely valve seals, very common thing you need not worry about right now. Bad rings will cause blue smoke when shifting or at high rpms.

 

Unless the code gets cleared at some point by the computer, the stalling doesn't set any codes.

Other than what I mentioned in my original post, I couldn't say when anything on the car was last changed. I know the previous owner barely drove it for the last year.

 

Run some injector cleaner with the next fill up and see if that helps. You might also want to check the ohms on them. If you still have the stock injectors in I'd bet at least one is out of acceptable range on the ohm reading.

 

Well, I replaced the O2 sensor, CTS and PCV valve. When I took it out for a drive there was a noticable difference. Throttle response was much crisper, and there seemed to be more power all around. It seemed to be going through gas pretty quickly though (even for the somewhat spirited driving I was doing).

I cleared the computer so it would relearn with the new sensors. Drove it for a bit... filled up the tank and threw in some fuel injector cleaner for good measure. There was a noticable drop in performance.. but it was still much better than before.

Drove around with it most of last night and today, and this evening, it stalled while poking along in some traffic. It started up fine, but now it runs like it did before I replaced the sensors. The stall didn't set any codes in the computer, it just flashes 12 over and over.

Any ideas?

BTW, the old O2 sensor was colored almost white at the end.

And I don't know if this has to do with anything, but when I'm stopped (in drive with the brake on or in park ), there'll be a click every 15 seconds or so and the engine rpms will go up or down by 50-100. It's quite noticeable. And annoying.

 

Check the impedence of all fuel injectors when you feel it is running good(if it does again) and when you feel it is sluggish. They should all be in the 12-14§Ù range give or take.

 

I checked the resistance on the injectors. They were all about 17 ohms (16.8 - 17.1). This was with a cold engine if that matters any....

What's this telling me? Forgive my ignorance.

BTW, thanks everyone for helping me out so far...

 

ttt

 

I had the same problem with my 89 Formula 350. Stall right after startup. I went to autozone and bought a new MAF. What a differance !!!

 

If the car is running rich, it is very possible that a plug or two could have fouled out. If the car was running very good after the work you did and then the problems began again, it could be that a plug fouled. Just a thought

 

There was nothing out of the ordinary with the old plugs when I removed them.

It seems to be running a bit better. Still, compared to my old 82 TA with a 305, it's nothing special. I'm going to see if my gas mileage improves with this tank of gas... if nothing's changed then I think I might just bite the bullet and get the local GM dealer to check it out.

 

Back at it again... I haven't tried solving this problem for a little while.. had other stuff on my mind.

This weekend I got a cable and Craig Moates software, and did a quick scan... The only values that I could find that were out of whack compared to what the GM service manual said they should be were BLM (146-149), coolant temp (a couple degrees hotter than the range they specified, and battery charging.. a few tenths lower than the specified range.

So the BLM numbers means the ECM is adding fuel right? What causes the BLM to be high? Where in the service manual does it talk about this?

 

lavamadness, it's always good to see someone else from the Lower Mainland (especially with a Formula 350)

The point of checking the resistance of the injectors when it's hot is that sometimes an intermittent short can happen, and it's usually when they get hot.

The clicking you hear is the IAC adjusting your idle. I'm starting to think you have a vacuum leak somewhere that is causing your poor mileage and your hunting idle. See what the computer is trying to do while your in idle. The stall saver might be kicking in.

Where abouts in Burnaby are you? I'm in Coquitlam and I work in Burnaby, so I wouldn't mind coming out to have a look. Maybe we could swap MAF sensors to see if that's giving you trouble.

 

Nice to meet you Alex... Dave here. I'm near Metrotown myself.

Found out the clicking was the AC clutch. Guess it comes when defrost is on as well as AC. *shrug* Apparently it's usually caused by low freon? I haven't noticed it at all lately since I haven't been using defrost much. (Or driving it for that matter... )

 

Hey I got bad mileage too like 11mpg. And I also feel my car isn't that fast, mines a 350 also, but it just doesn't have "350" power. Haven't gotten tuneup yet, waiting for it to be warmer. I tried fuel injector, one in full tank, another in full tank, and last one in low tank, all STP black bottles. I'll tell you what mileage I get next time I refuel. Right now I got 94 Ultra (Sunoco) in it. Also I've always thought the car wasn't really pulling on the highway. Well today I tried to push the pedal in as far as I could, and it wasn't till I totally squashed the pedal, that BAM I watched the rpms go flying straight up and heard my exhaust-real loud. I was in D to, so maybe I downshifted to 2nd gear? I'm still testin her out, my bro and bro in law are mechanics, and I got lots of connections so I can check out my car, without paying a crap load for nonsense work. If my sluggishness gets better I'll let you know what the problem was and how we fixed it. BTW my engine still clicks, near the spark plug/valve cover area. And it still clicks after engine is off?? But the back of my engine still make a cricket (bug) noise, I think it just might be the distributor??

 

I had the same problem with mine when I got it, and went through the same routine. I took it to the dealer had them check it out and set the timing. There was my problem I dont know why but when my cars timing is set at factory it is really sluggish almost wont even spin the tires at all. Try advancing your timing a little bit at a time get in try it and do it again until the car lights em up and takes off.
Later, Gary

 

I have a similar problem in my '88 gta. This is when a scantool really helps out. I had already done a full tuneup. I found that the oxygen sensor was keeping my car out of closed loop and caused me to get around 12-13 MPG. This all started when i put a new BOSCH sensor in there (before gas mileage was 23 hwy 16 city with a real old o2 sensor that was green when i pulled it out ). I bought a heated delco 3-wire o2 sensor off ebay and when it arrives i'm throwing it in there and hopefully that will solve my problem. My other car gets much better gas-mileage than that and if this keeps up the GTA's goin' in the garage and the fibreglass go-kart will be my driver (risky proposition with the way people drive around here.........).

 

RedFire -

How did it go with the AC Delco O2 sensor? The one I put in mine was Bosch as well. I had the problem before I replaced the O2 sensor though, so nothing changed when I put the new one in. But then.. I don't know what the old one was either.

 

Well it helped out a little. I hooked it up and wired it into the fuel pump circuit so o2 sensor heater will always be on when the car is running. After i put it in, i got out the autoxray and the was getting into closed loop real fast and staying there even when idling. However, I'm still getting bad gas mileage. Then again i'm having a few other problems with some few bad injectors and and my distributor eating ignition rotors (doesn't help out too much for performance when all the contacts in the cap are covered in plastic dust).