Hi there, first I would like to say thanks to the website and the people who make it all work... awsome place for info... and good stories

also plz excuse my english as I'm french

now to my problem.. my 94z28 is running like crap. It is missing like crazy and doing alot of backfires (the fact that I dont have a CAT installed doesnt help the backfires, but we dont have emmission tests here)

the problem seems to get worst as the engine temp goes up but it never goes past 1/4 on the gauge.

I give it gas and its like only half the cylinders are working.. under any acceleration its makes the car jump (accelerate, then misses and slows so its like riding in a bumper car getting hit every second...

things about the car. Right now it has 147 000 KMS meaning 91 340 miles on it.. when I bought it 3 years ago it was already cat-less so I havent touched that. the guy had told me the engine light was burnt because it was allways on since there's no cat..

I put a stainless steel pipe & muffler.
I put in a K&N pfik2, also put an LE1 (i think its that) rubber intake sleeve (without the long tube going down)

last year I had the same issue as I'm having now, I had brought it to GM, they changed the O2 sensor (left bank) and problem went away.
I stored the car about 1 month later (november) and took it out in April.

Problem is now back (and seems to be getting worst then b4).. so went back to GM to get a diagnostic and they tell me I have 3 codes..

11 -MIL he told me probably engine light burnt..
29 -Air system either air pump wasnt working or MAF..
44 -Lean Exhaust

"THIS CAR IS MODIFIED, TO WORK ON CAR NEED ORIGINAL EQUIPMENT."
is on the diagnostic report and they told me they would have to recheck it once I had put my original air filter back on...

so I asked what he thought the problem was, and he told me it was missing a rubber hose for air going from air intake (k&n tube) to the distributor, and he cant find the hose anywhere and I dont have an adapter on the K&N to have attached that on... I do have a small hose going into the side of the K&N tube not sure if it goes to the distributor or not... so he says without that cooling I fryed my distributor and thats my problem....?

Also told me the K&N would gunk up my MAF and that would also cause a lean mixture.. and I probably had a burnt o2 as well...

I would like any opinions about this from you guys.. I red alot of threads and most of them suggest coil (and wire) and you talk alot about Optispark (i suppose that's the distributor)... anyhow, I really would greatly appreciate all comments and suggestion you'd have for me... (I'm not verry good skilled mechanic.. this is my first car.. but I'm not scared of trying things myself.. like I changed my starter and have helped my dad with his 1970 Mach1 on some other things)

Ok well thank you all!

 

Optispark (distributor) is a wear item, and should be replaced at approx. 100k miles, also plugs and wires. These can cause chronic miss, which will melt and plug-up the CAT element. Why was the CAT removed?

For the Air pump, check the 20 amp fuse in the underhood fuse panel. It's probably burnt out. Replace it. If it burns out again, replace with a 25 amp. If that burns out, your air pump needs to be replaced (they tend to corrode on the inside, and short out).

K&N filters will contaminate the MAF, expecially if too much oil is applied. Remove the MAF, remove the MAF screen, and very carefully clean the hotwire element with solvent and cotton swab, etc. Re-install the screen, then the MAF. Disconnect your battery for about 10 minutes, then start it up. Should run better, although with a old optispark and plugs/wires, you'll still have a miss. Evertime I clean and re-oil my K$N, I clean the MAF after about 500 miles.

94'2 don't have the vent hose to the Optispark, so I'm not sure what the GM mechanic was talking about. The small hose on your K&N goes to the Air Pump.

BTW, I replaced my Opti, plugs, wires, and air pump at 160k miles. After tearing them down and inspecting their condition, I would suggest not waiting till 160k.

 

Excellent reply, thanks alot for the advise! I will go ahead and clean my K&N, drive it then clean the MAF, and try a 25 fuse for the air pump because I know she does burn that 20 when I start it.

I dont' know why the guy had removed the CAT on the car.. I never bothered to look into that since here we dont have emission tests and the cops dont bug me at all for the loudness of the exhaust.. they go for imports instead :P

Do you think not having a cat would negatively impact the car? I thought it would just give me more power, no?

how much do optisparks go for in the States? we pay double everything in Canada so I'm wondering if I should order it from the U.S.! (oh and if you could reccomend a good place that would be nice )

thanks again!

 

that code 44 means u prob need to change the left side 02 sensor.

I would start with plugs if its been a while, and check the wires. The cheapest you can get a new Opti for a 94 (I.e. nonventend)would be $300U.S. plus shipping from U.S. plus customs. You might get lucky on ebay with a used piece, but either way, i wouldnt try that first if money is an issue.

 

No CAT will just make your exhaust stink - no real HP gain or loss. My guess is the previous owner removed the CAT because it was plugged - due to a chronic miss. Probably opti. The opti is also prone to shorting on the outside of its housing when it gets dirty and wet. Buy a can of contact cleaner and douse the outside of the opti, wires and coil at least once a year, or if they get wet.

The stock platinum plugs are notorious for losing their platinum "pucks" well before 100K. I replaced mine at 100K, most of the pucks were gone. I replaced them again at 160K, 3 pucks were gone. So platinums are good for amybe 60K.

Forget the platinums, go for a good set of copper plugs, and replace them every 30K.

I bought my opti from Dal, although Jason seems to have better pricing. Do a search on opti pricing, you'll find a contact.

 

Great guys, thanks for the help! very much appreciated.. I did change the left bank O2 last year so I will start by going back and having it changed under warranty... then I'll be doing some work on it myself this week and I'll update you on the situation!

thanks again =D

 

w00t I got an update for yall!

Today brought the car to GM to have that left bank O2 sensor changed under warranty (since I did that exact same repair less then a year ago).

Problem has dissapeared... car's running in top shape! total cost = zero zip nada lol

I got a question though... How the heck could I burn two left bank O2s within one year and about 4000-5000 miles.. that can't be normal... any suggestions on what would cause the left bank O2 sensor to burn out as quickly as it did?

I would like to solve the cause of the problems so I don't end up doing this as a yearly thing...

I am not going to touch my opti since It seems to be working fine. One thing I want to do is change the plugs and wires since I have no idea when or if they've ever been changed!

Thanks for the help guys (and gals)!!

 

Get a back pressure reading on both sides and see if there is some sort of exhaust restriction on the left side. Also check for exhaust leaks that can cause the PCM to see a lean condition and richen the mixture too much. Also check the coolant level, burning coolant can wipe out O2s.