Hello,

I have a 1991 z28 with approx 29K miles that fails the Illinois emssions test. I have been working with a local mechanic that is highly rated by the state emissions testing facility.

The car slightly failed on hydrocarbons on the first test and passed all others.
After the first test I changed plugs, wires, cap and rotor.

2nd test failed hydrocarbons again, with improved co measurement. After the 2nd test I changed the oxygen sensor with a new bosch unit.

3rd test the car failed miserably on HC and CO, car was hotter than the previous tests.

I took it to the mechanic and he scanned it and noticed the new oygen sensor I installed was not responding well. He changed it and the PCV and it again failed the test. He has tried differenct ECM's, tested the cat and has performed numerous drive tests scanning the ecm and probing the exhaust. He tells me it passes his driving tests but fails the test station. He even takes it to the test station because he knows the testers and they let him have some liberty with how the car is handling directy before and during the test.

Any ideas? The only thing I know is wrong with the car is that the AC does not work well, low freon I think since the compressor cycles on and off. THe other thing that I think is bad is the seconday fan switch as it gets over 240 and the seconday fan does not kick in.

At what temperature does the ECM start to richen the mixture to help cool the engine if at all?

Can it get too warm to pass emissions?

SInce this test is a chassis dyno test that takes 5 to 6 minutes and the car is accelerating and decellerating in a stationary position the car gets real warm without the seconday fan kicking in.

It has not set any codes since I fixed the fuel pump relay, the injectors were replaced with standard injectors in the last 7000 miles and it did pass a previous emissions test with these injectors.

Any help at all would be appreciated, if I cn get some test data from the mechaninc I will, if I dont get this fixed soon the state will take my plate I guess.

Please help me before I go postal on some poor emissions test technician.

Thanks!

 

Hrmm hows the EGR vavle?

Kat

 

kick yer timing back, and if you have an aftermarket intake swap it with the stock one for the test. . My brother bombed emsiions for hydrocarbons so he kicked his timing real far back, and then put his stock intake on over the K&N. . he passed with flying colors after that


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1987 Pontiac Firebird Formula 350
1 of 2,384 made, Black with Silver decals
350 TPI
700R-4 Tranny with TCI shift kit and Corvette servo with TV boost sleeve
TCI saturday night special 2200-2500 stall converter
WS6 supsension
SLP headers with full 3" exhaust exiting through an SLP dual 2.5" tip muffler
SLP airfoil
180 degree thermostat
hypertech "performance" chip
3.73 rear
Viper talkin alarm with remote start
My 383 is in the process of being built right now, hopefully to make it's debut by middle December. . . many more mods to come in the summer. . maybe some experimentations with juice. . have some track times my independence day.

 

my friend fail every time until he put like 110 octain in. I know it's pricey but thats the only thing that helped his car.

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88 Formula 350 WS6
Upper and Lower SuperRam, 1000 CFM Accel Throttle Body, ZZ4 cam, 24# Motorsport Injectors, Larger Gutted Mass Sensor, Homemade Cold Air induction, PROM by performance resources, MSD 6a box, MSD Distributor, Accel SuperCoil, Taylor 8mm wires, TB Bypass, B&M shift Kit, 160* Thermostat, Flowmaster Muffler

Headers in the mail soon to be installed

 

CAN YOU SAY HIGH FLOW CATATLYTIC CONVERTER!!!!

 

Kat,

I asked my mechanic and he mentioned he stated he was positive the EGR vavle was working properly.

THis car has the stock intake.

Anybody recommend a good cat? for this car? Stock ehaust for now.

Thanks!

 

Generally the Random Technology cats are of higher quality. I bought a catco cat and was very impressed with it considering the price.

 

New cat and 10 bottles of dry gas (isoproyl alcohol) to 1/5 tank of gas.

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Hybrid Black 5.7L 5 Speed
'95 Competition Yellow Corvette Coupe ZF6

 

Well I passed yesterday with flying colors, 31 second test, shortest duration you can get in IL.

My mechanic found out that the mechanic that installed my new injectors 3 years ago put in injectors for a 350. No wonder my mileage was not a good as it used to be. Anyway I stopped by his shop Monday morning and told him my story, he agreed to replace all my injectors for no cost. Now I have new injectors but also a bill at the other shop trying to diagnose the problem this shop created 3 years ago. They also replaced the EGR since it was sticking from time to time but it still failed the test after the EGR was replaced, I have the old egr and can tell that is was sticking. It seems like the shop that replaced my injectors should owe me part of my bill at the shop that did my emissions diagnostic work.

What do you guys think about this?