ok, so i have an '87 irocz. 5.7 with a bit of engine work. it also has a hypertech chip with a 160* t-stat. i failed emissions so i've replaced a few things (EGR, the o2 in front of the cat). is there supposed to be a second o2 sensor towards the back?

now the SES light is on after i drive it down the street, but im scaning it with my obd1 scanner, and there arent any DTC's stored in the computer. the fan always seem to be on (i removed the fuse for the secondary fan because i deleted the AC.) it also surges at idle to the point of stalling. im not sure if the ECM is fried, i can unplug the MAF sensor and it will run. it still needs the tps to be plugged in. so im really at a loss. is my ecm fried?

any help will be appreciated, and if you need more info then please ask. im due for a retest in 20 days.

thanks

 

Did you reset the computer???? IE: disconnect neg side of battery or the ECMBATT fuse for about 30 seconds????

 

it was disconnected the whole time i was making the emissions repairs, but i will unplug it again tomorrow. im just concerned about not getting a response from the ecm with a scanner. the ses light flashes when you use the paperclip to flash the codes, but there were so many that i lost count. do you know offhand which fuse it is so i can check and replace it?

 

well i reset the computer, and took it for a drive and the ses light didn't come on. but i was curious when i got home and i disconnected the MAF sensor and the ses light came on, but no codes again when i scanned it.

when i plug the scanner in, i select my vehicle and then turn the ignition to on, and then hit enter/link and it skips right to codes retrieved and i hit enter to see them and it says that there arent any DTC's yet the SES light remains on.

 

Use the paper clip and count carefully. If the ECM is storing the codes, and flashing them on the SES light, that's all you should need to do.

 

ok, well ill try that again.

 

Chevelle, looking at your OP.. First you failed emissions, then you said SES and fans started running AFTER you replaced EGR and O2 sensor. You may have multiple problems or added a new problem after the EGR/O2 installations. First get the SES problem straightened out per post #5. Next - Do you have the emission sniffer printout ? Did you fail HC , CO, Nox or CO+CO2 and at any specific speed range.. EG: here in GA they dyno tested me at 25 MPH steady and then 50 to 15 MPH deceleration and at both speeds the engine RPM must be below 2500 RPM (high gear).

 

fans were running before the o2 and egr fix.

Failed ----HC----NOx
Standard --- 88 ----614
What i had --117---- 1348

all at 1302 RPM

CT Emissions

the SES is intermittent now.

 

Intermittent SES, fans running, surge to the point of stalling, high HC and NOx .. you really need to get the DCT failure codes. With high HC's it sounds like it's running rich, has an plug misfiring or another sensor out of wack. The O2 was a good 1st shot at the HC's and the EGR for the high NOx. However with a SES on you still have something else that's messed up .. I assume you have a good CAT installed on the setup ?

 

there is a cat, maybe the original, im not really sure.

but im going to hold off on reapirs, im just going to try to sell it. ive put too much money into it in the past few months.

 

ok, so i decided to finish a project and keep the car.

i took it out today for the first time since my last post, and it ran perfectly, no SES light.(about 3 miles through back roads around 40-45mph) im going out to do the timing now. i could feel it slightly hunting when i kept the accelerator steady, and i mean ever so slight. barely noticeable.

 

so i went out to do the timing and i discovered that somebody didnt hook the egr noid up when they put the motor back in, and i just reconnected it. it will idle nicely at around 1000rpm, it has a surging spell here and there. but when i went to time it, i got no response form my timing light (and i just bought it last week, never used it before.) i felt the fuel injectors, because i can hear them cicking, and the pulses feel weaker on some, and stronger on others. the rad fan is still running constantly as well.

oh, and if this has gone off topic from the computer diagnostics section then please feel free to move it to the l98 tech section. thanks!