OK, I am new to this site but, have been following it and seems like you guys have a handle on things. Just joined the site today and need some help. I am a 2-stroke GP motorcycle roadracer, build and tune my own bikes, am not totally inept and have worked on cars all my life. I'll give you as much info as I can. I have a '94 Z-28 with 175,000 mi. on it. I bought the car 2 years ago because it didn't run. Never worked on many computer controlled cars. Originally, after changing plugs, wires and fuel pump (Yikes!) I took it to a shop as the 2-prong code reader key wouldn't bring the codes up. The shop said codes were Opti-spark. Bought a reman Opti from NAPA, put ele. waterpump in, a Holley throttle body airfoil and last summer at the street drags I beat 15 sec. with a 14.880. The car started running badly weeks ago and now is almost undriveable. Took it back to the same shop (I trust them) and they said NO engine or trans. fault codes? Have tested (with the Chiltons book) MAP sensor, TPS, MAF, plugs and wires. Pulled fuel rail out and #'s on the fuel injectors seem to indicate original. It also went through 1/2 tank of gas in 50 mi. Is there an average lifespan to injectors? Can they fail open or am I looking at another Opti problem? Ran a can of B&G 44K thruogh it with no change. My gut tells me Opti, but?............
Thanks for any help

 

Daniel, you might want to make this a separate post, but you would need a scan tool or some sort (a laptop one like DataMAster preferrably that can record and playback) in order to diagnose it better, but the mpgs being way off, if its running fairly ok I'd guess the O2 sensors need replacing, it can make it run way rich or lean which will in no time foul the plugs and ruin the O2s if any of them where good. I bet after sitting for so long and not running, they should have been replaced...but a bad opti could do that also, the scan tool will help dianose.

 

RZRACE:

Generally not a good idea to tack your problem onto someone elses thread. I'll move your post to a "new" thread.

 

Thanks, I wasn't sure and that post seemed to be along the same lines as I was dealing with. Unfortunately I do not have access to diag. tool which is why I took it back to the same shop. Really stumped me as to no fault codes. They said it had to be something the PCM won't log, plugs, wires etc. I will pull it back in and check the O2 sensors. Thanks for your help!
Daniel

 

Sounds like Opti. There is a sticky above all the posts that runs through the way to diagnose a bad opti.

Hal

 

So, I pulled drivers side O2 sensor and could not get resistance readings the Chiltons book called for. Ordered two new sensors and compared values with old one. Not exact but, very close, telling me it's not O2 sensors. I did however change the O2 sensor on the passenger side as it is such a pain to get to (drop the y-pipe). Absolutely no change. Gotta be that Opti-spark!

 

im just gunna go out on a limb here and say you should be nice to it... 175k is alot of miles... thats what my car had on it well more like 172k but close enough and i tried pushing it hard a few times.... shortly after it started runnign weird and developed a knock thus i just went though a whole rebuild project and now have a pretty sweet car. i wouldnt be dragracing a car with 175k on it... i mean do what you want but if you car about the car i wouldnt... also the opti is know for dieing alot even if you buy a new one some of the remans arent too good dont buy a whole new opti..... try doing a spark check on all the plugs and find out if it really is the opti or check the coil. if it is the opti only do a cap and rotor a whole new one shoudlnt be needed unless u get a code for it.

 

Thanks for the advice. I realize 175k is alot of miles and no, I prob. won't take it to the track again until I rebuild it. Can't afford to rebuild it now, just want to get it running. Supposedly, about 50k ago, new fastburn pistons , a B&M shift improver, cold air kit were put in. I got this car 2 yrs. ago for 2k cause it didn't run. When it came back with NO fault codes, I went back to basics. All plugs and wires have spark. I replaced fuel pump when I bought it and have about 45 psi. I have printed out the opti-spark test mentioned earlier and my son and I will go through that asap. Thanks, I do like this car