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Need Help diagnosing 94 Z ! Posted By: NastyC4 On: 01-03-2008 @ 13:45:45 Reply | Edit 1994 z that has a continuous problem that has been going on for years. When driving, the car will feel like it loses power, almost as if it has 4 cylinders running at WOT. SOmetimes the power will just kick in like vtec (lol). It seems to be on/off all the time. For example. you would nail the throttle and it would accelerate pretty then all of a sudden the power would be reduced and maybe a second later it would kick back in. 3 years back the opti and plugs/wires were changed. it didnt help anything except pop an abs light after the work. Fast forward to now... Car drives but when gets hot will lose power, backfire and shut off. Will not restart until car cools down. Basically the longer it is left to cool the further it will drive. Only thing I've checked is fuel pressure and it stays up when the car shuts off or when we try to restart it. ANy guesses? ANy help or input would be appeciated. It's a 1994 Z28 6-spd. tia! Posted By: CRAZZ28 On: 09-25-2007 @ 17:41:17 Reply | Top | Edit Try the ICM and the coil. -- 
94' teal M6, ripper shifter, 373 gear,TB bypass ,A/C A.I.R and EGR delete,pacesetter lt's,3" hooker cat back, JET stage 2 chip Posted By: 94fireturd On: 09-25-2007 @ 20:30:26 Reply | Top | Edit ^^what he said^^ Sounds like you could have two problems. The first discription; losing power off and on, could be a bad connection with the knock sensor. Is on the passenger side of the block infront of the starter. Try getting some electric tape and tape the plug up tight to the knock sensor. Baybe a ghetto rig job but it worked for me. -- 
2000 WS6 Trans Am. Lid, smooth bellow, free mods, SpecII, Drill mod, Hurst shifter, !CAGS, Blowmaster. NEXT: Brembo blanks, SFC, STB & LCAs. Posted By: Airbornec507 On: 09-25-2007 @ 20:31:47 Reply | Top | Edit At night check to see if you are getting any arcing from any of the wires or terminals. The ignition coil can be sensative to heat as well if it is going bad. When is the last time the fuel filter was changed? Not saying this is the problem but fuel filters need to be changed about every 15k to 30k at the most on a performance vehicle. Also you can never check for wire burns too often. When checking for arcing also run down the wires at night to be sure. -- Brothers 94 Camaro  
95 383 Z28 w/CC306, P&P Heads(272cfm), 3600 VIG Stall, CPT Pro Race 4L60E, Moser 12 bolt, 1.601 60'(W/3200 Stall) Posted By: 94junker On: 09-25-2007 @ 23:17:19 Reply | Top | Edit i had a problem similar to that it didnt lose power but i would drive fine for like an hour then just die and when it cooled off for like 4 hours then it would start again it turned out it was the opti but not the basic cap and rotor part but the back of the opti the drive line or whatever it is and of course the opti was the last thing checked because it was new, but still bad nonetheless Posted By: NastyC4 On: 09-26-2007 @ 10:58:33 Reply | Top | Edit Thanks for the input so far guys Ill be checking everything out. I tried to unpulg the icm and clean it and to make sure the terminals were clean on the plug but it didnt help. the silver thermal coating didnt seem to be in good shape but I didnt have any to put back on the back of it. I have a spare coil from my 93 vette so I'll try swapping it out. I'll also check the plugs to see if they show anything and the wires as well. A friend on my street has a gm scanner so I'm going to try plugging it in and see if it shows any codes. Most recent update is the car shut off but when revving it to try and stay alive the speedo moves up and down too  This is when standing still. basically it starts sputtering and when trying to throttle it a bit to stay alive the speedometer starts to move from 10-20 mph.I will try the knock sensor trick. I have heard of teflon tape being used I'll try it. Also the fuel filter would be a good thing to replace as it hasn't been in a long time anyways. [ Edited on 09/26/2007 @ 11:36:37 ] Posted By: NastyC4 On: 10-03-2007 @ 12:53:02 Reply | Top | Edit Ok guys need some more help here. was able to plug in the gm scanner here's what I noticed. Code 16- Low res failure Code 42- EST grounded Desired Idle : 3180 rpm Can anyone chime in about the code 42 ? I know the 16 must be the opti optical sensor I believe or a bad wire connection. WHy would the idle show 3180 rpm? It idles fine when it is running ok and never has a high idle. Posted By: NastyC4 On: 10-03-2007 @ 15:27:02 Reply | Top | Edit I found this wire in the engine compartment near the ecm. ANyone have an idea where it is from? it is yellow (dirty) and comes from what looks like the main harness bundle that goes to the passenger side corner behind the ecm. Heres a link to my photobucket pic. It's the first pic in the album. you can check out the other pictures of my 8100 rpm grenade of my 388ci LT4 I just had in my vette. ANy input on the wire would be appreciated! http://smg.photobucket.com/albums/v141/5abivt/ [ Edited on 10/03/2007 @ 15:31:45 ] Posted By: NastyC4 On: 10-03-2007 @ 21:44:51 Reply | Top | Edit Ok I replaced the ICM with the one out of my 93 vette that was working fine. I also removed the plug from the opti cleaned the terminals and put it back on. Thats all i did i went out fro a drive everything seemed fine for 15 mins of straight driving. I drove it high rpms, low and wot a few times there wasn't a problem. I was coming back home thinking everything was fine when BAM.. car shuts off. I tried cranking it and it would almost fire and start but it would backfire a bit and stay off. With the car off and the key forward I notice one thing, theres a motor spinning in the engine compartment. it starts with the fuel pump as well and shuts on and off. The rpm guage goes nuts with the motor jumping from 0-4000 rpm up and down. This definitely seems electrical I can't see how it's the optispark when the car drives 100% for 15 minutes and then bang goes off. ANY input would be appreciated. Posted By: NastyC4 On: 10-11-2007 @ 23:04:51 Reply | Top | Edit ANy thoughts why the thing dies when it gets warm? Code 16 would that be opti for sure? code 42... anyone have any ideas ? I'm going to try changing the coil tonight. Posted By: NastyC4 On: 10-12-2007 @ 12:17:12 Reply | Top | Edit Tried swapping inthe coil from my 93 c4. Stil shut down on me in 20 mins of running. Things I notice: WHen I fired it up, it stumbled and almost died the same way when it gets hot. It got smooth and continued to run like I said earlier 20 mins or so later it did shut down and not want to start. I notice the fans turn on almost instantly. This is a very cold car, sitting for 4 days since i last started it at least. the passenger side fan turns on almost instantly and stays on :/ Does this still sound like the opti? the code 16 points to it. Posted By: HBHRacing On: 10-12-2007 @ 13:36:36 Reply | Top | Edit Inspect the opti harness very well. If it's ok, replace the opti with a new delco unit. -- Owner of HBHRacing.com Xtreme performance products Click for new Fbody Tech Articles 
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