Lt1 guru needed
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Lt1 guru needed OK i decided start a thread here in hopes someone here has theory or idea....
OK so I replaced my opti on 96 camaro lt1... All well riding fine, 2 days...Thrid day cruising and rpms start surging as im driving..Just rapidly fluctuating without additional or less gas 2300 2800 2300 2800 etc etc.. So come to red light sitting still car reving up to 3500 4k no gas.. So in panic hit car in front of me put in park...now damn thing starts red lining so turn it off wait on light.. Green light NO START. Tow it home, replace ignition control module same results..Wont start.. Go check on it next day still wont start. Today get it towed starts right up for tow driver.. He gets it to shop wont start... They had it all day said as it stands they think it opti.No leaking (infamous water pump etc) Just said not giving spark etc, and think it that or computer but doubt computer being it did start for tow driver.. Im at end of my rope and would LOVE a theory as to how opti do this? If indeed I got some fluke GM opti that died less than 100 miles
OK so I replaced my opti on 96 camaro lt1... All well riding fine, 2 days...Thrid day cruising and rpms start surging as im driving..Just rapidly fluctuating without additional or less gas 2300 2800 2300 2800 etc etc.. So come to red light sitting still car reving up to 3500 4k no gas.. So in panic hit car in front of me put in park...now damn thing starts red lining so turn it off wait on light.. Green light NO START. Tow it home, replace ignition control module same results..Wont start.. Go check on it next day still wont start. Today get it towed starts right up for tow driver.. He gets it to shop wont start... They had it all day said as it stands they think it opti.No leaking (infamous water pump etc) Just said not giving spark etc, and think it that or computer but doubt computer being it did start for tow driver.. Im at end of my rope and would LOVE a theory as to how opti do this? If indeed I got some fluke GM opti that died less than 100 miles
Last edited by KUTTER; Mar 16, 2009 at 07:08 PM.
OK i decided start a thread here in hopes someone here has theory or idea....
OK so I replaced my opti on 96 camaro lt1... All well riding fine, 2 days...Thrid day cruising and rpms start surging as im driving..Just rapidly fluctuating without additional or less gas 2300 2800 2300 2800 etc etc.. So come to red light sitting still car reving up to 3500 4k no gas.. So in panic hit car in front of me put in park...now damn thing starts red lining so turn it off wait on light.. Green light NO CRANK. Tow it home, replace ignition control module same results..Wont crank.. Go check on it next day still wont crank. Today get it towed starts right up for tow driver.. He gets it to shop wont crank... They had it all day said as it stands they think it opti.No leaking (infamous water pump etc) Just said not giving spark etc, and think it that or computer but doubt computer being it did crank for driver.. Im at end of my rope and would LOVE a theory as to how opti do this? If indeed I got some fluke GM opti that died less than 100 miles
OK so I replaced my opti on 96 camaro lt1... All well riding fine, 2 days...Thrid day cruising and rpms start surging as im driving..Just rapidly fluctuating without additional or less gas 2300 2800 2300 2800 etc etc.. So come to red light sitting still car reving up to 3500 4k no gas.. So in panic hit car in front of me put in park...now damn thing starts red lining so turn it off wait on light.. Green light NO CRANK. Tow it home, replace ignition control module same results..Wont crank.. Go check on it next day still wont crank. Today get it towed starts right up for tow driver.. He gets it to shop wont crank... They had it all day said as it stands they think it opti.No leaking (infamous water pump etc) Just said not giving spark etc, and think it that or computer but doubt computer being it did crank for driver.. Im at end of my rope and would LOVE a theory as to how opti do this? If indeed I got some fluke GM opti that died less than 100 miles
Let's try to figure out the no spark issue first...
What brand opti did you use?
How old is the coil?
I would perform this test, might shed some light on the issue:
http://shbox.com/1/4th_gen_tech2.html#opti_test
As usual, double check all the wiring to and from the coil, ICM, and opti.
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Gm opti of course lol, replaced plugs,opti harness,coil to msd and went with csr ewp. I mean I had heard of rough idle, misfire, and hard starts from opti going out. Was hoping it was ignition control module but wasnt same results. I pretty much did that trouble shooting based on that /\ ....I dont have a obd1 reader thats why said F it and had towed. The computer idea seems more logical to me but why would it be so hit or miss with starting? Also thought maybe a bad ground but that wouldnt explain rev surging (or i didnt see how). Im just trying to make sense of it before I pay to have it towed home to replace my opti AGAIN to have same thing happen.
-Again mechanically was running better than before hands down those 60-80 miles.Excellent response, no lag no noises, temp was great, oil pressure great etc... Then just went nuts,rpm needle had seizure that red light was not even 200 yards.. By then it was going crazy.
-Again mechanically was running better than before hands down those 60-80 miles.Excellent response, no lag no noises, temp was great, oil pressure great etc... Then just went nuts,rpm needle had seizure that red light was not even 200 yards.. By then it was going crazy.
When you say "no crank" do you mean no start? Did the engine actually turn over with the starter and not start?
The high idle has nothing to do with the opti. It cannot. You have to have the throttle blade open or a bad vacuum leak to get enough air in to idle that high. Make sure the throttle cable or lever isn't rubbing on something.
The opti needs to be diagnosed with an oscilloscope. That's the only REAL way to figure out if it has a high and low res signal.
From there you need to see if the PCM is triggering the module. I would doubt that the PCM is bad. They're pretty robust.
The high idle has nothing to do with the opti. It cannot. You have to have the throttle blade open or a bad vacuum leak to get enough air in to idle that high. Make sure the throttle cable or lever isn't rubbing on something.
The opti needs to be diagnosed with an oscilloscope. That's the only REAL way to figure out if it has a high and low res signal.
From there you need to see if the PCM is triggering the module. I would doubt that the PCM is bad. They're pretty robust.
When you say "no crank" do you mean no start? Did the engine actually turn over with the starter and not start?
The high idle has nothing to do with the opti. It cannot. You have to have the throttle blade open or a bad vacuum leak to get enough air in to idle that high. Make sure the throttle cable or lever isn't rubbing on something.
The opti needs to be diagnosed with an oscilloscope. That's the only REAL way to figure out if it has a high and low res signal.
From there you need to see if the PCM is triggering the module. I would doubt that the PCM is bad. They're pretty robust.
The high idle has nothing to do with the opti. It cannot. You have to have the throttle blade open or a bad vacuum leak to get enough air in to idle that high. Make sure the throttle cable or lever isn't rubbing on something.
The opti needs to be diagnosed with an oscilloscope. That's the only REAL way to figure out if it has a high and low res signal.
From there you need to see if the PCM is triggering the module. I would doubt that the PCM is bad. They're pretty robust.
I agree about the high rev, needs air.
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cranking but wouldnt turn over sorry.... Yeah I thought maybe egr valve or leak but none found. As far as something laying across cable not sure id have to double check on that. But wouldnt make sense to me how that cause the rev surges. Maybe if it would have just been stuck or opened to certain throttle posisition but it was like pulses or what not. Like when put in park spike to mid 3 to 0 then to 5k then 2k then redline and so on.As though I was giving little gas then letting off then MORE gas.. Right before I killed it when was reving high in park the service engine light came on whats throwing me off is that it wouldnt start after that. If it was leak or throttle position seemed like it still would been able to start
Could the vacuum on the base of opti, somehow cause these surges in rev?Like if somehow liquid made it into opti and was vented through? Or something?
Could the vacuum on the base of opti, somehow cause these surges in rev?Like if somehow liquid made it into opti and was vented through? Or something?
Last edited by KUTTER; Mar 16, 2009 at 07:11 PM.
cranking but wouldnt turn over sorry.... Yeah I thought maybe egr valve or leak but none found. As far as something laying across cable not sure id have to double check on that. But wouldnt make sense to me how that cause the rev surges. Maybe if it would have just been stuck or opened to certain throttle posisition but it was like pulses or what not. Like when put in park spike to mid 3 to 0 then to 5k then 2k then redline and so on.As though I was giving little gas then letting off then MORE gas.. Right before I killed it when was reving high in park the service engine light came on whats throwing me off is that it wouldnt start after that. If it was leak or throttle position seemed like it still would been able to start
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Ghost in the machine! Unless somehow your traction control/cruise control is literally fritzing out and pulling the throttle open... You wanted theories after all 
If our car can go into passing mode while holding the Accel button on the cruise switch, why can't it have an electrical problem?
If our car can go into passing mode while holding the Accel button on the cruise switch, why can't it have an electrical problem? LS1 Tech Stories
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Ghost in the machine! Unless somehow your traction control/cruise control is literally fritzing out and pulling the throttle open... You wanted theories after all If our car can go into passing mode while holding the Accel button on the cruise switch, why can't it have an electrical problem?
If our car can go into passing mode while holding the Accel button on the cruise switch, why can't it have an electrical problem?
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Something wrong, could've gone HORRIBLY wrong now and thus your problem. Now, if the fuse or whole cruise unit has been pulled, theory debunked. If there's still power to the unit then maybe it can hold water. Thread Starter
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No codes that I know of asked mechanic he just started explaining how he thinks opti or pcm...Didnt say any misfire etc.
Unit removed, as well as smog pump etc. Guess was along lines of weight reduction pretty much anything that could been pulled was lol minus ac. I just got done reading GM did a recall or what not "faulty" vent/vacuum hoses. Some even said to change these when doing opti, could this part faulty,clogged, or whatever been responsible for the surging? I mean it does run in intake elbow after MAF?
http://www.rmsautoparts.com/proddeta...?prod=12555323
Unit removed, as well as smog pump etc. Guess was along lines of weight reduction pretty much anything that could been pulled was lol minus ac. I just got done reading GM did a recall or what not "faulty" vent/vacuum hoses. Some even said to change these when doing opti, could this part faulty,clogged, or whatever been responsible for the surging? I mean it does run in intake elbow after MAF?
http://www.rmsautoparts.com/proddeta...?prod=12555323
No codes that I know of asked mechanic he just started explaining how he thinks opti or pcm...Didnt say any misfire etc.
Unit removed, as well as smog pump etc. Guess was along lines of weight reduction pretty much anything that could been pulled was lol minus ac. I just got done reading GM did a recall or what not "faulty" vent/vacuum hoses. Some even said to change these when doing opti, could this part faulty,clogged, or whatever been responsible for the surging? I mean it does run in intake elbow after MAF?
http://www.rmsautoparts.com/proddeta...?prod=12555323
Unit removed, as well as smog pump etc. Guess was along lines of weight reduction pretty much anything that could been pulled was lol minus ac. I just got done reading GM did a recall or what not "faulty" vent/vacuum hoses. Some even said to change these when doing opti, could this part faulty,clogged, or whatever been responsible for the surging? I mean it does run in intake elbow after MAF?
http://www.rmsautoparts.com/proddeta...?prod=12555323
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LOL pretty sure no codes thats why still trouble shooting.... This is my new theory AS IT STANDS...that there was issue or what not in vacuum/vent lines bottom opti maybe a leak I know it dumps in behind maf so something that wasnt getting read by MAF threw off my calculations which caused rev spikes etc.The opti in process wasnt venting out moisture. Thats why when I turned it off wouldnt start again..But it had time to dry so thats why started for the tow driver.Yet while it was running vent/vacuum still not functioning so it got saturated again. So wouldnt start for mechanic...THATS all i got not sure how hell the spiking would have happened but its only thing I can make any sense of..Opinions?
That test is testing the power to the module, and the PCM signal to fire it. Furthermore, testing the PCM signal to the module using the AC scale is kinda bullshit. It's not an alternating current pulse, it is a square wave, and should be checked with a scope. If that's not possible, it should be checked with the meter on frequency.
The high and low res signals from the opti are happening WAY too fast to use a meter to test them.
No, you can't. That's not what that test it testing. The only way you could POSSIBLY check an opti for high and low res with a volt meter is using the frequency scale, and that won't really give a clear picture.
That test is testing the power to the module, and the PCM signal to fire it. Furthermore, testing the PCM signal to the module using the AC scale is kinda bullshit. It's not an alternating current pulse, it is a square wave, and should be checked with a scope. If that's not possible, it should be checked with the meter on frequency.
The high and low res signals from the opti are happening WAY too fast to use a meter to test them.
That test is testing the power to the module, and the PCM signal to fire it. Furthermore, testing the PCM signal to the module using the AC scale is kinda bullshit. It's not an alternating current pulse, it is a square wave, and should be checked with a scope. If that's not possible, it should be checked with the meter on frequency.
The high and low res signals from the opti are happening WAY too fast to use a meter to test them.