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So it pretty much randomly my 97 Z28 has stopped running. It wont start unless I give about half throttle, and then it sounds and runs like complete sh*t almost like its only running on 3 cylinders. If I dont give it throttle, it will just clunk and die, but there is no revving the motor at all. Even if you give it WOT it just runs at about 2k rpm but still very rough.
So far I have put new plugs in it and new o2 sensors because I had a previous problem about a year and a half ago with it running extremely rich and fouling out one o2 sensor. I only replaced that 1 at the time and never solved why it was running so rich. So now I have 2 new o2 sensors and the extensions for long tubes. About 6-8 months ago I put a new Racetronix/Wahlbro fuel pump and relay in it. It is not throwing any codes and I have scanned it and cleared it about 10 times. I have no idea how it could run this terrible and not throw any codes. I hooked up a fuel pressure tester gauge and when priming the pump it is at 46 psi, since it wont idle I dont know what the pressure is there, but while giving it throttle its also about 46 psi. The last thing I did was take off the intake manifold to have a look, cleaned it up a bit, painted it, and put it back on with a felpro gasket. While I did that I looked for any clogged injectors and put new o-rings on them.
At this point I am completely stumped and have no idea what to do next. Can anyone help me out??
Yeah I guess that would be a good place to start. I have never actually done this before, I assume I can just pull each wire, put an extra plug in, then look for spark when it cranks? How do I check for fuel?
Yeah I guess that would be a good place to start. I have never actually done this before, I assume I can just pull each wire, put an extra plug in, then look for spark when it cranks? How do I check for fuel?
Ok, I checked all of the plug wires and I have spark in each one. I am looking into how to pull the injectors one by one and test them. I know a few weeks ago I checked several of them with a multimeter and they were good.
There is a tool you can buy that works like a timing light for your injectors, I saw it on the Scotty Kilmer show, (www.scottykilmer.com) OR you can remove your fuel rail and injectors from your intake manifold. Reconnect your injectors to the fuel rail along with all proper wiring but do NOT reinsert the injectors into the manifold. Have someone crank the car and watch each injector for proper volume and spray pattern. If the injectors are the case you can buy aftermarket replacements here, (www.fuelinjectorconnection.com) I replaced the injectors on my LT1 and haven't had a problem with them since.
So I tried to test my injectors, I pulled the fuel rail off and was going to plug them in one by one to watch the spray pattern, but turns out two of them are missing the injector clips that hold them to the fuel rail. Without them, once my pump primes and the lines are pressurized, the injectors pop off and fuel pours out. I guess I am going to order some online for $6 a piece I don't know how to test without them
So I was able to hold on those two injectors by using some clamps and clipping the injector to the fuel rail. Then I could test each of them one by one. So now I checked all of them and they all seem to spray just fine.
Now I know that I have spark and fuel at each cylinder, and I assume I am getting air because I can see the valve open up in the throttle body. Now I am officially stumped again and still have no check engine light. Anyone have some ideas on what's going on?
I sure hope it's not the PITA opti! I haven't replaced it in several years now, but I don't know what would cause it to go bad. How would I test something like that?
You take it off and take it apart. If loctite wasn't used on the rotor screws then they are prone to back out and cause symptoms exactly like what you're experiencing.
From: Lansing, MI via Bowling Green, KY, Dalton GA, Nashville, TN & Atlanta, GA
Originally Posted by derekstl
I sure hope it's not the PITA opti! I haven't replaced it in several years now, but I don't know what would cause it to go bad. How would I test something like that?
When you replaced it, what brand optispark did you use?
It's been about 5 years since I replaced it and I honestly can't ferment what kind it was . . . I've slept since then. I think it was a Jegs brand. I guess I can look to see if the screws backed out and the rotor is loose this weekend. I will probably do some more testing for vacuum leaks first before I go through the effort to pull the water pump off.
Any backfiring? It would have to be one huge *** vacuum leak to cause those symptoms.
Nope, no backfires at all, just consistently runs like sh*t or stumbles. I think it is more severe than a vacuum leak as well, but I figured I will try it.
So I finally got around to removing the opti this weekend. The books were still tight and thepin was in the right location so I don't think that was the root of my problems. Once I pulled the opti and inspected it, I noticed the connector and plug wire for cylinder 2 was very corroded. Do you guys think this would cause a major issue? Obviously is not good and would impact that one cylinder, but I don't know if it would be major enough to cause the symptoms I am having.
So I finally got around to removing the opti this weekend. The bolts were still tight and the pin was in the right location for the timing so I don't think that was the root of my problems. Once I pulled the opti and inspected it, I noticed the connector and plug wire for cylinder 2 was very corroded. Do you guys think this would cause a major issue? Obviously is not good and would impact that one cylinder, but I don't know if it would be major enough to cause the symptoms I am having.
Last edited by derekstl; Feb 15, 2015 at 12:28 PM.
One corroded plug wire will not cause the engine to stumble. Just a shot in the dart, but have you unplugged the MAF and started it? I honestly don't know the symptoms of a bad MAF (you can do a search. It has been covered before), and not sure if there is a possibility of a bad MAF w/out throwing codes.
Anybody have an idea on how big if an issue this is? I plan to clean it up a bit, maybe out some dialectic grease on it and put it back together. Just figured I would check with everyone else to see if you had other ideas.
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Car Not Running - Need Help 
I don't know how to test without them 
