bad EGR switch was causing All problems Including Spark Knock


Ok, I replaced the Fuel Injectors, And after many hours. I cant figure out why it has spark knock Or a miss.

At 1300 to 1400RPM in park it has a miss, Just off Idle, if i take her out on the road Power seems a lilttle low and It spark knocks Alot.

I have check the fuel pressure- 40PSI With Key on No drop
I checked all of the plugs, cap rotor, and wires all seemed good, The gap Was set @ .045
According to the parts store. The Spec on the car said .035 So i took them out and reset them at .035. Made no diifernce.

I check all of the emmission Lines and they are routed correct.
I checked the vaccum, I have a very steady 20in at idle, not erratic at all.

I have cleaned the fuel tank and put in a new filter, When I put in the fuel injectors I replaced the Intake Gaskets at the same time.

The timing is set @ 6 degrees BTC, As it calls for.

Has anyone else had a miss like this off Idle?

 

I'm asking because you didn't mention it---you do know about disconnecting the "electronic spark control" wire--before setting the base timing ?

 

What year vette? L98. Any codes? At the age your car is, I would check the plug pins on your electrical plugs to components. I had a MAF code about a month ago. All it was, was dirty pins on the plug where it plugged into the MAF. Mine looked rusty. Maybe check ground wires too.

Good luck

Corvette Mike

 

yes the tan and Black Stripped Wire was disconneted, timing Set, Codes clear the reconnected.

 

Thanks Mike, But nO codes... 1985 L98, MAF Sensor seems to work fine, I tapped on it. It did not cut out. Seems to work fine.

 

Try running the timing to 8* and see what it does. Helped mine.

 

I had it set to 8 before I moved it to 6

Thanks for the suggestion.

I hope somewhere somebody had this same problem, and will see this Post.

 

try spraying around with starter fluid to see if you have a vac leak somewhere, sounds like you are running lean for some reason....check wire that goes to the knock sensor on the pass side of block

 

The vaccum Gauge did not move erraticlly even when its idling rough,

Wouldnt it be erratic if i had a vaccum leak?

 

In theory, but a vac leak would explain your symptoms if you are sure FP is up to snuff and you have new injectors. What was the reason for the injector swap and did you have these problems before? If not and you had it apart, a leak could be a possibility. Also, the spray test is easy and would confirm the vac test. My next guess would be a faulty ESC, knock sensor or wiring problem.

 

If this problem did not exist before you changed injectors, go bach to where you worked.

As noted above, check the simple stuff first, like a vacuum leak around the injectors.

If the timing was correct before you changed the injectors, it should have been just fine after you changed the injectors.

dmeyers
90 coupe zf6 3 speed shocks

 

Damaged plug wire during plug change, defective or cracked plug during install, defective or incorrectly packaged injector or all of them. Try this wedge a matchbook or similar between the throttle stop and lever to get the rpm you hear the miss and unplug one injector at a time and see if the effect is the same for all. If one makes little difference compared to the others at least you have it narrowed down t what cylinder. You did check the firing order right? How much did you have to move the distributor to go from the 8 to 6 degrees it should have been very small amount. You might check for a spun damper or the wrong one if it never ran right. If it has been over 10 or 20k miles you might take a look at the cap rotor and wires carbon track in the cap or a burn between rotor and distributor shaft is not uncommon..
Dave

 

The car had sat for 10 years, The Sending unit Had rusted off Inside the tank. I bought an used Sending unit and a new fuel pump cleaned the tank by sucking out the fuel, After the tank was dry I use a small wet vac to clean out any dry rust particals. I replaced the fuel filter. put in some new fuel with a small can of sea foam. The car started But ran rough. My intent was to just get the car home.

I drover the car about ten Miles, Front brakes froze, I had the car wrecker to the house. I fixed the front brakes, Installed new Plugs and wires, cap and rotor. I recleaned the tank with same procedure.

it ran very Strong With No spark knock. With in a few day It was idling rough again. I decide instead of cleaning the tank with A wet vac I would remove it. I removed the tank cleaned with a pressure washer.

I wanted to clean The entire fuel system to get rid of any Rust throughout. I figured the injectors would be a part of that process.

I tokk the system all the way down, I also replaced the mainfold gaskets becasue on was leaking anti freeze. When I Installed i use the right stuff at the ends of the Mainfiold, felpro intake gaskets, I cleand the fuel rail And replaced all of the orings, I order FI from Jon At FIC, Bosh 3, I slo install Another Fuel Pump to be sure of no trash, and fuel filter.I reinstalled the fuel rail, Runners and plenum, I have double check Every Vacum line, Each one is in place No cracks, No leaks 40PSI at the rail. 20In of vacum At in idle, Solid Steady.

I have checked every Plug, I took the cap Off the car And Checked No burns ,No cracks, the wires a re new Ihave have look them up and down But dont see anything.

From My understanding the knock sensor will not make a dirence unpluged untill 190 degrees, It is plugged in but the car will miss a 1300 rpm Just after starting, it dosnt seem to miss at the higher rpm, but then its down on power, and sprk knocks.

I will try the spay test and Uhnplugging the Injectors, I wonder if the Control Mod, or the coil could be bad?

 

Excuse my spelling I think faster than i type....

 

EGR sensor unplugged: That solve the miss off Idle, But its still spark Knocking really BAd, Still looking......

 

im having the same prob. mine is a 90 mod . sat for 5 years cahnged every thing also even the coil . it will idel fine then all at once start cutting out . then smoth out same way driving down the road when you find the prob please post it need help bad.

 

Im thinking about replacing The distributor, Or at least the control module, Is the 90 an L98 also?


Did you check the fuel pump in the tank, Mine rusted completly off, No joke I mean the sending unit just rusted off. there is also a screen filter in side the tank on the end of the fuel pump.

 

How old are those wires anyhow? They're rated for 60,000 miles maximum service life (O.E.M.) and these HEI ignition equipped cars are really sensitive to bad wires.

Even a microscopic hole in just one of them can throw your spark off kilter.

Open your hood at night or in a dark area of your garage, remove the hood lamp fuse, then start the engine. Look closely at the plug and coil wires. If you see bluish white sparks or electrical creeply crawlies arcing along your wires, you know you have a bad set.

If that doesn't do it, you can mist the wires down with water from a spray bottle to reveal any electrical gremlins, too.

 

My wires are new or about 1000 miles old I guess one could be bad. I will try the Night thing, I did unplug one injector at a time and the # 3 clyinder made the least diffrence, but that was at idle.

 

Have you checked/replaced the fuel filter ? I see you said replaced filter.... just trying to be sure you replaced the inline filter and not just the one attached to the sender/pump assembly.