no spark with tach wire hooked up???

[bigblack]

Ok here is the run down.I just got this car(89 corvette)when I test drove it I noticed a pinging.The owner said it had cheap gas.Anyway guy had just had new injectors,egr,and battery done.I bought car toped off the fuel with supreme(only 9 gal)+ onl bottle of 108 octane booster.Still pinging BAD.Under any acceleration.So I decided to drain out some more the fuel and put more supreme in.Got about half out of car and figured I would take a drive to burn off some more before refueling.Was driving at about 50 when the car just shut down.Pulled to the side of the road and it started right up.Car did this two more times in a 10 mile span.On the fourth time It would not restart.After sitting on the side of the road for 20 min I started cheching around and found I had No spark.I remember reading somewhere that someone said to try and unplug tach wire.I did and it started right up.I still have a bad ping.And now no tach.What does this mean???I also think I may have a egr problem,but that will be another post.(one thing at a time)

 

[vetteoz]

Short to ground on the tacho (wht ) wire.

Pinging
Check timing first

 

[bigblack]

Well I found my tach problem tonight.As you stated shorting problem.I guess the shop that did the injectors never bolted the capacitor thing back to where ever it is supose to be bolted up,because it was just stuffed behind the motor and fell down and grounded out.(sort of melted wire on the end)---Now back to my pinging problem.Yes I checked timing first(with timing wire disc) set it at 6 degree btdc.Chcked wires(look new) cap,rotor,plugs(autolite 26) look good.Still thinking it may have somthing to do with egr or maybe knock sensor.Oh yeah I also checked for vacum leaks too.Any ideas??

 

[vetteoz]

Problem I have is that if the KC was working it would be seeing the pinging and retarding the spark.The fact you are getting pinging means it is not working BUT that is not the cause of the ping.

Assume pinging is WOT?

Main causes of knocking ; going lean or to much spark.
Low fuel pressure? Spark control module faulty?
back to basics ; check fuel pressure first

 

[bigblack]

Ping is more at a light acc.Than wot.I see the valve on the fuel rail,but do I need a special gauge to check fuel presure??I agree with you on the ks.It seems to not be working,but should not be neede everytime I step on the gas....I rechecked the injectors last night,even though they where said to be new.They all test out at great.Man this thing is kicking my...

 

[TedC]

I would verify that the replaced injectors are the right size? ECM/prom expects 22 lb injectors. If you plug the EGR vacuum line, does it increase the pinging issue? A properly working EGR is key in controlling combustion temps (dilutes combustion mixture). Don't try and disable it long-term unless you reprogram the prom. For the alum head L98s (i.e. 1988/89), GM really cranked up the spark advance tables and are timing sensitive.

 

[bigblack]

How would i tell if they are the right injectors?I thing he had a chevy dealer do them.I pulled the egr off tonight.The tpi runners and body itself have lots of carbon.I tried to clean the intake port out where egr goes.Pulled out gobs of carbon.The egr looks new.It is a gm part number 17086078 and has 135 and 81n stamped on it.I noticed also tonight that the tpi has a hypertech air foil on the front of it.I guess I need to see what else in not stock.Hpoefully a good upper engine cleaning will get rid of the pinging.

 

[TedC]

If the Chevy dealership replaced these injectors you should be able to pull the service records using the VIN. In most cases, a dealership would use stock GM parts. In 1989, the L98 switched over to Multec injectors. They physically look different than prior years. You can masure resistance on each injector. They should measure around 16 ohms. That carbon buildup can prevent the EGR from closing properly or simply plug the port defeating the value of the EGR. You should not hear any ping on WOT. Now that you have the EGR off, you can unscrew the tip and clean the tip if it shows carbon buildup. Regarding the air foil, just make sure it is not blocking the throttle body ports. Some of the air foils I've seen don't fit properly. You can file down the air foil as required. Air foils only produce marginal gains in HP and are over rated.

 

[doublefoxed]

Have you scanned for any codes? To me it almost sounds like a
vacum leak since you don't get it at WOT.

 

[bigblack]

I checked for codes and get nothing.I have checked for vacm leaks using carb cleaner,and again trying staring fluid.Both with no results.I did check the injectors and they all had 15.9-16.1 oms.So I guess that is good.I did notice that with the egr off it is ptetty tough to get it to open(takes quite abit of vacum to unseat it.But like I said it looks like new and holds vacum so I hate to buy a new one if it is good.I am hoping it is just the carbon build up causing the pinging.