LOL!! I do not like MSD Wires. Never have!. I have friends that have them and they have less than good longevity out of them They dont fit as good as the GM red wires or last as long. I also use the GM Performance Red Wires exclusively!! Best bang for the buck!

The MSD wire rubber boot material is very soft and can tear very easily.

 

Went back and re gapped to .040, cleaned the MAF. and TB again just to make sure and also checked the pvc hose and vacuum lines. Nothing has changed. I appreciate all your guys reply’s so far, any input helps.

 

I went through this for a while & ended up installing a Halltech high flow MAF screen which almost entirely cured the problem. I found other Z owners were having similar problems when using an aftermarket air intake system. In my case I had a bad idle with occasional lean codes and very high long term fuel trims. Do what others have suggested especially looking everywhere for a vacuum leak from the MAF sensor to the throttle body. I would also check the PCV hoses, TB gasket and intake gaskets. I replaced my intake and TB gaskets for the hell of it since these cars are old now, but still had that bad, shaky idle. Another possible problem would be the injectors. Run a couple bottles of strong injector cleaner through one tank and occasionally run some Techron through to keep it clean. A decent scan tool will help alot in reading your ST and LT fuel trims not to mention 02 readings.

Steve

 

I can agree with this statement. My MSD wires a like 2 years old. One came loose and burned against the header, causing an arc jump...and missfire

 

I had the the same thing you are describing as well. Miss fire, changed plugs, checked the coils, checked the injectors, changed the wires, everything.. Finally gave up and took it to a local Corvette shop here locally that came highly recommended. This was the issue for me and may not be your issue. I ended up having a broken valve spring. It was the bee hive type and it broke. Had them replace it and fixed the issue. Like I said this may not be your issues. You are getting alot of good information from some knowledgeable guys here. Mine was a last resort because I got frustrated on taking it to the dealer. Happened again about 5 months later ended replacing them all. Hope this finds your issue. It didn't make no noise either which was kinda of puzzling.

 

Yes, could possibly be a broken spring but the 02-03 I believe had the highest failure rate... a compression test should maybe be in order...a quick “clear flood mode” crank could be done and listening for any variances in cranking speed or sound !!

 

Update: I borrowed some coil packs and changed them out. Still no change. Swapped in some new AC Delco plugs. Still no change. So I’m thinking I should try injectors next? I have a buddy with a bench tester/cleaner so I was thinking of giving them to him and see how that goes.

 

One thing I did notice is the car seems to run a little better with the MAF unplugged.

 

I can try a compression test but I had the valve covers off not to long and the valve springs looked fine.

 

Also, will have the chance to borrow a co workers Solus
snap-on scan tool. Anything in particular I should be looking at or for, while I have it? You guys mentioned fuel trim?

 

First I would look at the misfire counters and see if there are any misfires present. If your long term fuel trims are over 10% I would look for a vacuum leak first. When you raise the RPM to around 3000 RPM and you see the short term fuel trims decrease immediately and the long terms decrease (sometimes slower) that confirms a vacuum leak. If you do have a vacuum leak you can use short term fuel trims to help you find them...you can use Brake Kleen but propane is much safer...just spray around the intake manifold, vacuum lines, air intake bellow connections and if there is a vacuum leak the short terms will decrease suddenly !! ...a smoke machine is the gold standard to find vacuum leaks but it isn’t in every DIY’ers toolbox !!...if the Solus is capable of doing an injector balance test and you have a fuel pressure gauge you can see if you have any injector flow problems...if an injector is flowing less fuel during the test it’s most likely clogged but I would OHM out the injector also..,you can even try using a long screwdriver, touch it to each injector and putting the end of the screwdriver to your ear see if the injector is “clicking” !!

 

MMM ??...I think you said you cleaned your MAF but it may be a MAF sensor..,the Solus should be able to show MAF grams/second and frequency...here is a snap shot of my 01 at idle...compare them to yours !!

 

Okay, I will look into the smoke test or doing it with a propane torch. I’m gonna hook up a fuel pressure gauge to the rail this morning and see what I have there. I really appreciate the reply’s and screenshots for your diagnostic tool. You guys are awesome on here and super helpful

 

this is what the fuel trim looks like at a warm idle. Tried to do a balance test but not sure what to look for? The rail pressurizes and then the selected injector, pumps it out? Also the scanner shows no misfire so cross that off the list. Any other things to check? Will have this scanner for a couple days.

 

I just see Long Term Bank 2 at 9% and Short Term Bank 2 at 0%...the others are averages but looking at "averages" on Bank 2 LTFT's it's also 9%....basically the O2 is seeing a lean condition and adding fuel....this is only a small piece of the puzzle... what do the O2 sensors look like ??.... Now you said the car ran better with the MAF sensor disconnected....if you raise the idle to 3000 RPM for a few minutes with a bad MAF the Long Terms will INCREASE OR you have a fuel delivery issue...i.e. fuel pump,fuel filter or injectors...if Long Terms DECREASE you have a vacuum leak. See what you have !!...what does your MAF read at idle ??...4-6 grams/second is good...should go over 200 when you give it "the beans"...if the scan tool shows frequency it should be around 2,000 Hz at idle and around 12,000 at WOT...as far as injectors you can find the "fuel injector balance test" probably under "special functions". You'll need a fuel pressure gauge connected to the rail...the scan tool pressurizes the fuel rail, you note the PSI and then the tool will pulse the injector...you write down the fuel pressure it drops to...they should be all the same...it's even easier using a scope on the secondary ignition and seeing if you have a "lean misfire" looking at the waveform !!...if one or more have less of a drop that's your clogged or bad injector !!...also compare your MAP sensor to mine....4.5 psi at idle and 1.1 volts !!

 

When I did the injector test, the gauge went to about 58 psi and then the selected injector energized and sprayed out all the fuel until it hit 0 psi. They all dropped in the same amount of time but I thought it was suppose to hold the pressure? I also did look at the MAF and it did match the pictures you posted of your car. I also sprayed propane around the motor to try and find a vacuum leak and I still couldn’t find anything. Would an exhaust leak at the header cause this? My buddy pointed out the very back bolt on the driver side header is missing but it also doesn’t sound like it has an exhaust leak. I will try taking it up 3000 rpm while looking at the fuel trim tables when I get home and see what I find. Thanks

 

NO !!...shouldn't drop to 0 !!....mine went from 58 to 30 psi if I can remember...the scan tool controls the injector pulse in milliseconds during the test but it shouldn't let it drop to 0... 58-30 (mine) equals 28 psi drop so you are looking at a psi number not a time....what did your MAF show ??...you can use the Short Terms to find a leak...when the propane or Brake Kleen gets sucked into the leak the fuel trims will go more negative...say from 0 or -2 to -10 for instance...YES, an exhaust leak like that will cause a lean condition and drive up your Long Terms...that air is unmetered...increasing the RPM's like I mentioned will nail down the vacuum leak also !!

 

Yeah all 8 injectors dropped to 0 psi once the injector energized. I’ll take some more pictures of the MAF specs tonight and I didn’t have an extra person to look at the scanner while I was spraying the propane. I was listening for the change in idle.

 

QUESTION??? Is the engine modified at all?? Do you have the OEM injectors for that specific model year and engine?

Bill

 

That's right Bill !!...we don't know what size injectors these are....OK, scratch that test...LOL !!...oh, BTW, Chris...aka coupeguy2001 is up and running !!