Did fuel injector cleaner cause problem?

[Lawdawg]

My 8500 mile Z had been running outstanding until recently.
While in the process of buying fuel at a local gas station I noticed a bottle of fuel injector cleaner on the shelf and thought to myself "You know, my Z has sat around quite a bit for many years". "Why don't I dump one of these bottles in to clean those injectors out".
About half way through the tank later that week, I noticed that after firing the car up it wanted to bogg or stumble at low rpm. If the RPM's drop down to low in high gear, same thing. Once I give it some juice, It goes away. The problem comes and goes and does not seem to affect the cars performance. The car still averaged 23MPG on a trip to the Keys last week. I also have had NO SES warning light.
Now it appears I have another issue. I'm hearing the dreaded rattle rattle from under the car in first gear along with the hum at low RPM when taking off. When the engine comes to a stop, the entire symphony ends to the rattling sound like that of a diesel motor.
Could these issues be connected? Am I losing my mind? (YES!) After searching other threads, it sounds like a couple of possibilities. Bad injectors, coils, ECM, or DM flywheel (at 8500 miles I really didn't expect flywheel issues)
Not being mechanical if you catch my drift, I checked the only thing I could figure out how to, the MAP sensor plug. Surprise! My life just isn't that easy, it was plugged in tight.
Is it possible that this entire sequence of events started with a little bottle of fuel injector cleaner, or am I bringing Lee Harvey Oswald back from the dead to take the rap again?
Do you think that one of my local Florida Chevy dealers will be able to diagnose the problem, or am I gonna have to drive to Georgia to see Arron Scott at SG corvettes?
Lastly will the car be safe to drive until the issue is addressed since there have been no warning lights?
Thanks in advance, Lawdawg.

[Z Factor]

Well it could be more than one issue but you would not be the first person to dump fuel injector cleaner into a ZR-1 and experience problems as a result. However the good news is that your concern about the flywheel is probably unfounded as a poor running LT5 can cause it to sound bad.

As to a Chevy dealer being able to properly diagnosis the problem, I'd say it is possible but unlikely. My guess is that you will need to replace the injectors, but before you do anything you need to have a knowledgeable person look at it. Aaron would be an excellent choice, but of course he is a decent distance away. I'd call him and see what his thoughts are.
There is a guy down in Miami that is very good, but I do not know if he has the time since he is so busy. . I can check with him for you and see what his schedule is like, so just let me know.

[tomtom72]

L'dawg, When you checked the MAP sensor you checked the electrical plug or you checked the plug and the hose?

The issue could be just coincidence although injector snake oil stuff is not advised...only the Techron stuff from Chevron I was told by a GM tech that that is what GM sells over the parts counter in a rebox.

Ya gotta pull the SES DTC(trouble code) & post up, or look it up if ya have a FSM(by Helm). If ya have or know some one with a scan tool with the correct software pkg for your yr Z you could run a scan and compare your data to the data in the Helm FSM. Section 6E, "Emissions and Driveability" chapter is where the codes are listed and the section has a page with what the scan data of a normal LT5 looks like in closed loop.

Usually he early 90 thru 92(?) injectors are the most problematic...they were designed before the ethanol was added to the fuel. So if you're in that group then the injectors are a prime suspect. The later cars seem to be less susceptable to the ethanol. Only thing with failing/failed injectors: the effects don't go away off idle....they can cause a miss but it's permanent till r & r is done. There are two modes of inj failure: coil shorts and nozzle junk. Shorts cause a non firing = lean cylinder. Junk can be either lean or rich because the junk disturbes the spray pattern....neither condition will necessarily set a "code" (DTC) because the injectors are monitored indirectly by the ECM...via the O2 sensors mostly.

The thing is if your miss is real & only at or just off idle speed then I would ask if it gets worse as the car gets to proper coolant temp? It's kind of okay when stone cold? It's there when cold but gets worse as she warms up? All those point to injector coil shorting....in that scenario the injector's short will get worse the more heat gets to the coil and that's the give-away to shorted coils, the miss doesn't go away rather it gets worse. If it is injectors it will get much worse as time passes...the miss that is.

I would also do some looking at all your vacuum connections and pull the plugs for inspection, oh and do a spark test while you're there. The more you can eliminate in the absence of a scan tool the further all of us might have some ideas to pass along. The scan makes it easy but diagnostics can be done without one....it's just back to basics. Ya know does it smell rich or lean, the fuel filter is new, the PCV's are good, the vac connections are all in place & there is no sucking noises, Your vac gauge says it's not lean or rich. You get the idea, right? Oh, yea the spark test will help you eliminate the wires and coils...ya know pull one at a time when shes at idle?

Sorry to be so long winded about this!

Good luck & post up!
Tom

[tccrab]

If your Z is a 90-92 most probable cause is fuel injectors.
Been there, done that.
If your Z is a 93-95, could be plugs, wires, coils.

Start and warm up your car until in closed loop. Pull the plug wires carefully one at a time and listen to the sound of engine. The engine should stumble and miss and sound different when you pull a working wire.
When you pull a plug wire and the engine sounds the same, there's your miss.
Coil pack problems usually cause misses to come in pairs, so if you've got two cylinders that are missing then it could be a coil going bad.
It could still be fuel injectors.

Are you mechanical at all? Do you have a Helms manual?
We can help you figure this out, but it does take a little basic knowledge of engines.

TomC
'90ZR1 #792

[Lawdawg]

Thanks for all of the information so far. I have since checked all of the plugs, connections, and fittings and have found no issues. The car is a 1991, so problems with injectors along with fuel/injector cleaner alcohol content seems like a possible culprit.

The condition seems to really present itself when the motor is cold and not up to temp. The problem is when the sputtering or bogging stops, the flywheel rattle continues at idle or when you shut her down.

I dont know, maybe a fuel pump or filter?

I dont have a scaner, but I will attempt to do a spark test next. I should have paid attention in shop class when I was younger, I'm not certain I even know what I'm looking for. Sorry guys, I just like to drive fast!

Z-Factor, do me a favor and check with your contact in Miami about him being able to take a look at it. I had planned to take it to Roger at Horsepower Sales in Pompano for a fidanza, ceramic clutch, and 3:91s, but wonder if I should wait to have this issue resolved first.

[40th#381]

I use the Redline fuel cleaner all the time in my 93. Th only time it ran bad the O2s needed changed.

Jan

[Lawdawg]

Ok just got done pulling the plugs and this is what happened.

I started with the plug on the driver side closest to the radiator and worked toward the windshield.

1st plug-faint sparking sounds, very slight skip in motor sound or idle.

2nd plug-faint sparking sounds, very slight skip in motor sound or idle.

3rd plug-once plug pulled a lot of sparking sounds untill plug completely out and away from motor, very slight skip in idle.

4th plug-once plug pulled a lot of sparking sounds untill plug completely out and away from motor, very slight skip in idle.

I then moved to the passenger side closest to the radiator and worked toward the windshield.

1st plug-once plug pulled a lot of sparking sounds untill plug completely out and away from motor, very slight skip in idle.

2nd plug-faint sparking sounds, very pronounced skip in motor sound and idle.

3rd plug-once plug pulled a lot of sparking sounds untill plug completely out and away from motor, very slight skip in idle.

4th plug-once plug pulled a lot of sparking sounds untill plug completely out and away from motor, very slight skip in idle.

[tccrab]

Lawdawg:

This is encouraging news.
It would appear that you're getting spark and fuel to each cylinder. This would infer that the fuel injectors are at least partially working.
The amount of fuel and spark are critical.
The variance in the spark could be indicitive of potential coil problems, but remember, spark plug wires have internal resistance so the shorter the wire the less voltage drop, thus the greater the spark.
Your LT5 uses "Waste Spark" ignition system where two cylinders are sparked by one coil.
Use your volt meter and measure the coil pairs from spark plug end to spark plug end, the pairs are:
1/6
2/3
4/7
5/8
They should measure around 20k ohms. What you are looking for are large differences. Obviously the shorter spark plug wires will have less resistance, so expect a variance, but not a lot.
If a coil pack is failing, it will be fairly obvious.

Good luck!

TomC
'90ZR1 #792

[ckulchar]

Is there a certain tool to remove the spark plug boot from the plug? If not, should I just rotate the boot slightly and pull gently?
Thanks

[Peaven]

Originally Posted by ckulchar

Is there a certain tool to remove the spark plug boot from the plug? If not, should I just rotate the boot slightly and pull gently?
Thanks

That's how I do it Charley, it works fine....although it probably doesn't take much to affect 13+ yr old plug wires, but that's another issue.