Interpreting Scan tool data

[tomtom72]

Hi guys, I borrowed a snap-on scan tool. I don't know what to do with the data. In my 90 Z's shop manual there is a page, 6E3-A-14, that has an example of what a normal 90Z's data should look like. I used Gordon's jumpers to look for codes in the ECM and CCM & didn't find any.

The scan tool said there were "history" codes H46 & H54. The scan tool said there were no current codes. I wrote down all the data that the tool gave while the motor was running in closed loop.
TPS = .54v angle = 0%
Left Int. =107 Right Int. = 126 to 131 think this is "counts" Helm says "varies
spark adv. = 8* Helm says= 0*
left BLM = 115 Right BLM = 126 Helm says 118 - 138
BLM cell =4 Is this = Block Learn Cell, Helm says = 0.
Battery V = 13.4 Helm says = 13.5 to 14.5
Fuel pump V = 13.4 and the 2* fuel pump = on. I don't get that, H2O = 219*
MAT = 109*
Cross Count, left=12 right=0 to 1
BPW, left=3.8 ms right=4.3 ms
MAP v=1.32 to 1.34 Kpa=34

The snap-on tool seems to use different language than the page in the Helm book, so I'm lost. The car smells lean and has a miss at idle and up thru the rpm range. Any light thrown my way would be appreciated.
Thanks,
Tom

[ZR1 MK]

Your left side fuel metering is too far off scale. The integrator (short term) and block learn (long term) ideal is 128. Block learn can go off scale and have the integrator compensate (add or substract fuel) as shown by a 128, but with a 107 integrator reading, you have a problem that the system is not able to compensate for and requires repair.
Does the oxygen senor reading mv go from approx 50-850 in a fast manner? If not, it could be a failing sensor, but I suspect its something else.

[tomtom72]

Thanks Mike! First for instructing me on "long term" & "short term".
O2 mv readings were:
Left O2 = 100 to 700
Right O2 = 93 to 700+
I don't know how fast they were changing. I didn't know to pay attention but I remember the right reading was changing almost too fast for me to take down numbers. The left one was changing slowly so I could keep up.

I forgot to include those #'s because I didn't know that they were important. Sorry.

Thanks for the help,
Tom

[ZR1 MK]

The Corvette manual gives descriptions of your monitiored info. The latest Corvette Fever magazine also has a technical article to help you understand many of the items you mention.
You have a rich condition on the left side. Reference the codes and diagnosis as outlined in the manual. The actual oxygen sensor readings are good when you dont have time to actualy read them. The integrator and block learn will proces the info to read.

[tomtom72]

Thank you again, Mike! Okay first I will look up rich conditions and see those diagnostic charts. Second I will go to Corvette Fever and see about an online subscription.

Thank you for the time you took to help me out! I've been away for 20 yrs and the Z is too much technology for me to swallow this quickly. A 72 LT-1 was such a simple car comparred to this marvel.

Thanks again!
Tom

[ZR1 MK]

I am always glad to help. I know how you feel as my previous car was a 1970 Z28 and the ZR1 is my first Corvette.

[tomtom72]

Hi Guys, I would like to put a result for this thread. Also as I'm a rookie these threads are like school to me, it's where I learn about a ZR-1. It always is nice to see a conclusion to a problem. It makes the lesson more complete.

I learned from a professional that my "miss" is the result of bad injectors. Exactly how many are not known at this point. Once the tear down is done I'll have an answer to that. I'm replacing all of them anyway so as not to wait for more to fail.

Thanks to all who offered their effort to help me out with ZRology-1.

Tom

I'm adding this for all the for all the rookie Z owners, like me, that don't know much about electronic engine controls (EEC systems) and FI. Okay you detect a slight miss and it gets pretty bad in a few minutes & the water temp is normal, hot. You park it cause it smells lean & is really missing & shaking & won't go when you give it some gas. It cools down & you run down the plugs & you check for spark & do a fuel pressure check and you come up good on all that. You have no SES light & no codes if you do the ALDL short thing. You notice if the car is stone cold the miss is barely there, still smells lean. Once it gets hot the miss is big time. If I knew something the scan data would have tipped me to bad injectors. If you don't have a scanner get it scanned by someone. If you can afford a scanner it's worth buying. Bad injector coils get worse as the motor gets hotter = more miss. Hope this helps some one down the road. Oh, I had no warning. It was fine one second and the next the miss showed up. Tom

[Jim Jones]

Tom it looks like we have the same problem. My car was missing and I was hoping I just had a bad spark plug. So I got some new plugs (Denso IT16) and changed all of them. You have to be some kind of magician to get to number 8!! Well, I discovered that six of my plugs were fouled and I had a sneaking suspicion that it might be my injectors. So I took the car to a mechanic I trust, he worked on the car for the original owner, (I'm 3rd) and he told me that I had eight bad injectors and four that were going bad. YIKES!! I told him to change them all. I was going to attempt it, but we were hoping to take the car to Nashville this Friday and if I tried to do it, well, being a rookie as well, it would've taken me a little longer.

Jim

[tomtom72]

Hi Jim, Maybe I should rename this thread.
The guy I took mine to said he had never changed so many early C4 injectors as he has been doing this year. He said that 90% of all the C4's he has done had bad coils and that the injectors were OE on all the cars he has done. He was amazed at first & did some research & ran across our site & read the thing about the early multi-tech coils not being designed with alcohol as an additive in mind.

Glad you found your problem & everything is Okay!

Tom