Have had the SES light come on twice during the past month, both times I store a code 45. Happened both times on the tollway after half an hour of +70 MPH. Light goes out after ten seconds, so it's not a failing component.

Checked all the usual suspects:
Injectors all in spec.
EGR and EGR solenoid check out.
Fuel pressure is fine.
O2 is about a year old.

Somebody with a service manual tell me the flow chart to follow to figure this out, please...
:yesnod:


[Modified by Vette73, 9:21 PM 2/5/2002]

 

The flow chart will not help you unless you have acess to a scan tool. I would check to make sure there is no leak at the fuel pressure regulator just remove the vaccumn hose and start the engine and make sure there is no gas spraying out the vaccumn port. You will probably need to get a hold of a scan tool just to see if it is running rich. You will also need to check the MAP sensor and TPS both of wich if off can cause the engine to run rich. Canister purge solenoid can also give you excessive gas into the intake giving you a code 45. What's the fuel pressure a kinked return line will also send the fuel pressure high and give you the same problem.

David Fulcher

 

Vette73,

I just went through the same thing about 2 months ago. I changed the O2 sensor, checked the canister purge, checked all the fuel lines, checked fuel pressure, checked egr valve, checked the injectors. Everything was within specs according to my Snap-On scanner.

I was at the point of giving up when someone referred me to Rich at http://www.cruzinperformance.com/ If this guy doesn't walk on water, he surely floats. I spent 30 minutes on the phone with him and he diagnosed the problem. Bad injectors. I assured him they were all with tolerance on the ohm meter. Then he points out the the injectors on our 1990 model cars were bad to start with.

I changed injectors and the problem went away. I spoke with Rich several times and emailed a bunch as well. He told me he no longer sells OEM replacement injectors for the 1990 and even when I offered to pay him for his time he refused to take any money. What a saint!

My 90 has never run better :D Feel free to email me with a phone number and I'll be happy to give you all the details.

Pete


[Modified by Blazer, 7:00 AM 2/6/2002]

 

Yes it's true a shorted injector can give you a code 45 and the only true test for a shorted injector world be using the Kent More injector tester that checks the voltage drop across an operating injector, the ohms test is is only a quick and dirty test and is real good at finding a real bad injector. But I do disagree with the claim that the OEM injector was bad from the start the multech in jector that was used from 89 to 96 was a real good injector(of course there were different flow rates depending on engine), the problem with them is that many people have murdered them with in the fuel rail injector cleaners, the mutech injectore use gas cooled coiles which is a good thing for consistent operation, the problem is that a strong consentration of some cleaners can wash the insulation off the windings and short the injector out. That is why GM does not recomend the cleaning of these injectors that way. Probably one of the reason people do not get involved in selling these injectors is the cost they are about twice as much as anyother injector on the market. But from what I have seen they if treated correctly are one of the most dependable injector for a street car I have seen, they are so to speak self cleaning, and very consistence. I have know many people who have had their injectors checked and found them very consistence. I also find many, many cars with over 100,000 miles on them with never an injector problem. Now with this said if I knew someone had a case of shorted injectors would I recoment the replacement back to the OEM injector? That's a hard question for many reasons, they are very expensive so unless I knew they would be owning the car for another 100,000 miles or so there probable no real reason to spend the extra money, there is just too many other good injectors out there to just have to go back with the OEM injector, also the fuel compines are all using injector cleaners in them so dirty injectors in not the problem it once was. The other thing you get in is if one injector shorts out there is a good chance what ever may have caused that injector to short may also damange the rest. So gettin back to the point the only way to realy test your injectors is with the use of the Kent More injector tester, but then again when you look at things you can get a set of some replacement injectore for just over $200.00 and you can spend $50.00 after the injectors are removed to have them tested at some places, you can take the car somewere to have the injectors tested on the car but you would pay $70.00 to $100.00 for that it'a catch 22 so I can understand that if you are unable to find anyother cause for the code 45 it just might be the best thing to just replace the injectors and go from there............


David Fulcher

 

I agree with Blazer and David Fulcher a bad injector is a strong possibility. (David knows Corvettes and is a great resource).

Even though an injector may be within electrical specs, it still may be leaking or "working lazily" and dumping fuel into the engine. Take a reading of your spark plugs and you may find one or more that are running rich.

If you have access to a scan tool and the readings are out of spec this can be verified. The scan should show (at idle, hot, closed throttle, park or neutral, closed loop, accessories off) a BLM of 128 and cell of 0 or 1. A BLM 5% less than 128 indicates the computer is seeing a rich fuel situation and is compensating for it to get to the "ideal" fuel/air ratio of 14.7. A BLM of 128 (+/- 5%) should show at all RPM/load ranges if things are operating correctly. Less than 128 = Rich, Over 128 = Lean.

Even though they are supposedly better than pre 1990, IMHO the 1990 is nototrious for weak/bad injectors. It only takes one to throw a code. :( Apparently the insulation breaks down on the windings over time and/or the use of injector cleaners (not recommended) erodes the internals.

The reason that I am familiar with the problem is that I have two bad ones that need to be changed out as soon as the weather gets warmer. It was 6 deg F. last night and even though I can put some heat in the garage it isn't enough AND I don't like to heat the place when there is a possiblity of gasoline fumes. Come on spring!


[Modified by Wildride, 8:44 AM 2/6/2002]


[Modified by Wildride, 8:46 AM 2/6/2002]

 

Thank you all very much for your long, but helpful answers. This is the sort of thing I like to get here on the forum: good, solid information, rather than the "I once heard that you can check your [fill in the blank], but I'm not sure" sort of answers. This kind of informed answer is very helpful, and reflects the kind of camaraderie that Corvette owners share :D .

I have access to a ScanTool, and if I have time after doing the brakes on my daughter's Toyota this weekend, I'll hook it up and see what I can find out.

I have heard from other sources as well, that there was a known problem with the injectors used on the '90, but I've never seen a TSB on this. Is there one?

The original owner of my '90 had six of the original injectors replaced under warranty in 1991, and I did the last two about two years ago -- all GM replacement parts (light and dark grey, not black, but not exactly like the OEM injectors). I suppose that one or more of them could be going again, but I'll confirm this with the ScanTool.

Thanks again.

 

Just a few more thoughts:

1. The first hint that I had a problem was that the "Instant MPG" readout started to give an outrageously inflated MPG at steady cruise speeds. Readings like 45 to 60 MPG at a steady 65 MPH! This was apparently caused by the computer adjusting the fuel injector constant to compensate for the two failing injectors. As the two duds started going rich, the computer leaned out the remaining injectors in an attempt to maintain the proper overall fuel/air ratio. The MPG alogrithm measures the fuel injector constant vs. MPH to give a calculated Instant MPG readout.

After driving about 300 miles with the erroneous MPG reading the car finally threw a Code 45.

2. Stock GM injectors are very expensive. Many people are substituting Ford Motor Sports 24# injectors. Much cheaper and they apparently fit.

Accel markets a replacement injector that some users have had good luck with but there have been several posts regarding them leaking in the seat at the fuel rail. No judgement on my part on that one since I don't have any personal experience with them.

3. The work involved in changing out one injector is the same as doing all eight. I would suggest doing them all!

Good luck!!!!




[Modified by Wildride, 11:55 AM 2/8/2002]