martino

I have the same problem as many other people with the 1990 C4. No codes, yet poor idle, surge, all plugs black have black soot. It runs good cold but when hot, very poor. I did what everyone does, changed plugs, plug wires, distributor cap, MAP, O2, checked vacuum lines, Idle air valve, etc. Still same problem exists.....rough, unstable idle and surging when in drive. Does anyone have data readings of a 1990 ECM that is perfect, steady, runs good and idles great? I would like to compare and obtain advise.

Sam Lam

Have you checked the resistance of your injectors? Suggest you do this and post results. Spec is 16.5 +/-.3 ohms and all should be very close to the same resistance value. You may be surprised what you find

martino

Yes
#1 #2 and #3 are out of spec low. I did not think this was the only problem because all of the spark plugs look the same....all black powdery soot. The dealer quoted replacing all 8injectors. Quite an investment if this is not the problem. The dealer quoted 8 injector kits GM17112285 for $1137, plus 2 GM12508751 Gasket Kits for $42.56, labor $550, tax, = $1875.

Thank you for the advise.

Sam Lam

martino: Spending almost $2,000 to replace injectors is absolute, first class BS! You can buy new parts for about $300, gaskets for less than $50 and do the work yourself. If you have low injector resistance, you have a problem. Here is some info for you.

Email from Rich Jensen at Cruzin Performane (he has a good reputation on the forum for injector service):

-----Original Message-----
From: Rich Jensen [mailto:rich@cruzinperformance.com]
Sent: Wednesday, October 08, 2003 10:24 PM
To: ar
Subject: Re: Need Injector Help!!!


Hi Bob,

The problem you currently have is that from 1989 through 1991 on the L98 engines GM installed Multec injectors. These injectors have one of the highest failure rates of any injector ever installed. It's not a matter of "if" they are going to fail, it's simply a matter of "when" they will fail. That is why some of your injectors look differently than the others. Some of them have obviously already failed and were replaced. Because of their design they cannot be repaired so the only solution is to replace them.

You can try to find some of the same injectors to use as replacements however they will likely eventually fail also so a better alternative is to replace them with an aftermarket set of replacement injectors or find some of the earlier Rochester injectors that were used from 1986 though 1988 on the L98's. These were a Bosch design injector and they don't have the problems that the Multecs do.

I don't sell any injectors so I can't help with supplying replacements but if you do find a set of the earlier design injectors I can service those and they have a very good track record of long life and serviceability. The part numbers you would be looking for are: 1986 = 5235211, 1987 and 1988 = 5235302. These are the part numbers that are on the injectors themselves. They are not the part numbers that would be listed in a GM parts catalog.

Sorry to be the bearer of bad news but that's just the way the Multec injectors are.

Hope this helps. Let me know if you need more info or have additional questions.

Rich Jensen


Here is a GM Service Bulletin on shorted injectors (low resistance):



I would suggest you consder replacing the injectors. I have a procedure where you can do this yourself. I can suggest a source of replacement injectors that will cost about $300 for a matched set.

Let me know if you have questions on this.

Bob

RRT vette

If the injectors do not ohm close to each other, then they either need servicing or replacing. Looks like they will need replacing if they are the factory originals. Sam Lam is correct. It will cost no more than $400 if you replace them yourself and Sam even has a write up on how to do it. Purchase the parts and have a buddy help. The job goes much easier with help remembering where everthing goes back. Should take about half a day to remove and install if you don't spend extra time cleaning the removed parts.

Replacing the injectors would be my next step in figuing out the problem, since they are the problem or contributing to it.

martino

Thank you Bob and Rick,

Yes, I would like to know where I can get a match set of the recommended fuel injectors, gasket kit(s) and your procedure. I am certain that that is my best option to solve this problem. $350 is so much better than the Chevy Dealer's $2000 offer. What a rip-off.

Best Regards
Martin

Sam Lam

Martino: The procedure for removing the injectors without pulling the runners can be found in this document:

http://webpages.charter.net/buddiel/...al)%201-04.doc

I would look at the comments of NHCorvette in the following thread for a possible source of injectors.

http://forums.corvetteforum.com/show...post1560357682

Hope this info is helpful to you.

Bob

dorney7

I had the same issues with my 91 vette...you need new injectors ...all 8 of them !