90 misfire
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Instructor
Joined: Jun 2005
Posts: 135
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90 misfire
Follow up to thread I posted some time ago; my 90 runs fine until it gets warmed up, then stalls out/misfires when I get on it. CF member suggested I check resistance of injectors. I did this and 6 read 16-17 ohms (slightly higher when hot) but two were at 3-5 ohms. This would appear to be the problem?
My question has several parts.
Should I replace the injectors that are bad. What is the likelyhood that this is the problem? Should I replace all of them? I have no idea if these are the originals or not. What kind of injectors? I've seen where the Ford "pink tops"? are well received by CF members.
Second, I'd like to do this myself, but as I'm a "newbie" I'm concerned about taking this project on. Reading a few threads from this forum about the difficulties invovled, I guess that I must admit I'm concerned. Also, while I've got it apart, would like to do plugs and wires. Once again, it seems like the wires (from what I've read in CF) could be a big job.
I have a shop manual, the tools (or will get what I need), and a garage so it seems like I should go ahead and "get involved" with my 90 vette.
Would like a few opinions. I guess the worst that could happen is that I'd have to have it towed to someone who knows what they are doing.
Thanks for any and all comments.
My question has several parts.
Should I replace the injectors that are bad. What is the likelyhood that this is the problem? Should I replace all of them? I have no idea if these are the originals or not. What kind of injectors? I've seen where the Ford "pink tops"? are well received by CF members.
Second, I'd like to do this myself, but as I'm a "newbie" I'm concerned about taking this project on. Reading a few threads from this forum about the difficulties invovled, I guess that I must admit I'm concerned. Also, while I've got it apart, would like to do plugs and wires. Once again, it seems like the wires (from what I've read in CF) could be a big job.
I have a shop manual, the tools (or will get what I need), and a garage so it seems like I should go ahead and "get involved" with my 90 vette.
Would like a few opinions. I guess the worst that could happen is that I'd have to have it towed to someone who knows what they are doing.
Thanks for any and all comments.
Cruising
Joined: Jul 2006
Posts: 10
Likes: 0
I would be curious to hear opinons also.
I currently have been fighting the same issue on a 90 convertible. I have replaced the distributor module, computer, coil, tested TPS, MAP and all connections to the computer. Then finally decided to check injectors and I have 4 with 17 ohms, 1 with 1.9 ohms and 3 with 10 ohms.
Ken
I currently have been fighting the same issue on a 90 convertible. I have replaced the distributor module, computer, coil, tested TPS, MAP and all connections to the computer. Then finally decided to check injectors and I have 4 with 17 ohms, 1 with 1.9 ohms and 3 with 10 ohms.
Ken
Race Director
Joined: Aug 2000
Posts: 14,130
Likes: 7
Cruise-In II Veteran
Bad ohm readings on injectors,you should def replace anyways to rule out anymore possible problems.
I also suggest if theres a forum member nearby or somewhat close to you that has torn down the TPI before,give ya a hand and even make new friends doing so.
Its not hard at all,especially after youve done it a few times.The first time is toughest,so take digi pics,notes and etc of where everything goes.
Clean all bolt threads off and apply a small amount of antisieze to them when reinstall.Lube allthe lower injector O rings before reinstall of the rail into the intake manifold.
Just a side note...Another possible problem is a leaky egr valve.If its not closing or opening all the way,it may leak egr gasses into the engine while the car is warming up,causing stumbling and stalling...even though its not being commanded to circulate egr yet...not to be confused with misfires though.Just brought that up in case someone may confuse the term of a misfire or a stumble in explaining whats wrong.
I also suggest if theres a forum member nearby or somewhat close to you that has torn down the TPI before,give ya a hand and even make new friends doing so.
Its not hard at all,especially after youve done it a few times.The first time is toughest,so take digi pics,notes and etc of where everything goes.
Clean all bolt threads off and apply a small amount of antisieze to them when reinstall.Lube allthe lower injector O rings before reinstall of the rail into the intake manifold.
Just a side note...Another possible problem is a leaky egr valve.If its not closing or opening all the way,it may leak egr gasses into the engine while the car is warming up,causing stumbling and stalling...even though its not being commanded to circulate egr yet...not to be confused with misfires though.Just brought that up in case someone may confuse the term of a misfire or a stumble in explaining whats wrong.
Melting Slicks
Joined: Apr 2002
Posts: 2,118
Likes: 0
From: St. Charles, MO Route 66 Corvette Club
TJVETTE90: If your car has the original injectors they will look like these (sorry for the quality of the photo) parts.....which are GM Multec injectors:
I had problems with the Multecs on my 89 and here is a note from Rich Jensen at Cruzin Performance on Multec injectors:
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
The injectors can be easily changed out .....with some useful information. I have a two page Word document that you are welcome to have (and use) to change out the injectors without pulling the runners. It is too long to post here! I have tried to add this to the "tech section" and have not been successful. Send my your email addrress and I will forward the info to you and others who may want to use it. Be careful and do not drive the car with shorted injectors as this can damage the ECM. Low resistance indicates the degree of the shorted coils. Hope this is helpful.....and you will get through this.
I had problems with the Multecs on my 89 and here is a note from Rich Jensen at Cruzin Performance on Multec injectors:
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
The injectors can be easily changed out .....with some useful information. I have a two page Word document that you are welcome to have (and use) to change out the injectors without pulling the runners. It is too long to post here! I have tried to add this to the "tech section" and have not been successful. Send my your email addrress and I will forward the info to you and others who may want to use it. Be careful and do not drive the car with shorted injectors as this can damage the ECM. Low resistance indicates the degree of the shorted coils. Hope this is helpful.....and you will get through this.
Last edited by Sam Lam; Jul 6, 2006 at 06:22 AM.
Racer
Joined: Sep 2005
Posts: 385
Likes: 8
From: north branford ct
I had a couple of injectors that ohmed low and the car had a bad skip,so being new to cars with injection,I was a little scared about doing the job ,but with the help of these great guys on the forum I got it done and it is so smooth and feels like an extra 50 hp. A warning to you Have whoever you buy the injectors from test them for flow before you buy them,I got mine and tested for ohms which was ok,but that wont tell you if one is stuck--YEA YOU GUESSED IT one of mine was NG and I got to do it all over again--much easyer the 2nd time. Take pics and get a big piece of cardboard that you can draw out the injection system and punch holes in for all your bolts,and some small cups for the small stuff and clips--label the cups. Its amazing how fast you can forget where things go. do the wires and plugs when you have it apart it will be easyer. GOOD LUCK
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
Funny, I was thinking of Mudslide while I was reading your post. Something for you guys to think about, if you find 1 or 2 bad injectors, how many times do you want to do the job, cause the others won't be far behind. Replace all 8 now.
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Melting Slicks
Joined: Apr 2002
Posts: 2,118
Likes: 0
From: St. Charles, MO Route 66 Corvette Club
Ken: Congragulations.....you have survived Multec Disease! Were you using any injector cleaner prior to your injector problems? I began the use the Chevron Techtron cleaner and shortly I got the disease. I do not know if the two events are related.
Were you using any injector cleaner prior to your injector problems? I began the use the Chevron Techtron cleaner and shortly I got the disease. I do not know if the two events are related.
