I have a 1989 IROC-Z I can't seem to get it figured out. I have a generic question. All my injectors have 13.67 volts to them which is fine. I realize that I have 2 injector circuits a left and a right one. So by having the same voltage on all 4 left ones, and all 4 right ones should match. My question is if I have 1 bad injector both on the right side, and 1 bad injector on the left side would it make the car hard to start and run real bad. Basically my question is asking does the bad injector on each side mess up the ECM being able to do it's job. The injector ohm's are as follows cyl1 =16.1ohm's, cyl3 =16.1ohm's, cyl5 =1.8ohm's, cyl7 =16.1ohm's. The other side of motor is cyl2 =3.9ohm's, cyl4 =16.2ohm's, cyl6 =15.0ohm's, cyl8 =16.4ohm's.

 

Yes, you found a problem. The two injectors at 1.8 and 3.9 ohms are bad. And, it will cause the ECM to have fits trying to drive the other 6 injectors. Even though each bank of 4 injectors have their own wire to the ECM, there is only one driver inside of the ECM.

Your best bet is to purchase 8 new injectors such as the SVO's (Bosch) in the same flow rating as the stock ones. The other 6 Multecs will be going out soon enough.

RBob.

 

Thanks for the answer you just confirmed what I was suspecting. This car wouldn't start at all unless you primed it with gas first. Than it would run at an idle real rough, if you tried to give it throttle it would run out of gas almost instantly fall on it's face and die. You would have to reprime it with gas to get it to start again. If you didn't give it any throttle it would idle for ever. Your explaining that their is only one driver in the ECM for the 2 injector circuits comfirms my theory. When both sides or all the data input going to the ECM is corrupted due to bad injectors the car is going to act like this. I've had on injector go bad before but never 2 at the same time, heck the car barely runs when 1 injector is shorted out not to mention 2 at the same time. I tried explaining my theory to a friend who also works on cars but he has only dealt with plugged injectors, which is totally different. A plugged injector can have the proper ohms going threw it and just not be squirting gas. You can have 3 or 4 partially plugged injectors and a car will still start and may only have a slight miss or something. When an injector is shorted out or having the wrong ohms it sends the computer (ECM) into a frizzy, when you have 2 of them doing this at the same time on opposite side of the injector rails (or injector circuit 1 and 2) the car won't even run. This all makes sense when you consider that every other signal is either from the right side or the left that the ECM is seeing. When both sides are sending bad info to the ECM it doesn't have a chance to be able to run properly. This is a good lesson learned their is a BIG DIFFERENCE between a plugged injector and a bad injector. Bad injectors with a bad ohm reading effects the computers ability to input the information coming to it, thefore it can't do its job which is to make the car run!!! A plugged injector or even several plugged ones send no signal back to the ECM therfore the ECM runs and acts like normal and the car still runs. "I would just like to for the record make a personal statment about the Multec injectors which are the stock ones". THEY ARE JUNK this car has 60,000 miles on it and this will be the 3rd time that they have been serviced. I've noticed that the guys that have alot of miles on their cars don't seem to have any problems with the multec's, but the cars like this one that doesn't get driven as much have a very high failure rate. This might be something to think about when doing injectors on your car. I'm putting in a new set of Bosch 22# injectors tomarrow and getting away from the factory Multec ones. If anybody out there has a use for the remaining 6 good Multecs I have send me a PM and I'll send them to you for the shipping. This car gets driven around 3 to 4 thousand miles a year and doesn't seem to like them. I personally wouldn't install used injectors in my car but not all people can afford a new set, and if you are trying to get by until you can get a new set or your car has a ton of miles and you don't want to invest in a new set let me know these are FREE!!!
Best Regards: cabsales1

 

I have not quite figured out why the coils should go bad on these injectors.

My Z has only 37k miles and had one injector at 4.5 ohms and a fair variance high and low on a couple others.

Probably would have taken you up on the multecs a while back, but the 22# Bosch/Ford injectors sure are working nicely in mine.

 

Multecs: the insulation on the wire used for the windings breaks down causing them to short out. The use of any fuel injector cleaner, tank or via fuel rail, will hasten their demise.

Not using a fuel injector cleaner causes buildup with subsequent leakage. It's a no win situation with them.

RBob.

 

Well I put my new Bosch injectors in today and it runs like a new car again. I went with the Bosch 0280150561 D9B-22# injectors I got them from fiveomotorsport.com. These are the ones that everyone asks about being to short. They are 3 mm shorter than stock ones (around 3/8th of an inch), but they work great. When you install them you don't use the clips on the fuel rails. Put them in push them all the way to the bottom and forget about them. You don't need the clips anyway, there is 40# of fuel pressure allready pushing them down and they will stay there. I priced all over the internet and found fiveomotorsports to be the cheapest. They wanted $267.00 for the set of 8 which I thought was fair, then I looked on E-Bay and fiveomotorsports also sells there. They had them for $199.99 on E-Bay Buy-it-now Price but they didn't offer overnight shipping so I called them. They honered the $199.99 price and overnighted them to me in Iowa for $40.00. Which is cheap from California to Iowa, Regular shipping is $11.00. Just thought I would let people know what you can get a good set for if you price around. You can give anywhere from $1200.00 (DEALER) to $200.00 for a set and the average price is around $450.00. Anybody needing any I would suggest giving fiveomotorsports a call or check out there website. Anyway just wanted to let everyone who helped me figure this car out know that it is now running good. Thanks to all. cabsales1

 

I have EXACTLY the same problem. A little over 60, 000 miles and perennial injector problems. I was getting ready to pull my injectors and send them down to Cruizin Performance but maybe I should replace my stock ones as I don't drive my IROC that much. It's funny, you think your doing a good thing not racking up the miles and you end up causing yourself more problems. Thanks for the tips.

 

CrimsonDragon you might want to check out fiveomotorsports.com if you are getting new injectors. I put in the Bosch ones like I stated earlier in this post and I'm very happy with them. They run great and were the best ones I could find that are 22# ones like the stock ones. If you stay with the 22# ones you don't have to reprogram your prom or anything, just put them in and go. The Bosch ones are a little noisy when the engine is idleing and the hood is up, but they are performing well and I'm very pleased. cabsales1

 

Now the question is how do we maintain the Bosch injectors so we don't run into the same problems as the Multecs? Well, I thought I would give a call to Rich at Cruizin Performance in Big Rapids, Michigan and ask him his thoughts.
To start with Rich is a class act with more integrity, humor, and knowledge than anyone I have spoken with concerning my IROC in awhile. He has been with TGO for awhile and he himself owns a Third Gen. Rich gave me a great history lesson of our injectors and some fantastic advice.
First, is the Multecs need to be thrown away! It was a major design flaw in our cars and there are a series of Technical Service Bulletins out concerning them. It is not a matter of "if" they'll go bad but "when". He likes the Bosch injectors and recommended a few things for our cars to keep the injectors happy.
First - "Dry gas" once a year - it absorbs the moisture from our fuel system,;Second - "Sta-bil" by Gold Eagle, it is a fuel stabilizer that will keep the gas from going bad; Third - Change our fuel filter every 20,000 miles.
I then asked him if at any point we would need to pull the Bosch injectors and have them cleaned and he said barring a bad tank of gas that got past the filter, and the number of miles you and I put on our cars, we should be old and gray racing around in our wheelchairs by the time they'll need to be cleaned. The guy cracked me up!
Concerning the use of Injector Cleaners - Rich said he has a love/hate relationship as they do a combination of some good and some bad so he doesn't recommend them.
He had some great R&R advice that I am going to send over to the "Third Gen Tech Articles- TPI injector swap" thread.
Lastly, I wish Rich sold injectors because this is the guy you want to spend your money with.

 

He is definitely one of the "Best" IMO as well.....

 

Have had the same issues with my multicraps have burnt up 7 in two years im just now getting to 81,000 miles. Cant wait to have the cash for some bosch injectors, im sure the car will run a little smoother.

 

My injectors are reading around 18.5. all of them what does this mean? I know i need 16.5 but dont know if 18.5 is ok. By the way its a 355 TPI 1991

 

Holy crap. Nothing like bringing up a old thread...

Dunno what the spec is for sure, but 18.5 ohms probably isn't the issue if you are having any sort of problems with fueling.

AFAIK, when they go bad due to the insulation failing, the resistance gets lower not higher. Temperature can affect the resistance reading too, as can the resistance of the multimeter leads. Touch the probes together and see what the reading is. Anything more than 0 has to be subtracted from your actual injector measurement.

 

All,

Good thread. However I'm not sure how much stock I put in the whole 'ECM seeing bad.... on .. side' or the other. I am not positive, but I don't believe the ECM sees anything of the injectors but rather, DRIVES them, all four per rail at once. OBD II is different story.

Secondly, being a 1989 TPI, all four injectors on each rail are wired in parallel. Yes, two wires drive the left rail, and two drive the right. Although 3.4 Ohms is a big drop in resistance, wired in Parallel the mathmatical change isn't that great for the resistance over 4 injectors. You are right about the Multecs; they are indeed gar-bage, or will be soon.

 

I think the ECM will "see" (or perhaps "feel") the parallel resistance of the injectors. Whether or not it interprets the resistance as anything other than a load to drive depends, as you say, how sophisticated the OBD is.

Certainly in a parallel bank of four injectors (at best) the ECM might be able to tell how many injectors are out of resistance spec, but not which ones specifically.

I had no codes when mine started going bad, and still had no codes when the one was confirmed as way out of spec using a multimeter.

 

Are the disc type or pintle type injectors best??

 

I would like to know also. Are the disks not as loud as the pintle injectors

 

ok here is my issue it sounds just like yours but you guys can tell me what you think. My car a 1990 Iroc z 5.7 litre TPI car will start and run great untill it warms up then it starts to idle real ruff and if i try to apply throttle at all then it dies. i had coil, module, and cats all checked to no avail. I bought a multimeter and the injectors are as follows.(Cylender) (1)17.0 (3)17.2 (5)7.4 (7)17.2//// (2)17.2 (4)12.6 (6)16 (8)8.8 Seems like i got some bad ones i have also already changed the fuel pump in it because the individual i purchased it from said he already checked and it was bad but that didnt fix it so that was a well spent two days...need to fix it asap so please help if you can thanx

 

Yes, you have a few bad ones, replace all 8 so you
won't have to do it again for a while

 

ok injectors it is, i found some on ebay accel 19# i know thATS a little lower than stock 22# ones but the part number on them is 150819 will they still work? or would i be better off buying the 21# stock replacement ones that accel recomends??? THE ONLY REASON I ASK IS BECAUSE THE ONES I FOUND ON EBAY are aboput a hundred dollars cheaper than buying them fro m another website...let me know

 

Stay away from accel, get the ford injectors,
accel has had problems, they may have fixed
them but the yellow ones are bad.
Do a search and see what I mean
if your car is stock get the stock ones