I need a suggestion on if I should replace my injector #4 or not...

My car failed emissions so I took it to a shop that a family friend recommended. They scoped it and found that some of the cylinders didnt have much hydrocarbon change when shutting off the spark, especially #4. Anyways they recommended trying their on-car injector/plenum recirculation cleaner to try and clean them. They scoped the car again and it cleaned up all the injectors except #4 which seemed to be worse. They took it through the aircare test for me for free and it barely failed hydrocarbons on the driving test.

Before taking the car through aircare again the next day I took out the #4 plug (what a bitch to get at) and it seemed just a bit brown but fine. I replaced it anyway and the car seemed to drive the same. Anyways I took it through aircare again twice (with the #4 injector unplugged and a small piece of hose on the idle screw to turn up the idle a bit) and gave up after that. It would either fail CO at idle or HC when driving.

My question is: is my #4 injector for sure screwed? If so, what should I replace it with? And how do I tell what kind of injectors I already have? I've heard taking apart the plenum is a big job. I'm sure I can find information in these forums on how to do it, but should I let a shop do it for me if I've never attempted something like this?

Thanks for any help, its much appreciated.

-Dave

 

Pulling apart everything to get to it is a pain but its not the end of the world i had to do it yesterday. The easiest way to test if the injector is dead is to get a multimeter or a ohms meter (if you get the multimeter you will just use the ohms part of it) and all you do is set it to a low ohms setting and attach the leads of the meter to the terminals oh the injector. Test them all and chances are if there is a bad injector they will all have the same reading except for one. The test is super easy to do you can do it with everything in the car you just have to pop off the cap for the injector and youll be able to do it right there. As far as replacing an injector id do it your self if you have some patience and basic mechanical ability. I would have no problem either explaining all of this better or talking you through doing an injector swap if you needed it.

 

Thank you my man. I will do the ohm test on all of the injectors tomorrow morning. What if the injector is just really dirty, will it still be noticable on the meter? I think I will do the work myself since I have time on my hands and I don't think I'll need any special tools. Thanks for the offer to help with the explaination of the process. If I decide to do it I'm sure I'll need some specifics. Thanks again.

-Dave

 

That's a good start. The resistance test will help reveal if an injector has a failed/weak solenoid. However, that doesn't necessarily reveal anything about the injector flow rate nor the spray pattern. An injector with a good coil but a clogged inlet screen still won't flow poperly. A worn pintle tip can still leak or cause a poor spray pattern, even if the coil resistance is perfect. Electrical tests on injectors are necessary to determine if the injectors CAN work properly, but there are other factors involved that will determine if an injector WILL work properly. Don't bet the bankroll solely on a resistance test.

As for the on-car cleaning, I've only had one experience with that, and it wasn't very successful. The only thing that got cleaned was my wallet. I ended up removing the injectors, sending them off for cleaning and flow matching, and enjoying much better performance as a result. One of the injectors was still 38% below the base flow rate AFTER the on-car cleaning. That's not just a little difference. You probably can't really blame the shop. They tried to do the best they could with what they have to work with. Most customers don't want to wait a week to get the injectors properly serviced, so they're left with the "Genie-in-a-Bottle" solutions.

Did the shop report the fuel pressure and pressure drop after shut-down? Did you get results of a cylinder power balance test? Cylinder leakage test? Anything but a bill? Some of that information could be very helpful.

 

I took the ohm readings of my injectors. Here's what I got:

#1: 16.5
#2: 16.4
#3: 16.5
#4: 9.1
#5: 16.7
#6: 16.6
#7: 16.7
#8: 16.7

Looks like #4 is failing? Should I buy just one injector and replace that one? What kind do I buy? I'm on a tight budget but of course I also want my car to run well.

Vader: I got a bunch of sheets with before and after "scopes" of the engine. I think the main thing they did was disable one spark at a time and they recorded RPM change, HC change, CO change, O2 change, and CO2 change for each cylinder. They also did a relative compression test which showed all cylinders at 100 except #4 at 98 and #6 at 96.

 

yup then it looks like #4 is dieing. Replace it and you should have a noticeable power improvement in your car and it should run a lot smoother. Basically all you have to do is remove all of the upper intake ie plenum tb and intake runners. You dont have to remove the intake runners but it makes 2 of the four fuel rail bolts a lot easier to get to. I think its actually possible if you just unbolted the intake runners you could pull it all off in one piece (i realized that after i had it apart ) Anyways once you get down to the fuel rail its 4 bolts then the thing lifts right up (it takes some coaxing because the injectors seal i used a screw driver to pry it up) and then you just have to fiddle with a little metal clip that holds the injector in. Its helpful to have someone help you while you do it just as an extra set of hands and the only necessary tools are a socket set. As for your budget problem injectors are expensive. A single one from the dealership ran me 200 canadian. not sure what your best/cheapest aftermarket solution would be but dont mix your injectors its just not the greatest either get one from a dealership or replace all 8. I'm sure someone will chime in with a good aftermarket set for cheap. If you have any other questions nows the time to ask.

 

Dave,

The #4 certainly looks like a failing operating coil. I'd get one replacement, make sure it's clean, and install it. If you're only replacing the #4 you don't have to completely disassemble the intake. As a matter of fact, you can leave teh runners on the left side it you want:



Notice that the fuel rails are removed and all injectors are gone in the photo. You would only have to loosen the left fuel rail bolts and remove the right ones to get the #4 out of there.

If you're not in a major rush, and can afford to have the car down for a week , you might want to consider having the injectors cleaned and flow matched. Of course, that won't help the failing coil on your #4, but you could match the set to the replacement injector. This would give you the option of getting a used injector from the salvage yard rather than buying new, then having them all cleaned - all for about the same price as a single new injector.

And if you opt for that process, you would have a few days wait time while the injectors are being cleaned/shipped to clean up the EGR valve and passages, possibly port the plenum, install or convert to an AFPR, and perform any other under-plenum modifications or service that might be warranted. At the very least, you'll want to clean up the EGR. And if the plenum has never been removed, at least match the gasket openings to the runners and clean up the area behind the throttle body, since the factory did so poorly at that. Those are basically no-cost procedures that can really have some benefits.

 

Wow. Thanks for all the great info guys. It sounds like its not that hard to get the fuel injectors out. I think I will buy a used (or few) 5235302 injectors from 87-88 in the classifieds. Will it be okay to mix and match my 89 injectors with those? If I go the used route I'll get them cleaned by Rich at Cruzin Performance.

About the removal of the injectors, do I need to disconnect the fuel rails? I'm not sure if I need to take necessary precautions on handling the fuel system. I'm also wondering about the gaskets. Can I use the old ones? Or should I be buying new ones? If so what do I need? Thanks a lot guys.

Thanks for those extra tips Vader about cleaning the EGR and possibly doing other things while its apart and I'm waiting. I'll have to do some searches about AFPR's and porting plenums. What do you mean by cleaning up the area behind the throttle body?

All the help is very appreciated, makes me happy to own a 3rd gen. I've been drooling over 96-97 WS6's recently, but no money for that.

Thanks.

-Dave

 

You'll have to get new gaskets. You should also plan on getting some anti seize compound.

Depressurize the fuel rails and remove the fuel pump/ECM fuse for safety.

The area behind the throttle body has some restriction. If you don't so any other porting, at least remove the obstructions there.

If you plan to send injectors to Rich @ Cruzin' Performance, contact him before you ship. I know he's been quite busy lately, even after adding another injector service unit. Plan ahead so you don't have any surprizes

 

vader your such a helpful guy

 

ya i'm almost tempted to join the dark side