All injectors ohm high?

[Exdamyankee]

Hi, hope I can get some guidance...

I've got a 95 Q45 with 130K. Started running rough and the check engine light came on. Per the posts here I pulled down the ECU and got the codes off it, it's throwing a 34 and a 51. Injector and knock sensor... I put a meter on the Knock sensor and injector connector pins. The knock sensors are not reading at all, and ALL the injectors are ohming out in the mid-50s, except for #1 which appears to be dead. Are all the injectors toast (or on the way to being toast), or is there something that could cause them all to read artificially high?

Thanks in advance!

regards,

Fred

[Q451990]

to NICO! I would check the #2 injector directly at it's connector to see if it still reads high... also make sure you have a fresh battery in your multimeter.

Good luck!

Heath

[SanCarlosQ45]

I know I had a problem with all the injectors ohming out at around 20 but nothing that high. It could be a combination of dirty harness connections and battery terminals causing the measurement to be higher. I think cleaning the battery terminals and the harness connectors solved the problem. The most simple explanation is your multimeter has problems, try a resistor that you know the value of and see if it reads right; or just try what Heath suggested.

Start by checking and cleaning all of the connectors. As an experiment try disconnecting #1 or #2 injector connector, clean it, reconnect them, and check the resistance through the harness.

[Exdamyankee]

Thanks for the welcome!

Well it's a brand new meter and battery, so unless the meter's calibration is way off something is adding ~40 ohms to the reading. I'll check it against a resistor of known value, that's my next move. Then clean up the terminals, they didn't look bad at all though. Then a direct check on #2. We shall see.

Thanks for the input!

I am dreading the thought of pulling the plenum to change out injector #1 and the knock sensors, though.

[SanCarlosQ45]

If its a new meter than its probably not that, I was figuring it was an old meter.

Injector #1, 2, and 8 can be changed without pulling the plenum. Looking at the engine from the front, the front right cylinder is #1 and the front left is #2. All cylinders after #2 are 4, 6, 8 and after #1 are 3, 5, 7. I've been really lucky as I have had to only replace #2 and #8, though I think I have another going bad under the plenum.



If you pull the plenum you are going to want to replace the injector and knock sensor sub-harness because it may be part of the problem. In fact some of the issues with the knock sensors not working is really just a bad harness.

[Exdamyankee]

I thought the plenum pull was a must-do. If I can replace the #1 injector without pulling the top off, I will be one very happy camper. I'll look at it tonight in the garage when I get home. Thanks!

[SanCarlosQ45]

You just pull the black plastic cover that has the power and torque ratings and then you can see #1 and #2. #3, 4, 5, 6, 7 require the intake be pulled.

[ericthered]

8 Injectors = $$$.
8 OEM Injectors = $$$$

What is very odd is that all of the injectors ohm at about the (very high) value. Usually my bad injectors are all over the place.
First double check in case you have a harness problem: I'd check #2 directly. If it ohms about the same as through the harness, your injectors are all toast, or you need a new ohm meter.

On my older Q (a 92 with much greater injector problems) I eventually stopped using OEM replacement injectors, I used a few remans instead for about $65. One of these eventually failed and was re-replaced.

I would change out #1 immediately (which you probably already have done) - one dead injector causes horrible engine roughness.

My experience is that if you have a high ohm reading now (say 22 ohms) the injector will eventually die. My advice is to replace them all after pulling the plenum if you are sure of your measurements.