ECU/Knock Sensors/Fuel Injectors

[snobrder]

I followed the guide over at Q45.org about ohming the injectors and knock sensors and I got some interesting results. The reason I was suspicious is because when idling the car shakes alot and when accelerating in the 0-40 range it shakes as well but after about 45+ its fine. Last, for a v8 my preformance is quite ****ty overall, sluggish acceleration.

Injectors - 1 and 6 I got no signal at allInjector 2 was real high at about 44OhmsAll of the rest (3,4,5,7,8) Ohmed just right at about 11-13 each

Knock Sensors - I got no signal at all when I attempted to ohm them



I then pulled the ECU out and I got 5 slower pulses and 5 quicker pulses meaning everything is ok (55)...why isn't the ECU showing these problems?? Please help!

[maxnix]

OBD I is stupid.

Please complete your profiile. Only by your post could I deduce you were referencing a G50.

[snobrder]

Oh sorry haha, I'm new at this. Its an 1991 Infiniti Q45

[goody90q45]

......Injectors - 1 and 6 I got no signal at all injector 2 was real high at about 44Ohms. All of the rest (3,4,5,7,8) Ohmed just right at about 11-13 each. Please help!

If there's a lottery in your state tonight you should go buy a couple of tickets because so far you've been pretty lucky. #1 and #2 injectors are going to be real easy to change out and it will at least get you up to 7 cylinders and make your Q somewhat driveable. In fact you should recheck your readings on #1 and #2 injectors by removing the center plastic engine shroud and check the resistance directly on the injector pins.

.....Knock Sensors - I got no signal at all when I attempted to ohm them......

Forget the bit about the lottery. Your luck has run out. Not having knock sensors is not what is causing your problems but it is something you'll want to get fixed after you get the injectors sorted out. You'll be replacing the knock sensors and harness when you remove the plenum to replace injector #6.

I then pulled the ECU out and I got 5 slower pulses and 5 quicker pulses meaning everything is ok (55)...why isn't the ECU showing these problems?? Please help!

I suspect that you turned the screw one too many times and cleared the codes before you read them. The instructions in the FSM are a bit confusing and it's happened before (me). I'll save you the trouble and tell you that you will have code 34 (KS), 45 (injector failure) and 51 (circuit failure?). Seriously, check it again after driving for a bit and this time turn the screw just once and a second time to clear after you've read the codes.

Leave the ECU on the floorboard for now and get back to us when you get the data. Good luck.

[snobrder]

If there's a lottery in your state tonight you should go buy a couple of tickets because so far you've been pretty lucky. #1 and #2 injectors are going to be real easy to change out and it will at least get you up to 7 cylinders and make your Q somewhat driveable. In fact you should recheck your readings on #1 and #2 injectors by removing the center plastic engine shroud and check the resistance directly on the injector pins.

Ok I just removed the shroud and I got no signal at all from injector 1 or 2. I will be driving in a few and will report back soon...Thanks for your help

[snobrder]

Jeez maybe something is wrong with ECU now too because I went for a drive, turned the car off but put the key in the ignition how it should be. But i still have the 55 code. And to top it off the damn screw that holds all the wires and the blue part to the ECU it self broke put is still holding.

[thejapino]

I have a few early G50 ecu's for sale if you need one.

[email protected]

I'll send you one cheap if you find thats your problem.

[Scotte123]

Don't forget to check the fuel pump & FPCU. My 94 is running slow as well. I've been researching this site for a month and came to the conclusion my FP was failing. Read Tangalora's "how to", I'm getting ready to replace my FP and it was invaluable. I hope to add some pictures of the install to advance the cause (not really necesary though, she was very thorough).

[snobrder]

Grr....I keep getting the 55 code..this is what I do:-Take car for spin-Turn car off-Put key in and turn it to just before starting so the radio and electronics work.-Turn nob once on ECU and read codes.

[Q45tech]

No codes created for fuel system [pump or fpcu] pressure or flow rate.

[snobrder]

Can anyone tell me if I am doing this right?

Grr....I keep getting the 55 code..this is what I do:-Take car for spin-Turn car off-Put key in and turn it to just before starting so the radio and electronics work.-Turn nob once on ECU and read codes.

[elwesso]

Make sure when you turn the car on the CEL comes on (before you crank the car).. That says the ECU is online.. If it doesnt maybe thats whats causing your issues!

Sounds like you're dealing with typical Q.

[goody90q45]

Grr....I keep getting the 55 code..this is what I do:-Take car for spin-Turn car off-Put key in and turn it to just before starting so the radio and electronics work.-Turn nob once on ECU and read codes.

Can anyone tell me if I am doing this right?

With 2 dead injectors and dead KS you should have stored codes. Is the CEL illuminated on the dash?

Here's the sequence:> Make sure the ECU screw is in the full CCW position. If not, turn it CCW before turning on the ignition.> Turn the ignition to the ON position (the last stop before the starter comes on)> With the key on, the light inside ECU should be solid red.> Rotate the screw fully CW, wait 3 seconds, turn fully CCW.> Read the codes

> To reset: Turn screw fully CW, wait 3 seconds, turn screw fully CCW.> The red light will now be solid, rotate again and it should read 55. If you have dead injectors, bad KS and a continuous or intermittent CEL the codes should return after a few moments of driving.

Don't leave the ECU in the flashing position and start the engine. You need to rotate the screw one more time to clear the 55 code and get the light solid again (This may be what you're doing wrong?).

No codes created for fuel system [pump or fpcu] pressure or flow rate.

The fuel pump is a whole different issue that can be tackled next. With the trunk lid open are you hearing what sounds like a swarm of bees? It wouldn't be a bad idea to check you're fuel pressure but at this point replacing the 2 easy-to-get-to dead injectors and pulling codes seems like a good start. The engine will run a lot better on 7 cylinders than it will on 5.

[snobrder]

dammit man I don't know wtf is wrong. I have done the exact procedure that goody has said at least 5 times to no avail. I keep getting the 55 code. Also I noticed that not once have I seen the CEL, could there possibly be something wrong with my ECU because my 3 injectors definitely are dead and wouldn't that trigger a CEL? If it is any help the ECU says:Nissan Genuine Remanufactured Electronics Control Unit. And the Code on it is:a18-a21 p66k

[snobrder]

No ideas guys? Should I get a new ECU?

[maxnix]

I think you need to worry less about your ECU and more about your injectors and KS and harness first. By implication, that also means your under plenum hoses, gaskets, VC gaskets, and maybe plugs if they have 50K on them.

Repair what is know bad, then it is much easier to isolate remaining defective parts.

[snobrder]

I know for a fact that the KS and injectors are dead, I am about to order injectors for 1 and 2 as they are easy. Whats odd though is that not once have I ever seen a CEL come on.....This might be a longshot but Is it possible the previous owner did something to stop the CEL from coming on and stop the ECU from storing codes in order to sell it?

[snobrder]

Ok I just pulled the codes and I got 21 Ignition Signal Circuit...now what is this

[elwesso]

I think you are overestimating the power of OBDI.

KS wont throw a CEL, and honestly if you're not getting a KS code from the ECU than I doubt they're bad, my guess is you didnt have the VOM on the right range or you didnt perform the test right..

Injectors DONT throw a code.. Theres no electrical test for them (that'd be nice, wouldnt it!), theres only an INJECTOR LEAK code which is often very misleading because it just looks in differences between the 2 o2 sensors..

[Q451990]

No ideas guys? Should I get a new ECU?

I don't think so. The ECU will not illuminate the "check engine" light for knock sensors - ever. It might (but probably will not) turn it on for injectors.

ECU failure is very, very rare. I think I have heard of one... and that was due to a bad body repair that allowed rainwater to get to it. Maybe a second one caused to some kind of short under the hood.

My guess is that you're somehow clearing the codes before you get a chance to read them - but I haven't done that many code readings with the ECU, so I can't really critique your method...

Heath

[elwesso]

not real hard to fry ECU's if you switch wires on the MAF while replacing the connector!!

[96Qowner]

Or cut the MAF plug off with the ignition on, as one member did! Poof!

Or, a short in the harness by the wheelwell ...

It happens.

[BLACKonBLACK98]

i see we are having the same issues. my theory is forget what the obd says if you have first hand proof of something not working (seems to be the general consensus).

my other theory is if youhaver to remove the plenum for any reason you might as well swap everything youcan afford too.