For about two weeks now I've had a misfire problem that motivated me to purchase ECUTalk I was so proud of the way it ran for a few weeks there.. Then it started missing after it would warm up. Initially it would run fine cold and begin misfiring once it warmed up.

On Friday, I got ECUTalk installed. After seeing the information in Mattd1979's recent thread, I suspected an O2 sensor problem. One sensor (L) doesn't move much while (RH) swings around at 2000 RPM from .06 to .9 like a yo-yo.

It's been like drinking from a fire hydrant taking in all this Q information. I'll be pouring through it again tomorrow and the troubleshooting guide in the manual. I was able to use Nissan ScanTech to isolate the misfiring cylinders down to number 3 and 7. I can turn cylinders 3 and 7 off and it doesn't change the way it runs -- where if I turn off others -- I feel a big difference.

Are the O2 sensor readings just reporting the obvious misfire problem with 3 and 7 or did I just catch some symptoms of sensors that are past replacement time? These are the 91 factory sensors -- so they must be ripe for changing.

No diagnostic codes on ECUTalk. I did notice some Hex valued (8 bit) ECU codes that didn’t make it as out as a Fox-Fox but were picked up by ScanTech in the ECU Finder operation as:

Hex Dec
D9 – 217
DC – 220
EA – 234
EF - 239

I tried to find something about these codes -- but no match on decimal value for anything I can see.

Some screen shots that you all might recognise and pick up on the issue are listed below. I’ve been up at work or doing something with the Q for about 22 hours so far today – so if I’ve totally lost it – you know why.

Early ScanTech reading.



Where I isolated the misfire problem down to cylinders 3 and 7.



Another ScanTech reading as it was idling down from 2000 RPM.



Start the rev up to 2000 PRM.



Almost 2000 where RH is starting to jump



On the way back down (RH) stays up at .9 then starts moving down.



Moving down to .4 (RH) with (L) hanging around .2.



The ECU Finder Codes from lookup run below.

If you haven't already it's time to ohm test the injectors. If you're lucky and they ohm within range they could be just be sticky or partially plugged. A bottle off fuel system cleaner might give some temporary relief and put off the inevitable plenum removal.

goody90q45 wrote:If you haven't already it's time to ohm test the injectors. If you're lucky and they ohm within range they could be just be sticky or partially plugged. A bottle off fuel system cleaner might give some temporary relief and put off the inevitable plenum removal.

I'm with Goody
I was having the same problem and it was injectors 1 & 7. It may also be the coil or the plug, but ohm the injectors first...

To make sure I'm in the right place here.

The Engine control sub-harness-1 connectors are below.



The Ohm Test procedure is in box C in EF & EC-121 like below?

This works too. Unplug the 6 pin connector to measure KS resistance.

The O2 sensors are ignored at idle and I think at Wide Open Throttle. And like Matt said stage 3 of the NICO ECU ignores them and the Knock Sensors all the time.

This:
Hex Dec
D9 – 217
DC – 220
EA – 234
EF - 239

Is just how the laptop Consult communicates with the desired Control Unit, In this case the Engine Control Unit.

The vehicle doesn't fully warm up till it hits 176*F. Until then the Fast Idle Cam holds the throttle open just a tiny bit so the car can warm up as you can see from the Throttle Position Sensor voltage from fully cold ~.50 volts to fully warm .44 volts.

When replacing the injector use hex bolts instead of Philips head because they come out easier.

Thanks for all the help here today.

The readings are:

Knock Sensors - .552 and .553 (left to right) following the picture.

No change from the default open reading of 0.F on any injector pin. All have the same reading.

Ideas for the next testing step? I would like to listen to the injectors with a stethoscope -- but I don't think they are accessible.

Has anyone tried the "dry plug" technique with success?

OwnerCS wrote:.....Knock Sensors - .552 and .553 (left to right) following the picture.
No change from the default open reading of 0.F on any injector pin. All have the same reading.....

The KS are good but something is not right about the injector readings. They should have ohmed in the 13.0 range. How did you take the FI readings?

Basically the same way I tested the KS. A small jumper to the battery for the negative meter pin. Then a small alligator clip jumper lead to latch on to a plug pin that connects to the meter's red pin. When I first tested the FIs, I thought something was wrong with my approach or the new multimeter.

So then I just moved the small alligator clip over to the KS pins and got the readings which seemed reasonable. I tested the new meter on some 4 ohm car speakers I have in the garage -- and sure enough got near 4 ohm readings.

I agree it is strange and even stranger that I was able to test the KS readings.

I'll be glad to snap a picture of the setup if it will help.

For the FI it's the positive probe to the positive battery post, negative probe to the pin.

For the KS it's the negative probe to the negative battery post, positive probe to the pin.

It sounds like you did the KS properly but may not have switched the probes for the FI?

You've got it! Let me check it out..

Here goes

Cyl #

1 - 1041
8 - 1250
7 - 1141
3 - 1340
6 - 0521
5 - 1013
4 - 0588
2 - 0640

On the ones with the low numbers, it took over a minute to climb up to the max reading listed here. Also, the multimeter flashed the numbers and the numbers fluctuated up and down over a 0050 range.

Now it looks like your multimeter is set to the wrong range. There should be a setting that reads X1000 and your readings for the good injectors will be in the 12.X to 14.X range. If you have time pull the center plastic shroud and measure #1 and #2 FI directly on the injector pins until you get the right setting on your meter then go back and measure all 8 injectors at the main connector.

Something isn't reading correctly to get these results. Make sure you're on the ohm scale on your meter. Then put the red lead of your meter to the positive terminal of the battery, and the negative probe on each pin of the connector as shown above. You should get something around 14 ohms on the good ones. The meter will tend to jump some, but you should be able to get a general idea of where you are. As a test to make sure your meter is set correctly, you can disconnect the connector to either injector 1 or 2 and test them directly between the two pins with your meter leads.

Heath

Goody beat me to it! Great minds think alive...

Thank you for the GREAT information. I think I'm going to return this multimeter as it seems to shift between X settings regardless of the one that is selected. Do you prefer digital or analog?

Digital auto ranging is the easier to use but analog is recommended in some places for testing on the Q45 such as the Anti-Theft.

I got a Craftsmen multimeter, but be careful buying Craftsmen tools is addictive.

Sears frequently has fantastic sales on their digital multimeters- I think I got their $99 model for around 1/2 off if I recall correctly......comes in handy for all things car and house related, same with a swiss army knife!

+1 for Sears tools. I'm sure you guys already know about Craftsman Club member benefits -- but if you don't I've saved some serious money by being a member.

I'm back from exchanging the multimeter. Stay tuned.

Cyl #
1 - 14.42
8 - 18.44
7 - No Reading
3 - No Reading
6 - 18.35
5 - 16.57
4 - 18.85
2 - 18.92

The readings climb up to a high mark then settle.

I pulled the plastic shroud and found the plastic injector sockets to be brittle. The rubber wiring boots have hardened. I'm sure I will break something it I try to unplug the sockets.

Sounds like you'll need to call Joe and get a harness, and have to remove the plenum and test all the injectors directly. If the connectors are that brittle you must assume the wires are too...

OwnerCS wrote:Cyl #
1 - 14.42
8 - 18.44
7 - No Reading
3 - No Reading
6 - 18.35
5 - 16.57
4 - 18.85
2 - 18.92

The readings climb up to a high mark then settle.

I pulled the plastic shroud and found the plastic injector sockets to be brittle. The rubber wiring boots have hardened. I'm sure I will break something it I try to unplug the sockets.

At least your open readings correspond with the information you got from the software! If your meter is accurate with a fresh battery, you have a whole bunch of marginal injectors... You might consider replacing them all at the same time... anything over 14 ohms indicates an injector that's going out of spec. You will tend to see higher numbers when the injectors are hot vs. after sitting overnight. The failure mode is getting higher and higer resistance numbers until they fail open. Deatschwerks has a new "house brand" injector that might be worth researching. I am running aftermarket "Phase 2" style injectors by BWD since September of 2008 and have been very satisfied with them - although I have only driven it about 5000 miles in that period.

Here is my thread on the BWD injectors. g50-aftermarket-injector-alternative-t347484.html

Heath

Thanks Heath! Great information as always. The Ohm meter has a new battery as well as the Q had been sitting over night. Somehow I think all are in about the same (or soon to arrive) condition.

It looks like the DW adapter is available for $229. I noticed there are different versions of BWD (depends on color).

Looks like a set of DW 370s are $632 compared to $1312 for BWD blacks. Once I pull the plenum, I will replace everything under it that is not made of metal. Ya'll know how I like to NAIL something once I open the box for maintenance. In addition, I like to follow the herd, especially this one.


Ideas?

I would consider replacing your rails with the Phase II style if you go with the DW adapter, as well as replacing your harness with the 94-96 style. It just seems like less to go wrong to me.

Heath

Q451990 wrote:I would consider replacing your rails with the Phase II style if you go with the DW adapter, as well as replacing your harness with the 94-96 style. It just seems like less to go wrong to me.

Heath

True but I have heard that Phase two injectors have nearly the same failures as Phase one injectors. If it were me and money were no obstacle I would go with BWD. 5000 miles in two years? Are saving the car for Barret Jackson or Pebble Beach Heath?

I'm not sure why I drive the truck so much. I guess because it runs on cheap gas and is parked in the driveway instead of the garage... I never intended on the Q becoming a garage queen but she's becoming one.

Heath

If I pick up a used rail and harness for a 94-96 from a salvage yard, I also need to get the adapter kit from DW?

I'm running phase 2's right now and haven't had an issue. I can't even tell my car is running when i hit a red light. soooooooooo smooth. deatschwerks just had a sale on the phase 2 injectors and harnesses in june, but your a month late . I think the injectors were on sale for 499$ (645$ orig) and the harnesses/adapter kit were 199$ (249$ orig). The adapter kit is needed, Its just the harnesses, maybe yhou could pull the harnesses off the 94-96 but i think you need the spacers. The adapter kit comes with all you need, spacers harnesses/clips etc. Just need to pick yourself up some crimps or whatever you want to use. Also you probably want to make your own sleeves or wrap for the wires and crimps so no road crud gets on or in em. Also, your going to need a crap load of hoses, gaskets and some fuel line from IOS, and also you probably want to get rid of those wire clamps on all the hoses in there. Them things alone eat the ends of your hoses. your looking at about 1500$ in just parts. Another route you can take depending on how long you want the car is to just pull the injectors, get them tested and flowed, and put them back in there with new rings and pindle caps.
Good luck

BCC93QT wrote:Another route you can take depending on how long you want the car is to just pull the injectors, get them tested and flowed, and put them back in there with new rings and pindle caps.

Good luck

If you do the above do not just trust Deatsch Werks, pressure test the rails yourself before putting them in to make sure they did the work correctly. I have heard at least one bad story about this and its sad really.