ECM?

[GerryO]

OK, so my 1993 J30 has been running really great, until this morning.

It started easily enough, but idlled/ran very rough and the Check Engine light was ON - no blinking codes - just ON constantly, so I didn't even back the car out of the driveway and into the street.

I got gas a Shell station yesterday on the way home from work, so I cleaned-up and re-tightened the gas cap to produce no immediate improvements.

So I disconnected the battery and removed the ECM and the cover from one side - all was bone dry outside and inside and looked good - zero signs of corrosion.

I re-assembled and re-installed the thing to check codes in modes I and II. Mode I shows just the Check Engine light and the red LED ON constantly. Mode II is ZERO from either light at all. No flashing at all.

I disconnected the camshaft/cranshaft position sensor and the engine just cranked and would not start at all. Re-connected and the engine starts, idles rough and with the Check Engine and ECM LED lights still ON.

It's getting dark, so I figure I'll drive it around the block before parking it and coming back to it tomorrow. It starts and runs perfectly, and the Check Engine light is now OFF.

I pull into the driveway and bang on side of the ECM a bit and the engine shuts OFF. I restart the engine and it's still running fine and showing no codes, and bang on the thing again, but this time nothing happens. That's good.

Tomorrow I'll check for any leads on the circuit board that might be able to contact the cover and maybe put thin plastic sheet between the back of the board and the cover, plus I'll put a longer screw in one position that seems to function as a spacer. More to follow.

Any suggestions?

Modified by GerryO at 8:48 PM 3/15/2008
Modified by GerryO at 8:50 PM 3/15/2008

[fogged306]

Did you get it figured out?

If not possibly check the ground(s) for the ECM.

[GerryO]

Did you get it figured out?

If not possibly check the ground(s) for the ECM.

Hi,

Thank you for asking and for the logical suggestion. Might you know exactly where the ground connections are located?

I'd also posted in the Technical forum and gotten a few responses, mostly pertaining to cleaning the fuel system.

Yesterday:All was OK on the way to work this morning (about 7 miles of city streets).

This evening about a mile from home the Check Engine light came ON and the car ran rough and was under-powered.

Parked it in the driveway and disconnected a few injector connections one at a time, noticing that disconnecting one didn't make much difference in the way the engine started and ran. Disconnected and reconnected all six of 'em, including a number of other under the hood connectors, using dielectric grease too.

Re-connected them all, started the engine and the it ran normally again and the Check Engine light was OFF. Took a four or five mile test drive, stopping at two different stores, dumped in a bottle of fuel system cleaner, drove home and called it a night.

Tomorrow we'll see what sort of Groundhog Day deal I've got going, and will be changing the fuel filter.

Today:Full power (I think) to and from work with NO Check Engine light, and I also read this:

From Nissan:Due to the introduction of contamination resistant "pintle-less" fuel injectors, Nissan no longer recommends using fuel injector cleaners in vehicles with injectors of this design. Use of fuel injector cleaner on these vehicles, while providing little cleaning benefit, may cause corrosion of the fuel injector coil and eventual failure of the injector. Do not use fuel injector cleaner on the models listed in the chart or subsequent models with "pintle-less" injectors.

News to me and something more to worry about, and I witnessed an accident this evening that sort of put a damper on things. A shiny new black Crossfire ran a red light and was hit by a small week-old Mazda. I could have been me in my 1993 J30.

[fogged306]

I don't know offhand where the grounds are for the ECM on the J's, but its a safe bet that they're close-by the ECM itself. As far as the injectors, did the connections look corroded in any way when you took them off? If you have access to a noid light, that might help you out a lot in trying to see whats going on. I don't really think its an injector failure problem as much as it might be a missing input to the injectors.

I'm more leaning to an ECM problem if you said you gave it a whack and the car shut off. That would be a pretty big coincidence if it wasn't ECM related. Did you pull it apart and give it a look?

Your best bet in my opinion is to see if you can get access to a real diagnostic machine and plug the car in, that should give you some better insight as to what the problem is. If you don't pull any hard codes, it might be a bad ECM.

[GerryO]

I did have the ECM on the floor of the car at the time that I thumped it and have had it apart for a look.

All was very clean and dry, with zero signs of corrosion. I am considering pulling it out again in order to spray some connection cleaner on the rotating mode selection switch, and view and clear all stored codes.

The car is a 1993, so it's OBD1 and blinking lights is all that I'm going to see as far as codes go, and it is curious that when I've been able to view the stored codes, the engine has been running fine. I haven't been able to view any codes at all when the idle has been rough and performance has been sluggish, but this is with the Check Engine light is OFF.

To recap:Mode I - Check Engine light ON - rough idleMode II - Check Engine light OFF - no codes displayedMode I - Check Engine light OFF - smooth idleMode II - stored Code 11 (caused by trying to start with the Crankshaft/Camshaft Sensor disconnected = no go) and stored Code 51

Thanks, Gerry

[GerryO]

A bad run all the way, to and from work today.

With the engine idling roughly and the Check Engine light ON, I disconnected and re-connected the wires to each coil pack this evening, one at a time, detecting NO change in idle speed at the cylinder #5 location.

I swapped cylinder #3 and #5 coil packs and the problem stayed with the #5 cylinder.

Measured the cylinder #1, #3 and #5 injector coil resistances at about 11.5, 11.8 and infinite, respectively.

Since I replaced all of the belts, water pump, etc a few thousand miles ago, I'm considering replacing all six injectors, the PCV valves and the EGR valve?

Is there anything else that I should do at the same time and which is the best new injector to go with?

Could a short have taken out the injector coil?
Modified by GerryO at 4:28 PM 3/20/2008

[gr8scott72]

A bad run all the way, to and from work today.

With the engine idling roughly and the Check Engine light ON, I disconnected and re-connected the wires to each coil pack this evening, on at a time, detecting a change in idle speed at the cylinder #5 location.

I swapped cylinder #3 and #5 coil packs and the problem stayed with the #5 cylinder.

Measured the cylinder #1, #3 and #5 injector coil resistances at about 11.5, 11.8 and infinite, respectively.

Since I replaced all of the belts, water pump, etc a few thousand miles ago, I'm considering replacing all six injectors, the PCV valves and the EGR valve?

Is there anything else that I should do at the same time and which is the best new injector to go with?

Could a short have taken out the injector coil?

I don't understand how you can have a check engine light and not have a code in the ecm. Are you sure you are checking for the codes correctly? You need to find out what the check engine light is from before you do anymore swapping/replacing.

[fogged306]

I agree with gr8scott. I wouldn't go throwing money at the problem before doing some more investigating. Also, It shouldn't matter that you are OBDI, you still can hook the car up to a scantool. It just needs to be a good one with the right software and plug assortment. I really think thats the first thing you should do before anything else.

[GerryO]

I don't understand how you can have a check engine light and not have a code in the ecm. Are you sure you are checking for the codes correctly? You need to find out what the check engine light is from before you do anymore swapping/replacing.

Hi Scott,

I am learning as I go.

It did seem that stored codes were only displayed in Mode II when the engine was running properly with Check Engine light was OFF, and that no codes were displayed when the Check Engine light was ON constantly in Mode I and OFF in Mode II.

When the engine was running properly with Check Engine light OFF, I was able to display Stored Codes 11 and 51 in Mode II.

I believe that I caused the Code 11 by attempting to start the engine with the Camshaft/Crankshaft sensor disconnected (it only cranked and would not start at all).

The Code 51 is injector, (Diagnostic Procedure 15 on page EF & EC-119 of the 1993 Service Manual) and there sure seems to be a problem with the coil of the Cylinder #5 injector, based on NO idle speed changes when disconnecting/reconnected the Cylinder #5 coil pack wires, the screwdriver listening method and the infinite coil resistance reading for the injector.

I do plan to recheck codes, but I buttoned everything back up when the car was running properly again and I also want to connect a Noid Light to a couple of the injector harness connector positions, including the one for Cylinder #5.

I may even connect a known good injector to the harness, just to confirm that nothing from the ECM took out the original injector, and as they do have 172,000 miles on them.

More suggestions/recommendations?

Thanks, Gerry

[fogged306]

I misread your post before this one. If you had no change in idle quality with the removal of number 5, then you know where the problem lies. I like the idea of swapping injectors.. especially if you are getting an open circuit on the num 5 injector. Check it again if you can get the car running correctly again and see if you get a reading then. If thats the case then its probably shot... I'm still wondering why the car shut off when you gave the ECM a whack.. maybe you hit the case with enough force to ground out a trace for a second and shut the car off, if there was no plastic between the case and the bottom of the circuit board then that is definitely possible.

[GerryO]

The only possible injector swap will be an out of the car one, unless I do something really drastic along the lines of grinding away portions of the intake to facilitate removal of the injector, and even then #5 cylinder/injector is sort of a worst possible case/location.

Somewhere along the line I may test replacing the Phillips head screws on the injector covers with socket-head cap screws that might be accessible using a ball-tipped hex-driver. A button-head cap screw would be lower profile, but wouldn't be as durable, but then again it could be as strong/grip-able as a Phillips head.