Cylinder problem, and ground wire.

[serpent_1977]

I have a maxima, 94GXE. WE recently replaced the transmission,and as I was hooking all the electrical back up, I noticed a ground wire that bolts to the frame right above the driver's side wheel well. I ahve searched for about 3 days, and I cannot find where that wire plugs into. It is driving me nuts. We are having some problems with the engine (It is only running on 3 cylinders) and the mechanic Iwas working with thinks that ground might have somehting to do with it. If anyone knows where that plugs into, could you please let me know. Thanks for any help.

[Nahkapohjola]

Originally Posted by serpent_1977

I have a maxima, 94GXE. WE recently replaced the transmission,and as I was hooking all the electrical back up, I noticed a ground wire that bolts to the frame right above the driver's side wheel well. I ahve searched for about 3 days, and I cannot find where that wire plugs into. It is driving me nuts. We are having some problems with the engine (It is only running on 3 cylinders) and the mechanic Iwas working with thinks that ground might have somehting to do with it. If anyone knows where that plugs into, could you please let me know. Thanks for any help.

Electrical devices need supply voltage. The current flow thru the device produces the energy for it. Thereby the flow needs a place to go. This is source to drain the current, is commonly called the ground.

Electronic devices are suspect to interference from spikes produced by powerful devices, like starter etc. Thereby they typically are isolated from this ground, and have their own gnd 'source'.

A car has battery (&alternator) and its negative pole -the gnd- is strapped to chassis and engine block. Typically this is enough on new and clean products. However, oxidation between various parts, result in disconnection and/or resistance inhibitng current flow.

The extra grounding straps ensure grounding between chassis and the engine parts. One part is the exhaust pipe, typically it has to be grounded cause the O2 sensor & other possible interference problems. Maybe your strap is for it?

Btw. Extra grounding from chassis to alternator is imperative. Manufacturers leave this device to ground itself just via its support bolts which will oxidize, question is just how fast. Oxidation will break this ground, and ruin battery as it will never become fully charged. Add one strap between alternator body and vehicle chassis - all connection points clean & electric conducting grease added.

In electrical devices, adding extra groundings will never do harm, only increases reliabiltity. In electronics one has to think also radio frequencies: a loop forms an antenna which may induce problems to the low voltage electronics devices. Thereby all electronics grounding cables networks must have to form a tree [never a loop].

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Btw. I do not think that gnd strap has no relation to u problem...

Listen to injectors: do they all click?
- If not, you're not getting any gas. Propably wiring to ECU. Clean all connectors with white carbon.
- If they do, check ingnition to those dead three by installing a spare plug and grounding the plug. A spark should be seen between gaps while engine running...

[infinman]

If this is a single wire , female spade connector , it may be the transaxle case ground.If you look on top of the transaxle , just where the left axle enters the differential, you will see a male spade terminal with one of the case bolts.This must have a ground connection.Your '94 transmission uses computer controlled shift solenoids that require a good case ground.This will not solve your misfire though.

[serpent_1977]

Well, I found where the little ground wire was supposed to go, and it fixed the small problems with my tranny, and I also noticed that when I put the transmission back together, that I hooked up some electric connectors wrong, and it fixed most of the missing problem, but it it still not firing on one cylinder. The injector is clicking, and where the plug wire goes into the distributor, there is spark, but it is only running on five cyliders... Any help would be appreciated, where do I go from here? Thanks for all the help so far!!!!

[Nahkapohjola]

Originally Posted by serpent_1977

... still not firing on one cylinder. The injector is clicking, and where the plug wire goes into the distributor, there is spark, but it is only running on five cyliders... Any help would be appreciated, where do I go from here? Thanks for all the help so far!!!!

Replace distr cap. (If you do not get one, clean and apply lacquer, works for a time) Wire or Spark plug problem... only copper wires do really work, the carbon rubberbags are crap even new.

"transmission uses computer controlled shift solenoids that require a good case ground."
Good note! This might be the cause for many problems.

[serpent_1977]

Ok, I ran the codes on the car and I got code 51 which is "Fuel Injector Signal Circuit Fault". What is that, and how do I check it?

[Nahkapohjola]

Originally Posted by serpent_1977

Ok, I ran the codes on the car and I got code 51 which is "Fuel Injector Signal Circuit Fault". What is that, and how do I check it?

1. How do you know that one cylinder does not work?

2. First there was three missing cylinders, what made two of them come alive?

3. Last changed situation = one cyl misfire: did you ??? change spark plug from that cylinder [even new one can be dead]

3b. Btw. Do you have coils ? on each cylinder or the older Distributor -system.

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4. If you are now sure that cylinder ign is 100% ok, this points to that particular injector. Measure all injector coils with ohmmeter and compare. If there are differences, its pointing to the faulty cylinder injector.
---> However, never heard that tranny change would break injectors. Is the harness to injectors perfect?

5.
---> The ECU can get its error code only electrically, eg. smtg wrong in the injector-wiring resistance. Clean all ECU pins ECU/Harness connectors with white cardboard, carefyllu, all. Maybe oxidation?
---> Find a spare injector and install it to the suspect-problematic one wire connector and test run. Now no injector code should be found... If true, the injector is some way bad, replace (quite a job).

Btw. O2 sensor should all the time give errors because one cylider does not burn its stuff. Or just maybe not...

[serpent_1977]

I have completely narrowed it down to that injector (with a mechanics help). It just happens to be the one injector that I CANNOT get to without taking the manifold off!! It is completely hidden underneath it. Is there a way to make sure the injector is bad, and not just clogged before I take it apart? If it is just clogged up, would Istill be getting that code on the PCM? Thank you for your patience and help!

[Nahkapohjola]

Yes, Manifold off... One might assume that the others need also replacement and maybe good idea to change all. Think - How many miles on them? 100k is just about it.

Try cleaner. That is a cheap test... Nissan has a TSB that says "do not use", but in this case its different.

I suppose nozzle can be broken [no click], and/or just clogged.

ECU is electronic device, it can detect only problems in electronics (resistances) and thats basically how sensors also 'work'. So -noflow- info to ECU comes only how well the gas burns =via exhaust O2 sensor. If no gas goes to cylinder, it will NOT burn bad-or-good, so maybe O2 does not detect this?

The injector is a ECU driven coil. It is technically possible to monitor if the coil actuates [click] the nozzle magnet into movement - but does ECU that, dunno.

[serpent_1977]

I think we found the problem with the car. We did a compression check on the cylinder, and it basically has none. The rest of the cylinders have enough, but that one doesn't. Don't know where to go from here except to a shop I guess. Fixing that is not something easy is it? It doesn't sound like it. Thanks for all your help.

[Nahkapohjola]

O boy. No electronic sorrows any more...

Burned valves most probably. Anyway, engine needs surgery...

Check it out first, possibly cheapest would be to buy another engine...

[infinman]

What are your exact compression readings.You need to do a wet and a dry compression test.By squirting a little oil in the offending cylinder see if the compression rises.If it does you have ring problems.If it doesn't , it's valve related.
Merry Christmas

[serpent_1977]

Thanks, I will try it when I get back from visiting my family...Merry Christmas to you too!!!