Soaknfused

I need some help here. I have a 92 GXE that I have done all your typical repairs to and do all regular maintenance. Most recently I replaced all the injectors and got new connectors for them as well, O2 sensor, plugs, wires, cap and rotor. When I had the intake off to replace the injectors I cleaned the throttle body and mainfold (didn't do the IACV yet) The car was running horribly and after replacing the injectors it got a lot better, however there is still a noticible miss so I started digging further into things. When I pull the plug wire on #4 there is no difference at all to engine rpm, sound or anything. I switched plugs around, tried swapping wires and all that stuff. cylinder #4 has a good strong spark, the injector is new etc. I haven't tested compression yet, but with the engine running there is no excessive blowby as would be with shot rings or a hole in the piston etc. The engine doesn't use a drop of oil or coolant ever.

I took a continuity tester and checked the wires to the injectors to see if there was a pulse coming through (at first I thought there may be a broken wire) when I did that to cylinders #2 and #6 the engine sputtered (assuming it interrupted the injector pulse) when I did the same to #4 the test light light up, but it didn't affect how the engine ran at all. Could this indicate a weak injector pulse to that cylinder?

It sure seems that cyliner #4 isn't prodicing any power at all, what in he double hockey sticks could be causing it? I'm open to any and all suggestions. Is there a way to test the injector pulse without some crazy expensive tool? is there something I can measure at the ecu? I'm very mechanically inclined, just need a bump in the right direction from someone who knows this stuff :-)

Thanks in advance to everyone who responds.

Greeny

iTrader: (43)

Sounds like might have a defective injector on #4.

Soaknfused

All injectors are new, ohm tested em all b4 I put them in as well. this condition existed prior to putting in the new injectors, I just assumed replacing them would fix the problem.

Alex_V

Was it a rebuilt or brand new bosch injector?

~Alex

Soaknfused

I ordered them from fiveomotorsports.com I am assuming they are remanufactured. I'm not overly worried about it being a bad injector as the condition on #4 was identical to what it is now prior to replacing them. What are the odds of one bad injector ending up on the same cylinder that had a known bad one prior to replacement? way unlikely I'd say. Even before replacing them it did the exact same thing as it is now on that cylinder.

LvR

Measuring the injector coil's resistance says nothing about its ability to mechanically open and close and function as an actual fuel injector - it just tell you that the coil is OK - thats all. You want to know if the actual injector mechanically opens when electrically told to do so by the ECU.

In your case I would do the following:

Get a fuel pressure meter and plumb it properly into the line between the fuel filter and injector fuel rails.

Switch on your ignition (don't start) and confirm fuel pressure rise to around 40psi and stay there (for quite some time - minutes) even after you switch off the ignition.

Now - The injectors have a 2 connector plug supplying it - remove that. Find, in your spares shop, 2 spade connectors that will allow you to fit a piece of wire (2 meters) manually to those 2 connectors on the injector. At an electronics shop get a 1 Ohm 1 Watt resistor and solder that to the other end of any one of the 2 wires now connected to the injector.

Switch on your ignition (don't start) - watch the fuel pressure meter stabilize and confirm the fuel pump stops pumping (you can normally hear it stop if engine is not started immediately after a few seconds). Switch off your ignition. Keeping an eye on the fuel pressure meter connect the wire rig you have made up to the battery terminals for about 1 second.

What you want to see, if the injector is working properly both mechanically and electrically, is for the fuel pressure meter indication to drop soon as you touch those wires on the battery.

If the meter indication drops, you know the injector is fine - if it doesn't drop, you have your problem.

DennisMik

iTrader: (2)

I agree with the others that the injector could be inoperative. Just because tge ohm reading is ok doesn't guarantee that the needle valve inside is being moved (i.e., mechanical problem). You have done a lot of diagnostics, but you say you haven't done a compression check. I would get that done and either confirm the fuel injector theory or eliminate it.

internetautomar

iTrader: (30)

rebuilt injectors = over 50% defect rate.
right now you are ahead of curve. we'll see how long that lasts.

Alex_V

That is a very good test, I'll remember that....

~Alex

Soaknfused

I'll do that fuel pressure test to see. 50% failure rate on remans eh? that seems a little out there. In that case, I'm just happy 3 of 6 are working then. the place I got them from does offer a 3 year warranty on all injectors, so I am not overly concerned about it. I doubt I'd rather spend the money on new injectors especially when my plans down the road will have my putting in larger injectors anyhow. Does anyone know what kind of readings I should be able to pull off the injector wires for resistance, continuity or volts etc??

LvR

Wires? - 0Ohm

Continuity? - suggest see the FSM for points to trace

Volts? - 12V pulses of around .5 to 2.5ms duration on an injector.

IMO if you need to involve yourself with these kind of measurements on the ECU, then you are screwed and possibly need a new ECU.

Check compression and the injector first before crying over unspilt milk.

Soaknfused

Agreed, I will check those items first. I just like to be able to plan ahead and educate myself in case I need to tackle things farther down the road that I am not sure about. I figure it never hurts to be prepared. I'm crossing my fingers and hoping on something that just came to me thig morning. When I was installing the caps that hold the injectors in place, and even more so on #4 than the others, that half circle metal "washer" with the hole in the center that sits on top of the injector was out of place and didnt want to sit in the cap right, maybe that is in there incorrectly? That would stop the injector from functioning as well, correct?

One more question, does anyone have any opinions on using rtv gasket maker instead of using a new intake manifold gasket if I have to rip it apart again? I've used it on other stuff before, but not so sure about a max intake, unless someone can confirm it would work just fine :-)

93pita

I have the same exact problem. I bought a test light and probed the #4 power lead to the injector and there's no fire to the injector at all. Followed that wire all the way to the firewall where it goes into the car and still no fire.

Soaknfused

hmm, anyone else with trouble at cylinder #4 we could start our own little club.

Soaknfused

Would I be ok, instead of using a iOhm 1watt resistor with the injector to battery test could I just use a test light in between the battery and the injector? I assume the purpose of the resistor would be to limit the current being applied to the injector, test light would do the same or is that not enough of a precaution? If thats not ok, how about a 470K resistor (have 5 left over from the pack I got when I needed to test my knock sensor) Thanks for all the replies thus far, I really appreciate it.

LvR

No - a 470K will not do - there will be no current flowing to the injector and therefore it will not be receiving the correct signal to respond to.

If you need to use a "testlight", then use an indicator bulb (about 20Watt) in place of the resistorHave a look at the FSM wiring diagram of the ECU etc - the injectors are fed off a common 12V line - if you have no 12V on just one injector plug (#4) then it has to be an actual wiring problem on that particular wire (pinched/cut/crimp/ etc etc). The ECU supplies only short pulses to ground when the injector is supposed to open - that you will also not be able to "detect or measure or see" with a pilot light - the bulbs response is way to long to any short current burst (2ms typically) running through it.

RTV for intake gasket? - lots of people posting that its fine - personally hate the stuff and would rather replace the gasket

Soaknfused

Little update, I've done a few simple tests since i last posted. Compression is actually much better than I had expected and very even among cylinders. I picked up some MAF and electrical cleaner and cleaned the MAF, TPS and all the electrical connectors I could get my grubby little hands on. After reading that there was a constant 12V to the injectors and that the ECU sent the pulse on the ground wire I got to testing, all wires are hot when should be and using a noid light I confirmed that the signal is going to #4 as should be, so all thats left is to watch the fuel pressure when manually applying power to the injector to see if it is working that way as LvR posted. The only hold up on that is finding a fuel pressure guage that will work for my application, got the new gaskets for the manifold so when I pull it apart again I can put it all back together properly. I'll post an update after I get that done. Work is really putting a dent in my time to work on the car, imagine that.

LvR

Don't go looking for a fancy "fuel pressure guage" - its exactly the same as a an "oil pressure guage" - the silk-screened labels are different - that's all

ogah_yellow

Add me to the #4 dead cylinder list...

Anyone know which spade of the injector is ground? As in passenger side or driver side.

Thanks!

LvR

Irrelevant - both terminals are/should be isolated from the body of the injector so you can test either way

92 Max

I got a cheapo Fuel Pressure Gauge from Harbor Frieght for about $35. Good enough for the occasional use.
http://www.harborfreight.com/cpi/cta...emnumber=92699

Soaknfused

Well, I finally got the time to rip it all apart and do some swapping, first I moved the injector from cylinder #4 to cylinder #6 to see if the trouble followed the injector, which it did. So, i tore it all apart again and took out that injector and replaced it with one that was in the engine prior to replacing all of them and poof, problem gone.. I guess that injector was defective when I got it.. So now I have 5 new remans and one old one in the engine and it is running absolutely fantastic. I will be sending the one bad one in with the other 5 cores to get a warranty replacement done at the same time I get my core credit for the other 5.. I can say I am very profecient at removing the intake manifold, did the last injector swap in 20 minutes from start to finish lol...

DennisMik

iTrader: (2)

20 minutes to replace an injector? Wow, I'm impressed. I can't get out of my chair that fast.

Soaknfused

Hate to revive a old thread, but just as a bit of info Cyl #1 is now a failure. Terrible misfire and loss of power started yesterday, tested resistance and poof... a big fat 0 to .05 ohms resistance on that injector. I have read that a failed injector with no resistance like that can damage the ecu due to excessive power drain???? Anyone have any more info on this or know if that is indeed a possibility I need to look into?

LvR

That resistance reading is indicating a short, and as such eventually will damage the ECU. I would rather pull the plug on that injector till you have the time to sort it if you absolutely must drive the car

Wiking

Good injector thread here ... couple of notes in troubleshooting, 'diagnoseing':

Fuel Pressure cant select #4 cylinder, its all six or none

Listening
...is cheap and easy: If injector pulse is present and injector is ok, then you WILL hear the click (with a screwdriver placed on it, ear on handle ... pls not vice versa). Cost = 1screwdriver

Seeing
...is cheap and also easy ... for good spark: spare plug, attach to wire, ground the plug on intake and crank (and run?) the engine.
Cost = 1plug ... and as an extra, few sparks on fingers (its NOT dangerous, but gloves is a plus

Smell
If fuel pressure & injection 'works', no ignition ---> awful gas smell.
Cost = 1nose.

.

Soaknfused

[QUOTE=

Fuel Pressure cant select #4 cylinder, its all six or none

[[/QUOTE]

Fuel pressure was referring to testing for mechanical operation of one injector at a time by monitoring fuel pressure while manually activating an injector. If the mechanical operation portion of the injector operation is working correctly you will notice a fuel pressure drop as you activate the injector as it will release fuel from the previously pressurized fuel system.