Just dropped the motor back into my son's truck, and the #4 cylinder is not firing (it's idling roughly, and pulling the #4 wire makes no difference, but it stalls if you pull #1, 2 or 3).

Compression is good and consistent in all cylinders. I swapped the spark plug, and the problem stayed in the cylinder. The plug wire is good. So, I'm thinking it must be the injector? Anything else it could be? Any way to test that theory other than disassemble the upper intake and swap out an injector?

Thanks!

 

Be sure to check for vacuum leaks before spending money , not to say that is what it is but it is one of many simple thing it could be...

 

How could a vacuum leak create a problem limited to one cylinder only?

 

Depending on where the vacuum leak is it can cause a miss in a particular cylinder, as a mech in a shop for many years my first thing to do is to check all the basic stuff first don't go to parts replacing mode until then...

 

Vacuum hoses seem to be okay. Could it be low fuel pressure? I used slightly thicker crush washers on the fuel filter. Wondering if the fuel flow into the rail might be slightly blocked. #4 is the furthest from the fuel inlet. I listened to the #4 injector with my stethoscope and it seemed to be firing okay.

 

You could swap the injector to another cylinder and see if the problem stays or moves. It is possible that the crimp that holds the injector in the harness has come loose. I have seen that before. I have also seen bad injector connectors.

 

You need to check that the plug is firing. The easiest way to do that is put your timing light pickup on that plug wire; if it flashes, it's firing. It's certainly possible to have a broken plug wire that looks okay.

Do the easiest stuff first.

 

Agree^^ make sure it is on the Firing side first then see if it is on the Fuel side next. If you are using part store wires, good chance that it is bad. If it is a bad plug wire Denso 671-6182 can be found off of ebay for about the same price as part store and much better quality.

 

Is there a way to swap wires just to confirm the wires integrity,I would visually check other secondary voltage components as well such as distributor cap. What does the plug look like after it has been running IE white (lean) wet with fuel, wet with coolant, ? I dont see how a thicker gasket on the fuel filter could cause this. When did the problem start? Could it be a tight valve, how was the compression checked?

 

I'm pretty sure that the wire is good. I have one of those adapters that you put inline between the wire and the spark plug and it lit up fine, showing it was firing. The plug looks literally unused.

I was talking about the crush washer I used on the banjo bolts fastening the fuel filter to the outbound line. It slightly thicker than the washers that came off, so I'm wondering if the hole in side of the banjo bolt might be slightly blocked. It sure seems like a low fuel pressure issue - takes lots of turning to finally catch. The problem seems worse at idle and smooths out at higher RPM, although it's pumping out a good bit of smoke (might be because I put a can of Seafoam into a relatively low fuel tank).

Problem started when I reassembled the motor with a new head, so a valve adjustment was part of the equation as well. I checked the compression with a standard compression gauge, turned the motor over with the coil wire disconnected and checked each cylinder one at a time.

I also replaced the timing chain and guides, but I'm certain I got that right (there are specific links to line up with the dots on the sprockets), as well as re-installing the distributor, which I did by sight to line up with #1 at TDC.

 

As Terrys87 said, try swapping the injector with another and see if it follows. I recently did my son's head gaskets on his Nissan Xterra and had a misfire, swapped and got it to follow. The injector was clicking away but would cause a miss when warm.

 

Okay, so I swapped in another set of injectors and the problem remains. New plug wires and the problem remains. Here's what I know......

1. Compression is good and consistent in all cylinders
2. I have spark, plug and wire are both known to be good
3. Injector is good, and is firing
4. Engine is blowing bluish smoke
5. Problem is in #4 cylinder - pulling the wire makes no change in how the engine idles or comes up to RPM. Pulling any other wire and it stalls out immediately.
6. The head that I pulled off this motor had completely crusty valves in #3, and no the motor had no compression in #3. Only mentioning that because the cylinders are adjacent.

I replaced the head (with a supposedly "gone through" head that looks really clean), all gaskets, timing chain and guides, etc. I reused the old "spider" with the cam and valve adjustments.

I did reset the valve clearance when I swapped in the new head, but only did it cold, to 7 and 11. I'm assuming that the good compression reading rules this out as a possible cause, although pulling the valve cover and checking the valve clearances is probably my next step.

The only other thing I can think of would be valve seals letting oil into the cylinder and creating the bluish smoke. But, I'd think I'd still have some power coming from that cylinder - at least enough to notice a difference when I pulled the wire.

Any thoughts?

 

Do you have access to a leak down tester, it is a more reliable way to find cylinder issues. What does the inside of the distributor cap look like ? If that cylinder is not firing what does the plug smell like " if your injector is working you plug is likely fuel soaked. You may need to deal with that by clearing that flooded cylinder .If you have the valve cover off check the clearances make sure you are on TDC compression stroke and also watch the motion of the valves make sure are not sticking.
Remember Suck , squeeze, bang , blow.... It's the cycle of a 4 cycle engine intake, compression,ignition, exhaust. Be careful I don't know what skill level or experience you have , but turning a engine over with a flooding cylinder can easily ignite by sparks jumping around open plug wires.

 

Compression test to out help on the cylinder. If the head was serviced which you never know.

With a new set of injectors,( assuming all 4 were good and not a freak chance that the 4th injector was bad as well), you are getting fire to the spark plug, no change when you pull the plug wire off while running, I think you have a problem on the Fuel side of the problem.

I suspect the crimp in the Injector harness. It is a very poor design. You can run a resistance check on the harness but it can pass and still fail. An injector issue is where I learned that just because it passes a test doesn't mean it is good. As another member explained it to me, if a wire has 50 strands in it and 49 are broken, it will pass a test, it just takes one wire to pass but not enough to pass the voltage needed.

Reason I say 4 is not firing is that 2 and 4 share the same wire.

 

Terry's 87, you are THE MAN. Pulling the #2 plug wire results in the same thing - no change at all in the idle. Pull #1 or #3 and it stalls out immediately. Weird because I can hear both injectors firing (well, at least clicking) with my stethoscope. Maybe there isn't enough voltage coming through? It's got to be in that circuit somewhere.

Can we replace just the injector harness?

 

Thanks for sharing info guys

 

You can replace the Injector harness. Just unplug it from the computer and run it thru the firewall and then you will need to remove the Plenum to get it the disconnected from the rest of the components. It is routed thru the firewall just under the hood. Looking from inside the cab it is the upper hole, the lower hole is part of the Main Harness.

Your truck looks like 89-94. I don't know them as well but the 85-87 harness looks identical but each year does have some kind of differences that most will not catch. Knowing Toyota, I am sure they did several changes in your generation of trucks as well. They change numerous things on the earlier generations. Get the exact year harness as your truck.

I suspect it is the crimp in your harness. It is located in the harness section between the Inner Fender well and the Intake what I would call the "saddle" or how the harness sags. There is about 5 crimps in the harness if you take it apart. The two crimps you need to remove is the yellow and blue wires, and just solder the wires together and that will fix your issue.

It has been a while since I have been in a harness but if you see a white wire with a black stripe and it is crimped, I would solder them as well, those will be the ground or return wire.

 

Unfortunately, I'm back to pulling my &*^% hair out on this.

You are correct that our truck is a '92, so somewhat different from what you're used to. Our wiring is nothing like what you shown above. There is no solenoid or relay on the passenger firewall. There are two wires to each injector. 1 and 3 have a white with a red stripe, and 2 and 4 have a plain white on one side. There is a white and a white/red coming out of the computer. But, those 4 wires are all connected together (to the two coming out of the computer) just on the engine side of the firewall.

The second wire to each injector is blue/red, and they all go into a wire bundle that goes back towards the solenoid on top of the coil. However, those wires are also connected together, with 1/2 on one circuit and 3/4 on another. Once I saw that, I didn't chase them all the way back, because I'd kind of ruled it out in my mind.

So, as logical as what you'd suggested seems, I don't see any way that there's anything electrical that could be affecting the injectors on 2/4 only.

Any other ideas? Am I missing something?

 

what about the efi main relay

 

Is there any way that could create an issue in cylinders 2 and 4 only?