Misfire, Shuddering/shaking, lopey idle...

[BlueCruiser84]

I unhooked the negative battery cable while the LC was running and turned on all the accessories (lights, blower, radio, hazards) and it ran. That makes me think that the alternator puts out at least enough to run the vehicle.

Can an alternator have a "dead" spot in it? So on average it would supply nearly the correct amount of voltage, or more if the voltage regulator is also bad, but the current supplied to the coil is broken up enough that it causes a misfire?

 

[BlueCruiser84]

It probably does need new o2 sensors but I really don't think that is what is causing this.

 

[BlueCruiser84]

I guess I'll just keep updating so maybe it will help someone in the future...

I load tested the alternator and with the fan blower on high, headlights on, radio blasting, and hazards on it was right around 12 volts, maybe 12.1-12.2 volts. I suppose that is a little low.

I then used my induction timing light around the coil wire and it was pretty broken up when the truck was running rough. It was not a steady "strobe". When the truck was running poorly the "strobe" had very noticeable misses in it. Hooked it to my buddies cherokee for reference and his was a nice, steady rapid strobe light.

Turned it off and right back on and it ran great.... hooked up the light to the coil wire and it was a much steadier. Turned it off and it sat for about 15 minutes and when I turned it back on it ran like sh*t.

I am thinking a new alternator and possibly a new coil are in order... I'm sure that won't be cheap.

 

[Wilson]

I'm dealing with this myself. Did the plugs, wires, cap, rotor last weeka nd it was still there. Symptoms started very shortly after a fill up on a road trip, so I was suspecting bad gas. Re-filled and tossed in some alcohol, was fine for 70 miles and now it's back

 

[Wilson]

Got everything torn down and am now buttoning it all up. While disconnecting all of the harness plugs, the #1 injector plug was not snapped down and was just sitting loosely on top of the injector. All others were ok. My harness at the EGR looked great and had about 3/8" of clearance, but I unwrapped it anyways to be sure. I found no damage and re-wrapped it with two layers of barrier tape. I bought a new coil because I had an intermittently failing coil when I first bought my '93 pickup. I'll put that on for good measure and hope my problems are gone.

 

[BlueCruiser84]

Any news wilson? I got the new alternator in and it made no difference... go figure.

I am ready to take it all apart again, recheck wires, ohm injectors and make sure all the connectors are on tight. The intake on the 80 is such a pain in the ass to work around.

 

[BlueCruiser84]

Would low fuel pressure or a clogged fuel filter make this thing run worse at idle than at WOT? I wouldn't think so, but whadda I know...?

 

[sea2skydad]

This sounds a lot like an issue I had a few years ago. Lopey idle, ran rough up to about 2200 rpm and then smoothed out after that. I checked the connectors onto the injectors--they make a definite click when they are fully engaged. The first five were fine but #6 was loose and snapped on with a beautiful "click". Problem solved. Of course, being #6, you won't be able to see it but you can feel it.

 

[Wilson]

waiting on fusible links. I'm not sure if I pinched the harness doing the valve cover or stressed them climbing around yet.... I ordered 3 so I have spares.

 

[eurorom]

Any news wilson? I got the new alternator in and it made no difference... go figure.

I am ready to take it all apart again, recheck wires, ohm injectors and make sure all the connectors are on tight. The intake on the 80 is such a pain in the ass to work around.

How is your computer doing?

 

[Wilson]

Mine seems to be fixed. I pinched the #6 injector wire, when doing the valve cover gasket. I missed it during my inspection this morning and wasted (1) of the three fusible links I ordered. Pretty sure my original issue was the #1 injector being unplugged/ loose.

 

[BlueCruiser84]

How is your computer doing?

Computer is Ok, I think. I know the 93s had some issues though. I am starting to think the problem is with the injectors/wiring even though I had it all apart and checked it thoroughly.

One thing that is weird is that when I measure voltage on the wire for the number two injector where it goes into the computer I get a VERY low reading, somewhere around .43, where the other five injector wires give me battery voltage.

However the number two injector is firing and working just fine. I pulled the wiring off the injector while the motor was running and it made a noticeable difference.

What do the wires labeled #10, #20, #30, etc. on the ECM do? are they taking information to or from the computer?

 

[BlueCruiser84]

Mine seems to be fixed. I pinched the #6 injector wire, when doing the valve cover gasket. I missed it during my inspection this morning and wasted (1) of the three fusible links I ordered. Pretty sure my original issue was the #1 injector being unplugged/ loose.

Congrats. I am going to go back in and investigate the injectors again. It's a pain in the ass that you can't run the truck and get to the injectors at the same time.

 

[PirateCoast]

BlueCruiser - Did you ever get this fixed? Am having a similar problem with my 91.

 

[95LCMachine]

Bump for updates.

 

[BlueCruiser84]

I did get it fixed actually!! It was the computer. I replaced it with one from a 94 and she runs like a top.

I tested all the wiring until I determined it was buggered somewhere inside the computer. Opened the old comp up and there was some weird soldering along with some burn marks. Replaced with "new" and she was good to go.

 

[eurorom]

I did get it fixed actually!! It was the computer. I replaced it with one from a 94 and she runs like a top.

I tested all the wiring until I determined it was buggered somewhere inside the computer. Opened the old comp up and there was some weird soldering along with some burn marks. Replaced with "new" and she was good to go.

Your symptoms were the computer!

 

[BlueCruiser84]

Your symptoms were the computer!

Yup!!! You were dead on with your suggestion!! I just didn't think the computer would be so sporadic. She's good to go now though. I shoulda listened earlier...

 

[Kmart]

Resurrecting an old thread because I am experiencing the same issues. I have all new plugs, wires, cap, rotor, air intake tube, fuel filter, pcv, valve cover gasket, spark plug seals, and air cleaner.

This issue came on slowly, but is now a full-time issue. I have a CEL now with a code 25 and 26. I have isolated the issue to cylinder #2 because when I remove the plug while running, engine performance is unchanged.

I just did a compression check and had 180 to 184 across the first 5 cylinders. Interestingly, #6 is reading 210. Carbon buildup? I also have a test kit to check for exhaust gas in the coolant, and the check I did about 3 months ago showed nothing abnormal.

Finally, I checked the spark at #2 and it was good. I also listened to the injector with a mechanics stethoscope, and it is clicking. I assume this means the injector is trying to put gas in the cylinder?

I examined the wires, and they appear to be ok--I am also thinking if the injector is clicking, it's probably not a wiring or computer issue.

Could it be that the injector itself is clogged? Any thoughts or next steps would be appreciated. She is a bit of a dog on 5 cylinders.

Thanks.

 

[DARKNESS]

I did get it fixed actually!! It was the computer. I replaced it with one from a 94 and she runs like a top.

I tested all the wiring until I determined it was buggered somewhere inside the computer. Opened the old comp up and there was some weird soldering along with some burn marks. Replaced with "new" and she was good to go.

Resurrecting an old thread, but the computer problems here were likely due to the capacitors leaking and damaging the board. It's apparently an issue with most Japanese cars from this era. Here is a good thread from a Lexus form on this problem:

All my crazy Lexus issues SOLVED!! (ECU-leaking capacitor) - Club Lexus Forums