Cylinders 1 & 4 - Misfire & Mystery

1999 4R Limited, 330k on the clock. Overall good shape. Short drive to store, enough to get it warm. Come back out, start it up, and it's missing. Limp it home and get flashing CEL.

Pull codes and it's 0300, 0301, 0304. The latter 2 indicate cyl's 1 and 4 are misfiring. Cool, they both share the same coil, replace that and I'm golden, right? That's gotta be it, right?

Nope. Replaced coil at Cyl 1 [which also feeds Cyl 4] and it does the same thing. Pull the codes, same codes. Just for grins I swap coils with Cyl 5 and the miss stays with Cyl's 1&4. Crap.

For no particular reason then, I change all 3 plug wires and the plugs from 1&4. The old plugs looked fine... Test drove it and... you guessed it. Same bloody thing. Runs fine at start-up, drive it a ways, turn it off then back on and BAM dead miss and same OBDII codes.

Having a hard time thinking I have two injectors failing at same time, and ignore the voltage-sharing of those two cylinders. I think the only things upstream of the coilpack for Cyl 1 is the Igniter and ECU -- either of which, if bad, would affect ALL cylinders, not just a couple -- right?

I'm going to try and check voltages on the wiring that feeds the coils, but I'm hoping one of you mechanical geniuses out there can shine some light on this mystery... My thanks in advance!

d

 

UPDATE: I recreated the misfire, yanked the #1 plug, grounded that sucker, and turned the motor over. Much to my surprise, I did have spark... That suggests to me that it's a fuel problem, most likely an injector. I didn't check for spark on Cyl 4, but spark on Cyl 1 blows my Cyl1&4 voltage theory...

Looks like there's no easy way to swap injectors around to see if the problem moves with it. If I have to take the time to yank the plenum off I may as well change those two injectors -- or all of them.

Does this sound reasonable? Anybody know if a good pro diagnostic machine could bird-dog a misfire, ie differentiate between an injector and an ignitor? Might be worth [shudder] taking it somewhere...

 

Could it be a bad ECM or something like that? I agree, 2 cylinders coming down with a misfire at exactly the same time begs for a single failure point. Although it is possible that 2 injectors just decided they'd had enough.

On the list for me is to send out my injectors for a flow matched set of OEMs (like $300). Hard for me to justify since my rig is running pretty well.

 

Hey man. Thanks for the input.. Yes.. I think it's possible it's a bad ECM. I agree with your single-point-of-failure assessment. Upstream of the coil for those two cylinders is the ignitor and upstream of that is the ECM -- and all the wiring in between.

I'm gonna check some voltages on the pigtail going to a Cyl 1 and compare it to Cyl 3 or 5. I think I can get a used but tested good ignitor for about $30. Might be worth it to try that before I take the time to replace some injectors.

Yep, if it ain't broke... Thanks man!

 

I am curious to know what the status of your issue is? Has it been resolved?

 

Unfortunately no. I took it to a local shop who claimed to have a high-end diagnostic machine, but they had it for almost two weeks before admitting they were stumped and gave it back... I have since replaced the igniter -- which was NOT the problem. I've recently cleaned the MAF, replaced the PCV, and cleaned all the grounds I could find in the engine bay. Haven't tested it since then, but optimism is lacking. Assuming that doesn't do it I'll likely: swap injectors around, see if the miss follows; check for vacuum leaks; check fuel pressure; check compression; take it to another shop. Hate to resort to taking it to the stealership. Dang, it only has 330k on it. Does no one make anything to last anymore?

 

Hello imjustdad! 26 year veteran Toyota Master Tech, Lexus Master Diagnostic Specialist here.. Email me your contact info at usbmine@yahoo.com so we can discuss this further. Unfortunately I am having the exact same problem and would like to see if we could help each other out. Thanks.

 

HI imjustdad and
G-Cowan
Did this get resolved I have the same problem going on. 1 and 4 cyl misfire I replaced the coil pack and it didn't fix the problem.

I'm investigating further.
I checked the timing because it was easy and it is fine as well.
I went to a Junk yard and replaced the igniter $3.50 .


Update It ended up being a bad plug and a bad wire. I moved some stuff around and the code moved on the bad plug. So I replaced the plugs.
Then I replaced the wires and the other code disappeared on Cyl 4.

I guess its better to go simple first.

 

Gentlemen, my apologies for not posting back sooner. I'm ecstatic to report this has been solved. To be brief, it was the Cyl 4 injector that was bad. I swapped injectors around, and the misfire followed that injector. I replaced it, and it runs fine now.

The tandem codes the system was throwing -- the two electrically-related 1&4 cylinders -- was, after all, just a red herring. I suspect the ECU was trying somehow to compensate for no fuel at Cyl 4, and it affected Cyl 1 in the process. In reality there NEVER WAS anything wrong with Cyl 1, it was just that lyin' SOB of a computer SAYING there was.

Hope this helps some poor soul out there save some time running this around the block multiple times. Thanks all for the input and God bless!

 

Well congratulations are in order and thanks for keeping us in the loop. Obviously the car is back together but you should have the remaining injectors be serviced. If one has gone bad, chances are high that rest may fail as well.

 

When I saw this thread I was gonna chime in but you've already got it fixed. But what I was gonna say is that I had a fairly similar problem on my 4th gen. Two cylinders started misfiring at exactly the same time and looking at the misfire counter they were exactly the same. Or so the scan tool said.... On mine the cylinders were not related. Different banks, separate coils etc. I ended up calling Identifix on mine because I was stumped. And my ex brother in law who has been Toyota dealer tech for over 35 years was stumped as well. But, the expert at Identifix knew something we didn't know. That is, you cannot believe the misfire codes on a Toyota product. Turns out only one of my two cylinders was misfiring. Ended up I had a bad spark plug. Replaced plugs and ran perfect. Moral of the story: Don't trust Toyotas misfire detection.