2+ year mystery of the P0304 code...

[LeeMajors]

I'm beginning to wonder if it's "normal" myself. My wife's Scion was the same way when we got it, 2 years later nothing has changed. Maybe it's a Toyota thing... it' not like it's hard to start, maybe 2-3 turns, just doesn't fire as soon as you twist the key like my other vehicles. Temperature doesn't make any difference on mine. I just didn't notice it when I was test driving other 4runners... doesn't mean it didn't happen though.

Even the guy starting the 1UZ conversion 4Runner took 4-5 turns to fire.

 

[gotdurt]

Update: Despite the longish starts, the truck ran fine ever since, with about 40k miles since... until now.

I thought it was the same problem, so I came back to this thread to see what all I did... it appears that I remembered wrong though; now it seems to be strictly a hot start issue, no codes (I forgot that it was more random before and threw codes). The hotter it is outside and the harder I drive it, the harder it is to re-start after turning it off, until it cools off for a while. It will also occasionally die if I briefly (like 2 seconds) floor it from a low speed to get into traffic, resulting in a stubborn restart... not sure if that is related though.

Going to re-visit the throttle body and IAC this weekend, plus clean the MAF sensor. Not sure how heat would affect these though...

 

[Xntrik7]

[MENTION=117964]gotdurt[/MENTION]- Have you replaced your PCV with an OEM one? The part number is 12204-62010. I feel like this helped my car start up a little better/easier.

 

[gotdurt]

[MENTION=117964]gotdurt[/MENTION]- Have you replaced your PCV with an OEM one? The part number is 12204-62010. I feel like this helped my car start up a little better/easier.

I haven't, but I'm sure it's due.
MAF was dirty, but not the problem. I have a CO trip coming up, but I'll dig in further after I get back.

 

[gotdurt]

The plot thickens...

On my way home from CO, the motor suddenly started running bad while accelerating from stoplight in Colorado Springs, at first I thought I was driving on rhythmic bumps, but the pavement was smooth. It "chug-chugged" at idle, but no codes at first. It happened in front of a Toyota dealer, so I bit the bullet and pulled in for a diagnostic. After talking to the service guy and going out to start the truck and bring it in, the CEL light came on; they wanted $125 just to pull the codes and wanted to keep it for the full day... but now I had codes and didn't need them anymore

I stopped at Oreilly and pulled the codes; P0120 and P0304... not sure how they could be related, but it's a start. With limited tools on hand and little for further testing, I went ahead replaced the TPS and #4 coil pack (after checking the plug and wire, and swapping the plug with #2 for a later code check) and hoped for the best... with no luck. I assumed it was probably the injector and decided to just aim for the shortest route back to Austin. The light would flash with downshifts and under load, but since the misfire seemed to be a result of no fuel (injector) vs unburned fuel (ignition), I took a gamble that it would just equal a dead cylinder and not damage anything further. I also noticed that it would occasionally suddenly idle smooth for brief periods, which in my mind eliminated a valve issue.

So now I'm home and the truck is in the driveway. I have a lot of catching up to do for work, so it will probably sit for a while before I can test the injector (still need to find out how to do that). Meanwhile, I came back to this thread to refresh my memory on what happened last time, a little over 40k ago... I was surprised to find that it was the #4 cylinder then too... coincidence? The post below has me scratching my head...

Well, I did plugs and wires today. I also cleaned the throttle body and and MAF while I was at it, even though they weren't in bad shape and I don't think were likely culprits or contributors anyway, given the intermittent nature (at least for the throttle body). Plugs looked good, but the contacts on the coils for 4 and 6 were heavily corroded, and the #4 wire was missing part of the female coil connector... I don't know if that was a coincidence (p0304), or the culprit, guess we'll find out.

As for hot starting, this issue doesn't seem to care about temperature; sometimes it'll happen on a cold morning, sometimes when stopping for 5 minutes after running errands all day. Something is failing/malfunctioning intermittently; possibly mechanical, but I'm betting electrical. An injector, or even fuel pump would make sense (at least for hard starting), although I'm not sure yet how fuel pressure before the rail would cause a misfire in only one cylinder... if it throws another code and doesn't follow the coil (would be p0306 now), I'll go ahead and replace the #4 injector. It does seem that failing injectors in these seem to be a fairly hot forum topic...

Edit: did some searching on fuel pumps and it seems that these tend to get tired between 150-200K miles, so I might do it anyway, since I'm at 195k. It sure wouldn't hurt anything.

 

[djr01974]

Mine would do what yours is doing on occasion. Than I was driving down a mountain grade and as I applied the brakes it stumbled and died. I was able to put it in neutral and restart it but that scared the crap out of me. No brakes nothing. Turns out I replaced the whole idle control valve and it hasn't done it since. Hope that helps

 

[gotdurt]

Mine would do what yours is doing on occasion. Than I was driving down a mountain grade and as I applied the brakes it stumbled and died. I was able to put it in neutral and restart it but that scared the crap out of me. No brakes nothing. Turns out I replaced the whole idle control valve and it hasn't done it since. Hope that helps

I did clean out the IAC last time (2 years ago) and I think that's what fixed the stalling/starting issue then, but it wouldn't explain the P0304 and bad misfire that has it out of commission right now. I also cleaned it out again this time while I had the TB off for the injector job.

So anyway... tore the plenum down to test the injectors, and all injectors tested at 14.7 ohms, except for #4... which tested at 14.5; still well within spec... just a coincidence that it is different than the other 5, or does this mean something? since the others were so consistent, I decided to order one replacement, and see what happens...

New injector came in a few days later, so I tested it out of curiosity; 14.3 ohms... I went out and tested the others again, and all of the good ones tested at 14.6 this time, while the "bad" one (#4) tested at 14.8...? I'm not sure if this is an indication of anything, but it sure has me scratching my head...

Meanwhile, I popped each one out for a cleaning and general check, only to have #3 come out without the insulator nozzle cap... tried popping it back in and out, and the cap just wouldn't come out. I eventually got it out with a tap:

So keep that in mind if you are ever in that situation.

So, now it appears I need to order another injector... guess I'll order 2 and just replace all of them on the driver side so I hopefully won't have to go there again...

 

[Beaumont67]

20 year ago, my 400 RAM AIR II GTO would not restart, after big block got warmed up.
- took Judge to an electronic expert mechanic
- he routinely gets Dealership warranty problems, no one else knows how to trouble shoot
- in my case, he diagnosed some ohms or resistance drop explanation thing-a-ma-jig
- the GM ground strap (-) on battery post, just needed a thicker gauge wire
- so a new 0 or 1 gauge negative ground strap, was installed
Problem solved.

 

[gotdurt]

So the saga continues... got it all back together with 3 new injectors on the driver's side and new o-rings on the passenger. Started it up and it idled okay at first, then the chug-chug started, then it went back and forth, then consistently chugged. So whatever it is, it can cut in and out, which still doesn't sound like a compression or valve issue. I guess I'll throw on a wire set, since these have over 40k on them, even though they tested ok (this would explain cutting in/out and getting worse with temp increase).

Meanwhile, I took the IAC apart for cleaning, and now it's idling high... I must've re-assembled it wrong... anyone know of a diagram that would show correct static positions of the components?

 

[BrianSD_42]

I had some symptoms similar to yours for about two years. Finally it got to the point of constant misfire and the mechanic did a leak down test, ended up failing. He said the problem was with the lower end, not the heads. I ended up getting a new engine. For me this was a long running very intermittent issue spanning several years. If you haven't already done it, perhaps get a proper leak down compression test, at a minimum for peace of mind.

 

[Ricktuk]

try the dealer

As much as it seams the dealers are exorbitantly priced, they can read a level of codes that are not available to the public. Check what the dealers in your area cost. Should be able to get it done quick if you make an appointment.

 

[gotdurt]

So, after posting a new thread about another vehicle, I found myself reading through this old thread...

I can't believe I didn't update with the fix to the last saga... I was at my whit's end, so I went back to square one, and pulled the plug wire on the problem cylinder again...

I had done a visual inspection while at the parts store in CO, and everything looked ok, didn't look burnt or anything. Tested it for continuity and it passed (cold), so I moved on to other things. Now, after 1k miles of arcing on the way home, the bottom insulator was badly burnt. I should have checked again before diving in; after all that headache, time, and money, it was just a plug wire; had I just grabbed a set at the parts store in CO Springs, which I considered, the problem would have been fixed right there.

So, hopefully that might help someone experiencing similar problems. Start with the easy solutions, and if it's cheap, it doesn't hurt to go ahead and replace, because bad components *can* "test" good.