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Discussion Starter #1
I sort of delved into this issue a little on my head-gasket job thread:
https://www.toyotanation.com/threads/replacing-single-head-gasket.1659842/

But I felt like I should start a new thread, since this problem is (I do not think) related to me changing head-gaskets.

The problem:

If I clear all codes and drive for roughly 20 miles or so, I will get a CEL with code P0301 (misfire on 1).
I can repeat this and it will always happen t he same way. I currently do not have a gauge where I can see real-time (but it is on my get-list).

So far, I have:

Swapped plugs, coil, and injector with 3...same result..problem did not move over to 3. I also used new o-rings when moving the injectors.
Checked for vacuum leaks using carb-cleaner. This method helped me find all the cracked vacuum hoses I had (and replaced). It is not showing any more vacuum leaks.
Cleaned MAF and throttle body.
Cleaned all grounds (including the brown grounds by the diagnostic port)

My guesses as to what might be causing this are:
semi-broken wire on the harness that breaks the circuit during driving ?
..or
I noticed that injector 1 does not seem as tight as the other injectors. I can wiggle it a little more freely than 3 and 5. Could my fuel-rail be slightly bent upwards on the end with injector ...so it is not tightening down as much as the other injectors....


Any other hunches? I read one post where a guy found a nick on the tone-ring of his crankshaft, which caused a random misfire. I might pull that lower cover off so I can look at it just to rule that out, but that seems like an obsure thing to happen.
 

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Sounds like a PITA...

Well, Bam already suggested to check grounds on the intake by connector. There is one more on the back side of the intake that held by small screw that you have to use stubby to screw in.

There is also another test I would probably do - cylinder leak down. Tool is readily available in Harbor Freight for 30 bucks. (link below)


Other than that... maybe pull up wiring manual and check continuity and short to ground of wires going to #1 injector.
 

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Discussion Starter #3
T
Sounds like a PITA...

Well, Bam already suggested to check grounds on the intake by connector. There is one more on the back side of the intake that held by small screw that you have to use stubby to screw in.

There is also another test I would probably do - cylinder leak down. Tool is readily available in Harbor Freight for 30 bucks. (link below)


Other than that... maybe pull up wiring manual and check continuity and short to ground of wires going to #1 injector.
Thanks for the suggestions. Yes, it is sort of a PITA. In my mind I now refer to the CEL as the HBL (High Blood Pressure Light)

The local NAPA lets me borrow tools, and they happen to have a nice Leakdown Tester. In fact, I used it a few months back to determine head gasket issues after over-heating.
 

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Since we've isolated the issue to be with only cylinder #1 and not the injector, coil, or spark plug, it's gonna come down to wiring. The injector should be gitting 12VDC at all times when the ignition key is on. It's the ground that's switched/pulsed from the ECU that fires the injector. ;)

The wire fer injector #1 is white/red stripe. It should be a straight connection from the injector connector to the ECU. According to my 1998 EWD, it looks like that wire is on the ECU connector D, pin 10. You'll have to do a continuity and resistance test from there to the injector connector to make sure there aren't any issues with the wire. The other suspect would be the power splice connector E3 but there are many other items running off of that connector that would be affected if that was the issue. Still wouldn't hurt to inspect it from there to the injector connector. You can also inspect the wiring harness connector just to make sure the wire isn't just hanging on by a thread or the insulation. ;)
 

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Discussion Starter #5
Since we've isolated the issue to be with only cylinder #1 and not the injector, coil, or spark plug, it's gonna come down to wiring. The injector should be gitting 12VDC at all times when the ignition key is on. It's the ground that's switched/pulsed from the ECU that fires the injector. ;)

The wire fer injector #1 is white/red stripe. It should be a straight connection from the injector connector to the ECU. According to my 1998 EWD, it looks like that wire is on the ECU connector D, pin 10. You'll have to do a continuity and resistance test from there to the injector connector to make sure there aren't any issues with the wire. The other suspect would be the power splice connector E3 but there are many other items running off of that connector that would be affected if that was the issue. Still wouldn't hurt to inspect it from there to the injector connector. You can also inspect the wiring harness connector just to make sure the wire isn't just hanging on by a thread or the insulation. ;)
Thanks Bam! That is good info to explore. Luckily I own a fairly decent volt/ohm meter with an audible continuity tester. I will check wiring and also do the leakdown test like CreoX suggested.
 

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Another thing to check is that the connector hasn't been compromised. Is the socket contacts the same distance apart or does it look like one or both are bent and loose? ;)
 

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Discussion Starter #7
It is possible that I have found the issue.

I was googling around and found some guys on youtube who were chasing down an identical issue as mine: random misfire on cylinder 1 after 20 miles or so. They were blasting the problem with what some people call the "New Parts Canon", replacing everything they could think of with new parts, starting with plugs, wires, injectors, MAF Sensor, both o2 sensors...etc.
Finally they identified some play in the crankshaft, and figured out the play was causing random misses on the crank-shaft sensor.

I checked my crankshaft, and do not have play; however, I took out my crankshaft position sensor to clean the connections and found it was covered in mud and debris. On top of that, the plastic part that bolts the sensor to the engine was cracked and fell to pieces when I pulled it out:

283140



When I was doing the timing belt this summer, I failed to pull that sensor out and inspect it. Also I sprayed out the area to clean it up before putting the new timing belt in. I must have blasted all that debris onto the sensor.

I am ordering a new sensor. Meanwhile, I am cleaning this one up and seeing if I can epoxy the bolt hole back together so I can test if it fixes the issue, but it looks like a likely culprit.


Stay tuned.....
 
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