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Old 02-17-2009, 08:13 PM   #1
bloomer510
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1998 Toyota 4Runner Possible Misfire

Some background. I have a 1998 Toyota 4Runner V6 2WD with about 150,000 miles. A few months ago the check engine light was flashing when I am travelling over 70mph. The dealership said nothing is wrong when I asked them to look into it. But I didn't get any codes from it. I read on-line that it could be a possible misfire so I changed the plugs and wires.

A few weeks ago, the check engine light came on and stayed on. I took it to a dealership to diagnosis the problem, they came up with Mass Air Flow sensor was shot. I replaced that, and reset the computer. It still comes on and flashes at highway speeds. I bought a low end computer to read the codes. I got P300 (Random/Multiple Misfire), P302 (Cylinder 2 Misfire) and P305 (Cylinder 5 Misfire). Cylinder 5 has the coil-pack and Cylinder 2 has the wire coming off the coil-pack for Cylinder 5. So I replaced the coil-pack. The light is still coming on and flashing. I was hoping someone could help me in figuring out how to stop the light from flashing. It comes on only when I am travelling past 70MPH. I have tried just rev'ing the engine up to the same RPM's as I am running when doing 70, but the light doesn't flash then.

Any help would be greatly appreciated.
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Old 03-06-2009, 06:33 PM   #2
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Re: 1998 Toyota 4Runner Possible Misfire

What code was found to indicate the MAF meter was bad?
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Old 03-07-2009, 08:30 PM   #3
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Re: 1998 Toyota 4Runner Possible Misfire

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What code was found to indicate the MAF meter was bad?
The code that came off the computer was P0171. That is the code that I read before I had the dealership try to figure out why that code came on.
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Old 03-08-2009, 01:30 AM   #4
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Re: 1998 Toyota 4Runner Possible Misfire

1. Are the new plugs DENSO K16TR11 or NGK BKR5EKB-11? Gap correct? (0.039-0.043")
2. Check vacuum hoses for bad fit or cracks.
3. Check injectors of 2 and 5 for correct voltage to open (9-14 V) and function.
4. Check resistance of injectors of 2 and 5 and opens and shorts in wiring harness for injectors.
5. Check fuel pressure and volume
6. Check MAF meter and ECT sensor
7. Check compression, valve clearance, and valve timing (timing belt).
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Old 03-09-2009, 07:49 PM   #5
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Re: 1998 Toyota 4Runner Possible Misfire

Quote:
Originally Posted by Brian R. View Post
1. Are the new plugs DENSO K16TR11 or NGK BKR5EKB-11? Gap correct? (0.039-0.043")
2. Check vacuum hoses for bad fit or cracks.
3. Check injectors of 2 and 5 for correct voltage to open (9-14 V) and function.
4. Check resistance of injectors of 2 and 5 and opens and shorts in wiring harness for injectors.
5. Check fuel pressure and volume
6. Check MAF meter and ECT sensor
7. Check compression, valve clearance, and valve timing (timing belt).

I did number one, and noticed I had the wrong plugs in, they only had the one prong, not the two. I replaced all the plugs with the double prong spark plugs. The light still came on. I moved to #2, I sprayed carb cleaner over the vacuum lines. The engine stalled out when I sprayed it on the PCV Valve hose, at the connection with the intake manifold. Tomorrow I am going to buy a clamp for that spot and put it on and re-test. I put a new hose on back in december when I replaced the PCV Valve, and noticed the hose was cracked.

Thanks for your help. I really hope this solves the problem.
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Old 03-11-2009, 10:10 AM   #6
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Re: 1998 Toyota 4Runner Possible Misfire

Even if it doesn't fix it, it was a good find.
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Old 04-06-2009, 02:05 PM   #7
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Re: 1998 Toyota 4Runner Possible Misfire

Quote:
Originally Posted by Brian R. View Post
1. Are the new plugs DENSO K16TR11 or NGK BKR5EKB-11? Gap correct? (0.039-0.043")
2. Check vacuum hoses for bad fit or cracks.
3. Check injectors of 2 and 5 for correct voltage to open (9-14 V) and function.
4. Check resistance of injectors of 2 and 5 and opens and shorts in wiring harness for injectors.
5. Check fuel pressure and volume
6. Check MAF meter and ECT sensor
7. Check compression, valve clearance, and valve timing (timing belt).
Status update. I am still in the process of going through all these tests to figure out the problem. I changed the plugs to DENSO K16TR11, they were bosch. I checked all hoses for cracks, bad fits or holes. Replaced as needed. I checked the injectors physically (not yet electronically). The injectors were physically damaged so they were replaced. When I did that, I replaced the intake manifold gaskets. The problem still occurs, and now is actually slowly getting worse and the light is coming on at 65mph. I will be checking the injectors for voltage, and resistance. Along with fuel pressure/volume, MAF meter, ECT sensor, and then the compression, clearance and timing in the near future.
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Old 04-06-2009, 04:22 PM   #8
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Re: 1998 Toyota 4Runner Possible Misfire

Thanks for the update.
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Old 04-13-2009, 06:18 AM   #9
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Re: 1998 Toyota 4Runner Possible Misfire

I am not sure if this matters, but out of curiosity I drove the truck at 55mph for 10-15 minutes, and turned over drive off, forcing the engine to be at a higher RPM(about 3100rpms) than when the over drive is on, and at 70mph (about 2500 rpms). The light did not come on. I do not understand why the light would flash at 70mphs and higher, but not at a higher RPM. I would assume that forcing it to a higher RPM would make it flash the light at a lower speed. Any ideas?
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Old 11-04-2015, 05:18 PM   #10
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Re: 1998 Toyota 4Runner Possible Misfire

Thanks for this post. I'm having the same issue on my 1999 4 Runner 4WD. I'm about ready to start looking at stuff. I've replaced the MAF 3 times already (running a K&N Air Filter which I found out is prone to mess those MAF's up) so I bought one from AutoZone with a lifetime warranty. Now I just take it in and swap it out. haha. If I find the issue, I'll let you know.
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