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Running problems

Tiny
MATS17
  • MEMBER
  • 1998 TOYOTA 4RUNNER
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 155,000 MILES
I have a 1998 Toyota 4runner. I have had the same problem for almost a couple years. When I accelerate the vehicle stumbles and hesitates, it also backfires during heavy acceleration.
I have scanned the computer and the code that comes up is p0340 (cam positioning sensor). There was also code for ignition coil pack but that went away when replaced with new coil packs.
The engine us 2.7L
I have replaced cam positioning sensor, ignition packs, wires and spark plugs.
One of the spark plugs was cracked and It ran great or about 2 weeks after the spark plugs were replaced. After about two weeks it started to stumble and backfire again.
About a week ago I was checking the crank position sensor for resistance and voltage an I noticed oil inside the plug. I cleaned the oil out and plugged it back in and it ran great for about a mile or two then it started to run rough again.
I have checked the the resistance and voltage on the cam and crank positioning sensors. I have checked the timing chain and it hadn't skipped a tooth. It appeared to be fine as well.
I'm really stumped and don't know what to do now.
I had also changed the fuel filters before a code had come up.
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Sunday, June 12th, 2011 AT 10:51 PM

10 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
If it's really a cam sensor the signal plate shold have been changed as well. It should have 835-1400 ohms cold. But it also says to check and make sure grounds are clean. If you noticed oil inside the plug on the crank sensor then where is oil coming from. Oil will conductelectricity and it may be shorting out the sensor givinga false code. You could have a short in the wiring as well, but the manual says the ecm may be at fault for this code as well. I would check for poor connections at the ecm tomake sure it's ok as poor connections will give you thesame problem.
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Sunday, June 12th, 2011 AT 11:41 PM
Tiny
MATS17
  • MEMBER
  • 7 POSTS
I have checked the ECM connections and they seem to be fine. No burnt odor or anything likethat. The only thing that I can think is that oil was spilt on the plug. I sprayed the plug with electrical cleaner and cleaned it the best I could. Where is the signal plate?
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Sunday, June 26th, 2011 AT 9:21 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Your cam sensor shod be n teh distributor so the plate would be either below it or where the cam sensor can see it. Like a magnetic strip or plate on bottom of dist. Have you cleaned the ground or disconnected one and not reconnected it.
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Sunday, June 26th, 2011 AT 10:20 PM
Tiny
MATS17
  • MEMBER
  • 7 POSTS
It is a distributerless system. It has the two ignition coils packs instead which have been replaced. Would the plate be on the cam then? I will double Check my ground connections.
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Sunday, June 26th, 2011 AT 10:35 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
The book I have says it's adistributor system but they can be wrong. And ya the plate wouldporbably be connected to the cam. The signal plate is mounted on teh intake cam, it is a one tooth thing. I'm sending the instructions on how to check this. Ther eis a red wire and green wire going to the cam sensor. The green wire goes to the crank sensor and then to the ecm at ne6 position. The red wire goes to g1 11. Check these for making good connections as there could be something broken in there.
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Sunday, June 26th, 2011 AT 11:35 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Screwd up, her eit is. Also one other thing. Looking in the tips sectionsomehow these vehicles screw up the computer as well and you need to disconnect the battery for 10 minutesand then reconnect it. This will reset and clear your computer andthat may all that may berequired. Try that first before checking the harnesses out.
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Sunday, June 26th, 2011 AT 11:37 PM
Tiny
MATS17
  • MEMBER
  • 7 POSTS
Thanks for the info. In regards to the signal plate, it should always be replaced when you replace the sensor? Or do you inspect it for wear, damage etc? In the past I have always had the battery disconnected when I have been working on this issue, which has always been well over a half hour at least and the engine light alwayscomes back on within a minute and when I scan the computer it spits out the same p0340 code. Cam pos sensor. I will look at the connections etc more closely.
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Monday, June 27th, 2011 AT 12:57 AM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
It's reccomended to replace the signal plate but it can be a loose connection as well screwing it up. Good luck on your checking it out. Ifnot take it to a pro and see if he can figure it out.
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Monday, June 27th, 2011 AT 1:27 AM
Tiny
MATS17
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  • 7 POSTS
I havnt been driving it lately. A friend who is a heavy duty mechanic mentioned about it could be the crank positioning sensor. About a month ago I unplugged the crank sensor and there was oil in the plug. I cleaned the oil out with q tip plugged it back in and drove for about 2 miles with it runnig perfectly then it started to run rough again. I cleaned it a second time with electrical contact cleaner and it didn't make adifferennce the second time. Someone told me that the oil shouldnt make a difference because it is a insulate. My mechanic fried told me otherwise. Was wondering what your thoughts are on this situation?
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Friday, September 2nd, 2011 AT 7:19 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
A crank sensor runs about.030-.60 fromt he crank soit is natually going to get bathed in oil. That is why they are sealed in epoxy. So oilwon't effect it at all. I initially gave bad advice about the oil n cranks sensor, I must have been tired. You could see if the distributor has a pin through it if it's got a gear and see if that has bent as that could give you a cam sensor problem as well. Also check your fuel pressure as you may have a bad pump, regulator or injector. It should be 31-37 psi then hold 21 psi for 5 minutes after turning pump off. The fp test gets a little involved and if you odn'thave a fp gauge then have apro do it.
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Friday, September 2nd, 2011 AT 8:20 PM

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