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Thread: 99 4runner rough start, strange idle, miss under load, help?

  1. #1
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    99 4runner rough start, strange idle, miss under load, help?

    Been going at this green turd for quite some time now and still have not figured it out.

    For starters:

    99 4runner Limited v-6
    173k miles
    Tune up last year
    Ignition coils 3 weeks ago
    Cleaned MAF and entire TB twice
    Replaced PVC and grommet
    No CEL's
    Head gasket leaks tested through radiator and none found.

    Originally the truck was starting with a rough 20-30 second idle that shook it like a tractor. It smoothed out and idled normally afterwards. I get a pretty big smoke show when it happens. The truck would feel like it is randomly missing when going up a hill around 3k rpms. It kinda felt like it was bucking and this made it hard to keep speed or accelerate. There will be a good 2-3 seconds before the truck would shut off as well. I had oil leaks coming from the valve cover (all around), oil pan, and oil fill cap. Oil was leaking into the throttle body as well.

    I was hinted that the PVC could be causing the issue so i ordered a Toyota PVC and swapped out my old one. The old one still rattled but was caked up pretty good. Over the next few days the symptoms slowly disappeared. The rough start was reduced down to 2-3 seconds. The misfire under load was gone. The shut down delay stopped and it would shut down immediately when you turned the key off. Start up smoke show was still there though but not as heavy. I thought I was good to go until the 20 second rough start and miss under load returned two days ago but no sign of it yesterday. Now.....wtf.

    I am guessing that pvc clogged up already but doubting that.

    Any ideas appreciated. I am at my wits end with this truck and about to get rid of it unless I can fix it. Two shops have had it and both were unable to figure it out. One shop recommended coils and injectors. Coils replaced but injectors on hold till i rob a bank.
    Last edited by muddeprived; 10-24-2018 at 12:18 PM.
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  2. #2
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    Did you check the fuel pressure? Make sure you're not losing pressure froma clogged filter or a pump on it's way out.

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    Quote Originally Posted by AngusGT View Post
    Did you check the fuel pressure? Make sure you're not losing pressure froma clogged filter or a pump on it's way out.
    I could be wrong but there is no valve on the fuel rails to check pressure. I did replace the filter about a month ago.

    I was thinking about the pump because I ran out of gas 4 times due to a faulty gauge and inconsistent mileage but everyone says Toyota pumps hardly ever fail but I am doubting that when you run out of gas as often as I do. I need to find a way to test fuel pressure.
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    I’m no Toyota expert by any means but I have had similar issues caused by a bad engine temp sensor. My truck would idle terribly, run so rich it smoked like a diesel and misfire randomly. If you have a decent scan tool you should be able to see what it’s reading to see if it’s erratic or inaccurate.
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    Right Wing Extremist! DMG's Avatar
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    Chris, what kind of plugs are in it? If you turn the key on to prime the fuel pump a few times will it start better?

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    Quote Originally Posted by Keith View Post
    Im no Toyota expert by any means but I have had similar issues caused by a bad engine temp sensor. My truck would idle terribly, run so rich it smoked like a diesel and misfire randomly. If you have a decent scan tool you should be able to see what its reading to see if its erratic or inaccurate.
    My 90 Suburban and 05 Ion both run like crap with a malfunctioning coolant temp sensor until they warm up and go into closed loop mode. I've had to fix that issue on both of those vehicles. So that may be related here.

    Also, if you don't have a pressure connection on the fuel rail then you need an inline piece that you install between two existing connections on the fuel line. The larger fuel injection pressure test kits have these. On my Suburban you remove the fuel filter and install one there.

    Good luck.
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    Quote Originally Posted by DMG View Post
    Chris, what kind of plugs are in it? If you turn the key on to prime the fuel pump a few times will it start better?
    It has a mind of it's own. Sometimes that helps, sometimes not.

    The plugs are the factory recommended dual tip NGK's. I forget the part number but it was what Toyota recommended. They are a year old.

    I replaced the temp sensor two days ago and it had no effect.

    Today I was driving up the big hill on 376 after the bridge in Monaca and the truck started bucking real hard and I could not accelerate any faster. I had to let it upshift to 4th and do 50 to the top. I went to Ohio for gas and then on the way home it felt like it was underpowered going up the hill to my house. I gave it more gas and nothing. It did not rev or downshift. I managed to limp it home.

    Last week I was locked and in 4-low hauling 1000 lbs of pellets up my backyard and it started bucking and cutting out.

    Seems to act up under load.

    No CEL's and no hidden codes (checked). I am stumped.
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    Quote Originally Posted by joshs1ofakindxj View Post
    My 90 Suburban and 05 Ion both run like crap with a malfunctioning coolant temp sensor until they warm up and go into closed loop mode. I've had to fix that issue on both of those vehicles. So that may be related here.

    Also, if you don't have a pressure connection on the fuel rail then you need an inline piece that you install between two existing connections on the fuel line. The larger fuel injection pressure test kits have these. On my Suburban you remove the fuel filter and install one there.

    Good luck.
    I have a fuel tester gauge that I've used on my Jeep's rail and I am trying to find an adapter to hook onto the fuel line. I think Toyota uses M14x1.5.
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    Well the pump died this morning. Pretty obvious now.

    Sucks I gotta tear it out in this cold weather.
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    Quote Originally Posted by muddeprived View Post
    Well the pump died this morning. Pretty obvious now.

    Sucks I gotta tear it out in this cold weather.
    Well that sucks but it should at least solve your problems with it running like crap.
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