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720 4x4 problem


ckm319

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Hello from Georgia with first time post. I know you guys can help so here it is: I recently bought a  1985 Nissan 720 king cab 4x4 from the original owner my neighbor. It has 86,000 original miles on it. 

I replaced the plugs, wires, cap and rotor and its been doing good, I've cleaned it up and its nice. I pressure washed underneath i and re under coated it and now she's not so good. My wife and I drove it about 30 miles and I never reved it over 3k rpm. Sunday it wouldn't idle but ran fine but I went back out later and it cranked and idled, today It wouldn't idle and began a tad of skipping while keeping it at 2k rpm so I could check it. The fuel pump is clicking but unsure of fuel pressure. I have the factory service manual but haven't dove in it yet. Any thoughts are welcome and appreciated gents!

I also noticed it doesn't seem to get as warm as it did, It was middle ways on temp gauge but now barely gets into normal range.

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Well first things first. Any mention of temperature problems, check the rad is full and then drain enough so you can change the thermostat. Get a $10 one 180F, don't cheap out and don't forget a new gasket. If the thermostat has a small hole in the outer edge or a jiggle valve this goes to the top and the spring side into the intake. You'll know what I mean when you see it.

 

The Z24 is known for blowing the head gasket. Sudden changes like that are troublesome. There is no harm in re-torquing the head bolts. If you haven't driven it then perhaps if the bolts are loose, tightening then in time may help.... it won't hurt. You'll need to borrow a torque wrench. On a cold engine...( let sit over night) take the valve cover off and there are 10 bolts. Loosen only one and then tighten it to 60 ft lbs. When tight, move to the next bolt and loosen and tighten to 60 ft lbs. Only one bolt is loose at a time so you are free to do any order, front to back,  side to side whatever you like. This should be done every year after this.

 

Other... Check your previous work, wire fell off a plug or the cap came loose? VERY important that you use only NGK plugs on a Nissan. BPR6ES on the intake side, BPR5ES on the exhaust. 

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A mostly plugged filter will restrict flow. As idle needs and uses the least amount of gas to operate, a plugged filter doesn't really affect this. However when driving under a load such as passing or climbing a hill or sustained acceleration through the gears you can easily use gas faster than it can get to and keep the carb full and it will act like it's running out of gas till you slow down. Then it resumes working and idling normally.  Now if you don't know when the filter was changed last or if over 2 years ago, it can never hurt to change it.

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Thanks guys, I used NGK plugs, I changed the inner fuel filter a few weeks ago, I'm guessing since he didn't know it had one that it had never been changed but it diddn't look as bad as I thought it would. It used to auto choke when I pumped the gas and it stopped that during this fit it's throwing. I had planned on re torque of the head bolts this saturday anyway and wish I had already done it before we took it for a stroll but I was very careful not to strain the engine. The temp was runiing middle of the gauge before and I think that's where it was supposed to be.

I'll try the head bolts firs but after reading all the posts on here I kinda think that may be it, Its a great looking truck in and out, We were justbringing her back to life a little a time.

I'll keep you guys updated on how it works out. Everything was going so well😒

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AFTER torquing the head bolts while the engine is cold, take the top off the air filter and look. Choke plate should be partly closed. Have someone step on the gas the plate should snap fully closed. Does it? Warn the engine choke plate should open fully to vertical in about 5-10 min of idling. Does it? If not, the choke partly on can also ruin the idle and running. This is an easieer fix than a head gasket change.

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Thanks guys! For giggles I came home tonight and tried to start it even though I shouldn't have. I stepped on the gas and she fired right up and was choked and running smooth as ever!

I took the choke off because I didn't want it to get warm before I re torque the head this weekend, As to what it's problem was and evidently is I really am clueless. LOL

I'm happier because I don't think its the head gasket yet but I wasn't wanting to push it. I took it off choke in 30 seconds and it died but I re cranked it and held the accelerator to 1500 for a minute or so and it idled at 1200 RPM, I cranked it back up a few times without gas and it fired up every time, I'll wait until I do the re torque to further troubleshoot so maybe it's something else. My wife and I have worked really hard on this project and were disappointed it was going to be work other than expected. any and all thoughts are appreciated guys!

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So I re torqued the head bolts today and a couple were questionable. I also took apart and cleaned the air charge vale in the front of the air cleaner, it had acorns in it believe it or not.

I changed the oil and put Rotella 15-40 in it.  It seems to run well but I'm thinking about doing the Weber carb swap and eliminating possible gremlins. Thanks for all the help! This is a very informative site!

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