# Worth doing?



## apmason (Jul 21, 2004)

I have a 1997 nissan pickup with a 4 cyl and am considering getting the head rebuilt. My odometer is broken but I think I am pushin 170k-200k miles. There is a shop nearby that will do a valve job, valve stem seals, mill it, acid clean it, pressure test and check for cracks for a couple hundred bux. Is all this worth doing on a truck that is running fine now? Wrong place to be spending money? Thanks in advance.


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## rogoman (Dec 16, 2004)

If the truck is running good, there's no reason to get the head rebuilt. Do a compression test on all cylinders to determine the condition of the motor.


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## apmason (Jul 21, 2004)

Thanks for the info. I suspected that was the case but I thought I would ask anyway b/c it may have been a good deal. Just wasn't sure.


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## apmason (Jul 21, 2004)

Great! I'll go pick up a compression test kit. What should the compression be on this engine?


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## CMax03 (Jan 17, 2009)

you don't have a book?


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## apmason (Jul 21, 2004)

My understanding was that higher mileage engines have a slightly different compression, so I was looking for the range I ought be within. I have books, but since I have been getting pretty good advice here, from actual people who have done the actual work, I figured this was better than a book. Its easy to post a snide remark, but its more helpful to respond to the question.


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## zanegrey (Dec 5, 2005)

just as long as it is well over 128 (172 high ) for the z24 and they are close 

the ka24e is142 to 192..and again they need tb close to each other..


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## apmason (Jul 21, 2004)

gotcha. Thanks!


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## apmason (Jul 21, 2004)

Ok, so I got (in order of cylinders) 135, 140, 135, and 150 dry and 140, 150, 150, 150 wet. The truck was warm and I held the throttle all the way open. Numbers sound ok, but not great. This was my first time performing this kind of test. Am I within the normal range for a truck with high mileage? Should I be concerned about the 15psi difference in cyl 3? Thanks!


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## rogoman (Dec 16, 2004)

I would say that with your high mileage motor, the readings are "par for the course". The readings after warming up the motor were no more then 10 psi differential so that's OK.


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## apmason (Jul 21, 2004)

thanks! could low compression cause the truck to idle low periodically? Thought it was the egr but that didn't fix it when I replaced it. Have a great day!


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## rogoman (Dec 16, 2004)

Lower compression will have no effect on an intermittent change in idle speed. The problem is most likely in the IACV assembly which controls the idle; it might need cleaning. There could be a lot of powdered carbon in it which would prevent the AAC valve from moving freely.


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## apmason (Jul 21, 2004)

Cool. I was thining it was either that or the maf. is there a place I can look for a diagram of the iacv and cleaning instructions? i notice that the rpms fade slowly as it idles while cold, but stay relatively steady once the engine is warm. once its warm though as it goes from driving rpm (say over 2k) to idle the rpms fall very low (close to 500) and creep back up. Tends to idle right under 1k. I'm thinking these two symptoms are related. Thanks!


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## rogoman (Dec 16, 2004)

Here's a picture of the IACV assembly. It can be removed and cleaned. There's a plunger and a spring, so be careful with the order of assembly.


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## apmason (Jul 21, 2004)

man that is a perfect pic. thanks! order of assembly, no problem. Carb cleaner or is it sensitive? The maf needs somethin special i know. but this?


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## rogoman (Dec 16, 2004)

Carb cleaner is OK for the IACV. However for the MAF, use only ELECTRICAL CONTACT CLEANER or a cleaner specifically made for MAF hot wire cleaning which you can buy at any auto parts store; this is the only thing you should use to clean your MAF. No windex, no carb cleaner, no brake cleaner, no rubbing alcohol, and no Q-Tips.


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## apmason (Jul 21, 2004)

sounds good then. I'll do the iacv and if that doesn't fix it I'll move on to the maf. I'll get this sucker runnin smooth eventually!


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## apmason (Jul 21, 2004)

The pic is a ka24de and mine is a sohc. I looked at the intake manifold and I'm pretty sure I recognize the part, but just for clarification... It is on the front of the intake mani behind the ps pump, right?


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## rogoman (Dec 16, 2004)

It should be in the same location at the back of the intake manifold as on the KA24DE. It bolts on to the back of collector box.


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## apmason (Jul 21, 2004)

huh. I was looking at the wrong part. w/o the air cleaner on its easier. in this pic it is the unit mounted on the throttle body with the two solenoids right? 










Looking at my engine I see the same part on the right (looking in from the front) on the tb and its facing the intake mani and valve cover. 4 screws. pretty tight clearances.


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## apmason (Jul 21, 2004)

Yep, that was the issue. or most of it at least. I couldnt get the iacv disassembled but I sprayed the heck out of it with carb cleaner and used a q-tip once it was off the tb and the solenoid was off. Works much better. Still not perfect, I may go ahead and clean the maf for the heck of it. Thanks for all ya'lls help.


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## zanegrey (Dec 5, 2005)

update.......


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## apmason (Jul 21, 2004)

update: the truck generally idles just fine now. it has some periodic low idle that I cant isolate situationally. I gotta say that the iacv cleaning and the egr replacement have made a heck of a difference with this truck. I am going to clean the maf tomorrow. Will update again monday. Am gearing up for the timing chain replacement in a couple weeks.


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## zanegrey (Dec 5, 2005)

did u go thru all the vac lines and look for cracks and holes ??

u can pull the maf and inspect it..check the wires to see if they have build up ...


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## apmason (Jul 21, 2004)

I checked most of the lines. They look great, except for the one that went to the bottom of the vvt from the egr bypass, which I replaced. The iacv was pretty bad. I am assuming that the maf needs cleaning, but I'll do a visual inspection first, of course. What does buildup look like on the wires? Is it carbon or something else?


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