Vaccume leak or fuel/electrical system problem? 86.5 Hardbody 4x4 4wd Z24 EFI

bonzo1605 · Nov 28th, 2006, 01:49 AM

So I have this problem, or (many problems depending on which wrench I take my truck to) For a while now I've had an Idle issue where the rpm's would fluctuate between 1k and 1.7k when your in nuetral, was told it was a vaccume leak but didn't now where at. however this never affected the power/performance of the engine (which was remanned about 8k miles ago) So the other day I'm driving around and when I would step on the gas as I am trying to get up to speed the truck would jerk and not respond proportionately to my foot on the gas pedal. Basically what ever gear I was in with RPM's below 2.3k the truck would sputter until it worked it's way up to about 2.5k and would then kick in and respond like normal? After running it awhile, getting on the freeway, and then off, the truck wouldn't hold an idle.

So I take it in to a mechanic and they can't figure out the problem. They then decide changing plugs, and plug wires would surely fix the problem, it doesn't. Then they dig deeper and find that the mass air flow sensor is shot, as well as the fuel pressure regulator (both located on the throttle body) So I have them replace those and my bill is up to $700 and then they find that there is a leak at the intake gasket. Well now I am out of money. The truck now holds and idle but still sputters under load below 2.5k rpm's.

Here is my question (sorry it took me 2 paragraphs to get here) Should replacing my intake gasket fix my power/performance issue? or is there probably more going on here than just that. Keep in mind I have been told the Cat. and muffler both need replacing. I want to keep this truck but it seems that this particular engine configuration is fairly troublesome for mechanics to diagnose problems which in turn cost me money. Should I just get rid of it? or will the intake gasket get me back to or (close to) normal?

Thanks for your help!

Jeff

NPath · Nov 28th, 2006, 07:13 PM

Tell you the truth... replacing the intake manifold that's leaking may solve the problem. I'd let them do that before anything else (cat converter & muffler) and if it doesn't run right... store it, sell it whole or parts. Replacing cat converter and muffler won't make the engine run right, but it'll fail exhaust testing.

The Z24I is a simple little engine and I've experienced the problem you had, but replacing the throttle body fixed my problem, but didn't completely on yours.

The problem I had on my Z24I engine was the throttle body wasn't getting 4.5v, it was getting about 2v making my engine run like crap, if it's able to run.

So yeah, replace the intake first and see how it goes. When you're out of money, it's hard to upkeep a vehicle.

gradechecker · Nov 30th, 2006, 04:59 PM

Hey, I had the same problem with mine once, its the primary ignition coil. 40 bucks at the local hardware store.

bonzo1605 · Dec 1st, 2006, 02:05 AM

Thank you both for your input. This is exactly the kind of info I was looking for. I've got a haynes manual that looks like it should guide me through the Intake gasket replacement and the ignition coil seems pretty simple and self explanatory. I am going to give them both a shot this weekend and hopefully all is good! I will post again w/ my results.

azmike · Jan 27th, 2008, 01:53 PM

i have the same truck. i took it for a tune up, after that the trucks rpm's ran up and down. shops wanted $125.00 to tell me what was wrong, u know what told them.......! I didn't fix it for years. then i took an auto electronics class just to see what i could find out. i looked at another nissan in class and discovered two small hoses from the air cleaner in the front to that branch of tubes, in the front, had been swiched around. question remains, did the tune-pu guy do this intensionally? the hoses do not cross, they drop down into positon, hmmm.

hope this helps.

d2e2 · Feb 3rd, 2008, 10:12 AM

I've been having similar problems with a ka24 engine. I replaced all the vacuum hoses, took awhile to find them all. And then I tightened the valve cover and intake manifold down a little. This helped a lot, the engine is now idling steady at about 800 to a 1000 rpm, not perfect. When I say "about," I mean the onboard tack reads 800 but the engine could actually be idling at a 1000 due to the calibration of the tack.

Someone reminded me that using propane gas to trouble shoot vacuum problems works real well and so I tried it and found I have a leak at the intake manifold between 1 and 2 cylinders.

This may be caused by a bad gasket or improperly torqued mounting bolts. I don't have a torque wrench yet but I'll get one this week and re torque the manifold.