z31 mysterious sputter

[eishiba]

I have an 85 300zx 5 speed turbo. When I start this car, it will run for about 2 minutes fine for the most part. Then it starts to act as if its not getting any gas and sputters REALLY bad. It will die if you dont give it any gas. The tach has gone down as low as 300rpm trying to stay running when I'm giving it gas so it doesn't die. After another 2 minutes, it stops and the cars power returns and runs just fine. You can drive it for hours after that and it runs fine. Its just those first few minutes that is has this problem. Once the sputter has stopped and it runs fine, you can turn it off, turn it back on, and its still fine. This sputter will happen again if you leave the car off for maybe an hour or so. I have changed the tps sensor, crank angle sensor, and the fuel filter. I thought if the fuel pump was bad, then you could simply NOT hear it run when you turned the car to the "on" position. I have two videos below. One outside the car, and one while driving.

https://www.youtube.com/watch?v=O-AHlzT ... hrC7SvcQGg

https://www.youtube.com/watch?v=J_66e4RkVm4

[evildky]

How about the Idle air circuit? The iacv could be gunked up and sticking, I'd start by cleaning and adjusting the iacv.

[G-E]

Could be a bad tps too? Check harness/plug for broken/corroded wires

[eishiba]

Ok, I am updating because I decided to take it to a shop. I'm going to type everything that they did and said in the report.



Test drove. During warm up, started running bad and hesitated. Only ran bad for a few minutes then ran ok. Checked codes. Has a code 12 for MAF problem. Tested MAF and passed in ALL DATA. I even checked input at the ecm. It matches the reading at the MAF.

Test Drove and coolant sensor input at ECM did not drop out or jump at too (I can't tell what they wrote here. I could be mistaken but I think it says "too cold or too hot") input when it acted up.

Scoped ignition system. All looks normal. Check ignition timing at 20 degrees BTDC. Spark plug #3 was loose. Tightened to torque specs.

There is a rattling, squeaking noise from behind the timing belt cover. Sounds like a bearing trying to lock up. If timing belt jumps on this engine it will bend the valves.

Test drove while monitoring MAF input at (I want to say it says ecm but it looks like pcm). The input did not drop out when car acted up. So I think the MAF is ok.

Checked fuel pressure. Has 30 psi with vacuum to regulator. 40psi with no vacuum. Has 30 psi when shut off. Spec is 30 psi and 37 psi. Fuel pressure is not the problem.

Every time my hand is near the distributor cap I get shocked. Found there is a secondary leakage out the cap around the #2 plug wire connection area. Needs a new cap but probably won't fix the problem.

I give up. I don't know whats wrong with this vehicle!



I found it funny that a certified auto mechanic put that last part in the report. I'm going to change the distributor cap tonight. Any other ideas?

[G-E]

Check to see if the EGR is stuck open, if you reach under the diaphragm, you should be able to freely push it up with 2 fingers, and it should come back down with equal force

Obviously if the cap is shocking the guy, replace the dist cap...

If it makes a squeezing noise near the distributor, it could be a slightly seized idle-control -- you'd have to remove/clean it

If it sounds like clattering anywhere in the valvecovers, you probably have one or more collapsed/stuck lifters -- there's a writeup on cleaning them

You might as well take the upper timing cover off to check the belt, and check the belt tension using the twist method, you should be able to twist the belt something like 75-80 degrees between cam gears with 2 fingers -- if it can't go past 40, it's too tight; if it goes past 90, it's too loose

Start there

[evildky]

If the cap or wires shock you you are loosing spark, replace the known bad parts and may well fix your problem.

This is an interference engine, if the belt breaks or strips you bend valves. If you do not know when the belt, tensioner and idler were last replaced, replace them!

[huangben1985]

Have you solved this problem? I have the same issue here!