Engine warmup

[norstar]

Each time I start my car, it sputters and a slight back fire. revving the engine and it almosts stalls. I have replaced all of the vacuum lines but I do hear a "sucking" noise.

 

after 5-10 minutes. It runs fine. if I drive it 2 hours later it is ok... If I wait 5 hours, same thing.

 

I am pretty sure it is a faulty vacuum hose but it running fine after 5 minutes is throwing me a little bit, does anyone have a diagram which shows all vacuum hoses?

[100dollarZ]

That sounds alot like a carb problem since it goes away after it runs.

 

however,

Have you tried a vacuum gauge hooked up to a dedicated vacuum source? if its a nice steady reading at approx 17-21 in/hg then that should be OK assuming its a stock engine.

Try a gauge and see if any of these symptoms are what youre getting:

http://www.classictruckshop.com/clubs/earlyburbs/projects/vac/uum.htm

 

Good luck.

[fisheric]

I am having the same problem. The car has always had this problem since I bought it. This summer I replaced all the vacuum hoses and did a full tune up and it was running really well. And not doing it at all.

 

When I bought it (81 zxt) the owner who is a friend told me it was the egr valve and that he tried to find one and couldn't buy it anywhere. I ordered one from black dragon. This didn't fix the problem but when the car was acting this way if i disconnected the tube to the egr the car would run fine. later i could reconnect it and it was fine again. and just like you after it was warm it would be fine,

 

however sometimes when the car is having this problem and it last more than 30 minutes i notice that the temperature gauge is reading only half what it should (about quarter way instead of half)

 

i've tried everything to fix this and cant. except adjusting the mass air flow sensor. i've been afraid of adjusting it incorrectly.

 

is you car Fuel INJ?

 

Please post if you figure this one out because I am out of ideas.

 

Oh and one time the car was doing this pretty bad and I changed the spark plugs which were only a few weeks old and the problem went away and the temperature was back into the range it should be. dont know if I knocked something while I was in there or if plugs somehow did something.

[mom'sZ]

OK... for the original poster (norstar)... you will help us diagnois your problem much easier if you post the year / model car with your question. Also for something like this, whether it is stock carb / fuel injection and if not, what mods. I'm going to guess you are talking about the car in your signature, 74 260z. If so it is a carb car. Since you stated that you've replaced all the vacumn lines, 100dollarz's suggestion that it's a carb problem may be a good place to start. Perhaps a warped throttle plate or bad gasket leaking air until it warms up and seals itself. Also maybe leaky intake manifold gasket. The sucking sound could be bad vacumn booster if you have power brakes or the line that runs to it. Just throwing stuff out there.

fisheric: thanks for posting year / model. I'm not super familiar with the zxt's FI but it is similiar to my 77. You also state that you replaced all the vacumn lines. Have you checked the big one that runs to the air regulator? This sort of makes sense because the problem occurs when cold. The air regulator helps during warm up to slightly raise the idle speed when the engine is cold. Check Dareon's sticky for the fuel injection bible at the top of this forum. Download it and read for more info on how the air regulator works and how to diagnois. You stated that this past summer you replaced all the vac lines and it cured it but came back. Could be that during the summer, when warmer, the air regulator wasn't needed and the problem was masked. Even if the big fat line that runs to it looks good, remove and inspect. Sometimes a line can look decent, but if you look close at it, bend it this way and that, it will crumble in your hand. The line to the brake booster could be a similiar issue. Slight crack, seals up when warm. Leaky intake could be your issue as well. Check the boots between air cleaner and AFM and AFM and throttle body. Again, pull them off, spread the pleats and look in there. Post up results, even if you cure it, so to help others.

[fisheric]

fisheric: thanks for posting year / model. I'm not super familiar with the zxt's FI but it is similiar to my 77.

mom'sZ

 

You know what you are talking about for sure. Yea I know alotta guys around here dont have the zxt but I know that alot of the members have the zxt's turbo engine.

 

Could be that during the summer, when warmer, the air regulator wasn't needed and the problem was masked.

Im almost positive this is the case because during the summer here in Sacramento we had warm weather all week and then one night it got pretty cold and that was the first time it did it all season.

Even if the big fat line that runs to it looks good, remove and inspect. Sometimes a line can look decent, but if you look close at it, bend it this way and that, it will crumble in your hand.

I don't understand which hose you are talking about. I do know that I didn't replace any hoses bigger than the fuel line. Could you be more specific as to which hose you are talking about?

 

The line to the brake booster could be a similiar issue.

where does the other end connect to?

 

Leaky intake could be your issue as well.

where would the intake leak from?

 

Check the boots between air cleaner and AFM and AFM and throttle body. Again, pull them off, spread the pleats and look in there.

I tried to get them off but they were stuck so I eventually gave up

 

Post up results, even if you cure it, so to help others.

I definately will. As you can see I've been a member of the board for awhile and I dont know if I ever posted before yesterday. I was able to solve my earlier problem by using the serch feature. I understand the importance of putting up all correct or useful information for the sake of the community.

 

 

Sorry for posting such a long reply with so many questions. Just if you get the time to answer id appreciate it.

 

 

Should I start my own thread? I only posted here because it originally sounded to me like we were perhaps suffering from the ailment(s)

[mom'sZ]

...then one night it got pretty cold and that was the first time it did it all season.

I don't understand which hose you are talking about. I do know that I didn't replace any hoses bigger than the fuel line. Could you be more specific as to which hose you are talking about?

first picture is line drawing of air regulator. Second picture is line drawing of engine from above with big red line pointing at air regulator

This picture is of oddmanout84's engine compartment (hope he doesn't mind) showing hose leading to regulator (click the pictures to make them bigger) Aux. air regulator feeds additional air into the intake when the engine is cold to raise the idle. Read up in the FI bible on how it works but, it has a big hose leading to it and coming out the back of it. If the hose is cracked, air could be sucked into the intake. Same with the hose running to the brake booster.

 

where does the other end connect to???

One end connects to the brake booster, the other to the intake manifold (on top near the back) with a one way valve mounted on the firewall halfway down the hose.

 

where would the intake leak from

Most likely at the gasket surface between the intake manifold and the cylinder head. This would be more likely if the manifolds had ever been off but could be from manifold warpage. Hard to discover, some guys spray carb cleaner on the area while the car is running, but be careful if you do so as not to catch yourself on fire!

 

I tried to get them off but they were stuck so I eventually gave up

Keep trying. Remove the clamps completely. Then peel the edge up slowly all the way around. If they are the original ones they are most likely cracked. Once it's off, spread the pleats and look down inside there.

 

I was able to solve my earlier problem by using the serch feature.

BRAVO!!!

 

Should I start my own thread? I only posted here because it originally sounded to me like we were perhaps suffering from the ailment(s)

Nope... very simaliar problems, good thread title

good luck!!!