vacuum leak?

nogoinsnow · Dec 15th, 2005, 09:12 PM

Hello all. I have a '87 z24 (tbi) and lately it has develped a misfire. I think it is a vacuum leak, but am not 100% sure. It happens mostly at light throttle and low rpm, but is getting worse and happening more. The problem is still intermittent, and sometimes it runs good for a while and then starts acting up.

I have changed all 8 spark plugs, and it has a new air cleaner filter. The vacuum control valve (canister)? is rusted, has a big hole in the top and some of the vacuum lines connecting to it are in bad shape. In real cold weather, I can see steam coming from the very left front corner of the hood, right where the vacuum control valve is located. The vacuum canister or whatever it is called has been rusted for a long time, but could it have gotten worse and is now bad enough to cause this problem?

Also, the engine stays cold in cold weather, which I assume is the thermostat? I also have heard a reverse power flush for the radiator can sometimes fix this if it is clogged. My temperature gauge needle stays buried past 'C' no matter how long the engine has ran.

Also, we checked the distributer to see if any condensation was in there, it is dry as a bone. I suppose it could be a bad ground or other spark related problem.

I am not getting any check engine light either. I am going to try to find a manual (FSM or other) tomorrow. If anybody has any advice, I would sure appreciate it. Thanks.

dvdswanson · Dec 16th, 2005, 01:50 PM

check your temp sensor and the gauge, you probably have a bad sensor or the wire came off. for the vacuum leaks if your cannister is rusted through replace it along with other damaged pieces and vacuum lines if they are cracked.

nogoinsnow · Dec 19th, 2005, 12:44 AM

Update:

The nissan dealer tells me that I need NGK-5 plugs on the exhaust side and NGK-6 plugs on the intake. I replaced all 8 plugs (again) per these OEM specs.

I also replaced the thermostat, that fixed the no heat problem.

Still have the problem of cutting out/sputtering. Unfortanately, the spark plugs did not fix the problem. I have also inspected the distributer cap and rotor, and don't see any problem. I don't know what is causing the misfire at this point. It could be a vacuum leak, but I suspect it is a spark problem.

I got my Chilton's manual, but I really don't know what to try next.

I talked to a local nissan specialist who said the canister rusts on every z24 he has seen, he didn't think that was enough to cause a misfire. Actually, the canister had been "bypassed" on the '87 truck he was working on while I was talking to him. He says it just recirculates exhaust. Besides, it has been rusted since I bought it 2 years ago, and I never had a prob before.

Anybody got anymore suggestions? Thanks.

dvdswanson · Dec 20th, 2005, 10:02 AM

Quote:

Originally Posted by nogoinsnow

Update:

The nissan dealer tells me that I need NGK-5 plugs on the exhaust side and NGK-6 plugs on the intake. I replaced all 8 plugs (again) per these OEM specs.

I also replaced the thermostat, that fixed the no heat problem.

Still have the problem of cutting out/sputtering. Unfortanately, the spark plugs did not fix the problem. I have also inspected the distributer cap and rotor, and don't see any problem. I don't know what is causing the misfire at this point. It could be a vacuum leak, but I suspect it is a spark problem.

I got my Chilton's manual, but I really don't know what to try next.

I talked to a local nissan specialist who said the canister rusts on every z24 he has seen, he didn't think that was enough to cause a misfire. Actually, the canister had been "bypassed" on the '87 truck he was working on while I was talking to him. He says it just recirculates exhaust. Besides, it has been rusted since I bought it 2 years ago, and I never had a prob before.

Anybody got anymore suggestions? Thanks.

take a garden hose with a nozzle or a spray bottle, with the engine running spray each spark plug wire one at a time if the idle changes worse the wire you are on is bad and needs replacement. the rough idle could be a vacuum leak as well, you can take a can of carb cleaner and spray around the base of the t-body/carb and vacuum hoses if the idle rises there's the leak. be careful not to use it over excessively because it is flameable so don't get it on the exhaust.

spat · Dec 24th, 2005, 08:32 PM

Quote:

Originally Posted by nogoinsnow

Update:

The nissan dealer tells me that I need NGK-5 plugs on the exhaust side and NGK-6 plugs on the intake. I replaced all 8 plugs (again) per these OEM specs.

I also replaced the thermostat, that fixed the no heat problem.

Still have the problem of cutting out/sputtering. Unfortanately, the spark plugs did not fix the problem. I have also inspected the distributer cap and rotor, and don't see any problem. I don't know what is causing the misfire at this point. It could be a vacuum leak, but I suspect it is a spark problem.

I got my Chilton's manual, but I really don't know what to try next.

I talked to a local nissan specialist who said the canister rusts on every z24 he has seen, he didn't think that was enough to cause a misfire. Actually, the canister had been "bypassed" on the '87 truck he was working on while I was talking to him. He says it just recirculates exhaust. Besides, it has been rusted since I bought it 2 years ago, and I never had a prob before.

Anybody got anymore suggestions? Thanks.

this should help. download

it is a trouble shooting guide I put together for the ignition system on these trucks. The vacumme controle you are talking about is usualy refered to as the "hot box" and does basicaly just recirculate hot exhuast to and from the catalytic converter. However it does have a few vaccumm lines that may cause some problems. You will need a vaccumme diagram to figure it all out just caping lines can cause other componets to have problems.

nogoinsnow · Jan 7th, 2006, 08:34 PM

Update (again):

I finally figured out how to read the computer codes thanks to my Haynes manual, Chiltons left out the details necessary (now I have both). The first time I tried to code it I got the engine to run but it ran bad and would die after a while. At this point it was showing only code 44 (no prob). I moved on to thinking the prob could be the fuel system.

Now the truck won't even start. I replaced the distributor cap and rotor, no improvement. I also replaced the fuel filter, no improvement. Now I am getting a code 21 though, which is loss of ignition signal. I even cleared the codes and recoded it 3 times, every time I now get code 21 if I try to start the engine and look at the codes afterwards.

Next I think I might replace all plug wires and coil wires even though they all checked out o.k. with my resistance test (accepatble resistance levels according to Chiltons).

And, FWIW, when the engine would start (but ran crappy) I was able to do the following test at idle: I pulled the wire from the distributor to exhaust coil and there was no change in rpm. I pulled the wire from the distributor to intake coil and engine died. As I pulled cylinder 1,2,3,4 intake spark plug wires from distributor (one at a time), rpm decreased. From this I determined that either the exhaust coil signal was not factoring in during idle or it was bad since there was no change. I determined the intake wires and coil might be o.k.

I was going to check the fuel pressure, but now that I am getting a code 21 I am back to thinking it is a spark problem. Perhaps I should check the ignition timing?

Spat, I couldn't open the link you gave for troubleshooting the ignition. Could you send me the info in a text file or do a screen capture or something?

This sucks considering my truck is supposed to be my daily driver. I bought it in order to be able to mod my neon. My turbo kit finally comes in 11 months after I order it, and then my truck dies so I can't install my turbo. Now my car is my daily driver until I can get the truck running again.