Jinjiro

So I doubt anyone on here is an expert with Zs, or even use to working on them, but it's worth a shot I guess.

Just finished up the final steps of the 120k/timing belt job. Did everything to spec, timing belt lined up perfectly. Now I've got tons of problems.

Rough idle, no power, electrical issues...Where to start?

As soon as it started to idle rough (basically as soon as I started her up) I checked codes. I got a code 21, which is ignition signal current. I figured it was the PTU, so I cleaned all the corrosion away and unbolted it, just to get it away from the heat. Code 21 went away, but then it came up with code 13 - coolant temperature sensor. Cleaned the corrosion from that, but still idled rough and had no power.

Checked codes again - code 55 (which means nothing is wrong) - wtf? Still idled rough, no power, etc.

When revving to ~4k the temperature control gauge would dim, flicker, go out, etc.

Next I tried the power balance test. I unplugged the coils individually, but what suprised me was I was able to unplug ALL 3 of the passenger side coils with no change in idle. WTF? Swapped a coil from the driver side, and the idle still changed. Not a coil pack problem?

When I went back and checked codes I was only coming up with code 34, which I've always gotten. Part of the problem? Not sure....

As I said, this is probably all foreign to most people on here, but it's worth a shot. I've got a couple of posts up on some Z forums, but I figured it can't hurt to post here.

-Jin

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Rick78

ive seen 3 cars in the past month at our shop that had a problem with the timing belt like this. Had a VW that wouldnt idle, and felt like it had 20hp. Took it apart, and the cam timing was off 1 tooth. After its all together and it looks like they are lined up, u'd be surprised after a one rev it can be 1 tooth off because of the tensioner being a *****. sounds like you skipped timing on the passanger side to me.

if not that, the biggest thing that causes rough running engines that is very common is vacuum leaks. If you do have skipped timing, the vacuum should be terrible, which will cause alot of problems.

But then theres also the cam positioning sensor, and the crank positioning sensor, but they worked b4 you did the timing belt,

i suggest, hook up a vacuum gauge, and then double check all your sensors are plugges in (cam sensor, crank sensor, mass air flow sensor, o2 sensors, all those)

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Jinjiro

Hmm, yeah, the belt was lined up perfectly. The thing that sucks is the timing belt covers are probably impossible to take off without removing the radiator, accessorie belts & pulleys, water inlet & outlet tubes, and who knows what else. I think I've got a timing light, I just don't know if it works. Maybe I should check the timing?

-Jin

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Dooms

What kind of Z do you have again? I've worked on a few 240 Z's and SX's so I'm kind of familiar with them. Knowing what kind might help.

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Jinjiro

'92 300ZX NA.

A guy on a Z forum said it does sound like a problem with the PTU, so I'm going to try and borrow one to see if that's the problem before dropping $175 for a new one.

He also said the dimming light on the dash could be from the alternator belt not being tight enough. Sound like a possibility?

-Jin

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Dooms

If the belt on the alternator is slipping that can definitely cause a few problems. Try fixing that first, who knows, the cause of all your problems might be you aren’t getting enough juice. If not, the I would try the power transistor unit, crank position sensor, ect. Testing the vacuum and timing can tell you a lot, I think I would do that right after I fixed the belt.

BTW, Do 300Z's have a timing belt or chain? I know the 240's had a chain and the guides love to break or wear off and cause problems. I've helped fix three of them and I've heard of plenty more.

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2003 Summer Super Moderator and Most Informative Award Winner

COG/TOG Member



It is my sworn duty to comfort the afflicted, and to inflict upon the comforted.

Jinjiro

The 300Zs have belts. I'll try all of that, hopefully it's a simple fix. I guess if I do have to adjust the belt I at least know what I'm doing and all the bolts & nuts have been freshly loosened.

-Jin

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Dooms

If you have a voltmeter start the car and test the battery. It should read somewhere around 14 volts if it's good.

__________________
2003 Summer Super Moderator and Most Informative Award Winner

COG/TOG Member



It is my sworn duty to comfort the afflicted, and to inflict upon the comforted.