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I seem to be having the same problem as a LOT of other l28et posts that i've read (iowa280zx). I already have a FPG hooked up (harbor freight :D) and its reading 30 PSI at idle, and I'm also getting that sputtering burping sound as I accelerate but its hitting the 36 psi mark. Deceleration sounds like a normal engine (when i let off accelerator) but if I accelerate it farts and pops and burps. I've tried everything, my AFM is clean and grounded, my TPS is questionably tuned and my vacuums are snug as a bug in a rug. SHouldn't it be running 36 PSI constantly through all situations? Does the 6PSI at idle make a difference, and If it does go up to 36 PSI why doesn't it give me power like it should?

 

This is driving me up a wal!!:fmad::fmad::fmad:

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fuel pressure increase from idle as you accelerate so that is normal. Have you checked your timing? what is the state of your spark plugs and wires? Dizzy cap and rotor? Are you boosting? need fuel, fire and air to run. one of em ain't doing right. just a fuel delivery problem would give you power loss but probably not the fits and starts. I'd look into the ignition system first.

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Okay this might be fuel and it might be electrical, I got drivable, but here's the thing:

 

Engine warm:

With the CHTS unplugged it will drop idle 4* to around 24* and ANY throttle will drop it to 30+

 

With the CHTS plugged IN It will idle at 20* (which is what I set it to) and ANY throttle will advance it to 10*

 

YUCK!!!

 

I cleaned ALL my electrical contacts, maybe a ground is off somewhere? Maybe the gremlins are having a field day in my engine bay.

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First clean all of your electrical connection. For my ecu connectors, I replaced them with 300zx ones(much better). It could be your AFM going bad. My car was doing the same thing you described when it went bad.

 

When you say that your timing changes when you unplug the water temp sensor, thats because the car runs leaner with it unplugged, which advances your timing. If you clean all of your electrical connections and the problem persists, check your TPS, test your water temp sensor, and then AFM. And were your pops coming out of the intake or the exhaust? Have you checked the color of your plugs? what color are they.

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Replace the chts. when you have a problem and unplugging a component makes it better you might think that would be a problem. You didn't say what year type z you have but if stock and not a swap you have a 81, 82, 83. There are differences in those years. The 81 is more different than the 82, 83. So what you got? The guy above is talking about Z not ZX. The z has a water temp sensor the zx has a cylinder head temp sensor. I'm assuming that when you say you have a 280et you mean you have a turbo L6 (S130). Which is it? you can get a lot better answers by specifying what auto you have.

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Replace the chts. when you have a problem and unplugging a component makes it better you might think that would be a problem. You didn't say what year type z you have but if stock and not a swap you have a 81, 82, 83. There are differences in those years. The 81 is more different than the 82, 83. So what you got?

 

True, but was not the case with me. My AFM went bad making my car run really rich. when I pulled my chts out, the car would idle much better. I thought it was my chts and was wrong.

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THank you for your replies! I'm VERY thankful that you guys are trying to help me out, really I am!

 

Yes, I've done a resistance check on the CHTS and it is very much working. My AFM I'm extremely dodgy about, I had it running when I tweaked it 5 teeth richer, and I'm not quite sure if the "factory" setting it was originally at was factory at all. The PO really messed with it, I had a plethora of problems because I had to adjust the flap to touch the carbon strip a while back, it wasn't even touching!! Don't ask me how, but I'm still pretty suspicious...I ordered one from cockerstar though, so I"ll see how that one treats me. I've tested every component just like the FSM says.

 

Its a '82 L28et with a non-hydraulic head and a Non-egr intake manifold. Other than that, everything is stock and freshly rebuilt by the hands that can't even get it drivable :fmad::fmad::fmad: I tell you what, it sure is frustrating.

 

Yes its giving all the signs of "lean": It doesn't accelerate good at all and letting off the throttle gives it that "freshly fueled" deceleration sound.

 

The TPS has been adjusted to just about every possible comination. The way my haynes says to adjust it is with a feeler gauge to the stopper screw, but the screw has been moved so I'm not sure how to about that, so I adjusted it using the cut off at 900 RPM part.

 

When I unplug the 02 sensor nothing changes.

When I unplug the TPS idle rises but still acceleration is terrible.

When I unplug the CHTS it runs very nicely but WITH LOAD it bogs out and coughs and sputters.

 

This is all pointing to some weird AFM problem, don't you think?

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You know this has put my car out of commission for around 5 weeks now, and I will be so happy when I can get it resolved! I just want to have it running for a while, and first major electrical component that goes out, i'll probably switch to Megasquirt :)

 

When I get the AFM from cockerstar, I will let you know first thing! Thanks for you advice!!

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  • 1 month later...

The ZXTs are very famous with this backfire problem and the problem is all originated from the bad connections at the ECU connectors. With many years of experience with these turbo ZXs I bet you anything that all you have to do is clean the connectors or replace those with the later 300ZXs connectors and it will fix ur problem for good. I had replaced these connectors on mine a long time ago and never had the same problem again. GL

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  • 2 months later...

according to the 83 FSM, the CHTS has lower resistance at higher temperatures. therefore, unplugging it should make the ECU think that the engine is cold (infinite resistance). when the engine is cold the ECCS is supposed to enrichen the fuel (longer injector pulse width) and also advance the timing. noting that the FSM also indicates that the TPS's "idle" signal will cause the timing to advance and that at least one person recommends unplugging the TPS when setting timing but that the FSM (and Haynes) do not mention this, i suspect that there are a lot of badly timed ZXT's in the world, starting with mine, which i'm going to go out and re-time now.

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