Still looking for answers why my car sputters

[Guest jjohart]

I've posted many times, tried to be patient with my car's condition and my limited understanding of mechanical things, but I just don't understand why there's a period a minute after startup, or quite soon upon warm restart, where it starts to buck, sputter underhood, if I don't either let the gas pedal go to idle (where she won't stall, but sounds poor like a bu-BUH

At this point, my local mechanic said I should put on an air fuel gauge and a electronic fuel pressure gauge (they installed adjustable FPR and raised 8psi over stock, and saw only a 32 to 30lb fuel press. drop when they checked it). I think they're just opening another big labor charge with not much chance of finding a solution, so I'm still trying.

1. Does the 83 280ZXT have a TB position switch? Is there a particular pole or sensor that could be adjusted to raise my part throttle richness (as opposed to WOT or idle)? This car has an NPR I/C, DSM BOV/Greddy PRofec B, 3 in exhaust and CAI.

2. Would a lower rated spark plug raise the richness/lessen sputter?

3. Does the fact that I'm using 0-20 Mobil One for turbos have any effect on such bad performance?

4. I sometimes smell gas w. window ajar on W.O.T...I don't know if that indicates a fuel leak? Is there an over the counter "sniffer" device I could use to see if I could find a leak source (with maybe a brick on the WOT pedal to hold it there)?

5. Is increasing the fuel pressure by adjustable FPR something that I should keep doing, to see if I can even out the mid throttle? Is there any fuel management unit I should look at?

6. I've been priming the car on warm restarts, like hearing the fuel pump kick in then kick out, then turning ignition off without starting, and doing that 2-3X, plus putting my gas pedal all the way down. This doesn't seem to positively improve the poor driveability/bucking until I get underway doing 30-40mph or keep revs 2,500 or above in any gear....is there any other "trick" I can use to push more fuel upon start up, w.o flooding it? Nothing I do seems to matter...but if the scenario is the car restarts fully warmed and runs like crap as above, what else could it be but a pressure drop?

7. Are these fuel pressure (elec) and air fuel gauges going to be like geiger counters for showing what's screwing up, or are they usually just ricey add ons to waste money on to show off bling factor? I mean, are they going to tell my mechanic anything he doesn't already notice?

8. Are there any other devices in the car that let the car start up nicely but then mechanically move to restrict extra fuel/flooding, but in my case may be provoking a lean condition?

9. Is there any thing other than a lit cigarette put at the fuel line's end to tell me if there's a kink in the fuel lines...or do I just assume so and do a fuel system clean up and change the fuel filter?

10. Would it be a good choice to put on the Bosch high pressure pump that I've had in hand, or would I be most likely wasting time and money? If I was to put that pump on, what do I need beyond a new fuel rail and SVO/Ford 370 injectors? Does anyone sell those two items with all fittings needed for 280ZXTs, other than JWT megaprices direct?

I know I"m a moron having a hybridZ without the ability to diagnose/fix it, but again, if anyone can name a really good mechanic on the east coast who might be able to tend to tuning this car, it'd be helpful...the closest I've gotten with experience in the brain leads me to N.B CANADA-in spring, if I'm crazy enough to go there!!

 

Thanks

John

[Deep]

How many miles on your 02 sensor? Grab a multimeter and check voltage across it, I don't know the spec but sombody here should have a Haynes or Chilton.

[BrandonsZ]

2500RPM??

 

Sounds suspisiously like a bad Mass Airflow Sensor, but the computer should have kicked out a code if it was, it might be something like "too rich or too lean" or "MAF failed to clean". Not sure how your codes are, I don't have my book with me. MAF only performes it's tasks at low RPM ~2500 and below. then a set program lookup table takes car of the fuel mixture for higher RPMs.

 

Try disconnecting the mass airflow sensor wire, clean it, put some tuneup grease in it and try it then. Happens when it's warm? Sounds like an intermittant connection in the electrical system, it could very well be this connector.

 

Otherwise, when it's idling so poorly, just pull the MAF sensor wire off and if nothing happens, it's definately the sensor or the connector.

[Guest Drive-ability]

I didn't read the hole post but it sounds like heat soak . Drive it and park it with the hood up so it can get some air. ????

[Guest jjohart]

Hi

the 02 sensor was replaced a month back, and that made the car driveable. I have had the local shop test the AFM, and it was found to be showing some resistance and unimpeded movement.

The weirdest thing I notice is that the car gets underway in the morning quite well, and atypically almost one minute later, I can feel the change in driveability, as if a hand was pinching the fuel supply...this results in the sputtering, surging (I can see the tach fluttering), unless I stay in lower gears and keep the revs up above 2500rpms. I can feel about one minute later, that that same impingement suddenly lets loose, and the car is restored to normal driveability.

Someone replied that they had the programming codes...is there something in the ECU cold start program that would have a "limp test mode" enacting underway while the car's cold +1"? I could swear that the anamoly I'm experiencing is some exaggeration of the way the program was designed. PERHAPS, what is most telling is, when I went to test drive the car, I noticed the owner had it running in his driveway for at least 10 mins, and then he drove with me in the passenger seat another 10"....there's no question the car was always balky from cold, but maybe he knew about this "kink" in the programming, or whatever it is (though he didn't put on all the I/C stuff I've added...I did experience this "heat soak" warm restart behaviour before doing the custom work, so yes, I think there's a heat soak condition of some kind. In fact, some kind folks in reply to one of my earlier posts last summer told me how to hook up the injector fan to come on everytime the car was shut off (rather than by thermotime/180+ temp reading). Someone else recently told me that I should restore the wiring, b/c he said the thermotime switch also has a wire going back to the ECU, so I tried restoring the wire (bullet connectors, rather than ground post), and I noticed that the injector fan still ALWAYS comes on....does this mean my thermotime switch is screwed up?!!?

Finally, I did a search about heat soak here on HybridZ, and I heard someone mentioning that the fuel pump can have a kink in the pressure regulative part that is supposed to keep pressure up when the car is shut off. The last fuel pressure checks I had done showed a drop from 34-32 when the car shut off, and back up again when started. I am tempted to put on my Bosch high pressure pump, since I"ve had it on hand (but haven't much interest in new fuel rail, higher pressure injectors, etc). My local shop says the new pump won't make a difference, b/c they say if it were messed up, it would be affecting driveability all the time, or at least only with WOT demand. Are they right, or is it possible a 22 year old stock fuel pump might make the car more succeptible to heat soak like conditions?

Thanks for any mercy you guys can offer...the replies are helpful, even though I'm paying through the nose...I'm not a DIY'er, though my car is!

BTW, I can barely reach my throttle position sensor, which the helpful posts from Atlantic Z club suggested might be to blame (the intercooler pipe that leads to the engine is right in front...I'll post some pics!