95 J30 Hesitation

[carlos_knology]

Hey guys, quick question. My '95 J30 (91k miles) has a recent hesitation-loss of power issue at low RPMs (2-3k). The problems seems to only occur if the car is hot. In the mornings, I never experience the problem. It only seems to happen when hot. Especially if I've driven it somewhere and start it up again (heat soak?).

The hesitation feels like the car is missing, almost feels like a lack of fuel issue but the fact that it only happens while hot makes me think it may be something like a sensor (O2, knock sensor, MAF?). I've always used the BG products (44k) so I don't think it's fuel related unless a fuel injector is acting up.

I did a search and found many posts with suggestions but nobody posted back saying whether or not the issue went away.

Carlos

[DAEDALUS]

I would agree either knock sensor or possibly temp-related timing retard.

[DominickJ30]

Check your CTS

[maxnix]

Fuel rail vaporization? Cast iron block will retain heat longer than aluminum, thus really cooking the fuel lines if they are above the V.

[carlos_knology]

Check your CTS

CTS? What's that?

[carlos_knology]

Fuel rail vaporization? Cast iron block will retain heat longer than aluminum, thus really cooking the fuel lines if they are above the V.

Wouldn't this be true of every summer though or every time the car gets hot? This just started happening a few days ago.

[DAEDALUS]

coolant temp sensor. Common problem on the 240sx from what I've read, not common on the Q, don't know about the J. If the ECU thinks the car's running cold (or too hot as well?) it'll run too rich. FSM should have some resistance values you can compare with.

[metaverse3]

Check your ignition coils. See if there are any cracks on them. OHM the coils to see if they are within spec.. Cracked coils arc and can cause poor driveability.

Your fuel injector suspicion is a good one. This is a known issue on the DOHC maxima engine, often confused with the VTC (variable timing camshaft) nissan vtec. I had weak injectors on my maxima that would go off the scope. To add confusion, my maxima is a california spec car that had fuel injector failure circuitry in the ECU mapping, yet, it did not trigger a MIL. After a full plenum removal, two of my six injectors were clearly leaking on a bench test. The car would lag and act like it was missing. I switched out injectors, coils, plugs, and a full-on cleaning of TB-IAC. That was over 2 years ago. It runs great year around...

Good luck..these issues are hard to troubleshoot...

[aerotigger]

I had a similar problem with my J30 having no power at low RPMs, but it was more in the 800 to 2500 range. It only happened when it was hot. I ohmed out the coils and checked sensors as best I could. I ended up replacing a throttle position sensor, a coolant temperature sensor, and a camshaft/crankshaft position sensor. They all seemed slightly out of spec. I also took the mass air flow sensor out and cleaned it with electronic cleaner. I'm not sure which specific thing solved it, but the car seems to be running strong.

Just a note--if you remove the CPS, you have to reset the timing with a light, and the car won't run at all if you leave the intake piece off so you can reach the CPS better. You may can mark it before you remove it to avoid the timing light. Hope this helps.