Thread: P10 hard start (hot & cold)

I'm getting aggravated with my daily P10, and I need someone to point out some ideas for me.

Car: 1995 P10 manual with no mods and 234,xxx miles (lowport).

My daily driver P10 started giving me a hard cold start condition a couple days back. If I gave the car 'some' throttle while cranking it would be fine. Once stable (5-10 seconds), I could turn the car off, crank it, and it would fire right up without any throttle. Now it requires nearly WOT to fire - cranks fine. The battery is a couple years old, but I snagged it from my NX which lives mostly in the garage.

I did some searching, and the Air Regulator seemed like the culprit. Pulled the upper plenum last weekend, and I cleaned the Regulator per SE-R.net. While doing that, I changed the plugs, wires, cap, rotor, fuel filter, and VC gasket (all OEM Nissan except Autozone NGK plugs - gaped at 0.35 I believe). Regulator tested fine, but I cleaned it anyway. No change.

Had injector #3 go out Sunday night, so I changed that injector on Tuesday. No change to the hard start.

I *believe* the cold start has slowly transformed into a warm start issue before the injector, but I lost track. I've looked through the FSM, and I was leaning towards an EGR malfunction when just a cold start issue. I'm just not sold that the EGR is my issue now, but I do plan to cap it when I get home. I did not replace the injector O ring when I swapped them, but I've done a injector swap 3 times in the last couple months, and the car runs well once started.

I did have a CEL for a knock sensor before, and I will have to check the current codes when I get home. Fuel pump comes to mind, but if it is weak I would expect power to be down across the board not just at start up. I'm just getting aggravated, and I'm not going to throw parts at it without just cause.

Any thoughts?

Josh

Still sounds like a closed Air Regulator. Pull it and verify its still working properly. If its stuck closed, voltage/ohm testing could still be good (b/c the electronics are fine).

Other culprits could be weak Voltage Regulator and/or coil. Or corroded Starter harness wires (remove and clean all connections).

Recheck your tuneup items: plugs gapped correctly per FSM, dizzy rotor is screwed in properly, wires are connected correctly. Check the timing & idle settings.

Just some things to check with your handy DVM...

i have had a problem with the cold start, take some carb cleaner and with the engine running spray it in the hose that goes to the IACV, make sure to give it some throttle and dont let the car die, spray for like 5 seconds straight, then let it run a little bit, give it some revvs, and do that 2 more times after that, i would think that will fix your problem.

I had another Air Regulator (from my newest purchase - 220k miles), and it acted the same as the one from my P10. I put both in the freezer to check how they responded, and both acted the same which was not to open too much - I guess both could be bad.

I had a code 32 & 34 just now - knock and EGR. The knock sensor has been bad for some time, so I cleared both codes. I also blocked the vacuum line between the EGR mushroom and the other mushroom.

I like the idea of the carb cleaner, but the Air Regulator could still be bad. I'll try to make it to the junkyard this weekend for a 3rd Air Regulator for a comparison.

Thanks for the ideas guys...and I'll take any more.

Josh

Leaky injector? Had that problem a while back on my SE-R. I skimmed so don't throw stones if you allready covered that.

To test, pull the rail out of the intake mani, turn the key. If one leaks. Leaky injector.

Great advice Blair.. The leakdown test is the best way to determine injector leak condition. Testing the injector ohms is also required for electronic operation validation..

Josh, the freezer test is what I was talking about. If only open a sliver, it indicates choking off air during startup. Spray it real good until it opens fully.

Dont forget to check the harness to the starter!! I have found on some cars, the invasion of the green corrosion stuff (like on battery terminals) around and inside of the starter wires. This will definitely steal amps during startup and strain your battery. Verify that this is not happening.

Replace that Knock Sensor. It causes the ECU to set strange things to idle & timing when triggered (but not usually starting). Found the updated knock sensors on ebay for $50 shipped.

Air regulator FTW. I checked mine with a DVM and cleaned it and the whole 9. It checked out fine visually, but obviously my car knows what she likes. Turned out to be bad anyway. Replaced it and high start up idle again.

hi guys! I am Adrian (zikkie). I have just joined the forum due to my Sr20 p10 having the same problem as Josh. I am yet to try the leaking injector and the dizzy. but josh, if you have found anything that has fixed your car please let me know. I have been trying to diagnose this problem for the past 5 months.
Thanks.

Welcome Zikkie!!

First off, you need to use the Search tool to lookup stuff before asking.
But, here is a good link to get you started. I has possible solutions to your P10.
Pay special attention to the Air Regulator testing as this is probably your problem.
Also search for IACV cleaning.

Go to AutoZone and check your car for codes. Post your results.

I haven't found my issue yet, but I've been busy and (in general) aggravated. I cleaned and tested my air regulator; and I did not have a change. I also have 2 other air regulators that I compared, and they acted the same as the one on my car when off and tested.

I am currently leaning towards the IACV being dirty/gunked up. I sprayed some carb cleaner into that hose last weekend, but it did not change - after doing it I realized that I sprayed the carb cleaner AFTER the IACV, so it did not get cleaned. I plan on pulling the IACV off this weekend, and cleaning it thoroughly. I've been reading the FSM, and just thinking it through.

DC Scotty: thanks for the e-mail that I forgot to respond too. I think I have the same sheet in my FSM. It has been busy and cold around my house lately.

Josh

Edit after reading the entire thread linked above: my idle is pretty good. The car starts and idles +-1100 and it will slowly raise to +-1500 after a couple seconds. Then it drops back to +-1100 (normal cold idle) after 60 seconds which seems to correspond to how the Air Regulator should act. The car just needs (me giving it) full throttle to start. It will start without any help if just turned off, but if it sits for 10+ minutes then I have to give it throttle to start. No CEL right now (I cleared them, but the EGR is still disabled).