InNeedOfBoost

i have an 88 n/a. for some reason on cold starts it still hunts (rpms keep going up and down) for about 5min. ive replaced the coolant temp sensor cause i had a few people say it was more than likely that. still does it. after it warms up, it doesnt do it any more. would the pulsation damnpner make it do that as well? i know mine has a small crack in it, i just havent had time to put in my new fuel rails yet.

i was thinking the TPS, but wouldnt it hunt all the time?

any advice would be helpful!

NZConvertible

What speeds is it hunting between? Are you sure there aren't any vac leaks? Is the TPS set correctly?

For future reference, you replace parts because you've tested them and proven they're faulty, not just because someone though it might be. That advice was completely wrong.

No.

Not necessarily; it's more likely to occur when the engine is cold and the idle control systems are keeping the idle higher than normal.

pfsantos

iTrader: (1)

^1 NZ post. Test before replacing. The FSM (in my sig.) has resistances based on temperature for this and many sensors. Read his post again, make a check list (vacuum leaks, TPS, etc.).

When you adjus the TPS, make sure the engine is fully warmed up and that the fast idle cam releases, to let the throttle shut completely.

InNeedOfBoost

well, ill keep that in mind for future reference. the car has been sitting in a garage for 8 years, so i figured it could use new anything...lol

but yea, ill set the TPS, thats my guess. if it was vacuum, wouldnt it do it more often? ill look anyway, im going to be taking it all apart soon anyway to replace the fuel rail.

HAILERS

Water thermowax device is not getting a good flow of water. Clean the passages.

If you set the TPS then do it when the engine is HOT and there is no up/down rpm non sense going on. As when it has stopped doing the up/down thing.

NZConvertible

Nope, engines often act differently when cold compared to when hot.

If that were the case the engine would idle fast when hot. He didn't say if it was doing that, but the hunting idle stops once it's warmed up.

InNeedOfBoost

yea, forgot to mention that. once it warms up, it idles perfect. it did idle around 500-550 and it sputtered when i got it, but after running some seafoam, taking out the old plugs, cleaning out the plug holes, putting new ones in and replacing the wires...it idles at 800 now.

InNeedOfBoost

ok, i adjusted the TPS, its now idling around 850 where as it idled around 650 before. ill see how it does on cold start tomorrow

turboIIrotary

iTrader: (9)

if it still hunts change to a new tps that you know works....for example my car worked perfectly but i had a hunting idle i fixed everything to try to fix it but nothing worked until i tried a new tps then it was all fixed.

InNeedOfBoost

thanks for the advice...if adjusting it didnt work, ill be looking for a working TPS. im not buying a new one though, i work at Advance Auto and even with my discount the thing is still 300+

Go48

iTrader: (7)

That's a smart move. I have a hunting idle in my S5, tried a couple of used TPSs and finally sprung for a new one at a cost of well over $300 and that did not correct the problem. I adjusted it myself according to the 2-bulb method and also had a Mazda rotary tech adjust it, but the problem is still there, although it only lasts for a few tens of seconds during warmup, so I'm living with it.

I suspect that in my case it has something to do with the "thermowax" or the associated linkage. Since the linkage is next to impossible to get to without removing the throttle body, I will wait until the next time I remove the throttle body to check.

Good luck finding the source of your problem. Make sure that all the components involved in the warmup cycle are within spec according to the shop manual. Also, you might want to pick up a used throttle body to use in troubleshooting or to permanently replace yours. I did the latter, but haven't gotten motivated yet to swap out parts with the installed throttle body.

InNeedOfBoost

yea...im begning to think its not the TPS. its adjusted and i diagnosed it like the how-to said and now its running even worse.

im backfiring a little, it keeps wanting to die when i stop and now its idling at about 400-500. it sounds like its missing BAD, but i JUST put new plugs and wires. once i get moving past 1500rpms, it runs smooth as glass, no problems.

Bama420

iTrader: (1)

sounds like a bad TPS. And what does the timing on the CAS look like? All too often little shops that don't really know what they're doing will super advance or retard the timing to solve an idle issue.

InNeedOfBoost

well, i havent checked the timing lately..but the car has never been to a shop except to get a flywheel bolt off. its been in a garage for the past 8 years.

forgive me for sounding like a newb, but im still learning about rotaries. i see CAS and i think Cam Angle Sensor...lol, i was in the nissan game for a LONG time before this.

what is the CAS and how do i check timing?

CyberPitz

Sadly, the only part of this post I can answer is CAS = Crank Angle Sensor *prettle close!*

InNeedOfBoost

aa...that was my next guess. i knew it wasnt cam...well, cause obviously there are no cams...lol

im going to do some research on how to check the timing at the CAS. if anyone has any good links with some detailed dierections...itll def help. i need to get this thing running right.

InNeedOfBoost

ok...checked the timing...it was def off, cause after a few minor adjustments to the CAS and to the idle screw, its idling perfect now. i checked the resistance in the CAS plug too...that read fine as well.

still doesnt solve the hunting issue. im going to be getting a new TPS here soon...just need to wait till i get some extra cash.

VAXHeadroom

Check this thread: https://www.rx7club.com/2nd-generation-specific-1986-1992-17/video-still-crappy-idle-no-response-idle-adjustment-657023/, specifically post 264.
I have the same problem with my 88 N/A Convertible, so I'm gonna go work it too

Emory

InNeedOfBoost

thanks for that....i had no idea the ECU would change the timing like that.

i have one issue....i dont have timing marks. atleast the yellow ones... the red ones i can still see but the yellow marks are non existent. from what i was reading, the red ones are for trailing and the yellow for leading. are the timing marks painted on or etched also?

we sat there with the timing light and saw nothing.

Go48

iTrader: (7)

The timing marks are notches in the pulley and they were originally painted at the factory. They are likely dirty or the paint has come off. Find the notches and paint them with a little airplane dope or fingernail polish.

You should be referring to the shop manual for instructions on setting the timing. Shop manuals are free for the download from links in the 2nd gen FAQ.