CloudPump

iTrader: (2)

Car: 1992 RHD FD

Mods:
Streetported rebuild 5k on motor
HKS downpipe
Greddy Arinix
Bonez Cat
5Zigen Exhaust
99 Efini twins
PFC
PS Delete
AC Delete
HKS Twinpower
FMIC
Koyo Rad
Efini Y Pipe
Walbro pump

Problem:

Was on my way home from work today, sitting in traffic. As the traffic cleared I shifted into second and stomped on it to get up to highway speeds and the car hesitated very badly, almost stumbling but managed to push through it, same thing happens in third/fourth

As I was getting onto the highway I was in third and giving it heck, no problems. Something seems to have gone wrong since sitting in traffic waiting for an accident to clear.

The car runs great until about 3psi of boost and then the hesitation and lots of backfires.

Any suggestions?

-Geoff

oyvindjs

iTrader: (4)

hmmm, ignition breakup from old plugs? Rich fuelmap causing plugs to soot up and leading to bad ignition?

CloudPump

iTrader: (2)

Well the plugs only have 5k on them, but I've ordered a new set and some new wires just to be safe.

I did a bit of diagnosing and I feel that I can ease my way through the RPMs at about 1/2 throttle and not get much bogging, but when I go to WOT the car stutters very badly with an extremely noticeable drop in power.

I won't be able to test it on the highway again until tomorrow, but she runs completely fine without boost so it I don't think it's spark breakup at high revs as I can rev high just fine, just not under boost.

Any further help or ideas would be great.

-Geoff

o3nisoaso3

iTrader: (14)

my car seems to be doing something similar to this. i ordered step colder plugs, new fuel filter, changed the oil and oil filter today (was just about to 2000miles on this past change). My car sometimes does the "3k hesitation" then goes again but its anywhere between 2-3k and it will go until 4500, or like when the 2nd turbo would spool, and it kinda poops down on me like a bog or maybe backfire but it havent had it WOT, only 1/2 throttle when that happens. havent really taken it hard WOT yet. any ideas?

moconnor

iTrader: (14)

Wild stab in the dark, but have you checked your IAT? You mention a PFC so presumably you have a Commander to check the various sensors.

1QWIK7

iTrader: (33)

Maybe tps went out of whack?

CloudPump

iTrader: (2)

That's one that crossed my mind, I'll have to test it after work today.





I did some more testing and the hesitation only happens when the primary turbo begins to spool and clears up around 4k rpms, just before the switch to the secondary. After 4k and throughout the duration of the secondary there are no problems...

Sigh...

-Geoff

RotoryDreamer

What's your boost look like? Did it overheat sitting there?

Polak Graphics

iTrader: (4)

^

Check for a boost leak/ over boosting issue. Along with making sure the twin power is in order.

CloudPump

iTrader: (2)

Never overheated, I watch my temperature like a hawk. The car never went warmer than 93*C at it's hottest.

Since this started happening I've been watching my boost and I almost want to say it's spooling up faster than normal (IE: hitting 10lbs at lower rpms than I'd expect I'm not 100% positive on this though) but I'm not spiking.

-Geoff

CloudPump

iTrader: (2)

The Twin power crossed my mind, but I disconnected it to test and the car ran just as "chuggy" without as with.

-Geoff

RotoryDreamer

Still hitting your transition? If a solinoid died could be running in parallel and that would make it feel kinda doggy down low due to slower boost build and the map being a bit fat until boost builds.

DaleClark

iTrader: (55)

I had my car run like *** on the way to Deal's Gap last year when I filled up with a bad tank of gas (F U, Racetrak). Cruised OK, but put any power down and it would stumble and miss. First time it happened I thought I blew the engine it was so bad. I put some octane booster in, babied that tank out (which was highway driving from Atlanta to North Carolina) then filled up with good 93.

Could also be fuel pressure.

Check all your PFC sensors and make sure you're getting good inputs. I doubt it would be anything with the sequential system, it's more of a motor running problem.

Dale

neit_jnf

iTrader: (17)

bad coil perhaps

CloudPump

iTrader: (2)

Hrm... a bad tank of gas didn't cross my mind... I've almost run through this full tank, so I'll be filling up again soon. However the same gas that was in the car long before the stumbling happened is the same gas that's in it now. I had been running on this tank for at least 3 days before any issues showed up.

I always fill with 94 octane from brand name stations, no "mom & pop" gas for me.




Further updating:

Messing with the car some more: I am getting my changeover at 4.5k, the car runs MUCH better into the secondary turbo however I do notice very very minor hesitation above 4.5k I might not have even noticed it if I wasn't looking for it.

I can drive all the way to redline in any gear (well not any gear I wasn't redlining it in 5th) without boost and I have no hiccups whatsoever. Only when I boost do things go south.

My (uneducated) guess would be the MAP, but if anyone thinks otherwise, please point me where to go.

TPS is still on the table. My tools are kept in my mothers garage (no room at my apartment) and I won't be out there for a few days to start tinkering.

-Geoff

phrost

iTrader: (14)

If you have a commander for your PFC, load the sensor check screen. VTA 1 and VTA 2 = your TPS voltages, makes it pretty easy to check if that is in spec or not.

Here's a link for TPS adjusting : https://www.rx7club.com/showthread.p...osition+sensor

I don't know if MAP sensors just go bad, but at least you should check if the vacuum line and electrical connectors are still attached, properly...

CloudPump

iTrader: (2)

And the culprit was:







Bad plug wires!

All is better now.

-Geoff

neit_jnf

iTrader: (17)

did you get new oem wires or aftermarket?

GoodfellaFD3S

iTrader: (213)

What plug wires did you have before? Makes sense to me, years ago my Jacobs 'Piece o Poo' ignition amplifier crapped out on me, so no spark on leading plugs. Car ran with barely any power but boost built very quickly.

CloudPump

iTrader: (2)

I had OEM wires on before, I ordered Magnacore wires from Banzai Racing as my replacement.

-Geoff

o3nisoaso3

iTrader: (14)

glad to hear your cars running better.

my car seems to be doing the opposite it seems. i tried to see if bigger turbo solinoid was bad but it didnt seem like it. i ordered new plugs, wires, fuel filter and air filter that should be here tomorrow, just did an oil change last week at 1950miles. hope the plugs/wires fix my car. or the fuel filter, just hope its not the rats nest giving me problems. i just ordered a petit racing downpipe w/o the precat... hope all turns out well for me

advice anyone?