R_PROWESS

iTrader: (3)

(s4 tII) I have 90 compression front and back on all 6 faces, i tested the computer and it shows no errors. tps is set at .999 ohm idle 4.2 WOT. ive tried 3 diffrent tps same problem occurs. soo why am i having hot start issues?!?! also why can't i get above 4k rpm without bogging down?? can not hear see or feel any vaccum leaks... im getin pissed. it doesnt matter if im under load or just free reving i can not get past 4k rpm without it backfiring and all. It will let me get into boost below 4k rpm if that helps anyone.. any ideas because im all out oh yah.. fuel filter is brand new and put on correctly. injectors have been cleaned and test perfect

HAILERS

Stock injectors????? 550 stock injectors?

Stock fuel pump? NO waldo?

Hot starts.......make a fuel cut switch and locate it near the ignition switch for ease of use.

Bogging usually means too much fuel.

OH. You indicate no over four grand even free reving. I've a thought, a good thought. Here's the deal. IF the boost sensor does not see vacuum or is non functional, then ANY time you rev to above 3800 rpm, the secondary injectors come online. Your engine seems to me to have the symptoms of a lack of vacuum to the boost sensor OR the wrong sensor in the car (non turbo pressure sensor).

So start the engine and let it idle. PUll the vacuum line off the boost sensor and see if you feel vacuum on the Line. No vacuum, then that is PART of your problem.

Got vacuum? Check to see if you have the right sensor. An easy way is to check with a meter and see what the output is on the brown/red wire with the key to ON and engine not running. Compare that reading with the one in the online FSM or write back your findings and someone can tell you if the output voltage is NORMAL for a turbo, OR for a non turbo.

Remember the basics. The secondarys only come on line over 3800rpm and only if there is a LOAD on the engine (foot planted to the floor). The EXCEPTION is if the boost sensor is NOT seeing vacuum, then the secondarys come online ANY time your above 3800 rpm.

HAILERS

Another way to check to see if this is a secondary problem is to warm the engine up.

Now slowly rev the engine up to above the 3800 mark.

What I have found will happen, if the vacuum hose is not getting vacuum to the boost sensor, is that as you reach 3800 rpm (reving very slowly to get there), the engine will cyle up/down, up/down at 3800 rpms unless you press the pedal down all the way,then it will get over the 3800 humping and almost sound normal, but not normal.

I assume the engine more or less idles ok because you did not mention a idle problem.

R_PROWESS

iTrader: (3)

Hailers, Im glad you chimmed in. you appear to have something here, I don't doubt you one bit and i hope your right. okay yes i have stock injectors and yes stock fuel pump too. i already have a fuel cut switch and it has saved me countless times. but i don't know if it's this cold weather or what that it just isn't cutting it lately before my battery runs too low. yes i do see vaccum when i pull the vac line and thats funny you mention the wrong sensor. at first when i broke the car in i DID have the wrong sensor, i used the n/a one unknowing that it wasn't going to work because during breakin i never went above 3k rpm. the time came when i wanted to and it would bog at atmospheric on the boost gauge. after a car show with chris from banzai racing he informed me the reason being the n/a sensor. i switched it with a turbo sensor after that and i could get into boost then. but not bass 4k rpms STILL which is where i am today. so it appears the turbo sensor i have is bad, but i dont know this for sure quite yet i havent tested it.

"An easy way is to check with a meter and see what the output is on the brown/red wire with the key to ON and engine not running"

i understand the process except i don't understand what am i checking for. voltage, ohms, or continuity? i cant seem to find a fsm online right now does anyoen have a link?

FCKing1995

iTrader: (3)

worn fuel pump maybe? Stopped up or old rotten fuel lines?

HAILERS

You could unbolt that sensor so you can turn it over and backprobe the brown/red wire with the key to ON. THe voltage should be approx 2.3 vdc give or take. If its a NON TURBO sensor the voltage will be approx 3.5vdc give or take a little.

That's with the engine off but the key to ON and backprobing the sensors brown/red wire. I just did this. I unbolted the sensor and took the vac hose off. Turned it more or less upside down. PUt the meter black lead to a known ground. I used the batt neg post. Red lead in the backside of the brown/red wire with the connector connected to the sensor.

Then I installed a known non turbo sensor (N327) and got the 3.5vdc.

As you can see, there's a big difference in the output of a non turbo vs a turbo.

So let's say all worked out right and you had the 2.3 vdc. What I'd do is go to the ECU and make sure that signal is reaching the ECU. Just backprobe the brown/red wire in the middle plug. Pin 2B if memory serves (might be wrong) but itls still a brown/red wire. Same 2.5vdc should be observed there with engine off, key ON.

If there anything peculiar about your car??? N/a to turbo swap?????? JSPEC engine??????

The fuel pressure idea isn't out of the possible things wrong.

R_PROWESS

iTrader: (3)

thanx for the more clear instructions haillers. and yes the car is n/a to turbo.. does this change things? i should have mentioned that.

R_PROWESS

iTrader: (3)

unfortunataly the reading from the sensor and the reading at the computer are the same, 2.31 vdc my problem lies elswhere it appears.

HAILERS

There's nothing wrong with a n/a engin to a turbo engine. I have one of those along with a normal 87turbo and I like the n/a to turbo better. To each his own.

I just asked to see if there's something else to think about.

What ECU are you running? The N332 or N333 or the stock N326/N327???

And what injectors? The turbo or the non turbo injectors i.e. the 550 or 460's?

You really should not use a N326/N327 n/a ECU on a turbo engine and turbo boost sensor combination.

The n/a ECU can be used to start and run a turbo engine but I wouldn't run the car like that myself.

Also, I suggest using the n/a EM harness and never the Turbo EM harness (the one that has the fuel injector plugs, afm plug boost plug etc. Theres too many problems using a Turbo EM harness instead of the N/A harness.

R_PROWESS

iTrader: (3)

ahh i see, the computer i have is N332. my setup is basicly this

My ex g/fs father gave me his TII for free, he didnt wan't it siting in the driveway to rust away. The body was beyond repair (in my eyes) and the engine had a blown apex seal. I decided to rebuild it and put the engine and harnes and computer ect it in my car.

upon tearing the engine down the rotor had a damaged apex. I then tore the n/a engine down from my car. the rotors were mint looking. basicly everything under my hood in my n/a 86 now is from the 87 tII car. The only n/a parts in there are the rotors because i had to replace the turbo rotors with my n/a rotors sence i only had 1 good turbo rotor.. it only made sence. unless i wanted to buy turbo rotors. (was on a tight budget and liked the added performance out of boost and quicker spool up time ect ect ect.)

with that said i also did the tb mod and removed all emissions. I used the injector harness from the tII because i thought it only made sence being a tII engine just with n/a rotors

whats the chances my computer is shot? and can you think of anything els that activates the secondary injectors like that when they arent supose to come online besides the manifold pressure sensor? last night i hooked up my mass airflow sensor from the n/a and free reved it up to 4k (3800) rpm and it did the same thing so i don't think the turbo mass airflow sensor is the problem either. as in broken or something.. i tested the water temp sensor and ai rintake sensor and they seem fine.. (process of elimination).. i was curious.. is there suppose to be a diffrent reading between the n/a air intake temp sensor and the turbo intake temp sensor? i have tested both n/a sensors that i have and they are the same where the turbo sensor is far off. the n/a both were 52 ohm and the turbo was 32 ohm in the same temperature. this sensor i doubt is the cause of my problems but id like to replace any and all malfunctioning sensors regardless of how important they are

R_PROWESS

iTrader: (3)

https://www.rx7club.com/attachment.p...hmentid=185500

maybe i shoudnt have assumed but if you look at this pic of my car, the pressure sensor i remounted on the inside of the shock well instead of on the front side of it, the vac line runs from it to the side of the engine, would it be better to have it mounted to one of those three vac outlets inline right behing the TB? that would make it in front of the dynamic chamber.. or did i do it right as it is? its hard to see.. pic isn't too big.. disreguard the industrial shopvac hose haha was for brake in

HAILERS

The pressure sensor usually goes to a nipple on the ACV, but I assume that ACV is removed.

On the front of the throttle body are three nipples. The TOP nipple is definetly vacuum, the one below is also (fairly sure) but the bottom one is NOT vacuum so don't attach it there.

On the back of the throttle body are four nipples one above the other (some only have three nipples). Only ONE is vacuum. That would be the bottom one.

Just behind the BAC is a nipple for the blow off valve. You could tee into that one.

I don't like turboII EM harness mating with a non turbo Front harness unless you take care of business and rework the turbo EM harness. What happens if some changes are not made, is that 12v from the METER fuse (memory here) will backfeed into the Boost signal and put 12vdc approx on the ECU's pin 2B (boost sensor input).

But from your readings in previous posts, that isn't happening because you read the right voltage at the boost sensor and the ECU.

Pin 2B is the brown/red wire in the middle plug on the ECU. It should never see 12vdc. IF it sees over something like 3.65 (memory again) it'll cut fuel to the rear rotor. if your over 3800 rpm.

The turbo EM harness will plug into all the N/A plugs but the wiring is different at the two large yellow (maybe orange) plugs inside the car that mate with the Front harness. If things are not rearranged in those plugs you won't have the right wires going to the alternator small plug (shoot, there won't be a alt small plug) and you lose your water temp reading in the dash and oil pressure also (I think).

The turbo EM harness can be made to work with the n/a Front harness, no doubt about that at all. Just some work needs to be done.

I think you might have already taken care of that. If not, say so.

I forgot about this thread.

HAILERS

Correction: where I said METER fuse is wrong. Engine fuse would be the fuse backfeeding. Can't pull that fuse because the fuel pump and Main Relay won't pull in.

What the deal is, is on a non turbo car, the boost/pressure sensors output wire, the brown/red one goes STRAIGHT to the ECU pin 2B.

On a Turbo EM harness it does that and more. The MORE is that it has a wire spliced to it. That *extra* wire goes to a plug called X-15 on a series four turbo and from there it goes to the boost gauge.

Well, if you have a n/a Front harness that that X-15 plug of a turbo EM harness is connecting to, the the brown/red wire will be mating with a white/black wire that goes directly to the ENGINE fuse. The ENGINE fuse will have 12vcd on it any tiime the key is to ON and that 12v will head straight for the ECU pin 2B and make the ECU think your boosting about fifty psi boost, so it'll cut fuel to the rear rotor and the engine will be, well, cranky at best.

The easy way around this would be to find the X-15 plug and snip the brown/red wire about two-three inches back on the EM side of the harness. Done. Won't be messing things up no mo, IF you cap off the bare end of that wire so it won't short out.

Most of the above makes no sense UNLESS your staring at a wiring schematic.

R_PROWESS

iTrader: (3)

i just thought of something, i have the 86 n/a cluster in my consol. would that mess up the turbo computer somehow since the n/a cluster has no boost gaugeor does the cluster have nothing to do with how the car operates. the turbo car didnt have the cluster in it when it was given to me

HAILERS

Nope. The instrument cluster has nadda to do with it.

Question: does your water temp and oil temp gauges work?

And what did you do for the alternators small plug?? That plug for the alt is on the n/a EM harness but not the turbo EM harness.

The only possible thing in the wiring that could cause a problem like you have, is the brown/red wire at the plug called X-15. The plug is one of the two large plugs on the EM harnesss and are located above and to the right of the passengers feet.

The plug has 15 wires in it. The brown/red wire is in the EM half of that plug. It is in the top row, third wire from one end. Cut it about two to three inches back from the plug. Then tape off the end so it won't short out. About a thirty minute job.

The other problems with using a turbo EM harness in a N/A car won't effect anything other than lack of water/oil pressure gauges, and no voltage to the alternator and no input from the alt to the alt relay in the CPU (not ECU but CPU).

I run with the stock n/a instrument cluster. No need for a turbo clluster. This is NOT your problem.

Attached is a jpg of the X-15 plug. It's the {EM} half of the plug that is in question. See on the top right of the plug where at the third socket is BW and there is an arrow pointing to it with (BrR)?

Well, your turbo EM harness plug has the BrR wire in there and it should NOT be there, because it's going to mate with the Front side of the plug to a BW wire that leads straight to the ENGINE fuse which has 12vdc on it and that 12vdc is going to back feed into the BrR wire and go straight to the ECU pin 2B and head fake that ECU into thinking your boosting a godawful amount of boost when your not.

On the other hand, other than the above, I don't or can't figure out what is wrong with your car.

R_PROWESS

iTrader: (3)

"Question: does your water temp and oil temp gauges work?" Yes and Yes "accurate" as they can be infact

It has a GM alternator from a Buick lasaber(sp) i didn't do the wiring ill have to ask my old man

what i don't understand is why my harness would be wrong at all. i mean i just swaped everything over and theres not a single N/A harness or computer or even part (besides the rotors) even under the hood or in the cabbin. so basicly it's just as if I left everything in the turbo car and rebuilt the engine and am driving it.. never touching the harness or wiring. so why why woudl a stock wire not belong in a stock car?

but it's funny you mention the engine fuse.. okay I think we are getting somewhere.

Once when i was backing out of the driveway looking behind me the engine died.. I thought I just killed it but I went to crank it over and it cranked... I noticed the tach was not bouncing with the rpms and the engien wasn't bogging down (flooding) while cranking. Well the engine fuse blew and i never found the cause and I spent days searching for a short but couldn't find it. I decided to be stuid and replace the fuse.. it hasn't blown sence which upsets me I really wanted to find the cause... do you think maybe this BrR wire has something to do with this?

im just trying to gather the knowledge to tackle this problem when i get back home in 2 weeks. I left it back home because of the hot start problems i can deal with the 3800 rpm limit. i just want to pre-thank you for not being condescending like some people round here.. I won't name names and for workin with me here.

R_PROWESS

iTrader: (3)

what does the vaccum line off the firewall side of the secondary fuel rail do? if it's leaking or not seeing vaccum what would the symptoms be? anyone know?

R_PROWESS

iTrader: (3)

to update this thread in hopes of helping those in trouble with similar or the same symptoms the cause of my problem turned out to be the now infamous faulty -variable resistor pack- it wasn't allowing the secondary injectors to operate. i simply replaced it with a spare after trying everything else and all as fine