Well..just finally got the rebuild in and on it's way last night. The good news is that after the inital drive it now starts on the first crank, idles right a 750 rpm and does not smoke. I'm pretty pumped about that..my rebuild man knows his stuff. Now, however, the bad news. First off, the oil pressure gauge is absolutley pegged. 150 miles into the rebuild and still have the correct amount of oil in there according to the dipstick...so surprisingly its not just my own stupidity of over filling it or anything I don't think thats causing that.
Problem number two goes as follows: The car runs fine, will accellerate smoothly to 3000 or so rpm (will vary, sometimes 3000, sometimes up to 4000, but never above that) and then it just fights accelleration with all it has. Seemingly more than just the 3800 hesitation. FAQ's really didn't match what i'm looking for.. Backfires real hard, sputters, just basically tells you that it is no longer open to the idea of continued accelleration. All the while the tach is really kinda freaking out. At times, it will even just stop working all together. BTW, this is with, or without boost. Its still in break in so i keep out as much as possible, but it still creeps some from time to time. If i were to compare it to anything, it feels like a piston motor with bad plug wires missing in the upper rpm's..only maybe a little more..bad feeling Thats really all i can compare it to. I apologize for lack of a better comparison.
Anyways, the car right now is missing its o2 sensor all together which i'm sure isn't helping things. Rebuilds go like that though..it just kinda jumped ship and wasn't ever found. Also the plug wires are stock i believe so needless to say that i will be fixing both of those problems. Well, if you guys need any more info or anything just ask. Hopefully someone has possibly run across something similar in the past that may shed some light as to whats up. Thanks guys.

 

o2 sensor is the cause of most of your problems. Install one and come back with results.

 

Will do.

 

Although that shouldn't have anything to do with the oil pressure or the tach...not sure about those.

 

did you replace the oil sending unit when you did the rebuild?

 

no we used the original oil sending unit.

 

that's your problem.. mine did the same thing... i just went out to my car one day, turned my key to "on" (Didn't even crank it) and saw that I had more than measureable oil pressure...

As for the the hesitaiton: get a new set of NGK spark plugs, new wires and a fresh O2 sensor, and see what happens.

The reason I think you may need new wires and plugs, is because the Tach is driven off of the (leading?) coils, so if that's not getting proper spark to the engine, you'll have trouble with the tach, too.

 

So take the wire off the sender unit. Does the gauge still peg? Was it pegging all the time? Or just when??????

The tach going dead/acting funny....something is killing the trail coil. I know not what.

O2 sensor has nothing to do with your problems. Install it won't hurt anything...also won't help.

The backfiring combined with the tach(trail coil related) coming and going would make me think there's a loose connection for the ignition sys somewhere. ECU plug connection? CAS plug connection? AFM connection? Are the Trail plugs where they belong?? T1 top fwd plug, T2 top aft plug.

Did you use a timing light to set the timing??? I would do that for sure.

Does it rev freely in neutral?

Is the boost/pressure sensor vac line on and it's electrical plug? Did you change boost sensors lately and maybe put the wrong type in the car?

Did you put the ECU's ground ring connector on the top of the rear rotor housing on?? Ring connector held with a bolt?

 

tach is driven off the TRAILING coils.

 

Are you serious? There is no way a bad O2 sensor ia causing this.

 

When you put the motor back in you should have done this.......it will solve the hesitation/ accelerating problem/ tach problem.

https://www.rx7club.com/showthread.p...hreadid=308184

 

Sounds kind of like timing to me if it struggles to go up in RPM and back fires.

Altough a coil not igniting or something will cause all those problems too.

Backfire,Tach goin goofy,struggle to Rev.

 

We did use a timing light to set it and it was dead on. We unplugged the sending unit and the pressure gauge fell back down to nothing...actually, less than nothing. It didn't even 0 up, it dropped even below that. We plugged it in again and i then realized that when the car is off, its always below 0 like that. At least the oil pressure itself isn't actually that high... I did install the o2 sensor and new plug wires and really didn't make much difference. Peace of mind i guess anyways.
I suppose the once over of all connections and all that is in order. Maybe i'll get lucky. Haven't replaced, or even checked the boost sensors honestly. Hopefully that ground is on and correct..i'll check it and beef up grounding. Oh, and it will rev somewhat better in neutral than it will while in gear, but not perfect either.
On a side note, while driving today i allowed it to boost just a little to see if maybe while in boost maybe it would be okay..I dunno what i was thinking. Hit maybe 3 psi and heard a massive clank...the old "hammer against the block" sound. It seems to have survived it though. Scary. I traded cars with my rebuild guy and hes gonna give the car some TLC. Hopefully we can figure this all out. Thanks guys.

 

Umm no. If you don't know what you're talking about, don't say anything. Period.

I have an 87 base model in my shop right now getting a nitrous install that has NO oxygen sensor installed. Still gets decent fuel economy, still runs 14's.

 

The sender seems toast. Question: just turning the key to ON and the engine not running...what does the oil pressure gauge do??

Nothing wrong with having a new 02 sensor

When you did the small boost event.....does the FACTORY boost gauge move??? With the key to ON..does it rise up from dead bottom to approx zero??

Did the car boost prior to the rebuild and....does this car still have the same boost/pressure sensor that it did then and does it have the same ECU????

And you know that the engine NEEDS to be warm/hot prior to setting the timing with the light because the timing is retarded by the ECU when the water temp is cold. But you knew that. Just threw that in. And the rpms HAVE to be below 1000 rpm when setting the timing with the light, preferably close to 750rpm.

 

The factory boost gauge is all i have at the moment and i was just going on estimation of the actual PSI from the stocker (accuracy=none) The boost gauge is functioning what seems to be properly. It sets at approx 0 reguardless of circumstances. As far as anything prior to rebuild goes, i honestly dont know. Got the car not running. Same boost/pressure sensor and same ecu.
Timing is dead on. When fully warm it idles right at 750 +/- 50 rpm and thats when we checked it last and its still on.
Also, upon inspection of the ecu today we noticed some cutting and other alterations. Luckily my main man (Sesshoumaru on the forums) has a re-loomed harness that hes gonna hook me up with this weekend so if any of this is caused by that, hopefully that will fix it.
Thanks again for your input.

 

Check your secondary injectors more than likely they are not coming on.For the oil pressure sending unit, make sure its connected at the sender and that the capacitor(condensor) is grounded to the slave unit.

 

Also you shouldn't be revving past 3800 rpm so the secondarys come on with a new rebuilt until its broken in properly.

 

I know..i've maintained a civil foot for 99% of the time only tempting fate once or twice just out of curiousity and to see if anything obvious was causing the problems.

 

So ...if you decide to suspect the secondary injectors, ..........you can drive a car over 80 mph (oh heck, up to five grand) without the secondary injectors coming online if you don't put a heavy load on the engine. You just have to ease your way to that speed. What I'm saying is that if you ease the throttle to those speeds and the engine does not buck/hesitate/do whatever it's been doing, then it might be the secondary injectors. IF it still does what you describe, then it's most lilkely not the secondary injectors.

So....what numbers are written on your boost/pressure sensor??? And errr, ahhh, has this throttle body had the *throttle body mod* done on it???

 

Your oil pressure problem is do to you not regrounding or breaking off the the little black capacitor for the oil pressure guage that is usually mounted to the clutch slave cylinder on the tranny bellhousing, my wire broke off in the harness for that, and the oil pressure was pegged, just look for it , its about a 1/4 think and about 3/4" square with mounting tab on it, and single wire goiing into it...

I would check all the ground straps,and clean up the grounds on the leading coils as well, make sure the cas plug and harness is intact, I went through 2 cas's that had broken wires where they go through the rubber into the cas..max

 

Like he said i was the one that did the swap/install

Well after I had the car for the weekend I slapped it around for a bit...........

That damn hesitation was hell to diagnose but it ended up being a short in the BATTERY harness. Was shorting out coils/ecu and just being naughty in general. That harness also really needs to be reloomed.

I checked nearly everything but didnt' think it would be a short. NO fuses were ever blown which is really weird.......

There are some electrical gremlens left but i'm getting them.

The oil pressure is perfect (30/60). I checked it with an after market gauge. The reason the oil level was pegged is b/c the sending unit was dented in (i visually compared it with another one i had- ask c_mart_28 how that happened)

anyway that car pissed me off........ and I still haven't cleaned my garage........

but atleast it runs