its weird...

I have a 87 RX-7 T2 and the power comes and goes with it...

with power it will be really fast; just as fast as it should be with the mods... and sometimes it will be really slow...

at first I thought it was the boost... because normally at full power the car will run up to 10psi in 3rd gear...
but when its dead it will only pull about 7psi...

i thought that might be the problem until i drove my car back from lunch today...

i got on it in 1st gear and it pulled harder even before the boost kicked in; and when it did; it hauled ***... I was at 60 in no time and I let off... I made about 7psi in first and 9psi in 2nd... both came in hard and didn't creep to it...

what is the problem here? can the ignition timing be pulled by the computer? what would cause it to do this...
if it can't or there's a better explanation; PLEASE someone let me know... i lost to a supercharged Civic Sat. night that I would have smeared if the car had been running right... there's a big seat of the pants feel when its making power; i mean you can really tell...

please help me!

thx

 

I have a similar problem. Once in a while the car will have noticably more power than otherwise and idle better, I'm thinking electrical in my case as it seems to 'decide' which mode to run in when first started; ie if its running good, then it will do so for that whole trip, same if its not so good. Unfortunately, I haven't found the key yet. When running better, the boost also comes up quicker.

Do you still have the double throttle plates? If so, check that they are opening when you get on the throttle. You may also want to check the thermo switch at the bottom of the rad on the drivers side, this is used to tell the ECU to go closed loop (in open loop while warming up the mixture will be rich). Check the timing and the knock sensor (it can retard the timing).

If you find anything let me know!

Henrik
87TII

 

trouble is i can't even make it idle now

If i slightly press the gas down the engine burbles real bad at any rpm; and if the rpms drop below 1000 or so it just wants to die...

i think i have a combination of a bad TPS and bad idle mixture or something...

but i dunno about this problem... this should boost it up to the top; maybe someone can comment now that everyone is back from work... it feels like ignition timing to me... mine is set right at idle... back when it did idle...

 

Do you hear any abnormal or elevated noise when you it doe run slow under boost?




-Ted

 

Were you fiddling with things and the idle went bad or did it just go bad 'by itself'? Any vacuum leaks? Popped a hose off from
boost? Even losing a small hose will cause terrible idle, if not outright stalling.

Henrik
87TII

 

yeah the surge valve that connects between the small intercooler hose and the BAC valve has a plastic nipple; it broke

i fixed it temporarily by supergluing it with some super strong stuff; its holding but i think its leaking out the side...
the two plastiform hoses from the intercooler to the surge valve and then another to the BAC valve were cracked a good bit so i got temporary hoses...

my new hoses should be in on thursday and i've got a source for a replacement surge valve...

trouble is; this was happening before any of this happened...

the car idled but it idled BAD... and even after temporarily fixing this stuff; the idle was still ok... it got worse and worse over the past week...

but thats just the idle; would that cause the ignition timing to get yanked? i'm pretty sure i'm not getting knock since it worked in the 90degree heat and in the 70degree night... and comes and goes...

 

guys,

Are you sure about the purpose of the switch in the radiator? I thought that was only used for the AWS. Mine is unplugged (I broke one of the contacts).

Todd

 

bump

need some input;

any suggetions on why the timing (which would affect spoolup) would be yanked?

i know if its detecting knock it would yank the timing; is there a sensor i can jack a LED into and see if the ECU is detecting it?

 

Akageals: I'm not 100% sure but I seem to recall reading somewhere that it is used for deciding on going into closed loop or not - it may not be the sole input for this tho. I do believe that you are correct that it is used for the AWS (as well).

Bean: Re the knock sensor, the signal comes in on pin 1R on the ECU. According to the factory manual, it should be at 3-5v at idle (no knock of course) so I'm pretty sure its an active low signal. It comes from a conditioning box so it should be capable of driving an LED - you may need a pusle stretcher to make the signal human visible. You could also try disconnecting the knock sensor (temporarily of course) if you believe its falsing and see if it makes a diff or not. I have not tried either so make your own decision before trying anything.

The TPS is also used to advance the timing, to check it, warm up the engine and stop it. Put a voltmeter on the sensor (the middle pin I believe) and measure to ground. Turn the key to 'on' but don't start the car. You should see 1v at 'idle' position. Open the throttle slowly and the voltage should smoothly increase to almost 5v - I think you need to see more than 4.something for the ECU to read WOT. If there are any dropouts or it doesn't go above 4v, then you got a bad TPS.

Hope this helps,

Henrik
87TII

 

well i tested the TPS once and right before it went to 4k ohms it jumped to 40000+ basically infinity... then settled back down and went to 4.9 at WOT

i'm pretty sure my idle problem is due to vacuum leaks and other stuff...

but i'm gonna try that knock sensor test once i get my idle fixed (because it may cure both problems if its the tps)
which it could very well be the TPS not registering full throttle so not bumping the timing like it should

so just to sum up that theory... if the timing were not being bumped up to where it should be at WOT because of the TPS... then the car would NOT gain boost near as fast and would NOT make near as much power because of that AND the loss of power from ignition retard...
i just need a confirmation on that to make me feel better

 

My friend had that problem in his 10th AE. Sometime it would haul ***, sometimes it wouldn't.

Tore the engine down, found that ALL 6 apex seals were cracked!! It still ran (hard as **** to start though)....

Hope this isn't the case for you.

 

nah i doubt it; it starts and runs just fine...

as long as its not idling hehe

 

Theory sounds good to me, although I don't know if the TPS is the only input into the ECU for determining 'gimme power now', its conceivable that it may also use the boost sensor input (ie if boost is above some amount, consider the throttle at WOT regardless of the TPS). Anybody have a ROM dump of the ECU??

About your TPS readings BTW, it should not go open circuit - in the voltage domain, the volts will drop to zero to the ECU which may be interpreted as go to idle (idle is at 1v).

Henrik
87TII