S4 FC strange starting and running issues.
 

Hey guys, I have an 87 S4 NA 5spd Rx7, and I'm having some trouble.
The Engine was rebuilt at most 10K miles ago. The car is having two troubles since. It is very hard to start, If I let it sit more than a week, It will not start again without going through 2 or 3 batteries worth of starting, and this time, it will not start at all. When it does start, it seems to run flawlessly. But The second issue I am having is that at random the car will die in mid drive. All of the accessories will still be working, but no throttle response at all. I am able to simply take it out of gear, put it back in and drop the clutch, bump starting it, or take it out of gear and turn the key, and it will start back up again.

Since I discovered the problems I have replaced the fuel pump, the fuel filter in tank and in line. I have had the injectors cleaned and rebuilt. I have replaced the spark plugs and wires and have tested for spark. I replaced the air filter, and done my best to make sure all the vacuum hoses are in the right spot. I have also replaced, for separate issues, the Crank angle sensor the TPS and the alternator.

At first I thought flooding was my issue, but I have gone through de-flooding procedures many times, with no help. and have even installed a fuel cut switch to make sure I am not flooding. I am at my wits ends with this, and any help would be greatly appreciated.

Re: S4 FC strange starting and running issues.
 

Sounds like voltage and wiring issues, check both the alternator and the battery for current voltage first, if both are fine, then it's either the battery cable, the alternator wire, or the grounds.

Something is eating up your voltage juice, what does the voltage meter read when you have the car running?

Re: S4 FC strange starting and running issues.
 

I'd suggest checking voltage at the fuel pump. Many recommend a re-wire of the fuel pump simply due to age. And check the grounds, as noted.

Re: S4 FC strange starting and running issues.
 

Voltage is good on Battery, alternator and at the fuel pump. Volt meter reads 14 volts. I'm not sure it is a voltage problem here. I have used multiple batteries with the same results. I have also cleaned up all of the grounds as per Proper RX-7 Grounding Procedures. One thing I have noticed though, when trying to start, once a battery appears to be completely dead, I can take it out, put it in my Supra, and it has enough juice to easily fire up.

Re: S4 FC strange starting and running issues.
 

Then it may either be the starter or the distributor... either of those could be one of the culprit here.

Dying half way??? :sly:
Considering that you have replaced so many things, I don't see how exactly that could still be happening... then again, I'm no expert.

What about the fuses? Have you checked those?

Re: S4 FC strange starting and running issues.
 

I have replaced the Starter and the Crank angle sensor(distributor). I have checked all the fuses, they are good.

Re: S4 FC strange starting and running issues.
 

I'm out of ideas as to what the possible cause would be.... I don't want to keep on shooting out stuff to check and wasting your time.

Anyone else?

Re: S4 FC strange starting and running issues.
 

It's ur water temp sensor. It's hidden behind ur water pump, so buy gaskets. Fix this and it will start easy every time

Re: S4 FC strange starting and running issues.
 

You don't need any gaskets to replace a water thermo sensor!
Take the Connector off it,Unscrew it,and quickly put the new one on.
it's green,at the back of the water pump,
That is,IF that is the problem.

Re: S4 FC strange starting and running issues.
 

Try this as it solved a sinilar problem I was having. If you have spark plug wires that are touching, you could be experiencig arcing. Make sure no spark plug wires touch. Reroute them if necessary. Then, at some point yopu probably ought to replace the spark plug wires. Use an 8-8.5 mm plug wire that is well shielded.