So this is my problem. I have owned my 1991 convertible for a year and a half now. The engine has always been great. Replaced the injector rings about two months ago, and an oil line like 8 months ago. Other than that no problems. Now something new has come up. When it is really hot out and I am making long highway drives the car starts to act up after a couple hours. When driving on cruise set usually at 90 the engine starts to cut out. It gets progressively worse until I stop and let the motor cool down for like 15 minutes and then it is fine for another couple hours. This first happened a month ago when I drove my car down to school towing a trailer, when I hit South Carolina and it was really hot the car started to act up and continued to do so till the sun went down. No problems after that till last week when I was coming home from Texas and had been driving about three hours or so at 90. It did it again. The ecu seems like it can be fooled into working again by shutting off the ignition and turning it back on again. This only works for like ten minutes or so though. I am stumped. Any and all suggestions or advice would be greatly appreciated.

 

ttt

 

Ever thought you may be overheating?

besides the obvious I mean...

 

overheating what is the question, the car does not boil out any fluid, overflow does not change, temp guage does not move

 

the stock guage sucks though go aftermarket

 

I am thinking something basic, like an O2 sensor or clogged cat, but you say there is a Bonez race pipe, so I am assuming that the cats have been removed?

 

oh yeah
full free flowing exhaust
would a bad O2 sensor cause it to cut out like that
after a long time heating up
is there a way to diagnose that without just replacing it
and how much is a new one??
also would that be harmful to the car??

 

Gee thats nice, but completely useless here in this thread since the car never boils any water out and never varies the level in the overflow.

 

i had similar problems with my old 86 sport that were derived from some kind of a thermostat problem (dont remember exactly) but it was more of a problem of actually shutting it off and it wouldn restart more often than actual acting up while driving. but same procedure...i had to wait for a while for it to start and never had problems at night or in winter..

hope this helps

 

I also had/have some similar problems (*almost* similar): after driving the car for a while (so that it warmed up), it would start to hunt for idle, hesitate a little bit, wouldnt respond as fast when I mashed the pedal etc etc....

Because I havent exactly figured all these out, I'm guessing that, as the engine warms up, every little plastic hose expands, and every little crack in the existing hoses starts to open up, and create even bigger leaks (or create new where they didnt exist before).

Of course, when the car/engine cools down, all return to their "normal" cool shape and position, so car behaves normally again. Only solution to this problem (I think) is to make sure that you dont have any leaks (at all), and replace all hoses that you can with silicone ones...

 

Hmmm... Runs progressively worse when fully warm, and runs good after shutdown/restart?
It's got to be electical. Bad coil? Ground? High resistance in a electrical connector (plug) or ignition switch.
Unplug Everything, check for corrosion. Look hard at ground connections everywhere: under the dash, and pay serious attention to chassis and engine groud wires.

 

Hmmm... Runs progressively worse when fully warm, and runs good after shutdown/restart?
It's got to be electical. Bad coil? Ground? High resistance in a electrical connector (plug) or ignition switch.
Unplug Everything, check for corrosion. Look hard at ground connections everywhere: under the dash, and pay serious attention to chassis and engine groud wires.

 

Sorry about the double post.

 

Have you checked the ECU codes? Are you getting a check engine light?

Dale

 

Don't rule out the fuel pump, it might be on its way out
Make sure your fuel filter isn't clogged. Check spark plugs during normal operation and compare to plug condition when engine quits.
Spark plugs/wires/02 sensor/fuel filter are cheap enough to replace if unknown age or condition.

But, check for ECU codes pronto. Could be a pseudo/temp limp home warning. Something electrical(02/MOP/TPS/AFM/MAP/COIL/ECU/Injector) might be temperature/time sensitive.

http://www.1300cc.com/howto/how2/codes.html
http://home.rmci.net/panther/89_91ecu.htm

 

no check engine light and I do not have a code puller

 

this is a new motor by the way, less than 35,000 miles

 

Geez, don't bother to read the links I posted. Code puller is NOT needed. It is simple to pull codes on the Rx7. It is also possible to have codes without a check engine light going off(reliability of decade old wiring). Also, the sign at Autozone says free engine code check if you can't figure it out.
If you pull a mop/omp code, that new motor of yours is dying quickly.

 

Yeah, pull the codes and change the fuel filter if it hasn't been done in recent memory. The problem you describe is similar to a clogged fuel filter - as more fuel flows through it, it clogs up and starves the car for fuel. After it sits, the clog backwashes and frees up again.

Dale

 

thanks guys, much obliged, I'll do that this weekend

 

Did you replace your watertemp sensor for your ECU? Or is it the original one?

 

I did not do the motor swap maself, it had been done just before the purchase of the car so I am not sure if the sensor was changed or not.

 

My vote is for fuel pump. When they start to go bad the car gets vapor lock when hot, the pump can't push the fuel past that until the car is given a chance to cool down. I'd almost bet that's your problem....

 

Well lets see now, I replaced the fuel filter, I pulled the codes and got none, and the problem is much worse now. Any way to test the pump besides jumpering it and listening?

 

bump