I have a 90 Rx7 with a 13b injection in it. I just bought the car and when I start it the rpms sometime jump up to about 3000 rpms then go back down to normal idle after a few seconds. All while the check engine light is out. I can take the car down the road and it will run very well If I don't get on the throttle hard. But if I get on it hard in first then shift to second and ride out second the check engine light will come on usually before I have to shift to third or no later than like 30 seconds after i shift to third. When the light comes on the car sort of wants to fall on its face until I come off the throttle. when the light is on i can drive the car easy [not matting it] and it will not effect driveability. But if a I lay in to the throttle the car holds back and doesn't want to respond. But If I ease in on the throttle it will run fine at high rpms and everything. The car is in really good condition besides this problem. The person before me did the following mods: A/C delete, rats nest removal, racing beat header and full exhaust, relocated the battery to behind the passenger seat, and has a cold air intake that is only like 12 inches away from the maf sensor. Could any of these mods cause these problems?

 

Its an accelerated warm up process, its supposed to jump to 3000 rpm at startup.

 

Nothing to worry about, it is designed to do that.

Just dont thrash it til its warmed up properly

 

When your check engine light is on your car goes into a limp/ failsafe mode which significatly lowers your performance until the problem is fixed. I take it you always let the car warm up before you get on it. The first thing to check would be to see if you have any codes present. Look up how to check S5 codes. then if there is a code fix that component making the problem. Personally it sounds like you TPS might be shot and gives the wrong WOT reading to the computer which puts the computer into a limp mode and sets a code off. Check for codes and fix if any, then set the the TPS based on what the FSM (factory service manual) or look up TPS adjustment and see if that fixes it. Do that and get back to us

 

Lol its your Accelerated Warm Up System...just start it in gear if you don't want it to work.

 

That's actually not true, you can drive around with certain error codes.

I drive with a check engine light on, since I intentionally have it on.

 

When a car goes into limp mode it won't cruise at 70 down the highway when the check engine light is on. The problem of the hesitation and want to fall on it's face only happens when i try to accelerate quickly.

 

Sorry man, every S5 that has had an engine light on for me has gone into limp mode, they all wouldn't run right with the light. Didn't know you could get by with it on and run the car normally. And ya you can get a 7 up to 70 in limp mode, its been done in one of my cars, but it won't get up there too quick. A customers car of mine would not have the check engine light come on until I would floor it and then it would fall on its face until I let up and eased it up to speed with less throttle. I did fix the problem though, I'll look in through my work orders and see if I can find that car and the repair to make it run right again. have you re adjusted the Tps and done some basic maintnence? like change the fuel filter? although a cloged filter won't throw a code it will act the same way you describe

 

if it's an O2 sensor code, it'll run fine.

 

ha ha I forgot that one. very true