bshusted

iTrader: (1)

I just finished installing my new Borla Pro XS under my car and went out for a test drive. When I first started the car after the installation it idled fine. After 2 or 3 runs to the buzzer, it began idling around 2k rpm. Bank in the garage I checked to see if the throttle cable had gotten stuck, but all of the throttle plates were closed. With it running I pushed on the shafts to make sure that they were all the way closed and nothing changed. I've begun looking for vacuum leaks, but haven't found anything. The car is running extremely rich (I smell like unburnt fuel after driving for a few minutes). Is this a vac leak that I'm missing or a carb problem. I have a hard time believing that the new exhaust has had anything to do with this.

Mods to the engine: Rats nest removed, header, and racing beat intake.

I hope someone has some ideas on this. I don't really want to put any money into this 12a since I've been building a 13b to replace it. Any and all help is appreciated.

Rx-7Doctor

iTrader: (13)

What all did you remove during the installation?

bshusted

iTrader: (1)

For the installation of the muffler the only thing that was removed was the header, so I don't think there was anything reassembled incorrectly or forgotten.

One thing I will mention is that while working on something else the other day I noticed that my ignition was backwards. I have replaced the plug wired on my car but only did it wire for wire, never questioned the order of things. While installing my headlight relays I noticed the stampings of "T" and "L" on the rotor housings. The Trailing on the housing was connected to the leading on the distributor. After switching them around it ran like a new car. That was probably a week prior to the installation of the muffler and it ran like a dream.

Could someone have screwed up the wires and then adjusted the idle mixture and throttle to make it run? And now that I've fixed it, it's idling high? The thing is that even though it is idling high, it probably running the best it ever has. I've had vacuum leaks before and usually they make the car run like ****. I don't get it.

yetterben

play with your idle screw lower it down see if it stabilizes!

bshusted

iTrader: (1)

Sorry I didn't post back very quickly, but when I went out to work on it, it was idling fine. Rock steady at about 800. I did want to play with the idle mixture to see if I could make it better, but failed at getting the cap off. I didn't want to break it. Is there a secret?

Anyway, so thanks to Doc and yetterben for helping out, but until it does it again, I don't have much to go from.

Rx-7Doctor

iTrader: (13)

Don't adjust anything. Wait until you see if if acts up again.

bshusted

iTrader: (1)

Did it again today. Running really rich. Pulling up on the pedal did nothing but pushing on the shaft for the primaries calmed it down. It only happened after I got on it. A minivan thought it was going to pass me getting on the freeway and cut me off, so I ran it though 2nd and into 3rd to the buzzer. Then the idle was back up to 2k. Could it just be that when the throttle gets opened all the way that it hangs up a little bit? Maybe the return spring is failing.

Kentetsu

Hi Brian. I missed this thread the first time around. What kind of carb are you running? I recently had an issue like this and found two things, the nut on the shaft that holds the linkage on was loose, and the oil pump was also keeping the throttle from closing all the way.

However, since you mentioned the plug wires I was wondering if you adjusted the timing afterwards. The timing will be way off if it was originally timed with the plugs the wrong way. That would also explain the high idle, but not why it only happens sometimes.

You also mentioned that you pulled the header off. Any chance you bumped a hose on the back of the intake manifold?

Good luck with it. We missed you at the ABC autocross, and hope you can make June 15th at US 131 dragway.

bshusted

iTrader: (1)

The carb is stock with the emissions removed. I'll check to see if the linkage is loose. I don't see how the OMP can keep the idle high like that. I did some more fiddling with it and testing and it's not like it's just idling high on a leak because it has power. Our Porsche had vacuum leaks everywhere and at an idle it would just race, but as soon as you let the clutch out, it would die. Mine seems to be getting enough fuel, in fact it runs rich as a pig. When it idles high and you shut it off a few seconds later there is a pretty large backfire. I'll check the hoses on the carb again. I hope to be at the next autocross.

Kentetsu

What about the timing? I thought some more about it, and by moving the wires back to the leading position as they should have been, you also would have advanced the timing a lot. This would also explain the jump in idle speed. Make sure you aren't getting any detonation before you get on it too much (sounds like marbles in a tin coffee can at wide open throttle).

I'm not sure how the OMP was messing up my idle, but when I disconnected the rod the problem went away. This was on a new (for me) motor, so maybe the pump was hung up in the open position, and putting pressure on the linkage (since its all tied together).

bshusted

iTrader: (1)

Definitely no detonation, but I'll hit it with a timing light. I don't think it can be the timing because it calms down sometimes. I can see how advancing the timing would increase the idle speed, but since it's not always high.....I couldn't find any loose hoses or nuts. I've got a can of starting fluid in my car now and if it does it again, I'll start spraying around the carb to find any leaks.