Hey guys, the other night I turned off the engine after driving for some time and had a great backfire out of the carb. The next day I started the car and it won't idle. It will start and if I rev it I can keep it alive, but if I stop giving it gas it dies. Also to note, when I do let it die after several seconds I notice a fairly heavy smell of gas. It's making a sound as if maybe a vacuum line was blown off in the backfire, but I've yet to discover a stray line. I'll get into it further this morning and see if I can come up with anything. I'll keep you guys up to date just in case I figure out the problem Take care!

 

Is the noise real loud? It's sound like it could be the shutter valve. Take the air cleaner assembly off and plug the large hose that seems to go below the carb on the passenger side of the carb and see if the noise goes away and the engine idles.

 

Also, under the carb, engine side, towards the rear, there is an unused vacuum port that was capped at the factory. The rubber cap tends to rot, and can easily fall off. Having a backfire thru the carb can blow it off. Since it just had a cap on it, you won't find a hose that is disconnected, and with the location of the port, you can barely see it unless you know its there.

 

Thanks very very much for the responses! I'm going to try both of those approaches and let you know what happens.

 

Hey Doc, the noise isn't so much loud as it's kind of a pulse you can feel. It's very evident at low rpms, making the engine shake, but once you get it to 1200rpm or so it feels like a fast pulse (pulsing with the rpm of the engine?). I still have not had a problem getting the engine started (giving a little gas as it cranks). I did block that shutter valve hose to no avail. I checked all the hoses going to the air cleaner assembly and they are intact. Rogue, I didn't find any rotted or missing caps so hopefully I looked in the right spots for those. I'm going to look for an exploded view of the carb so I can make sure I'm looking in the right place. Thanks for the advice and any other suggestions you guys might have. I know it must be a pain trying to diagnose over the internet but the suggestions you guys made I would never had thought of.

 

The vacuum port I mentioned, is well hidden under the shutter valve. I know where it is, and I still have to look carefully to actually see it. It is not on the carb, but on the intake.

 

Ohhh, thanks for the clarification, I really appreciate it. I'm pretty sure I was looking in the wrong place altogether I'll give it another go and see if I can locate it.

 

this could be my problem aswell, i bought the car and it has never idles properly, i have to rev it up or it dies. i rebuilt the carb still happens. so that is making me think maybe this factory cap has rotted out over time, cause i have tried to find a vacuum leak and cant seem to find one

 

rxtory, I'm going in search of the problem again today, so if I do end up with a solution I'll let you know. At this point I have no clue, but I'm going to look more closely for that port Rogue was talking about. Hopefully that's all it is.

 

Does anyone have a pic of said "factory capped" area?

 

My camera crapped out, so I cannot post a pic. But, I have an 85 intake laying here, and the port I am reffering to, is directly under the shutter valve, between the vacuum pod, and the flapper. On earlier intakes, without the shutter valve, it is located *almost* under the throttle linkage.

 

Okay, so what I've found is on the air intake all of the hoses that are supposed to be attached are all intact. If I'm looking in the right place, there is a large corrugated hose that goes from the bottom of the air intake (right under the shutter valve) down to the smog pump. That is intact also.

Now, I could Still be looking in all the wrong places, as Rogue, you may be talking about a place on the intake manifold, rather than the air intake, and in that case I'll be thoroughly embarrassed, haha. But as for the hoses leading from the air intake, those are fine, and after close inspection I couldn't find a port that would have been factory capped.

 

Shutter valve is in the intake, engine side. There is about 1/2" hose that comes from the underside of the air cleaner to the shutter valve.
I believe you mistook the shutter valve for the preheat valve.

 

That's exactly what I did, and so I am indeed embarrassed, haha. I'll try to do a better search in the right place tomorrow.

 

Go here and download the carb manual, and the FSM for your model year of car too.

http://www.wankel.net/~krwright/cars/rx7/manuals.html

 

Thanks so much for the link Trochoid. I was only just able to log onto this site so I just saw your post. I'll let you guys know if anything turns up.

 

Hey Trochoid and Rogue, I can't thank you enough for your suggestions. Using the onilne manual, I was able to find the shutter valve, so I plugged the hose like you said Rogue. Unfortunately, that doesn't seem to be the problem. I was still getting the same noises. Because of the smell of gas after the engine shuts off I figured there might be a fouled plug so I removed them. Whether they are carbon fouled or if it's just normal wear, I'm not sure, but I figure it can't hurt to replace them. I don't know the history of the car so I'm not sure how long the plugs have been in there. Once I get the plugs in I'll let you guys know if that fixes the problem. Thanks again!

 

Went ahead and replaced the plugs, but it's still doing the same thing as it's been doing. I verified that the factory port cap is still in place and not rotted away, which I was hoping was the problem. I replaced the plugs on a whim because I still have the feeling that the backfire the night before has something to do with the problem I now have. Any other suggestions would be greatly appreciated.

 

I have a SIMILAR problem, but I'm not sure if it's the same. My car sat in a garage for 2 years and was only taken out during the summer months, 4th of July sort of occasions, you know, used as a toy. It started and ran fine when I test drove and bought it, but on the way home, it died out at a stoplight, and ever since (it sat for about a week without running) I'll start it and it'll idle really REALLY low and start choking out. The really scary thing is that when I try to give it gas, I feel this horrible shuddering and it dies out.

Funny thing is, it goes away after the car runs for a bit, it still idles a little lower than the manual says it should, somewhere around 500-600 rpm, but i'm wondering if anyone in here has any ideas. Like I said, after about 5 minutes of rough running and a few stalls, it starts running like a champ.

O, another thing to be noted is the previous owner said he had the stock carburetor's fuel mixture running richer than normal, but i havn't figured out how to adjust that and I'm a little nervous without the EGT.

Woo, that got wordy, anyways, feedback on a possibly related topic?

 

What about an an ignitor failure? Do you have spark on the leading plugs? When my leading ignitor went it ran but stumbled at low RPM and jumped around maddly at higher rpm. That could explain the gas smell too. Im EFI not carbed so im not schooled on carb workings so sorry if I missed something that would rule this out....

 

Check your coils, I pulled off all the plug wires and had some turn the ingnition for me and with a spark plug laying on the strut tower checked all the wires L1 was dead, NAPA has replacements for around $29.00 and a more expensive one for around $48.00.

 

First off check this sol. make sure it has 12v goint to the plug. THen touch the connector to the sol and make sure it clicks.



Then make sure this isn't plugged or capped off.



Then double check your vac lines should look like this.



Look at your oil filler neck suction lines too. Check the brake booster hose. Spray some quickstart all around your vac lines carb base etc. The engine will idle up if it sucks any fluid in an open vac leaks. Now might be a good time to do your ratnest removal mod so you can clear out the garbage and get down to basics. Makes trouble shooting alot easier!

If all that checks good, get out your compression tester and pray... Surgeing at idle is a sign of a blown motor. Backfire could just be an unrelated issue. Then again, if the car was working fine up till teh backfire I'd guess it's just a hose.