I've been having a problem with my 94 since April. The car is mostly stock (downpipe, and catback at the only engine mods).



What happens is that when the car is hot it doesn't always start. It cranks and fires then dies. I can always get it to start eventually but it takes quite a few tries and some working of the gas pedal. Once it does start I have to give it some gas to keep it from stalling - then everything is fine.



Cold starts are rough, but it always starts, it runs rough for about 20-30 seconds and then clears up. I've also noticed that it idles rich - before the problem started my a/f gauge used to flash all over the place at idle, now its usually over on the rich side or flashing between rich and stoich.



Sometimes it will start up perfectly.



Here is what I know and what I've done so far:



- no smoke at startup or any other time, no bubbles in the coolant and no loss of coolant.

- engine compression is 90 on the 3 faces of the rear rotor, and 95 on the 3 faces of the front rotor.

- when the engine is running properly the vac at idle is 14-16. (sometimes while sitting, when the idle drops down it will get rough and vac drops to 10, then it idles back up).

- the motor runs strong and doesn't seem to be any different while driving.



I have replaced the following:



- plugs and plug wires

- fuel pressure regulator

- had the injectors cleaned, flow tested and rebuilt

- replaced the majority of the vacuum lines

- replaced the water temp sensor



I've tested the intake air sensor, fuel temp sensor, MAP sensor, and TPS sensor (all checked out ok).



When I replaced the water temp sensor the car ran perfect for about 3 weeks and then started acting up again. I just replaced the water temp sensor again, but this time it did not clear up the problem.



I'm really starting to get frustrated with this problem, it has me pulling my hair out. So, any help would be greatly appreciated.



Thanks,

-Charlie

Are you positive on the compression?



Mabye check it hot?

maybe you have a problem with your accelerated warmup system? valve opens at the wrong times? or possibly emissions related? partially cloggled cat or bad air pump?

Yeah, accelerated warmup system is where i would look next. However, the vacume at idle sounds a little suspicious. With a stock motor and your mods, vac at idle should be a rock solid 18-20. The 14-16 range is normally seen in a engine which has been ported. After the car has been warmed up and driven for a while, does it still show 14-16 vac when you come to a stop?

I suspected the AWS, the valve that opens it up works fine when I connect a 12v source. It also seems to come on once the engine has cleared up when I do a cold start. The few weeks after I replaced the water temp sensor the first time it worked flawlessly. I've visually inspected the air pump, and it seems to be working. I tried unhooking it once and the problem persisted.





I'm pretty sure the big drop in vac at idle is due to a drop in rpms. It acts like I turn on the A/C and then quickly recovers. As far as 18-20, are you sure? I've read that 15 is about perfect for 900rpm. When my car is idling above 1,000 (before it drops down to 900) it pulls 18-20. Yes, the vac numbers I'm mentioning are all after the car is fully warmed up.



I go to school 2 hours away so the only time I'm able to work on the car is the weekends... So please keep the suggestions coming guys, that way I have a nice long list of things to check when I get home this weekend.



A few other things I've been thinking of... Could I have a bad O2 sensor? and... I noticed that the knock sensor is leaking its goo out - I've read this makes it more sensative - could a false knock signal to the ECU cause the engine to run rich?



Thanks again,

-Charlie

I should also mention that the problem first started after I flooded the car for the first time. I had pulled it out of the garage and shut it off before it warmed up fully - then when I went to start it again it was hard to start. Ever since then it has been doing this periodically.



-Charlie

Sorry in a rush, and didnt read the whole post.





Did anyone suggest fouled injectors?

I've had the injectors rebuilt and leak tested. Thanks for the tip though.



Does anyone know of a tool that can give a readout of the signals that the ECU is getting from all of the sensors? I'd really like to see what signals are being sent from the various temp sensors, knock sensor, and 02 sensor.



-Charlie

Try reseting the computer.

any good news on the RX-7?? this is just a thought but is there any way it could be related to the ignition coils?> mabey when it heats up the wires expand making a better contact??



just a guess