DMTNinja

Hello, everyone. DMT here. So, the issue I am having is that I just recently acquired a 1988 RX7 GXL. (I do know in my "new member threads" I said a 1990. But, that's a story for later. Down to the tech issue. I am well versed in engine electronics, and have yet to resolve the issue myself.

Multiple issues while idling:
1. When car starts, sometimes it does not go through the rotary rpm stages, first around 2k rpms, then down to 1.5k rpms, and finally a steady idle around 800-1k rpms. Possible cause and fix?

2. Car bounces around on rpms while idling. 6-700 rpm bounces to 1k rpms. and repeats bouncing from low to high.

3. Car starts up and idles like normal and then just dies when getting down to normal idle rpm range.


Ok, so now that I told you 3 of my issues, (find it pointless to make multiple threads over the same topic), I am a decent mechanic. I have a certificate of completion of the Automotive Tech. program and my local tech school. And then attended a year at Linn State Technical College for Automotives in Missouri. So, I know a few things.

Case 1 & 2, I am pretty sure there is a vacuum leak somewhere. There are two vacuum plugs on the back of the stock air box that have no vacuum lines going to it, and then behind the motor there is a 1"ish looking hose that is not connected to anything. Will post pictures tomorrow.

Case 3, I am completely lost on this one. I don't know if it have a common problem that is universal to piston engines and rotaries. Or if it's an issue that is just rotary.

I thank anyone that can possibly help me.

Aaron Cake

iTrader: (1)

Your question is a bit unclear. What is happening? Are you saying it starts at 2K, then down to 1.5K, then gradually falls down to 800-1000? That's almost right, with the main issue being the 800-1000 RPM idle, which I will cover below...

Vacuum leaks and a maladjusted TPS. Also test and clean the BAC valve.

It sounds as though you are missing the air pump?

satch

iTrader: (1)

#1. On a cold start the car should rev up to 3000 rpm or so for 17 seconds then the idle drops to about 1500 rpm then slowly drops to about 800rpm. This process "only" occurs if the coolant temp is above a particular threshold such as 62 degrees or so (this is measured by a sendor in the lower region of the radiator)). If the coolant is cooler, the car will not cold start beginning with the 3000 rpm rev but bypass this feature and rather starts up at about 1500 rpm before slowly dropping down to 800 rpm.

DMTNinja

That is exactly what I am saying.

Sorry I haven't responded in a couple of days. Been busy with college final projects and studying for finals. Physical Therapy, is definitely a nightmare, but it's what I wanna do. XD

Regardless,

UPDATE:

The car has since died. Actually, the day after I posted this, the car died. I was being good to her. You know, completely cleaning the interior; removing the seats, vacuuming in the bins, removing unneeded tools, fixing panels that didn't have to be replaced, you know, the works.

After this complete interior maintenance, I started up the "7" like normal, normal idle startup (no cold start), and then it idles around 4-500 rpms and then dies.

In my mind, "Ok, this is normal, just start it up again and give it a touch of gas to warm her up and we'll be fine." NOPE! All I get is the rotors turning with gas being introduced like normal, but no spark.

What do I do? I pull the plug wires and check to see if they have spark. I put a screwdriver in the end of the spark plug end of the wire and arc it on the strut tower bar on the front. Believe me, it's a Super Awesome Fun Time! Especially, when you forget you are standing in a puddle of water.

So, I have thought about it. For a gasoline engine to run, you have to have Fuel, Spark and compression. I have the first two. So, I've narrowed it down to compression.

Possible compression test walkthrough from someone? I know that rotaries don't use conventional compression tests.

Right now, the car is at a trusted mechanic. I figured I'd let him look at it while I am busy with school and such.

If he can't figure it out, I am afraid that my apex seals have gone bad. I've talked to a few RX7 guys here in my town. They have told me that it could possibly be the apex seals, because the OEM seals are two piece, and over time a piece of the seal breaks and scratches the rotor housing walls and the plate in between rotors.

Is this information correct? Anyone care to elaborate more?

DMTNinja

UPDATE:

Found an easy way to run a compression test using a standard compression tester. Ran compression tests and found that the rear rotor has a bad apex seal. So, now I am going to have to remove the motor and tear it apart.

Time for me to learn all there is about the internal workings of a 13B.

Cpeters

Get the DVD =p there fun to take apart but watch those corner seals they are small as hell and look like trash lmao think i sent a few flying.

Aaron Cake

iTrader: (1)

Here's a rebuild video to get you started:

http://www.youtube.com/watch?v=ijJeUk_GqiI

DMTNinja

UPDATE:

After talking to a few rotary guys here in my hometown, I followed a few suggestions. Just to rule out a few of the other possibilities before I removed and disassembled my engine, I wanted to check a few other things out.

I checked to see if the spark plugs were fouled, they were. Replaced. Checked to see if there was continuity from the coils to the spark plugs. Replaced plug wires. (The clip on the inside of the boot that plugs onto the plug on rear rotor plug wires, non-existent.) After replacing this, I disconnected the fuel pump plug (On right rear speaker,strut support under carpeting) to burn out excess fuel in the rotor housing. She fired up, but died quickly thereafter.

Had a buddy come over to help plug the fuel pump connector plug back in when I fired it up again. Would run when given gas, but would die when let idle. Instant flag in my head, Idle or TPS. After messing around with the idle screw and AAC screw on top of throttle body, realized that it had nothing to do with idle. Unbolted TPS and started her up, idled like a dream.

DIAGNOSIS:
- Faulty TPS - Possible cause due to shorting out inside TPS or near connector.


P.S. - I know this is an old thread, and I'm unsure if anyone is even watching it, but I figured that I would post my work and experience in hopes that it may help another member of the forums.

P.S.S. - In bringing this "dinosaur" back to life, my car has been dubbed the "Rex 7".