Hello all. New user, first post.

Got an 89 NA that I’m getting stumped with.

The car didn’t run run when I got, I’ve since rebuild the motor an got it running however now I can’t get her to idle right. When I first start it, she jumps to about 4K, then comes down to about 1500, then slowly drops. It sounds like it’s missing, almost feels like it’s got a shake to the motor that you can notice at low idle.

I’ve replaced about 8 feet of vacuum line. Intake system is clear, with a new filter. It’s got new air an fuel filters. I’ve bleed the coolant system. The thermo sensor an the BAC have tested good. Coils test good, but I can’t set the timing because it won’t idle right

Any tips or ideas would be awesome.

Thanks.

 

Have you adjusted the TPS (throttle position sensor)?

 

Two ideas:

1. If the MAF is unplugged, the car will usually start, then drop down and die. Double check that it's plugged in.

2. Have you used the idle air bypass screw?

On top of the throttle body (sometimes under a rubber plug) is a small screw. Turn it outward (counterclockwise) to raise the idle.

First try raising it enough to get the car to idle properly, then once it's all the way warmed up (1/4 on the gauge, the radiator should be hot because the thermostat is open) you can set idle to 750 and go through the normal idle set procedure.

 

I haven’t adjust the TPS yet. When reading the manual it says to adjust it the TPS after its warmed up an idling. I can get it to warm up, just not idle

I’ll double check the MAF an make sure that plugged in. I also haven’t adjust the idle bypass. I didn’t want to start turning it without it idling. When I got the car, it was burning coolant but would still start an idle. Didn’t think I would have to make a bunch of adjustments to the throttles after the rebuild.

 

Since you rebuilt it, it's possible that before the break-in period the engine has a harder time idling. This means you may need to tweak the idle again after the break-in period.

To be clear, don't adjust the throttles. The Rx7 has a screw specifically to adjust idle using bypass air, without messing with the throttle stops. I know you probably know this, but I thought I'd mention it since messing with the throttle stop can cause other problems.

 

WondrousBread,

You’re talking about the adjusting screw on the top of the intake correct? That’s under the black rubber cover?

 

Yes, that's the one. Make sure to put the cover back on when done.

 

Well she’s idling know, thanks to an adjustment of that top idle screw. She still seems to be missing, which is preventing me from setting the base timing correctly. My leading coil tested good, but my trailing seem to be inconsistent. I’ll change plugs an she’ll fire for a bit then stop. If it put a different set of plugs in she’ll fire again. I’ve got all new plugs an wires but something is preventing the coil from firing constantly.

 

You should be able to set base timing using the leading coils, so if they're firing consistently and idle is below 1000rpm then you should be good to go. Remember the initial set connector needs to be jumpered (two pin green connector by the leading coils). Make sure the CAS is stabbed correctly (this is a pain and I never get it right myself, but it's important). You want to make sure the L1 coil is firing okay, and the first marker (yellow, I think) on the pulley is the one you want to align with the needle on the front cover.

The trailing timing follows where you set the leading timing, so as long as you set leading properly don't worry about trailing timing. You can confirm it using the timing light to be sure, but that won't be easy until you've fixed the misfire.

As long as this goes according to plan, I would set the TPS (I like the two-lamp method) next since that can cause rough idle. Then I'd try removing the trailing coils and cleaning both them and their mounting points to make sure they're grounding properly. Also measure resistance from the engine to the negative terminal of the battery cable. If you aren't getting zero, you have some grounding issues.

 

Remember the initial set connector needs to be jumpered (two pin green connector by the leading coils).

That’s the first time I’ve heard that for setting the timing. Just jump it to itself? I’m messing with her now. I have a new (trailing) coil that I’m going to install an see if that fixes my no firing scenario.

 

Yes, just put a jumper between the two contacts.

This jumper tells the ecu to not try and mess with the idle or timing. Basically it stops the bac valve from doing its thing and locks the timing so it doesn't advance. This should be jumped when setting idle (750rpm) and timing, then remember to take it off when you are done or else you'll have a loss of power and no bac function.

There should be only 1 green two pin connector in that area by the leading coils, but my hood has some stuff on top of it right now so I can't confirm the color of the wires. Make sure not to jumper the 6 pin connector, that's a diagnostic port. Only touch the two pin green connector.