swapped in a new motor after my 86 n/a has been sitting for about a year. It won't idle for the life of me, and it doesn't have any power/ backfires a little after 4k when the throttle is depressed. This is the problem I've been trying to fix all weekend.

- would idle previously around 1,300 rpm, then found a vacuum leak: this stopped all idleing

Checked:

BAC
TPS
MAF
injector resistor pack
Firewall ground
timing (several times), cant use a light as it wont idle
plugs
plug wires (resistance)

also fouled a set of plugs trying to get it to run.

any help is appreciated. Thanks

 

The ground with the black box that goes to the slave cylinder think its the oil level sensor ground but that can cause all of those issues on a 86.

 

That's a condensor and it's part of the oil pressure gauge circuit.
Worst that can happen if it's wire gets grounded is killing the gauge, it has nothing to do with how the engine actually runs.

 

You have a huge vacuum leak somewhere.
Check your Maf elbow to throttle, intake manifold ..
Your issue is exactly what happens when there's a huge
vacuum leak.

All those you listed will not cause that.

 

thanks for the input. I'm leaning to an intake leak. I replaced the upper intake gasket and put some "gasket coating" on that my gf's dad recommended... he also sanded off the old gasket on the manifold, so maybe didn't use a fine enough paper. either way I have manifolds to spare

 

My '86 had stuck aux ports.
PB Blaster and a little persuasion freed them up and I couldn't believe the difference.
While not really related to the idle problem. it could contribute to the power upper end.

 

little update:

managed to get the car running better with some fresh new spark plugs, it got to the point of not starting at all before. (I may have added too much premix eyeballing it like an idiot hence fouling some plugs).It still smokes... quite a bit, and wont idle once it warms up.

I added 20L of fresh gas to the tax and its still smoking... quite a bit, under load and at idle.

The car sort of sputters itself up the RPM range between 2k-4k and then will go right up to redline no problem.

At this point I've replaced every sensor that could cause an issue (except the o2). Im hoping it's not oil seals that could be the issue.

Any input is appreciated to help me out.

 

Are you sure your spark plug wires are hooked up correctly? If they're hooked up to the wrong places it will make the car run like sh*t.

I'd double check that.

https://www.rx7club.com/2nd-generati...-order-326259/

Here's a thread telling you exactly how they go, good luck.

 

Plus and wiring are good, I have been over that procedure earlier this week. Also tested resistance of wires.

 

There's a hard idle screw on the throttle body. See if it's sdtill there and if it is, screw it in clockwise (little at a time) to open the throttle plates. There's a lock nut on there as well.

It's something simple that you're missing.
Start with the obvious first and go from there. I still say it's a big vacuum leak. If you can get to idle , spray some carb cleaner around and see if idle changes.
To check if you have bad oil seals, rev to past 4000 and hold couple minutes. If you have bad seals, it will smoke a lot.
Bad gas will make it idle like **** but will still idle.

 

Solved! The MAF was stuck open causing the mixture to be super rich. No doubt the plugs fouled so easy

 

Howd you figure it out, run it with no air filter?

 

Checked all the sensors over, then disassembled the intake and looked at the maf, almost stuck fully open. A little carb cleaner, some WD, and a bit of lube. Good as new

 

If u had a shady shop do it they'd make up some BS and charged you 50 bucks for what you just did or more. Lol