So I’ve recently acquired an 87 Formula with 48k miles on it. It won’t run unless I give it throttle and even then it shudders and spits. I was told it could be the injectors or mass air sensor but the injectors tested out at 16.6 ohms and the mass air tested out to be good. The distributor is corroded so I’m going to replace it along with cap, rotor and plugs but I feel it won’t change the idle situation. What could possibly be throwing everything out of sync so much that it doesn’t want to run?





My 87 Formula with 88 wheels.

 

I don't recommend parts cannoning the distributor until you fix the problem with the idle. The factory service manual has a troubleshooting guide with appropriate steps to try in this situation, but things I would be looking at would be fuel pressure, TPS, IAC, and CTS. A datalog might give you an idea of what those sensors are seeing quickly. The injectors could also be physically clogged, the ohm test only verifies the coils are electrically capable of operating.

 

Id check fuel pressure... that sounds like my 87 when the pump was going bad... then it just quit!

 

This is all exactly correct (after some hard lessons over the years). Check your fuel pressure first with a simple gauge on the schraeder valve. Its well worth it to purchase a fuel pressure gauge to have around.

 

The fuel pump has been recently been replaced so aside from the sensors I’ve not checked yet, is there anything else that should be inspected before I take the top of the manifold apart to test injectors?

 

Yes, fuel pressure.

 

Sensors should throw codes most of the time. I agree to check those by pulling codes. I’m assuming timing was double checked? Any back story on when this srarted?

 

Purchased the car this past Tuesday, was told it was fuel injectors or MAF but neither of which have shown any indication of being bad. I haven’t done a fuel pressure test yet and the pump was replaced a few years ago before I purchased the car. Next thing I was going to inspect was IAC, TPS and the CTS.

 

Don't just throw parts at it screwing with the originality. As said, datalog it.
Fuel psi test, regulator vac line -look for raw fuel in it-if so its bad.
ohm'd injs cold don't mean they are good hot or if they are even clean. Fuel filer new?
another thing is the 87s still had the cold start fuel inj setup, if that has gone wonky the extra fuel needed for start up wont be there or could be 2 much (If there is an issue, 89 up tune will bypass all that and you can leave the parts on it to keep it original looking.
pop cap off and look around, check for corrosion on cap/rotor terminals.
have a look at the reluctor wheel to, if light corrosion is there its ok, cracks around the rivets means it needs replaced. Just replace the shaft(with gm parts). Keep as any original parts as you can, they work the best.
maf was a common issue with these cars when new and later years especially if a over oiled air filter was used.
Another thing, if it's sat for a couple years after fuel pump replacement, the fuel itself could be bad.
get out as much as you can put in new. If fuel psi tests check ok.

 

It sounds like your IAC needs cleaned out. When it goes to idle, it stumbles and dies. Simple and cheap. Take the intake hose off the throttle body and spray the inside of the throttle body with carb cleaner. Flip the plates, spray the shaft, shoot some inside the plenum also. AND, there should be a couple of small holes at the bottom. Get those too ( I spray directly into them ). If it doesn't work, it costs nothing.

 

I just went through this. Car wouldn't idle for shiiiit. Injectors, IAC, TPS. Injectors again!! Years of throwing parts at it.
Finally, I pulled the corroded distributor. Replaced it for $65, and car idles great. Not sure why these distributors internally rust, but they do.