Since I've owned my 89 formula, it has always displayed 3 symptoms I could never cure despite replacing a ton of parts/tune ups over the 8 years I've owned it. Car runs great except for

1) exhaust always smells very very rich
2) sluggish throttle response, there is always a small delay when I press the gas before the rpms shoot up
3) occasional blips in the rpms when idling

I have done all the basic tune up parts (plugs, wires ignition), proper timing, injectors, MAF, egr. I also have replaced the vacuum lines.

I have a theory (please chime in with thoughts) this year the car might be getting too much air, bc i have a big conical air filter the previous owner installed i never replaced. Basically only non stock thing on the car. Do u think this could be causing the ecm to think it's running lean and be dumping more fuel? Hence the rich exhaust and poor throttle response/delay...I really want to solve these so any thoughts/suggestions are appreciated!!

 

I doubt the air filter is the issue, an engine is only going to suck in as much air as it needs. the open element conical filter only allows it to breathe easier.

 

Any trouble codes, have you swept the tps, checked the cts ?
A bad o2 sticks at .450-.500mv and does not swing this could cause a rich condition as well.

 

Yes, I've replaced cts, tps, several times bc they always seem to go bad, also have replaced o2 sensor last year, never tested it though but hoping a new part works out of the box...no trouble codes. Good point about the air box I guess it won't take in too much air

Part of me just wonders if it's these cars, they are almost 30 years old. Do u guys notice the exhaust smells really rich?

 

I don't have 1 or 2, but #3 happens to me. Sometimes it's the car switching open/closed loop, otherwise.. feels like it just misses once out of nowhere. I've never had to replace my TPS nor CTS; they've all read fine since I've owned the car (datalogging confirms). I'm thinking the wiring harness is the cause of lingering issues I have. Everything is in new/working order.

You have a vacuum ball in the drivers side bumper/fender. Check it out. Often the vacuum line degrades there. It's for AC stuff but causes a vacuum leak.

 

IMO, just because it smells rich, doesn't necessarily mean it is.

Verify, don't guess.

 

Thanks for the suggestions so far guys. I have gone over all the vacuum lines in the car and replaced where necessary.

I always suspected the o2 was at fault so I replaced it on a whim last year and nothing changed. I suppose ita possible I got a faulty one so I think it's probably smart to test it.

With a multimeter, I think all I have to do is back probe the purple wire coming off the sensor with the red probe and ground the black probe, and look for readings around .45 volts, but making sure it's bouncing around to indicate it's actually reading and not sticking. Can u confirm that?

 

I wouldn't rule out a vacuum leak completely yet, my throttlebody shaft bushings were worn causing a vacuum leak that gave a code 44. was a huge pain trying to troubleshoot that.

I'd remove the air duct up to the maf, tape up the end of the maf thats exposed, and puff a cigar and blow it into different vacuum lines. this is a cheap way of smoke testing for vacuum leaks and is what allowed me to find all the remaining vacuum leaks.

If you're not a smoker, there's many ways to make a smoke test out of a coffee can and aquarium air pump for very cheap.

 

go ignition hunting, sounds like suboptimal spark conditions. leads and plugs are a good start, maybe some distributor service parts (rotor button, spring, rotor etc)

 

I just checked fuel pressure and verified 42 psi on initial prime, (key in, no crank) and it held there for several minutes. Ran it and it held at 35, revved the motor and it popped to 45 psi quickly and and back the 35 so it seems to be working normally

I can go over the ignition again but the cap, rotor, plugs, coil and wires are all new. Timing is correct as well. The ignition control module that sits on the distributor was replaced a few years ago but has less than 500 miles on it. (She's a weekend warrior). Am I missing any other spots?

 

Pickup coil and coil.

 

Also clean all grounds. Sometimes means brushing off corrosion etc with a wire brush at ground points etc.

 

Which grounds and where are they? I can check my manual this weekend but if u had specific ones in mind pls let me know

 

The efi grounds are the passengers side head.

 

What is your air/fuel reading at idle and part throttle? It will underline it for you...

Too much air getting in. Your O2 correction will compensate in your VE as you drive, but it might not be enough in your AE upon heavier throttle, so there will be a delay until the fueling catches up with the extra incoming air. Remember, once you key off, your VE goes back to the predetermined factory settings, so it would need to relearn the VE every time you startup. Try changing your air filter back to the stock one to see if this corrects it, and if it does, you will need tuning with the aftermarket one...

Are they sequential blips or sporadic?

 

Street lethal, that's very helpful info, ty. Unfortunately I haven't dove into the world of computer tuning so I'm not sure how I could check the air/fuel ratio easily or cheaply. The readers are over 100 bucks, is there a better way to check?

regarding sluggish throttle response, Does it make sense that when I first start the car the delay is not there but after a minute or so (I assume when it flips to closed loop) the delay shows up?

The blips during idle are sporadic

Tyvm

 

Some companies offer free diagnostics, I would reach out to one and tell them you are seeing an occasional SES light and that you want to confirm if it is sensor/code related, or just a glitch. They should be able to read the air/fuel or BLM while they are in there, just to get an idea where you are. You could also pull the plugs to confirm richness.

Yes because the fueling method is slightly different in Open Loop than during Closed Loop. When the loop is closed the system relies on a number of different factors to determine fueling, and if the data is skewed by one of the sensors then the fueling, as well as the timing, begins to play tug of war because of the targeted air/fuel, which also points towards those sporadic blips during idle. If the blips were linear and sequential it would be in a particular cylinder(s), which would point to an injector, plug or wire. I would give your local auto parts store a call like Pep Boys and see if they can read your ECM to check for any codes, and while there, see if the guy will share the data numbers of each sensor with you, just make sure you are in Closed Loop with the engine running in operating temperature...

 

Thank you so much this was extremely helpful. Let u know what I find when I get out there