Redline SI-1 in 7 month old gas

[Nick29]

My '96 neon has been sitting since november while waiting for the engine to be rebuilt. The friend of mine (a mechanic) who did the rebuild noticed the check engine light came on the other day, indicating a lean condition while the car was idling at a traffic light after driving on the highway. This is especially weird considering that the cars are known for running rich.

We both figured it could be due to the old fuel in the car, as there isn't really anything else out of the ordinary with the car.

I have a few bottles of Redline SI-1 fuel system cleaner sitting at home. I've read through a bunch of threads here about the residues that can be left by evaporated gas after sitting for a long time. Would the Redline help with this at all? I plan to try to keep the car topped off with gas for a while (to dilute the old gas) and use a maintenance dose of the Redline, but I'm wondering if putting in an entire bottle now would be worthwhile.

btw, I know the best thing would have been to add something like Stabil or FP60 in November. But, I didn't expect the car to sit for as long as it has and it never really occurred to me that the age of the gas would matter.

 

[qadsan]

Did you friend put a scanner on the vehicle to determine that your mixture is lean or are you assuming it's lean because the check light is on? If he put a scanner on it, what was the exact scan code(s) read?

Does your friend have access to equipment to sniff the tail pipe to check a/f ratio, co2, egt, etc to confirm that the mixture truly is lean?

 

[Nick29]

he ran the codes and it was "engine running lean." He didn't check the air/fuel and said the car is still running fine.

 

[qadsan]

See if your friend can measure the fuel pressure on the fuel rail to make sure it's in spec. It should probably be somewhere around 45 to 50 psi, but check your service manual to make sure. If the fuel pressure is low, then you'll need to determine if its a clogged fuel filter on the pump inlet or outlet, the regulator or the pump itself.

If fuel pressure is good, then look for sticky injectors. If your friend can scope them, then he'll be able to see if an injector is sticking by comparing & analyzing waveforms from the different injectors. Don't rule out a weak coil and there's also the possibility of a vacuum leak (manifold, tubing, etc), a cracked exhaust manifold and you'll also have to rule out the MAP sensor, oxygen sensors, etc.

The Redline SI-1 fuel system cleaner shouldn't hurt a thing and there's a chance it might help. I'd use it at the maximum 'recommended' strength and see what happens.

 

[Nick29]

I picked up the car tonight. My friend said that the Idle Air Controller (IAC) needs to be replaced. The car doesn't want to idle, and keeps trying to idle at ~500rpm (normal is just under 1000rpm). He has a neon and had the same idle problems when his IAC died.

He had cleared the codes and the car ran fine other than the rough idle. I stopped for gas a couple miles from his house (it had 1/4 tank) and put in the recommended full dose of SI-1. After I started the car up again, the idle was still rough. I revved it up to 1500 and when I let off the gas, the engine went down to 500rpm and stalled and gave the lean code again.

This makes me think the IAC is the main problem. I'm going to replace it this weekend and see if that fixes the problem. If it doesn't, I'll start looking at the ignition, but an insufficient spark would trigger another code, as would a bad oxygen sensor. The injectors were cleaned while the car was down, and there isn't an exhaust or vacuum leak (he checked for both of those after the rebuild).

 

[qadsan]

If you test the IAC electronics and they're good, then you can also try cleaning the IAC with intake spray cleaner to see if that helps. They do get carboned up with time. If it's bad, then it's bad, but sometimes a good cleaning will do the trick. Also inspect the IAC gasket base and or o-ring and any accompanying hoses.

Make sure to spray the intake cleaner in the IAC port of the throttle body as well and the tip of the solenoid, etc. Clean the IAC solenoid tip throughly & gently and don't twist or force the plunger or you will damage the IAC solenoid. Hopefully a good cleaning is all that's needed.

 

[Big Jim]

I would try cleaning the IAC before replacing it. Clean the throttle body at the same time. I would run the stale gas out of the car before adding the injector cleaner. I guess you nearly did if it was reading 1/4 tank.

 

[Nick29]

I thought of cleaning the IAC right before I read your posts. I just sprayed some PB blaster on the IAC screws (they like to break when you remove them) and will pickup some carb cleaner in the morning.

Hopefully this solves the problem since changing the IAC is a big of a PITA. You have to splice updated connectors into the IAC wiring.

Is there any specific cleaner I should look for, or is any carb/choke cleaner OK? Knowing this site, I'd bet someone knows a specific brand to look for

 

[Big Jim]

I like Berryman's for this, but there are many that will work just as well.

 

[Nick29]

I tried cleaning out the IAC and throttle body today and it didn't help. Hopefully installing a new IAC will do the trick.

 

[babyhuey]

i have seen a lot of IAC's replaced due to air leaks in ducting before throttle body*also dried out base gasket under throttle body will cause vacuumleak}IAC has nothing to do with lean running,its just trying to stabilize the airflow*due to unmetered air playing havoc with system}.Bottle of propane will find any leaks.Remember MAP engines idle high with air leaks,port injected engines usually idle low*maf is out front}

 

[Nick29]

Thanks for the input, but I found the problem last week.

After racking my brain and wasting my time trying to figure out which sensor it was on the intake side of the motor, it was the upstream O2 sensor.

For some reason (maybe it's common to other cars too), it seems pretty common for upstream O2 sensors to go bad without triggering an O2 sensor CEL on a neon. I still don't understand why it gave some symptoms of a vacuum leak though (hanging RPMs, high idle), but that all went away with the new O2 sensor so I won't worry about it.