86 N/A rough idle / loss of power / stalling / red light NEWBIE help

[jimtweet]

ok, so here we go...

1986 NA, car was sitting for 7 years with blown engine (1/4 tank of gas, when I got it)

Purchased engine from John on here, perfect compression and perfect leak down

Idle is jumping between 900 and 1200 sometimes as low as stalling and the Red ! flashes on the gauge cluster.

I can feather the throttle and get it back up sometimes, then when driving, its sudden loss of power, can will not go over 1800-1900 RPMs

Car ran great the day the engine was dropped in and fired up and now the problems seems to be getting worse and almost all the time (hot or cold)

When the car is running right for the moment, If I blurp the throttle a bit, its takes a second, extremely rough to come back to idle (950RPM)



here is what mechanic did so far: Mechanic replaced belts, water pump, thermostat, motor mounts, intake manifold gaskets, exhaust gaskets

here is what I did so far:
1. replace distributor car and rotor (I honestly think it was original one on car. There was nothing left on rotor and points in cap were black and corroded)
Problem seemed to go away for an hour
2. Replaced air filter (again, I think this was original to car, completely black.
no real diference here
3. Throttle body removed, it was extremely dirty and gummed up. Cleaned, installed with new O Ring, reset idle per Clarks Garage
Problem seemed to go away for a day, then returned, even more often now
4. drained the gas that had been sitting in the tank, replaced fuel filter, filled tank with 93
Problem still exists

What I have no done:
1. I have not checked spark plugs, I just ordered a set of Bosch Supers from local mechanic and should be here tomorrow
I might pull one today to inspect


Im thinking:

1. Bad Fuel pump? or bad tank screen?
2. Bad Throttle Position Sensor?
3. Bad O2 Sensor?
4. Bad Air Flow Meter
5. Fuel Pressure Regulator?

I don't know these cars well enough to diagnose, but for some reason my gut is telling me fuel pump. I had a 2004 wrx that experienced these same issues. I cleaned the MAF and replaced fuel pump and problems never returned.

[Tom944]

Take a look at the spark plugs. It could be that you have a problem with one or more injector.

[jimtweet]

Originally Posted by Tom944

Take a look at the spark plugs. It could be that you have a problem with one or more injector.

Just pulled spark plugs, look fine to me, old but fine. I will replace anyway.

I did notice that the number 1 cylinder spark plug wire was not snapped onto the spark plug, it was just sitting on top. I pushed this on, started car and same symptoms

[djnolan]

I 2nd that. Take a look at the plugs and see if they are colored evenly, and if you can tell if it is running rich or lean.

[jimtweet]

ok, problem is definitely getting / gotten worse

today, I noticed the "MPG" needle pegs to 20 as soon as car is started and jumps around up there

idle is still bouncing but now if I try to feather the throttle or hit throttle at all, it gets worse and just about shuts off. If I take my foot off throttle, idle comes back up and bounces around

I did notice the inside of the terminals on plug wires are completely corroded , green, and rust

[jimtweet]

[jimtweet]

thinking out loud

the gas pedal isn't really a fuel pedal, its an "air pedal".

So something needs to tell the computer to send more fuel, TPS??

is this why it ok to idle (jumpy, but will idle), then it dies as soon as I hit gas. So im letting more air in, but nothing is sending more fuel

[djnolan]

It might take a while to sort this out, but here is a couple of good references to help you...

Troubleshooting - Engine

Sensors and Gauges - Information, Troubleshooting, and Testing

[fiily]

The way i always handle any issues on a 944 is triple check the work done by the mechanic that installed the engine, easy to miss vacuum hoses on these cars, or misconfigured vacuum lines.

I also go from free diagnostic stuff to check, then replace vacuum lines always, ISV hoses, and verify all clamps are tight.

Verify your afm is plugged in, check vacuum lines are all correctly connected, and last I would check the your ISV hoses are good under the intake.

Both my 951 and 944 had split, rock hard hoses going to the ISV, and pelican has both hoses for pretty cheap, sometimes the ISV valve is gunked up and hunts to regulate and causes these issues.

Remove the ISV from under the intake and spray/clean it out with carb cleaner, install the new hoses and go from there.

[DeadPorsche944]

It could still be a fuel delivery issue. Check the pressure at the rail at idle and while raising the RPMs. I'm betting it drops when you raise the RPMs.

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[jimtweet]

Originally Posted by DeadPorsche944

It could still be a fuel delivery issue. Check the pressure at the rail at idle and while raising the RPMs. I'm betting it drops when you raise the RPMs.

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I'm trying to locate a tester now

[DeadPorsche944]

Most auto parts stores have a testor you can borrow. Getting the right size adapter for the fuel rail seems impossible. I just took a piece of hose and clamped it on. You'll also get to see what your gas looks like... Make sure you let a little fuel come out the bleed valve of the tester so that it reads properly. Just be careful with the gas. Don't set fire to your new toy. ;-)

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[DannoXYZ]

Plugs look fine, a little too much fuel if anything. Most likely a vacuum leak after the AFM. Measure:

- measure AFM voltage @ idle, use throttle to maintain idle-speed. Should read 0.8-0.9v. Lower voltage indicates AFM is not measuring all air going into engine.

- measure intake-manifold vacuum with warmed up engine. Should be in 20-22inHg range

- measure vacuum at FPR and dampener (use rubber T). Should be same as earlier test

- measure fuel-pressure in rail with vacuum hose to FPR disconnected, should be around 38psi

- measure fuel-pressure in rail with vacuum hose to FPR connected. Should be around 28psi

Obviously these tests have to go in order. Without proper seal from AFM to intake, AFM-voltage and vacuum will be wrong and DME & FPR will send improper fuel amounts.

Check all intake hoses and clamps. The intake hose loves to split underneath. Or it can also slip off the throttle-body. Also check all the big hoses coming off the intake-manifold.

[DeadPorsche944]

Any update?

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[Fast Freddy 944]

Bosch plugs are strange, when the new platinum plug came out I put it in every car I had. They would run great for a few miles, then it seemed like my fuel consumption would go up, and the performance would drop. Very strange, I use a different brand, I'm planning to purchase some ngk irridum plugs very soon.

[jimtweet]

Originally Posted by DeadPorsche944

Any update?

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I believe this was bad o2. I replaced o2 and it's been okay for 3 days now