90 GT Running rich, backfiring?? Help!

afiveo · Nov 8, 2009

65ShelbyClone said:
Use the DC setting. If it has a range selector, put it on a voltage window of 20.

thanks. It's just marked 600V DC or 600V AC, I'll use the DC.

ID89GT · Nov 8, 2009

It sounds like a possible vacuum leak to me. Do you have any whistling noises or have done any thing under the hood recently?

afiveo · Nov 8, 2009

I really do appreciate the info given so far. I will be honest though, I am a bit overwhelmed. I mean I don't have a clue what most of it even means. I'm not a total idiot by any means but I guess I need more of a "mustang repair for dummies". I am pretty mechanically inclined but most of the info seems to be right out of a ford manual that only certified ford mechanics can understand. I'm trying to follow everything the best I can.

I know noone can diagnose a problem on a forum, but does it seem it may be a bad EGR?

afiveo · Nov 8, 2009

ID89GT

I had a BBK 70mm TB and spacer, 24lb injectors, C&L mass air, K&N cone filter and a upper with a ported TB openning. It never did run right so I put it all back to stock. (except a K&N panel filter) I thought that there was a problem with something I put on so I went back to stock with brand new 19lb injectors, plugs, wires, cap, rotor, O2 sensors, and fuel pump and nothing has changed.

jrichker · Nov 8, 2009

If the cone air filter is located in the engine compartment, it can cause all sorts of strange problems. The hot engine air causes turbulence in the filter and air inlet ducting. This causes problems with the MAF and upsets the air/fuel metering.

afiveo · Nov 8, 2009

jrichker said:
If the cone air filter is located in the engine compartment, it can cause all sorts of strange problems. The hot engine air causes turbulence in the filter and air inlet ducting. This causes problems with the MAF and upsets the air/fuel metering.

It has a panel filter in the stock air box.

afiveo · Nov 8, 2009

There is a hose about 6-8" long coming from the top of the charcoal canister that is not connected to anything. Is it a vent or something, or should it be connected to something.

jrichker · Nov 8, 2009

Charcoal canister plumbing - one 3/8" tube from the bottom of the upper manifold to the rubber hose. Rubber hose connects to one side of the canister solenoid valve. Other side of the solenoid valve connects to one side of the canister. The other side of the canister connects to a rubber hose that connects to a line that goes all the way back to the gas tank. There is an electrical connector coming from the passenger side injector harness near #1 injector that plugs into the canister solenoid valve. It's purpose is to vent the gas tank. The solenoid valve opens at cruse to provide some extra fuel. The canister is normally mounted on the passenger side frame rail near the smog pump pulley.

It does not weigh but a pound or so and helps richen up the cruse mixture. It draws no HP & keeps the car from smelling like gasoline in a closed garage. So with all these good things and no bad ones, why not hook it up & use it?

The purge valve solenoid connector is a dangling wire that is near the ECT sensor and oil filler on the passenger side rocker cover. The actual solenoid valve is down next to the carbon canister. There is about 12"-16" of wire that runs parallel to the canister vent hose that comes off the bottom side of the upper intake manifold. That hose connects one port of the solenoid valve; the other port connects to the carbon canister.
Purge valve solenoid:

The carbon canister is normally mounted on the passenger side frame rail near the smog pump pulley.
Carbon Canister:

afiveo · Nov 8, 2009

The line from the charcoal canister to the hard plastic line (to fuel tank?) was not connected. I just went and removed the air box and found it. Would that have anything to do with the troubles or just solely for keeping the fuel fumes down?

jrichker · Nov 9, 2009

afiveo said:
The line from the charcoal canister to the hard plastic line (to fuel tank?) was not connected. I just went and removed the air box and found it. Would that have anything to do with the troubles or just solely for keeping the fuel fumes down?

Put it back on and dive it to find out...

afiveo · Nov 9, 2009

It turned out there was a chip in my computer. Hypertech. I removed it, disconnected the battery for 20 minutes. I warmed the car up and ran the test again. KOEO I got 11. Engine running I got 33 41 and 91 again. I'm going to go test the EGR and O2 sensors now. Also remove the smog crossover tube to check for blockages.

afiveo · Nov 9, 2009

I connected my mitivac to the EGR diaphram and when I applied 5 in of vacuum, the engine stumbled and tried to stall. I could also see the diaphram moving. This tells me the EGR is good and the passage is clear.

I then connected the mitivac to the vacuum line going to the EGR diaphram and snapped the throttle to 2500rpm. The gauge did not move. This tells me the EVR has failed.

When I jumper the car into test mode and turn on the key, I can hear the EVR cycle so it is getting a signal from the computer. That is if the EVR is mounted on the back side of the passanger side strut tower. ??

I also tried to test the O2 sensors by using pin 29 and then pin 43 on the computer. I probed one and tested it, then the other. The red to the pin I used to probe, and the black to the computer/chassis ground. I didn't get a reading on either one with the car idling. (should be .2 - .9)I'm not sure if my mulimeter will read such a low voltage because there is not a decimal place on the setting I was using. 600V DC. It does however read 14 volts when I touched it to the battery terminals while the car was running so I know it is working.

Does it sound like the EVR needs replaced? What about the O2 sensors? They are new, 3 wire, and are plugged in? Do you think it's a problem with the mulimeter not reading that low of voltage?

KOEO I am getting a 66 and now a 34.

afiveo · Nov 9, 2009

OK, I replaced the EGR Vacuum regulator. I also jumpered the connection while in test mode and the test light did flicker so the computer is sending the correct signal. Snap the throttle to 2500rpm, still no movement on the vacuum gauge. ??

I just bought a voltmeter and tested the O2 sensors again. At the pin on the computer, they both read 0.01 Volts at idle . NOT 0.1 but 0.01. Seems to be a problem there. Still running pig rich.

I disconnected the battery again for 10 minutes and ran the tests again.

KOEO I get an 11. (systems ok)
Engine running I still get 41 and 91.... O2 sensors.

I can't find any vacuum leaks anywhere. The low coolant light is on (coolant not low) and the door chime sounds very faint and weak. I keep getting shocked when I exit the car too. The motor to chassis ground is good and intact, as is the computer ground.
I can't work on it anymore today. I am working 7pm to 7am nights this week and I need to get a little sleep before work. This is really starting to get me down.

I have no horn, turn signals, or heater blower motor. Keeps blowing the fuse. I had the dash out to put a heater core in it several years ago and think i pinched a wire putting the dash back in. Damn, what else......

liljoe07 · Nov 10, 2009

Posted via Mobile Device

Make sure the O2 signal ground on the back of the intake is hooked up. Its orange and if not hooked up, the O2's will not power up and code 91 and 41 will be logged in the system.

afiveo · Nov 10, 2009

liljoe07 said:
Posted via Mobile Device

Make sure the O2 signal ground on the back of the intake is hooked up. Its orange and if not hooked up, the O2's will not power up and code 91 and 41 will be logged in the system.

Edited **UPDATE**

I located the Orange ground wire and it is connected.

liljoe07 · Nov 10, 2009

Posted via Mobile Device

Lower intake or back of the head on the passenger side is the normal spot for it.

If its hooked up, then go over the 10 PIN connectors, the O2 harness connector also. Make sure the PINs are good and clean and making contact. If that's OK. Turn the Key on and get under the csr and check that the O2s are actually getting a 12v source.

afiveo · Nov 10, 2009

I guess when I get time I will pull the upper intake and look around. I'm running out of ideas.

afiveo · Nov 10, 2009

liljoe07 said:
Posted via Mobile Device

Lower intake or back of the head on the passenger side is the normal spot for it.

If its hooked up, then go over the 10 PIN connectors, the O2 harness connector also. Make sure the PINs are good and clean and making contact. If that's OK. Turn the Key on and get under the csr and check that the O2s are actually getting a 12v source.

Thanks for the tips. Ground is hooked up. How do I check the O2's under the car? Do I unplug them and check the connectors with a voltmeter?

Also I tried to unplug the 10 pins on the back of the intake and couldn't get them apart. They say push on the plug but I can't seem to unplug them.

liljoe07 · Nov 10, 2009

Turn the key on and get a volt meter. One lead to one white wire and the other lead to the other whit wire on the 02, 12v should show on the meter.

ID89GT · Nov 10, 2009

afiveo said:
ID89GT

I had a BBK 70mm TB and spacer, 24lb injectors, C&L mass air, K&N cone filter and a upper with a ported TB openning. It never did run right so I put it all back to stock. (except a K&N panel filter) I thought that there was a problem with something I put on so I went back to stock with brand new 19lb injectors, plugs, wires, cap, rotor, O2 sensors, and fuel pump and nothing has changed.

Hmm when you did the throttle body and upper intake, did you use new gaskets and such? Hook all the vacuum lines back up to the upper intake?

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