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90 GT Running rich, backfiring?? Help!

  • Thread starter Thread starter afiveo
  • Start date Start date Nov 7, 2009
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blackstangt

Member
May 31, 2004
460
1
19
ny
Nov 11, 2009
#41
  • Nov 11, 2009
  • #41
Before you go spending tons of money on new sensors and gadgets, remember that the car is basically 20 years old. My 90 was having very similar problems.

1. Buy some electronic parts cleaner and dielectric grease.

2. Disconnect all of your plugs leading to your sensors, especially the black and white 10-pin connectors at the back of the engine compartment.

3. Spray all of the contact points liberally with the electronic parts cleaner and let dry.

4. Fill all of the female contacts with dielectric grease.

5. Plug everything back in.

Be careful with the plastic clips, they break pretty easily.
This is the cheapest way to fix the problem and should be tried before anything else. At minimum, it will make the car run better when fixed and for longer. Essentially a maintenance item.

Good luck and I hope that's all it is on your car too.
 

blackstangt

Member
May 31, 2004
460
1
19
ny
Nov 11, 2009
#42
  • Nov 11, 2009
  • #42
afiveo said:
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.
Click to expand...

Be careful, the clips break easily, get someone to pull the plugs apart, while you pull the clips outward with a screwdriver or pick tool. It took me about 10 minutes to get mine apart by myself.
 

afiveo

New Member
Jul 10, 2006
34
0
0
Ohio
Nov 11, 2009
#43
  • Nov 11, 2009
  • #43
liljoe07 said:
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.
Click to expand...

Thanks, I'll do that the first chance I get. Probably Friday or Sat.
 

afiveo

New Member
Jul 10, 2006
34
0
0
Ohio
Nov 11, 2009
#44
  • Nov 11, 2009
  • #44
ID89GT said:
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?
Click to expand...

Yes, I used new gaskets. I marked all the lines and their locations so I could re-install everything correctly. I am going to pull the upper again and see if something was missed. Thanks
 

afiveo

New Member
Jul 10, 2006
34
0
0
Ohio
Nov 11, 2009
#45
  • Nov 11, 2009
  • #45
blackstangt said:
Before you go spending tons of money on new sensors and gadgets, remember that the car is basically 20 years old. My 90 was having very similar problems.

1. Buy some electronic parts cleaner and dielectric grease.

2. Disconnect all of your plugs leading to your sensors, especially the black and white 10-pin connectors at the back of the engine compartment.

3. Spray all of the contact points liberally with the electronic parts cleaner and let dry.

4. Fill all of the female contacts with dielectric grease.

5. Plug everything back in.

Be careful with the plastic clips, they break pretty easily.
This is the cheapest way to fix the problem and should be tried before anything else. At minimum, it will make the car run better when fixed and for longer. Essentially a maintenance item.

Good luck and I hope that's all it is on your car too.
Click to expand...


Thanks for the tips. This is on my "to do" list this weekend as well.
 

Strype

Cuthbert catcher
Founding Member
May 11, 1999
61
34
104
Huntsvegas, AL
Nov 12, 2009
#46
  • Nov 12, 2009
  • #46
The only times that I have ever had backfiring problems were when my distributor went out and when I tried adjusting my fuel pressure regulator without a gauge. A vacuum loss will cause it too.
 

afiveo

New Member
Jul 10, 2006
34
0
0
Ohio
Nov 20, 2009
#47
  • Nov 20, 2009
  • #47
I'm getting 11.7 volts at the O2 sensors on the white wires. My battery is low so I assume why it's not 12V.??

Why are there jumper connections at my 10 pin connectors at the back of the intake? I'm talking about the between the wiring harness connections. It seems to only extend then 4 inches or so. Is that all they are for? I pulled all 4 of them apart and they look pretty clean. I'm going to spray them down and clean them since I have them apart.

Upper intake is off again and everything was connected properly and the gaskets looked fine. I'm going to go get some more brake cleaner, a new throttle body gasket and some vacuum line to replace it from the front of the intake to below the airbox. It's looks chaulky and the black comes off on your hands.
 

afiveo

New Member
Jul 10, 2006
34
0
0
Ohio
Nov 20, 2009
#48
  • Nov 20, 2009
  • #48
I cleaned the ground and connectors at the back of the block and re-installed. still 11.5 11.7 volts at the O2 connections under the car. What is the solenoid that is attched to the charcoal cannister and has the wire running up to th injector harness? The vacuum lines that run to it are old and brittle. Going to get some new lines now.
 

afiveo

New Member
Jul 10, 2006
34
0
0
Ohio
Nov 20, 2009
#49
  • Nov 20, 2009
  • #49
I put everything back together. Also went ahead and put new valve cover gaskets on.

I cleaned the salt and pepper 10 pins and ran a new vacuum line to the charcoal cannister. I also sprayed all elec connections with cleaner and applied new dielectric grease. I also set the TPS at .96 volts. Spent all f...ing day woking on it and still getting a 41 and 91. Running out of ideas now. WTF?
 

liljoe07

5 Year Member
Feb 18, 2009
1,622
363
124
Cartersville,Ga
Nov 20, 2009
#50
  • Nov 20, 2009
  • #50
Do you still have the Mass Air low voltage code in the KOEO test?
 

afiveo

New Member
Jul 10, 2006
34
0
0
Ohio
Nov 20, 2009
#51
  • Nov 20, 2009
  • #51
What code is that? I don't now but I think I have earlier in this post. only 41 91 engine one now.
 

liljoe07

5 Year Member
Feb 18, 2009
1,622
363
124
Cartersville,Ga
Nov 20, 2009
#52
  • Nov 20, 2009
  • #52
Scratch that........ As it would have shown in the KOER test also.

Hmmmmm?
 

liljoe07

5 Year Member
Feb 18, 2009
1,622
363
124
Cartersville,Ga
Nov 20, 2009
#53
  • Nov 20, 2009
  • #53
How are the plugs?

Whats the fuel pressure?
 

afiveo

New Member
Jul 10, 2006
34
0
0
Ohio
Nov 20, 2009
#54
  • Nov 20, 2009
  • #54
The plugs are new, no miles, only trouble shooting. Fuel pressure is unknown. New fuel pump, new fuel filter, new 19 #injectors. How do I check pressure?
 

liljoe07

5 Year Member
Feb 18, 2009
1,622
363
124
Cartersville,Ga
Nov 20, 2009
#55
  • Nov 20, 2009
  • #55
Posted via Mobile Device

You can rent a fuel pressure gauge from most auto parts stores. Then they will refund you money upon return.


What about the O2 harness connector. Have you tried cleaning the connections on it? It may help.
 

afiveo

New Member
Jul 10, 2006
34
0
0
Ohio
Nov 21, 2009
#56
  • Nov 21, 2009
  • #56
liljoe07 said:
Posted via Mobile Device

You can rent a fuel pressure gauge from most auto parts stores. Then they will refund you money upon return.


What about the O2 harness connector. Have you tried cleaning the connections on it? It may help.
Click to expand...

The fuel pressure reg. is newer. I cleaned the O2 connections under the car with brake cleaner and put new dielectic grease on them too. I am getting 11.5 volts on one and 11.7 on the other.

If I check the voltage at the computer pins again, should the car be running or just key on. It should be between .2 and .9 volts and change often, correct? before I got like 0.01v and it didn't change.
 

liljoe07

5 Year Member
Feb 18, 2009
1,622
363
124
Cartersville,Ga
Nov 21, 2009
#57
  • Nov 21, 2009
  • #57
Should be running.
 
C

cheese_05_70

New Member
Aug 29, 2005
58
0
0
IL
Nov 22, 2009
#58
  • Nov 22, 2009
  • #58
Posted via Mobile Device when you check them again hit the throttle and see if you get any change from them
 
R

real57vetteguy

New Member
Nov 17, 2009
18
0
0
Nov 23, 2009
#59
  • Nov 23, 2009
  • #59
running rich backfiring

Hi all, Now I am no expert by any means but for two weeks I have been trouble shooting an issue of my own under the 331 trickflow will not run good thread, the car was running terribly rich at idle, then backfiring it was undriveable, I hauled it to the ford dealer and the computer threw all kind of codes but none of them were the problem after all the trouble shooting, it actually ended up being the ignition module, cleared the running rich and backfiring right up, I Know it doesnt make alot of sense but what he describes sounds exactly what I was going through. What are your thoughts?
 
R

real57vetteguy

New Member
Nov 17, 2009
18
0
0
Nov 24, 2009
#60
  • Nov 24, 2009
  • #60
re

any new feedback?
 
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