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Have to hold hand over mass air to start vehicle

91GTZ

FoxBody junky
Hey guys! Just signed up and this is my first post.

I have a 1991 GT that I just grabbed out of a barn in Missouri.

The previous owner showed me how he had to get the car started. (doesn't stay running) . He put his hand over the mass air and had someone else start the car. He then had to keep putting his hand on and off to keep the car running. He said there is a vacuum leak behind the air intake that he heard.

I unplugged the Mass Air Meter and still the same exact issue without any changes.

What would be the issue that the car wouldn't start without having to do this?
 

Fenrader

New Member
Not sure if the attached troubleshooting steps may help in your case. Found it in a repair manual I have.
 

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91GTZ

FoxBody junky
Not sure if the attached troubleshooting steps may help in your case. Found it in a repair manual I have.
Thanks for the help but I don't believe this is going to help. I can't get the car running without having to entirely cover the mass air. I believe I may be creating a large amount of vacuum to compensate for another system that has failed.
Thanks again!
 

91GTZ

FoxBody junky
Think I have a huge vacuum leak coming from the EGR valve. Taped it up and now the car starts after 10 seconds or so.....runs for about 5 seconds and then dies.

Any ideas????
 

broncojunkie

Well-Known Member
Car is running closed-loop until it reaches operating temp, so you can pretty much rule out most of the engine mgt parts, such as sensors (maf, o2, temp, etc). Look at the iac. Take it off and give it a good cleaning along with the opening where it connects. If that doesn't do it, see if you can keep it running a little longer with quick bursts of starting fluid. If so, then it's probably a fuel issue.

If a fuel issue is suspected, start by measuring pressure. I believe 30 lbs is required to run...38-40 is ideal. Another thing you can check quickly is the pressure regulator. Pull the vacuum hose off the top and see if any fuel is present. The diaphragm is a common failure point and will let gas come through. Fuel issues are usually going to be a failure of some type to bring enough fuel (bad pump, rust/bad fuel in tank, etc) but can also show up as too much fuel (bad regulator, bad injectors). Pull a few plugs and inspect. That will tell you if it's rich or lean.

Also pull the distributor cap and inspect the contact points on the cap and rotor. Very common for them to have corrosion...particularly with the cheap ones with aluminum contacts. The brass are much better.

You can use a timing light to quickly check if spark is being sent through each plug wire. That won't tell you how good of a spark, but it's a quick and dirty method to help narrow down your problem. These are just a few ideas to keep you busy lol! Let us know what you find. We like following these things! Good luck!
 

91GTZ

FoxBody junky
@broncojunkie Thank you so much!

This was very helpful and will definitely keep me busy for a while!
Little back story — the car sat outside of a barn in Missouri. Looks like a good tune up wouldn't hurt either.

I'll get started on going through your list today.
I'll keep you all posted on the progress.

So glad I joined this forum.
Thanks, everyone!
 

broncojunkie

Well-Known Member
I have 3 that sat out behind a barn for 15 or so years. I've completed (mostly) my 88gt. I have a build thread on it. You can see what a basket case it started out as lol! I think fuel lines and brake lines are the only mechanical parts left that I haven't replaced. You should go take a look at it. You'll get a kick out of the condition of the fuel pump!
 

91GTZ

FoxBody junky
@broncojunkie

Very helpful information.

The car is throwing a code 51 and 23:
51 = ECT sensor out of range indicated/circuit open
23 = Throttle position signal out of specified range

I pulled the factory distributor cover off and realized that the ECT wire was cut. Code 51 would explain that.

Cleaned out the IAC and found some gunk and debris in there.

Will be checking to see if fuel is an issue tomorrow. Will probably rip down the entire top half and replace injectors, rails, and intake soon but would like to see if I could get this thing just running decently for now.

Here is the photo of the cut wires — any suggestions on fixing that?
Also, here is a video of the car running and then stalling out:

Thanks for all the help. So thankful I found you guys and the amazing support this forum has brought.

Have a great night!
 

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