Speed Density running rich

[mbanach]

I just rebuilt my motor on my 1988 GT convertible. It ran really well, but it had a low oil pressure issue. Well i just fired it up the other night and it started fine, but it idles lumpy at about 800 rpm and it smells like its running rich.

The car is basically stock- the only adds prior to the rebuild were under drive pullys and a cold air intake. With the rebuild the only added changes were stainless headers, off road H pipe, new 19lbs injectors. Everything else is stock.

Now back to the issue- in reading the other threads it seems i should be looking at my coolant sensor, MAP sensor, Oxygen sensors, make sure the Vac line is on my fuel pressure regulator.

What am I missing? Is it possible that the lack of pack pressure is part of the issue? Any insights from you all that have more experience would be helpful.

Thanks

 

[General karthief]

Back pressure?
sorry that is quite the subject.
we have a tech thread that has lots of info, here is one that will keep you from chasing your tail.

Help me create the "Surging Idle Checklist"

Updated 26-Oct-2019 to clarify creeping idle RPM increase as the car is being driven. Many of you are familiar with the "Cranks OK, but No Start Checklist for Fuel Injected Mustangs" checklist and the No Crank Checklist. They are very effective in finding and eliminating the problems by use of...

forums.stangnet.com

 

[Boostedpimp]

Was the battery pulled? ecm relearning? I would probably start with a code reader or test light and count the blinks to see what codes are set and go from there. The exhuast wouldn't be effecting the cars tune I would say you probably aren't used to a car that doesn't have cats

 

[a91what]

do you have the vacuum line connected to the MAP sensor?

 

[mbanach]

Back pressure?
sorry that is quite the subject.
we have a tech thread that has lots of info, here is one that will keep you from chasing your tail.

Help me create the "Surging Idle Checklist"

Updated 26-Oct-2019 to clarify creeping idle RPM increase as the car is being driven. Many of you are familiar with the "Cranks OK, but No Start Checklist for Fuel Injected Mustangs" checklist and the No Crank Checklist. They are very effective in finding and eliminating the problems by use of...

forums.stangnet.com

Yeah I may have gone to the wrong spot in the forum- I'll learn the ropes

 

[Mustang5L5]

Where is the map sensor vac line hooked to? Direct vacuum from manifold?

I'd pull the codes. The speed density cars do not have a functional check engine light, so you just need to pull the codes on a whim

 

[mbanach]

Thanks- I’m pretty sure I had the MAP hooked up, but it’s now on the list to check. Work is crazy this week so i wanted to do my research on how the system really worked and common issues. I’ve never really done much to it other than new 02 sensors and Tps sensor.
Thanks

 

[General karthief]

Yeah I may have gone to the wrong spot in the forum- I'll learn the ropes

You are good, I moved this to the tech threads for ya, on the main tech page there is a technical/how to thread, thats where I got the link, lots of stuff in there.

 

[jrichker]

I just rebuilt my motor on my 1988 GT convertible. It ran really well, but it had a low oil pressure issue. Well i just fired it up the other night and it started fine, but it idles lumpy at about 800 rpm and it smells like its running rich.

The car is basically stock- the only adds prior to the rebuild were under drive pullys and a cold air intake. With the rebuild the only added changes were stainless headers, off road H pipe, new 19lbs injectors. Everything else is stock.

Now back to the issue- in reading the other threads it seems i should be looking at my coolant sensor, MAP sensor, Oxygen sensors, make sure the Vac line is on my fuel pressure regulator.

What am I missing? Is it possible that the lack of pack pressure is part of the issue? Any insights from you all that have more experience would be helpful.

Thanks

Dump codes sticky

Look at the top of the 5.0 Tech forum where the sticky threads are posted. One of them is how to dump the computer codes. Codes may be present even if the CEL (Check Engine Light) isn’t on. You don’t need a code reader or scanner – all you need is a paper clip, or if your lady friend has a hair pin, that will do the job.
I highly suggest that you read it and follow the instructions to dump the codes. http://www.stangnet.com/mustang-forums/threads/how-to-pull-codes-from-eec4.889006/

 

[mbanach]

So it was a very simple problem, broken hose going to the map sensor.

Thanks for all the help

 

[Noobz347]

So it was a very simple problem, broken hose going to the map sensor.

Thanks for all the help

This is an indication that you need to carefully go through and replace all of the old hoses. Many of them are more than 30 years old!

 

[mbanach]

Yep- Most have been replaced- I hit all the critical ones, this one i just did not realize how critical it was.

 

[a91what]

Yep- Most have been replaced- I hit all the critical ones, this one i just did not realize how critical it was.

lol, very. in a SD based system the fuel tables are based on MAP vs RPM, the map sensor is the main load value.