5.0 chugs while holding speed

Neltech · May 3, 2011

so i've sorted out quite a few things since i bought my stang 4 weeks ago but one thing still remains, when im trying to hold a speed it chugs, bad. it lurches back and forth.

its the worse when its at low rpms. once i give it gas it speeds up just fine. idles just fine as well.

87gt, ford racing MAF conversion, trick flow intake, bbk headers, flowmasters, 306, speedpro pistons

BlackGT89 · May 3, 2011

I've heard timing that is advanced too far can cause this. Also, consider possible slack or wear in your timing chain, possible fuel mixture problems (maybe the oxygen sensors). Check your codes and see if anything shows up.

Neltech · May 4, 2011

the timing is one thing that i havn't checked yet. i think i remember it throwing code 31 (plus a bunch of ones for the smog crap)

Mustang5L5 · May 4, 2011

When the MAF conversion was done, were the VSS wires tapped?

Neltech · May 4, 2011

Mustang5L5 said:
When the MAF conversion was done, were the VSS wires tapped?

I know what a VSS is, if it is tapped, i have no idea. How do i check this? The MAF conversion is a ford motorsports part. The MAF wires directly to a connector that goes between the computer and the main computer harness

wythors · May 4, 2011

What cam do you have?

Gearbanger 101 · May 4, 2011

Sounds like excessive ignition timing to me. Try knocking it back 1-2 degrees and see if it makes a difference. Alternatively, bad plug wires will cause a miss at lower rpm which will cause the car to buck and chug. The miss generally tends to clear up as the RPM climbs.

Neltech · May 4, 2011

stock cam, stock injectors

Mustang5L5 · May 4, 2011

Neltech said:
I know what a VSS is, if it is tapped, i have no idea. How do i check this? The MAF conversion is a ford motorsports part. The MAF wires directly to a connector that goes between the computer and the main computer harness

I am unfamiliar with the ford racing connector. It might swap the necessary pins around inside the connector.

Basically the vss tells the computer the car is at speed or idling and prevents the stalling and lugging.

However, a code 31 could do this as well. What are the exact codes you received? Can you post numbers? Koeo, and engine running.

2000xp8 · May 4, 2011

I've had this problem multiple times.
Check your cap/rotor and sparkplug wires.

Neltech · May 4, 2011

ill pull the codes tomorrow morning. I tried doing my TPS at .9 volts but when the screw is in that far it idles at like 4 or 5k rpms, like the screw is holding it open that far. wtf

Neltech · May 5, 2011

I messed with the timing a little bit today, i don't have a light gun or a vacuum so i just slowly turned it counter clockwise a tad. it helped the motor quite a bit. the idle is smoother, has more power, and doesn't chug as much, it still does in 3rd gear a tad but on the highway its pretty much golden.

Mustang5L5 · May 6, 2011

Neltech said:
ill pull the codes tomorrow morning. I tried doing my TPS at .9 volts but when the screw is in that far it idles at like 4 or 5k rpms, like the screw is holding it open that far. wtf

No need to. Anything between 0.5v and 1.1v is fine. Chasing the 0.99v monster is a myth that needs to die

http://www.stangnet.com/mustang-forums/825424-adjusting-your-tps-0-98v-not-necessary.html

You're not adjusting the idle stop screw to set TPS are you? If so, that's not really the right way to do this. Adjusting the TPS (if necessary) is done by loosening the two screws holding it on the TB and twisting.

You should prob adjust your idle to make sure your IAC isn't staying fully closed and unable to control idle. First, unplug the IAC and turn the idle screw in. Start engine and let it idle for a few mins. If it doesn't start, turn the screw in some more. Once idling steady, with the IAC unpluged, back the idle screw out to drop the idle. You want to back it down to the lowest point where the engine will run, but before it gets to the point where it wants to stall. Turn off engine, plug the IAC back in. Now, you should NEVER have to touch this screw again unless you want to reset the idle again. Unplug the battery for 30 mins to reset the computer. Hook it back up, and check TPS voltage. Anythijg between 0.5v and 1.1 is fine. If you test it and it shows 0.65v..LEAVE IT.

Start engine, let it idle for 10-15 mins with accessories on and off. Once it relearns idle strategy, drive it for a day, THEN pull the codes. Make sure you run the KOEO, CM and KOER codes..as well as perform the cylinder balance test at the end. Then come back here with your list of codes and we can start troubleshooting from there.

Neltech · May 7, 2011

Mustang5L5 said:
No need to. Anything between 0.5v and 1.1v is fine. Chasing the 0.99v monster is a myth that needs to die

http://www.stangnet.com/mustang-forums/825424-adjusting-your-tps-0-98v-not-necessary.html

You're not adjusting the idle stop screw to set TPS are you? If so, that's not really the right way to do this. Adjusting the TPS (if necessary) is done by loosening the two screws holding it on the TB and twisting.

You should prob adjust your idle to make sure your IAC isn't staying fully closed and unable to control idle. First, unplug the IAC and turn the idle screw in. Start engine and let it idle for a few mins. If it doesn't start, turn the screw in some more. Once idling steady, with the IAC unpluged, back the idle screw out to drop the idle. You want to back it down to the lowest point where the engine will run, but before it gets to the point where it wants to stall. Turn off engine, plug the IAC back in. Now, you should NEVER have to touch this screw again unless you want to reset the idle again. Unplug the battery for 30 mins to reset the computer. Hook it back up, and check TPS voltage. Anythijg between 0.5v and 1.1 is fine. If you test it and it shows 0.65v..LEAVE IT.

Start engine, let it idle for 10-15 mins with accessories on and off. Once it relearns idle strategy, drive it for a day, THEN pull the codes. Make sure you run the KOEO, CM and KOER codes..as well as perform the cylinder balance test at the end. Then come back here with your list of codes and we can start troubleshooting from there.

you mean thats not the way you adjust it? lol **** me

i'll do it your way tomorrow. thanks for the help!

5.0 chugs while holding speed

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