Car decelerates on its own, stalls at intersection

DVANLANDUYT

MEMBER
2005 FORD MUSTANG
4.0L
6 CYL
2WD
MANUAL
200,000 MILES

Driving along at a constant speed 60-70, the car will decelerate like it has lost fuel or ignition. It does this for a few seconds then catches and comes back up to speed. This will happen with or without the cruise control or the A/C on. Sometimes at a stop sign the car will shut off. This morning it shut off and took about 30 seconds to get it re-fired.
I have had small stumbles in the past, but this really got worse yesterday and this morning. I do not have a engine light showing. I will stop on my way home from work to have my engine codes checked.
I called a friend that works on cars. He came across a similar issue that ended up being a DPFE Sensor.

6 Replies

BMDOUBLE

MECHANIC
1,139 POSTS

A broken catalytic converter, failing fuel pump, or various electrical issues can cause similar symptoms. Have the codes been retrieved? I have also had problems with the wiring under the rear seat on the driver side, wires get chafed against a sharp edge on the body, the wires go to the fuel pump. I've illustrated a picture of the areas that you should pay close attention to.

Image (Click to make bigger)

SPONSORED LINKS

Was this

answer

helpful?

Yes

Tuesday, November 5th, 2019 AT 3:40 PM

DVANLANDUYT

MEMBER
3 POSTS

On my way home from work that day I stopped by O'Reilly to have the codes checked. Only thing that came up was a lean condition which leads me to believe it's a fuel delivery problem. I checked the wires under the seat. Mine are on the underside and they're fine. I changed the fuel filter and swapped the fuel pump relay with another relay. So far driving to work yesterday and today, I haven't had any problems. The car has 200,000 miles on it and I don't know the previous owner's maintenance records so it could have just been a clogged filter.

Was this

answer

helpful?

Yes

Thursday, November 7th, 2019 AT 5:35 AM

KEN L

MASTER CERTIFIED MECHANIC
47,690 POSTS

Yes, the fuel filter can cause issues, but to me it sounds like the throttle bore needs to be serviced causing the engine to go into limp mode. here is a guide to help us first the problem:

https://www.2carpros.com/articles/throttle-actuator-service

This guide can help as well:

https://www.2carpros.com/articles/reduced-power-limp-mode

Please run down these guides and report back.

Was this

answer

helpful?

Yes

Saturday, November 9th, 2019 AT 12:57 PM

DVANLANDUYT

MEMBER
3 POSTS

Ken,

I tried cleaning out the throttle body and it did seem to improve. Unfortunately the problem came back. I was having new codes come up on the computer. P0193 Fuel pressure Sensor High. I researched this and the 2 possible causes for this code are either a clogged return line or a bad fuel pressure regulator. I found a good price online so I went ahead and bought one since I have 200,000 miles, I'm sure it's due for replacement. I changed it yesterday and reset the codes. So far the engine light hasn't come on and I haven't had any stumbling issues. Hopefully this fixed the problem.

Was this

answer

helpful?

Yes

Monday, November 18th, 2019 AT 6:18 PM

KEN L

MASTER CERTIFIED MECHANIC
47,690 POSTS

I have seen the fuel pressure sensors go bad on these cars. Here is the location in case the cods comes back. Check out the diagrams (below). Please let us know what happens.

Images (Click to make bigger)