1981 Ford Fiesta poor running when hot

ANDEMK1FIESTA

MEMBER
1981 FORD FIESTA
4 CYL
FWD
MANUAL
33,000 MILES

Hi, I have a Mk1 fiesta 1981 1.1L, the problem is: when I start my car and drive away from cold it will pull away lovely with just a touch on the accelerator, the pedal feels nice and light and responsive and the car revs freely and pulls along lovely, then as the car warms up it seems to bog down and needs to be revved harder just to get it to pull, and feels like I only want to use a light acceleration and change up as soon as I can because it seems to be killing it if I try and drag each gear out. I have changed the points, rotor arm, leads, dizzy cap, plugs, condensor, air filter, oil and oil filter, set the dwell angle with a dwell meter, set the timing but it still wont play ball, I am convinced it's once the car is warmed up that is causing the problem.

7 Replies

DAVE H

MECHANIC
13,384 POSTS

Check you have good fuel pressure from fuel pump when warm

Was this

answer

helpful?

Yes

Wednesday, June 30th, 2010 AT 5:02 AM

ANDEMK1FIESTA

MEMBER
3 POSTS

Hi, I have a spare fuel pump I could try, is it the fuel pump you mean? Plus, what could make it have low fuel pressure when warm, that would be really handy to know.

SPONSORED LINKS

Was this

answer

helpful?

Yes

Sunday, July 4th, 2010 AT 6:38 AM

NORMAN AINSLIE

MEMBER
1 POST

Hi there, hope you pick this up. I have a 1983 mk1 fiesta and I have been having exactly the same symptoms as you for 8 years. Have carried out all the appropriate measures without any improvement. I just wondered if you ever solved your problem?
Regards,
Norm

Was this

answer

helpful?

Yes

Thursday, May 19th, 2022 AT 2:57 AM

KASEKENNY

MECHANIC
18,907 POSTS

Thanks for the addition. It is unlikely that they will respond to this due to it being so old but I think we can solve your issue with a little more investigation.

So let's start where they did. When this is happening we need to monitor the fuel pressure and rule that out.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

The next thing we need to do is monitor the o2 sensor voltage and find out if this engine is running rich or lean. That will help with determining where to look.

However, if the sensor data shows that the engine is running properly then the o2 sensor is most likely the issue.

https://www.2carpros.com/articles/how-to-test-an-oxygen-sensor-02-sensor

Let's start with this info and then we can take the next step which will depend on what we find with the o2 sensor info.

Image (Click to make bigger)