7a-fe Engine Misfiring When Breaking

[formalin-fixed]

Toyota Carina E (1997, R reg), 1.8 7A-FE leanburn engine, automatic transmission

I have noticed that the engine has started to misfire briefly when stopping/breaking at traffic lights (so far there were 5 or 6 episodes in the last month), this leads to car jerking quite noticeably and revs dropping from 700 to 400-500. This has never happened when engine is cold, always at the end of the journey. It seems that breaking starts it off as this doesn't happen if engine is just idling when stationary.

Plugs have been changed recently but this made no difference.

Could you suggest what part could be to blame?

Thanks for your advice.

[brett h]

Toyota Carina E (1997, R reg), 1.8 7A-FE leanburn engine, automatic transmission

I have noticed that the engine has started to misfire briefly when stopping/breaking at traffic lights (so far there were 5 or 6 episodes in the last month), this leads to car jerking quite noticeably and revs dropping from 700 to 400-500. This has never happened when engine is cold, always at the end of the journey. It seems that breaking starts it off as this doesn't happen if engine is just idling when stationary.

Plugs have been changed recently but this made no difference.

Could you suggest what part could be to blame?

Thanks for your advice.

Try checking the vac hose which runs from the brake master cylinder servo to the rear of the plenum chamber....cant be 100% but its worth a try...

[4afte]

with the 4A/7A-FE series this sympton is often result of a failing lambda sensor, it's worth getting that checked.

[formalin-fixed]

Thank you. I will look into these options today.

The car has just passed MOT with no problems and normal CO levels. Could this still be lambda sensor ?

[formalin-fixed]

In addition to aforementioned symptoms the engine started to misfire occasionally when driving with steady speed around 50-60mph but again only when engine is hot. Misfiring feels like loss of power and vibration. Bizzarely, misfiring episodes often occur approximately at the same parts of commuting route I am taking (probably due to the same speeds around 50-60mph on these segments). Short term acceleration makes misfiring/vibration worse, but steady driving at above 70mph seems to "cure" the symptoms. I have noticed that with the onset of colder weather problem became less frequent.

I was suspecting the injectors so tested them with ohmmeter as suggested on this forum - i.e. after the appearance of the "symptoms" while engine is hot. However, all of them have given the same reading (1st - 15.5 ohm, 2nd - 15.7, 3rd - 15.9, 4th - 15.8) - ? suggesting that the problem is elsewhere.

The garage where I took my car on a number of occassions failed to reproduce the symptoms and thefore said that there is nothing to be fixed ! Despite the fact that I explained that I suspected few parts (as you kindly suggested).

Your comments/help will be very much appreciated. Shall I just wait until the problem deteriorates to make the car completely undrivable and then take it garage to persuade them to have it checked?

[MJJ]

In addition to aforementioned symptoms the engine started to misfire occasionally when driving with steady speed around 50-60mph but again only when engine is hot. Misfiring feels like loss of power and vibration. Bizzarely, misfiring episodes often occur approximately at the same parts of commuting route I am taking (probably due to the same speeds around 50-60mph on these segments). Short term acceleration makes misfiring/vibration worse, but steady driving at above 70mph seems to "cure" the symptoms. I have noticed that with the onset of colder weather problem became less frequent.

I was suspecting the injectors so tested them with ohmmeter as suggested on this forum - i.e. after the appearance of the "symptoms" while engine is hot. However, all of them have given the same reading (1st - 15.5 ohm, 2nd - 15.7, 3rd - 15.9, 4th - 15.8) - ? suggesting that the problem is elsewhere.

The garage where I took my car on a number of occassions failed to reproduce the symptoms and thefore said that there is nothing to be fixed ! Despite the fact that I explained that I suspected few parts (as you kindly suggested).

Your comments/help will be very much appreciated. Shall I just wait until the problem deteriorates to make the car completely undrivable and then take it garage to persuade them to have it checked?

Sounds very like an injector playing up. The electrical component breaks down sporadicaly in hot conditions and it stops firing.

I read this somewhere on here and it worked for me .... keep a pencil in the car, when the misfire is happening pull over, pop the bonnett, touch each injector with the pencil. A working injector you will feel the regular quick clicking of the injector firing through the pencil. An injector that isnt working you wont feel this vibration through the pencil. To confirm, unplug the electrical connector from the suspect injector and there will be no difference in engine revs.

My car had this problem and it didnt happen very often to begin with but it gradually got worse and worse to the point where every journey the car would misfire. The problem I had was every time I got out the car to perform the pencil test, the car would stop misfiring just as i was about to touch the injectors! very annoying!!!!

The lambda sensor failing will not cause your car to misfire. I know cause I ran my car with a failed one for nearly a year !

[sarpe]

I agree that one of the injectors creates problems. You can also try to measure the electrical resistence of the injector coils (just unplug the electrical connector and measure with an ohmeter on the injector side) when they are hot. The one with a higher resistence has a higher probability to create the misfiring.

[formalin-fixed]

Just wanted to say that it was indeed injector (N3) that was creating a problem. The ohm readings were fine, but when I replaced 3rd injector with a working one from scrap yard the problem has dissapeared.

Thank you everyone for your help.

[johnmac99]

Just wanted to say that it was indeed injector (N3) that was creating a problem. The ohm readings were fine, but when I replaced 3rd injector with a working one from scrap yard the problem has dissapeared.

Thank you everyone for your help.

Thinking of doing the same myself, but not sure how. Could you help? :)

[Josh_]

Just wanted to say that it was indeed injector (N3) that was creating a problem. The ohm readings were fine, but when I replaced 3rd injector with a working one from scrap yard the problem has dissapeared.

Thank you everyone for your help.

Thinking of doing the same myself, but not sure how. Could you help? :)

Search on the forum for 'injector' - there are a few threads about it. It's easy enough, especially with a copy of the Haynes manual.

[johnmac99]

Just wanted to say that it was indeed injector (N3) that was creating a problem. The ohm readings were fine, but when I replaced 3rd injector with a working one from scrap yard the problem has dissapeared.

Thank you everyone for your help.

Thinking of doing the same myself, but not sure how. Could you help? :)

Search on the forum for 'injector' - there are a few threads about it. It's easy enough, especially with a copy of the Haynes manual.

Thanks Josh, I have a copy of Haynes manual now, but it doesn't sound easy to me. I'll try my son-in-law as he's more competent with a spanner.

[Josh_]

Thanks Josh, I have a copy of Haynes manual now, but it doesn't sound easy to me. I'll try my son-in-law as he's more competent with a spanner.

Haynes manuals always make things sound harder than they are, but then gloss over the tricky bits with something like 'remove [totally inaccessible and hard to turn] bolt' :)

It's really not hard, because everything you need to reach is on top of the engine in plain view. It's just a matter of undoing a few bolts. If you can change a wheel, you should manage. If you can build Ikea furniture, you're over-qualified.

[johnmac99]

Thanks Josh, I have a copy of Haynes manual now, but it doesn't sound easy to me. I'll try my son-in-law as he's more competent with a spanner.

Haynes manuals always make things sound harder than they are, but then gloss over the tricky bits with something like 'remove [totally inaccessible and hard to turn] bolt' :)

It's really not hard, because everything you need to reach is on top of the engine in plain view. It's just a matter of undoing a few bolts. If you can change a wheel, you should manage. If you can build Ikea furniture, you're over-qualified.

Well, problem now solved.

I registered with 1st Choice.co.uk and got several replies from breakers. Contacted one called Orange Spares who quoted me £25 inc delivery who sent it straight away.

I bottled the fitting and son-in-law said he was 'busy' so went to local repairer who charged £21.85 (half hour) to fit. Job done. :D

Thanks for your help folks.