Hesitant And Jerky Under Acceleration

[Obey_R 23]

So I recently removed my SAD valve for a bit of a clean up, found it wasn't working so plugged up the pipes and left it off for the time being. The car's been running fiine for a few days but recently it has been very jerky when applying the power.

 

In the mornings it will be fine, 7 miles to work without a problem, this is after a good few mins warm up due to no SAD. Then after work, it would start to become hesitant, even after a few mins of warming up. No matter what the revs, gear etc, it will keep jerking and spluttering.

 

Today it was okay for a good 4 miles but then started playing up again.

 

I've changed dizzy cap, rotor arm, plug leads, plugs and ECU temp sensor.

 

It's been suggested it could be the AFM or TPS but I've not got any good working spares to test!

 

 

Any ideas?! It's driving me crazy

 

Oh I recorded a bit of it playing up on the way home, I'll upload the video in a bit to see i that helps.

[feb 47]

Ignition coil?

[Obey_R 23]

Funny you should say that, I was going to leave straight from work to go to DaveWs house and try his spare, but I left work with the car behaving itself and put all the problems down to just not being warmed up properly, wish I had carried on now!

 

Dave if you see this, I might pop round later!

[Obey_R 23]

Just watched the video back and the sound quality is quite poor so that's not going to help

[Tom Fenton 1,542]

My experience is that the coil either works or it doesn't.

 

For jerking spluttering I would be looking at the ignition amp and also the AFM.

[Obey_R 23]

Is changing the fuel filter likely to cure it? I can't imagine it would but I have one sitting on the shelf in the workshop so wouldn't hurt it change it, but I'm very short on time!

[Anthony 1,003]

My experience is that the coil either works or it doesn't.

I have seen them fail so that they appear to work but then misfire under load when hot, so it is worth swapping out to rule out if you've access to a spare.

[Lan 24 1 Cars]

I have seen them fail so that they appear to work but then misfire under load when hot, so it is worth swapping out to rule out if you've access to a spare.

 

+1 before they completly pack in they can still work just not very well, i've drove a car with a dying coil and it was a pig to keep going till i got back home

[Obey_R 23]

Cheers guys, I'll get the other coil in there as soon as poss. For the meantime I stuck an injector cleaner through it and it seems to be fine. What I'm struggeling to get my head around is that sometimes it is absolutly fine, with no problems at all. Whereas others it's a complete pig! Surrely if it was coil or something, that wouldn't come and go?

[Obey_R 23]

Well that hasn't solved it, just been out for a little drive, about 30 mins from when I got in from work (it was fine all the way home) it's doing it again. Jerkying and very hesitant to accelerate, keeps jumping like its either not sparking or over fueling. It's not regular, like if you were running on 3 cylinders, but it's constant.

 

 

EDIT, it is still lumpy at idle, more than normal, it keeps dropping revs to the point of almost stalling but recovers. Again, it's not regular, but perhaps once or twice a minute.

Edited June 4, 2011 by Obey_R

[harryskid 193]

Hesitant and jerky, sounds like a woman!

[lagonda 42]

Does it clear if you really boot it? If so, could be cracked head....had this with mine, all the symptoms of blown head gasket but perfect compressions every time I checked it....the cracks were opening up & closing according to temperature, load & general 205 arsiness.

 

Also try swapping the signal wire from the distributor, mine was electrically perfect...but...205 arsiness coming in to play!

 

Unlikely but I also had this because of ongoing condensation in the distributor cap.

 

Also...having swapped everything & having injectors cleaned...the only spare I didn't have was an AFM. Borrowed an AFM....car ran fine. Put my AFM on his car....his car ran fine! Put my AFM back on my car...my car ran fine. These cars do like to take the p*ss.

 

Also make sure HT leads, distributor cap & top of coil are really clean. Unplugging & plugging in the ignition amp a few times is also worthwhile to clean up any dodgy contacts there.

 

Have fun.

[Obey_R 23]

Doesn't really go if you boot it, infact its much worse. Just checked the Dizzy cap for condensation and it'd clean and a whistle, given the Afm, dizzy plug, coil and injector connections a good clean with contact cleaner and still no change...

[gaz832 7 1 Cars]

Doesn't really go if you boot it, infact its much worse. Just checked the Dizzy cap for condensation and it'd clean and a whistle, given the Afm, dizzy plug, coil and injector connections a good clean with contact cleaner and still no change...

i have the exact same problems with my motor. doing my head IN

[smithy 1]

Sounds very electrical to me as it gets worse with heat,coil and module would Defo be favourites for this kind of fault.

But could also be plug leads aswell,try getting it to play up but do it at night pop bonnet and see if there are any sparks coming from them.I had a 405 Sri years back that was playing up like this at night you could see sparks coming from the leads.

 

Did you get a new vac advance for it?

[Obey_R 23]

I didn't get a new vac advance, it's still on the list. It has been suggseted that it could be the timing that is out, but it just suddenly came on, where I know the vac advance hasn't been working for a while.

 

I tried another ignition coil yesterday and made sod all difference, so it's not that. I'm currently in the process of swapping the injectors over to see if it's that, as it did seem to ease up after a bottle of Redex. I've also done the fuel filter whilst the fuel rail is off, so that's another thing off the list to rule out.

 

One biggie though, when I was removing the SAD valve last week, I also cleaned up all the oil filler cap/tubes as we know they can get quite mayo'ey. Less than a week later and they're quite bad again, I know this is a normal problem, but with it using a bit of coolant every so often, could the symptoms I'm getting be a result of possible headgasket failure?

 

I've got a compression tester at work, so I'll give it a go when I'm back, but could that explain why it only gets worse with temperature? I read the comment above about the split block, but I'm trying to leave that out of my head until I've tried everything else!

 

Thanks

[Obey_R 23]

Update, I've just fitted the other set of injectors I had which were 1.9 items, and done the fuel filter. I've taken it out for a quick spin and it's now very down on power throughout the revs. It's knocking slightly under acceleration, too. I've adjusted the Dizzy almost fully each way and it doesn't seem to have made any difference.

 

Could the original problem have been that the cambelt has slipped a tooth hense the knocking?! Getting very annoyed with this to say the least...

 

Shame someone didn't bother to answer my calls at FCS when he said he would meet me, too!

 

UPDATE TWO;

 

The reason it was down on power was that one of the injectors wasn't plugged in properly. Plugged it back in and the lack of power isn't a problem anymore. It seems to still have the original problem, but I will see how it goes with the new injectors and fuel filter. Now the injector is plugged in, I will experiement with changing the dizzy a bit to see if that gets rid of the original problem!

Edited June 6, 2011 by Obey_R

[gaz832 7 1 Cars]

let us know how you gte on mate,, been following your posts and you have the exacr same symptoms as me. ive done the plugs leads. etc. going to send my injectors off to be ultrasonically cleaned.

[Obey_R 23]

Well after putting in my old injectors it's made no difference, I know they weren't clean, but it hasn't changed a bit, let me know how you get on though.

 

Today I will change the ingition amp and if that doesn't do anything, a compression test will hopefully show up any underlying problems.

 

Have you managed to try a known working AFM?

[Obey_R 23]

This is really grinding me now! I've changed the ignition amp today and still no difference!

 

So to recap:

Dizzy Cap

Rotor Arm

Leads

Plugs

Injectors

ECU Temp sensor

Ignition Amp

Compression test results of 180 175 180 190, dry

 

The problem has now got worse whereby it doesn't only do it when it's hot, it's constant now, right throughout the revs.

 

This is driving me crazy, any suggestions? I'm still to try another AFM but that's because I can't find anyone local with a known working one to try!

[Phil H 16]

Does the SAD send any form of data to the ECU and having it unplugged means the engine is running with missing data?

[Obey_R 23]

The SAD is now back in so shouldn't be that, I have moved it to a different position but I can't see that would affect it at all. Will try a new throttle position switch tomorrow, failing that it will have to be another AFM on Monday.

[gaz832 7 1 Cars]

havent tried another afm or iginition module yet. i cleaned my dizzy and rotor yesterday. new leads . ran ok for 10 min then straight back to juddering going over 3k limit.

[Anthony 1,003]

Does the SAD send any form of data to the ECU and having it unplugged means the engine is running with missing data?

You're very much over-complicating exactly what the SAD is and does.

 

It's basically just an air valve that is open when it's cold and closed when it's hot. When it's cold and open, it allows air through into the inlet manifold, effectively being like you had your foot gently on the throttle, increasing idle speed a little. As it warms up and closes, no air gets past and thus the idle speed drops. It closes by a mixture of engine heat, and the electric heating element inside which is powered from the wiring connector.

 

There is absolutely no feedback to the ECU and the ECU has absolutely zero control over the SAD. If you unplugged the wiring connector, the only difference is that it would take a bit longer for the idle speed to come down when the engine warmed up as it would be completely reliant on engine heat and not the internal heating element.

[Paul_13 212 1 Cars]

Test the alternator?

Had the same symptoms before and it was this.

 

Fuel pump failing?