Engine won't rev and hunts

[ANDTWENTY]

Originally Posted by Laird Scooby

Let us know how it goes! If it seems to cure the hunting, unwillingness to rev, switch off and pull fuse #1 for 30+ seconds and replace it. Then give it a test run and see what's happening.

The mini power station works!! The alternator is now charging the battery!!

Sadly though my issue of not revving has not gone with the introduction of more volts 😪 is it worth pulling the fuse still? I feel like I'm gonna be going round in circles for a while now

[Laird Scooby]

Originally Posted by ANDTWENTY

The mini power station works!! The alternator is now charging the battery!!

Sadly though my issue of not revving has not gone with the introduction of more volts 😪 is it worth pulling the fuse still? I feel like I'm gonna be going round in circles for a while now

Excellent news on the alternator! All warning lights should have gone out on start up but the bulb check function should have lit many of them on position 2 of the key before starting.

Now would be a good time to pull fuse #1, leave it out for at least 30 seconds and then refit. While it's out, check the large diameter rubber hose between the MAF and the throttle body to make sure it's tight and has no splits or pinholes in it. Also check where any hoses tee into it such as for the AICV (idle valve) ensuring those are tight too without splits/holes etc.

Check your air filter is clean too and nothing is blocking it.

[ANDTWENTY]

Originally Posted by Laird Scooby

Excellent news on the alternator! All warning lights should have gone out on start up but the bulb check function should have lit many of them on position 2 of the key before starting.

Now would be a good time to pull fuse #1, leave it out for at least 30 seconds and then refit. While it's out, check the large diameter rubber hose between the MAF and the throttle body to make sure it's tight and has no splits or pinholes in it. Also check where any hoses tee into it such as for the AICV (idle valve) ensuring those are tight too without splits/holes etc.

Check your air filter is clean too and nothing is blocking it.

Okay will pull the fuse out and see if that changes anything. the lights are all as they were on the dash, no engine or oil, all on dimly except ABS which is bright. Is it normal for them to be dim?

I checked for leaks and couldn't see anything, puller the hose off at the air filter before the man sensor and put my hand on the end, it pretty much collapsed the hose so pretty confident there are no leaks there.

I pulled off the map sensor while running and the engine almost died but then ran badly on idle so would guess thats okay?

the throttle position sensor also tested okay and doesn't affect the running when removed so would assume thats okay?

I took off the idle air control valve to clean but its an electronic one so didn't do much, there is a slide type thing that blocks off one air port but when this "shuts" it doesn't fully shut, it leaves a slight gap, there is an adjustment screw but its glued over, should this be completely shut?

it supposedly has a service 14 miles before but the filter is dirty so I will replace this along with the plugs as these haven't been done I don't think.

my other thoughts were:
*knock sensor
*crank sensor
*cold start injector
*blocked exhaust, rusty water spitting out although this has reduced and theres lots of pressure at the tail pipe

supposedly the led computer thing can test sensors so might give this a go too.

[Laird Scooby]

Originally Posted by ANDTWENTY

I checked for leaks and couldn't see anything, puller the hose off at the air filter before the man sensor and put my hand on the end, it pretty much collapsed the hose so pretty confident there are no leaks there.


my other thoughts were:
*knock sensor
*crank sensor
*cold start injector
*blocked exhaust, rusty water spitting out although this has reduced and theres lots of pressure at the tail pipe

supposedly the led computer thing can test sensors so might give this a go too.

Funny enough, i wouldn't put too much store by putting your hand over the hose and it collapsing as a check for leaks. You've got a huge vacuum pump (engine) pulling in 2.3L of air, 350 times a minute at 700rpm so will collapse the hose easily, even with leaks that would be enough to upset the MAF - doesn't take a big leak to upset it!

Knock sensor can be checked by unplugging and revving, if it still won't rev it's not that, likewise the cold start injector (if it has one, some did, others didn't) and if the CPS (Crank sensor) was faulty, it wouldn't run at all.

The MAF seems to be playing the game from what you've said so far so the most likely cause is either a blocked/collapsed cat or the carbon brush inside the dizzy cap and/or the rotor arm. Could also be loose HT leads.
Good news is if the cat has collapsed, being a 1990 model you can delete it and either just knock the innards out, cut it out and fit a straight pipe or a small resonator silencer.

There are a couple of other fuel related possibilities as well but those are less likely than what i've suggested so far.

[ANDTWENTY]

Originally Posted by Laird Scooby

Funny enough, i wouldn't put too much store by putting your hand over the hose and it collapsing as a check for leaks. You've got a huge vacuum pump (engine) pulling in 2.3L of air, 350 times a minute at 700rpm so will collapse the hose easily, even with leaks that would be enough to upset the MAF - doesn't take a big leak to upset it!

Knock sensor can be checked by unplugging and revving, if it still won't rev it's not that, likewise the cold start injector (if it has one, some did, others didn't) and if the CPS (Crank sensor) was faulty, it wouldn't run at all.

The MAF seems to be playing the game from what you've said so far so the most likely cause is either a blocked/collapsed cat or the carbon brush inside the dizzy cap and/or the rotor arm. Could also be loose HT leads.
Good news is if the cat has collapsed, being a 1990 model you can delete it and either just knock the innards out, cut it out and fit a straight pipe or a small resonator silencer.

There are a couple of other fuel related possibilities as well but those are less likely than what i've suggested so far.

yea I did think that was the case with the hose but I also couldn't find any leaks, i'll check again for sure.

I shall now go check the knock sensor and cold start injector (it is fitted)

The dizzy cap and arm is brand new so will check connections and bushing is okay.

How can I get away with removing the cat, won't it be an MOT issue? There is also a lambda sensor in it so this would cause an Issue too right? although it looks pre cat meaning it wouldn't change if the cat is removed.

[Laird Scooby]

Originally Posted by ANDTWENTY

yea I did think that was the case with the hose but I also couldn't find any leaks, i'll check again for sure.

I shall now go check the knock sensor and cold start injector (it is fitted)

The dizzy cap and arm is brand new so will check connections and bushing is okay.

How can I get away with removing the cat, won't it be an MOT issue? There is also a lambda sensor in it so this would cause an Issue too right? although it looks pre cat meaning it wouldn't change if the cat is removed.

Normally if a cold-start injector plays up and overfuels, revving it will help to ease the problem rather it not being able to rev.

Bushing? Carbon brush inside the cap, they have a habit of breaking, especially if they were fitted by someone errr.......... "not quite as sympathetic as they could be". Usually it's a crack to start with that can't be seen and then breaks later.

What year is your car? I'm sure you said it was 1990 - therefore it doesn't need a cat, whether one was factory fitted or not. Even some post-92 cars can get away without cats for various reasons, if that's the cause of your problems then removing it will release power and economy without compromising the law or MoT status.

If it has a Lambda sensor then it almost certainly has a cat. The Lambda sensor isn't used until the engine is warm so it won't cause a problem from cold, might even help once it's hot - too many people put cold running problems down to the Lambda sensor and wonder why nothing changes when they spend £££ on a new sensor and it does nothing for the problem.

*** EDIT *** Just had a thought, have you checked fuses 11 and 12? If in doubt (including if the blades are dirty/burnt/corroded) renew them. These control your fuel pumps - yes, there are two! One is in the tank, the other is underneath. If the in-tank pump isn't running, the underbody pump may struggle to get the fuel pulled through, enough to start it and let it idle but not enough to let it run properly.

Is it an estate by the way?

[ANDTWENTY]

Originally Posted by Laird Scooby

Normally if a cold-start injector plays up and overfuels, revving it will help to ease the problem rather it not being able to rev.

Bushing? Carbon brush inside the cap, they have a habit of breaking, especially if they were fitted by someone errr.......... "not quite as sympathetic as they could be". Usually it's a crack to start with that can't be seen and then breaks later.

What year is your car? I'm sure you said it was 1990 - therefore it doesn't need a cat, whether one was factory fitted or not. Even some post-92 cars can get away without cats for various reasons, if that's the cause of your problems then removing it will release power and economy without compromising the law or MoT status.

If it has a Lambda sensor then it almost certainly has a cat. The Lambda sensor isn't used until the engine is warm so it won't cause a problem from cold, might even help once it's hot - too many people put cold running problems down to the Lambda sensor and wonder why nothing changes when they spend £££ on a new sensor and it does nothing for the problem.

*** EDIT *** Just had a thought, have you checked fuses 11 and 12? If in doubt (including if the blades are dirty/burnt/corroded) renew them. These control your fuel pumps - yes, there are two! One is in the tank, the other is underneath. If the in-tank pump isn't running, the underbody pump may struggle to get the fuel pulled through, enough to start it and let it idle but not enough to let it run properly.

Is it an estate by the way?

Okay so I have done some more playing, checked the air intake pipes again and can't feel anything anywhere, took them off and taped up one end and blowing in it hard I couldn't feel, hear or see any air coming out so confident these are air tight including the joints where the crankcase breather and idle valve join. is it normal to be able to blow straight through the idle air control valve when its off? could air be bypassing this and causing the issue?

I disconnected and reconnected the knock sensor and cold start injector which didn't help so these should be okay?

Sorry I meant to say brush, this I will check now and failing that will check the cat.

I am just grabbing some new plugs and fuses so I can renew the ones you suggest but haven't tried these yet but will do.

how do I get around taking the cat out though, surely the mot centre require it or is it because its older than a certain age?

[ANDTWENTY]

I removed fuse 1 for a couple of minutes while checking fuse 11 and 12, both fuses are fine, 11 is labeled as internal fuel pump but 12 wasn't and no others are labeled with fuel pump either. this hasn't sorted any issues though sadly.

[Rversteeg]

All the air that passes through the idle air control valve has also passed the LMM, hence the correct amount of fuel should be injected, irrespective of the position of th idle air control valve. It merely controls the idling speed, no mixture enrichment.
Have you checked the MAF for loose chips of foam that could have come out of the air filter box? The foam can desintegrate and if a flake is sticking to the measuring wire inside the MAF it will stop working correctly.
No LPG installed? It could in that case be running on two fuels.

[Laird Scooby]

Originally Posted by ANDTWENTY

Sorry I meant to say brush, this I will check now and failing that will check the cat.

I am just grabbing some new plugs and fuses so I can renew the ones you suggest but haven't tried these yet but will do.

how do I get around taking the cat out though, surely the mot centre require it or is it because its older than a certain age?

Just wanted to make sure you meant the brush and not a bush, Has caused a few problems in the past!

Plugs, i prefer NGK but most reputable makes are good - Champion is not a reputable make! Make sure you check and set the gap correctly, 0.65-0.70mm, no more, no less or you will have problems. If it had a service, the plugs should be new or at least in good condition but bearing in mind the air filter, they may be on their last legs!

If you car is 1990, it DOESN'T NEED A CAT!!!

Only cars from 1992 onwards need one and sometimes even then, they don't, depending on chassis and engine codes.

For example my other beast is 1994 and is eligible for the BET Emissions test otherwise known as the non-cat test.

If you lay under the car and hit the cat with the palm of your hand, if you hear any rattles from inside it, there's a fair chance the honeycomb structure inside has collapsed.
When i say hit, i mean just hard enough to rattle it, don't hit it like you'd hit someone as if you wanted to kill them!