Engine won’t rev up

[J88TEO]

I used to work on older Mercedes and BMWs and in most cases the cause was a weak fuel pump, not supplying enough fuel to go pass certain revs.
Replace the fuel pump always solve the problem.
Maybe this is the case?

[Alex Knight]

I think it's a testament to these cars' normal reliability that we are all just kind of clutching at straws here.

Hope you fix your issue.

[Iain]

Sounds fuel related to me. Pump, injectors maybe

[mr2garageswindon]

I'm going with pre cat failed gone on holiday to the main cat. Blocked won't rev...
My apprentice MR2 has done the same.

[LozB]

After a couple of weeks delay we are into alternator and crank sensor this weekend.  Anyone ever replaced a crank sensor? I've removed the sensor itself but the wire disappears behind the engine and I can't see how you get to the connector on the other end.  Looks like you have to remove the whole intake manifold assembly? Any tips?

[Joesson]

After a couple of weeks delay we are into alternator and crank sensor this weekend.  Anyone ever replaced a crank sensor? I've removed the sensor itself but the wire disappears behind the engine and I can't see how you get to the connector on the other end.  Looks like you have to remove the whole intake manifold assembly? Any tips?

https://www.mr2roc.org/index.php?msg=822676

The above may be helpful, includes a photo of the complete unit with wiring.
The crank sensor has been troublesome on other members cars and I found this using the Search Function and Crank sensor.

[LozB]

Ok so today's update.........

We couldn't find out how to disconnect the crank sensor despite checking search engine on here and fishing around with an endoscope.  The wire just disappears into the engine and no clear route to getting to connector.  I think you would have to remove the whole intake manifold and assembly to do this.  Happy to be corrected.  Anyhow I cleaned up all connections and the old sensor itself and re fitted.

We then fitted a new alternator and belt..........which was tricky but we did it in the end. YouTube is our friend particular 'Ottos Garage' channel.

And the result was........no change....... still won't rev above 2500

We then removed the o2 sensors to check out the pre cats using our endoscope.  On the left side there was evidence of partial cat breakdown around the edges, but on the right side it had gone completely, nothing there. So it looks like that may well be the problem.  We also checked out the cylinders with the endoscope and they were very black and oily.

So the question now is do we look for a complete replacement engine and exhaust system or is there merit in changing the exhaust manifold for one without pre cats and changing the exhaust/main cat. When running (below 2500 rpm) the engine does sound quite good and doesn't obviously seem to burn any oil.

Advice on next steps greatly appreciated.

Will upload pics if I can work out how to do it.

[Carolyn]

The main cat will be blocked with the debris from the precat.  That will stop it revving.  This has happened before.

An after market manifold is a good idea.  There are a couple available. If you can get a Toyosports one, they are pretty well made, ( https://www.toyosports.co.uk/toyota-193-c.asp They have some in stock right now and they only do them in batches so jump on that! The gaskets that come with them are bobbins - use OEM manifold to head and OEM crush rings for the connection to the cat.

A Cats2U main cat will cost around £150 and they do the job well.

Sort that before you start on engine swaps. I've seen a lot worse oil fouling than that.  A bit of oil burning isn't always fatal.  The spark plug doesn't look too bad.

You don't have to remove the inlet manifold to get at that connector.  You could drop the AC pump (no need to disconnect it) to get a better view. 

[Topdownman]

Could you disconnect the exhaust system from the manifold to see if it revs higher?
That is free to try and may give you more confidence to order new exhaust parts if it revs higher once the gases can escape.

[Joesson]

Could you disconnect the exhaust system from the manifold to see if it revs higher?
That is free to try and may give you more confidence to order new exhaust parts if it revs higher once the gases can escape.

Just be aware that what comes out will be a health hazard!

[Iain]

Take the cat off and unblock it?

[shnazzle]

Could you disconnect the exhaust system from the manifold to see if it revs higher?
That is free to try and may give you more confidence to order new exhaust parts if it revs higher once the gases can escape.

And it'll sound WICKED

[jvanzyl]

I have a spare stock manifold and exhaust system you can try if needed? I'm down near Watford.

[LozB]

Thanks for all the advice and offers of parts etc.  We ordered the bits suggested by Carolyn above as soon as we read the post so will report back once fitted.  Hoping the engine isn't too badly damaged by the pre cat debris.  How will we know if it is? Rate of oil burning or could we test compression or something?

[Carolyn]

You can just see how well it runs, if there's blue smoke when you give it some beans, and see how much oil it goes through. 

Toyota is happy with 1Ltr per 1,000 miles, and it will pass emissions testing at that rate of consumption.

Fingers crossed this will solve the problem

[Ardent]

I thought 1000km (621 miles) still s lot either way.

[mr2garageswindon]

I thought 1000km (621 miles) still s lot either way.

So the one I have in from Chris that drinks over 2 litres from Birmingham to Swindon is probably not ok?

[Ardent]

Def outside of spec.

[LozB]

So today we removed the old manifold and CAT.  Bit of a nightmare job but got there in the end.  Pre CAT in left leg of manifold was there but cracked and decomposing.  Pre CAT in right leg was completely absent. See photos

We have new manifold and main CAT to install next weekend.  Just waiting on a few new studs and nuts and for welding on subframe (see separate post)

[LozB]

Yesterday we fitted the Toyosport manifold and new main CAT and it now revs properly.  Clearly that was the answer all along, the pre cat in the right downpipe had completely disintegrated and blocked the main CAT.

I guess the question now is whether bits were also sucked back into the bores giving us a car with a serious oil drinking problem. On the face of it the engine seems ok.  On start up there is lots of steam but after a few minutes it seems to run clear and idles smoothly.  I'm hoping the previous owner experienced a catastrophic CAT failure event which rendered the car immediately undriveable such that bore damage was limited......is that even possible?

I guess that we wont know until we get the car on a road test and we are currently a long long way off that.  Suspension, brakes and power steering all need an overhaul plus misty headlights and some rust issues.  I'm sure I'll be back on here asking more questions soon. You lot are amazingly knowledgeable, thanks so much for sharing your wisdom.

[Gaz mr-s]

You might get an indication by getting the engine fully warmed up, let it idle for a minute, then BOOT the throttle, easier with a helper to see the exhaust output.  Well done in persevering.

[fawtytoo]

Get a borescope and poke it in through a spark plug hole.