4A-GE doesn't want to rev

[Wedgepilot]

My '84 MR2 has a problem that is bugging the hell out of me - I'm hoping someone can give me a few pointers.

It starts fine and goes great at low revs and small throttle openings. No problem there.

If I go WOT at low revs, it's 'lumpy' and hesitates, and there isn't a whole lot of urge. If I back off the throttle, it picks up again.

Once I get to ~4,000 RPM, it's really not happy - it doesn't want to rev at all, there's no power, nothing. Like when you get near the rev limit in a diesel.

It used to pull cleanly to the redline, but has been getting progressively worse over the last year or so.

It's a 'redtop' engine (late 80's - no TVIS), but with the original 'bluetop' ECU and injectors. What else...no blue smoke on acceleration, so compression should be ok. Plugs, oil/filter and air filter were all changed in the last year.

[Pigeon]

Running weak - check fuel delivery

[Daveuk9xx]

A new fuel filter would be my first choice. Then check the pump output if that doesn't cure it.

Dave Baker

[Wedgepilot]

Thanks for the quick replies - I just had a look at the plugs, and they're definitely a bit grey, which I think means it's too lean?

First stop, fuel filter...

[wizzbilly]

i presume you are a member of the 4age forum , some good info on there .

[Snake the Sniper]

If it's been getting worse over a period of time, it might be an air leak from a degrading pipe somewhere, or a problem with the fuel flow rate. Either way, definitely sounds like it's going lean.

[badders]

Sounds like a misfire to me.

Id check ignition amp, coil, distributer cap etc

[Snake the Sniper]

badders said:

Sounds like a misfire to me.

Id check ignition amp, coil, distributer cap etc

Actually, that might be more likely. Either way, sounds like a general check over would be worth it.

[odyssey2200]

Daveuk9xx said:

A new fuel filter would be my first choice. Then check the pump output if that doesn't cure it.

Dave Baker

[Wedgepilot]

Ok, I put a new fuel filter in (which is a right fiddly job on the MR2), and it hasn't made a whole lot of difference. The plugs are still grey after a good thrash.

Is there an easy way to check the pump and/or regulator? Getting to the pump is a bit of a mission.

It doesn't feel like a misfire, but it never hurts to check the ignition I guess.

Another bit of info - the base of the plug threads were they poke into the chamber are matt black and sooty - I think this means oil getting past the valve guides? Could this be related in some way, or is that a separate issue?

Thanks again for the replies so far.

[rev-erend]

Do a cr test on the engine to make sure it's in good order.

My money would be on fuel though .. perhaps a failing pump.

[renrut]

Just a stab but could it be something like the throttle pot? That can be checked out with a meter quite easily and one less thing to worry about.

[Wedgepilot]

Ok, a bit more info. I pulled the vacuum pipe off the FPR with the engine warmed up and idling, and it made bu@@er all difference - no change in idle speed. No fuel spurting out either though, so at least the diaphram is ok.

I then blocked up the vaccum pipe (still disconnected) and went for a drive. I honestly couldn't notice any difference.

Does that indicate a stuffed FPR?