Car under powered - what might be the problem ?

[New POD]

Car Poverty Spec 90 bhp Mk1 MX5 monza

 

Cam Belt changed Professionally * 

Power steering retro-fitted Professionally *

New plug leads and plugs fitted

 

 

Symptoms.

 

1) Needs 2500 rpm to pull away - less and it bogs down

2) Once on the move has NO acceleration on the flat at 2000 rpm, and very little until 3500 rpm.

3) At 4000 rpm it's like a two stroke coming onto the power band

4) On inclines you therefore need to be in a much lower gear than it used to need. Coming through the Derbyshire Dales and over the Cat and Fiddle Pass, I was forever having to change into 3rd to keep up with traffic.

 

I've taken to running it on super unleaded which has removed some but not all midrange hesitation

 

 

*PH sports cars in Shardlow near Derby.

 

I have to say, I'm not sure if the fuel filter has ever been replaced.

Car is fitted with a Cobalt Blue Stainless cat back which is too noisy for my middle aged tastes.  

 

 

Ideas ?

[Christine]

Driver's had too many pies

[billyboy406v6]

Move to Holland, less hills/dales ? Has fault been there since cambelt change, belt jumped a tooth ?

[castros_bro]

Did it go well before the cam belt change then not well after? 

 

 

 

 

 

 

 

 

 

 

 

 

 

Edit....Fucktards   looks like someone got there before me.

[New POD]

Did it go well before the cam belt change then not well after? 

 

 

 

 

 

 

 

 

 

 

 

 

 

Edit....Fucktards   looks like someone got there before me.

 

Would that be enough ? 

[dollywobbler]

Rear calipers seized?

[castros_bro]

Would that be enough ? 

 

One tooth out can make it run badly and if it ran ok before the cambelt change but badly after then that's the thing to check. I've not done a MX5 cam belt but the engine is in the right direction  to check easily so someone on here will know how the cam pulley marks line up.

[twosmoke300]

Air inlet pipe between air filter and engine split ?

[TRW]

Coil packs?

Sorry, I know naff all about the MX5

[Tamworthbay]

Move to Holland, less hills/dales ? Has fault been there since cambelt change, belt jumped a tooth ?

that was my first thought as it goes well after. The fuel filters are notorious for being neglected as the bolt on the cover rusts so people just don't bother, coil packs are also known to fail. Wild mad guess would be that someone has fitted a later vvti type engine without the gubbins to run it (I have seen this once), or swapped the diff over so a silly ratio. The 90bhp ones are always a bit gutless compared to the full fat ones but shouldn't be that bad.

[John F]

New POD, on 25 Mar 2016 - 08:01 AM, said:New POD, on 25 Mar 2016 - 08:01 AM, said:

Would that be enough ? 

 

Yes, absolutely. I had the cam belt professionally' changed in my Cav SRi in the early 2000s and they got it two teeth out, it was utterly gutless as a consequence.

[2MB]

+2, on some engines a tooth or two out can cause hesitant acceleration. Managed to do it on my Rover SD3 as an incompetent youth and that drove, and sounded, a bit like a two stroke. The meaty exhaust on your Mazda may be masking the odd engine noise

[Pillock]

That absolutely sounds like a timing issue, most likely with the cambelt being a tooth out since that has been fettled recently. Had a similar problem with my Golf after a garage fitted a new engine with new timing belt, got it home (just) and had to slide the belt off and adjust using the timing marks.

[SiC]

Non interference engine too, so if out of time it won't bend valves. Does sound like timings set wrong.

 

From experience, the ecu is thick as shit on these, so not a lot electrical can go wrong. Check the air flow sensor is moving properly and freely (flap in airbox). Coolant temp sensor is reading the right resistance. Should be able to disconnect it and it'll run, just be very rich. Also will force it to run open loop, so rules out o2 sensor too. Also as said fuel filter.