Running rich and low power

[QUIKS1LVER]

Hi all, Recently i've had my 1988 mr2 on the dyno. Its got really low power (96bhp) and its running really rich. Whilst it was on the dyno they checked the AFR, and its running at 9.8 on full throttle. I've recently given the car a service, oil, fuel, air filter (aftermarket japspeed), magnecor ignition leads, ngk spark plugs, distributor cap, rotor arm and new oil. I serviced it because i was getting pre-ignition. The car is in pretty good condition and has only done 81500 miles. Has anybody got any ideas. I've only owned the car 3 months and i'm really trying to get it running as good as new.

[_Al_]

First, get rid of the aftermarket air filter and replace with OEM. They really are snake oil. Every test I've seen shows that unless they're MASSIVE they can't flow air as well as stock.

Which engine do you have? I can't say much more without knowing, but generally rich running would be:

- air leak
- O2 sensor
- Coolant temp sensor
- Air intake temp sensor
- ECU capacitors giving up with age

[QUIKS1LVER]

Thanks for the response. The engine is a 1.6 NA. The airfilter is pretty big. I had a right game getting it to fit in the engine bay. If after i've checked everything else i'll return it to OEM if its still not improved

[_Al_]

I'd be looking at the coolant temp and O2 sensors. I'm assuming that the mk1 has one! Not so hot on that and hasn't realised this was a mk1 when I replied...

[QUIKS1LVER]

The mk1 does have an O2 sensor. I am thinking of replacing it too see if it helps. Gotta try one thing at a time. Once again thanks for responding

[jimi]

The UK MK1 doesn't have an O2 sensor, so no point in looking for one
An after market air filter won't make a difference to a MK1 other than the noise, you may even lose a bit of bottom end torque.
Mk1 ECU's aren't (in my experience) prone to the same capacitor failure that some MK2's seem to suffer from.
It's worth checking the the ECU coolant sensor and the ignition timing.
Personally I'd be checking for a leak on the intake after the throttle body butterfly, especially the vacuum lines to the FPR and MAP sensor, paying carefully attention to the 2 hard lines bolted on the right side of the intake plenum.

If it's an early 88 it may have the 1a configuration which only has a single line like this

I've seen these lines fracture at the securing bracket and cause over fuelling.
It's worth bearing in mind that the MK1 runs rich at WOT (by design, Mr T did to assist cylinder cooling) and that the engine only had 123 BHP when new. Is the 98 bhp measured at the wheels or a flywheel guesstimate ?

[QUIKS1LVER]

Ok thanks. I won't bother looking for a O2 sensor if it hasn't got one. Mine has 2 hardlines by the intake plenum. I'll start having a look round that area and see if i can see anything. The hp is measured at the engine. Its even less at the wheels. Thanks for info

[jimi]

Unless it's an engine dyno (and you would need to take the engine out to use that) then it's measured at the wheels and guesstimated at the flywheel. What was the actual wheel figure ?

[QUIKS1LVER]

Power to the wheels was 77hp

[jimi]

27.3% run down losses for a MK1 ? I doubt that very much, more like 15%. I'd take those dyno figures with a large pinch of salt.
I'd expect a good standard MK1 to be running around 105 whp (wheel HP) If your dyno figure of 77 whp is any where near accurate then your engine is seriously down on power, much more than I would expect from a over fuelling problem. Be well worth getting your compression checked as well as the timing.

[QUIKS1LVER]

Ok thanks. I'll def get my compression looked at as well. I really want it running well. I appriciate all the help . Jimi i have sent you a private message