Loss Of Power, Rich Fuelling

[simonbuk]

Took my car to a dyno after a faulty O2 sensor was found (had base timing and emissions checked after which were spot on). Only produced 126bhp and was found to be running richer and richer as the revs rose.

Any obvious pointers to go investigate ?

Will get a new Elanscan file tomorrow, previous files suggested it was boosting correctly

[Tuga2112]

Have you checked compression?

In the last year I found my 4runner was very low on power, after a lot of head scratching and a handful of parts. I finally realised the owners telling me 120 compression is "normal" were the same that called it "3 point slow engine" and only 2 people said their cars were running at 170...

Turned out both heads were 1tooth out of alignment

In my green car, I had a slightly different issue. The fact that I couldn't adjust the distributor far enough to get the timing right was the main clue, but it's also running extremely rich .

The exhaust cam was 1 tooth out of alignment in that car,

Your exhaust cam will be aligned with the crank because your timing is right, but intake could be out of sync.

I'm thinking the faster your rpm, the more your injectiors will put in, if the valves close too early you won't have the right mixture as a result?

I assume you have checked the spark plugs, both for wear as well as the gap?
I have received plugs pre-gapped to na specs that were sold for the se engine in the past.

Nothing else comes to mind. Both those are easy checks. And you can check plugs while their out to do compression

[simonbuk]

Thanks for the reply - I did check the plugs, the gaps were slightly big so brought them down, they looked fine.
If I've lost compression wouldn't I also get some signs out of the exhaust ? Some smoke ? As that is fine.

[Tuga2112]

Thanks for the reply - I did check the plugs, the gaps were slightly big so brought them down, they looked fine.
If I've lost compression wouldn't I also get some signs out of the exhaust ? Some smoke ? As that is fine.

No smoke in either car, but both cars issues were with exhaust cam.

I'm suggesting checking the compression to rule out your intake cam being out of sync.

Have you ever done a compression test? It's a very easy one to do on the elan.

[simonbuk]

OK cheers - i'll get a compression tester (no, never done it ). I assume you have to stop the car from firing so pull a fuse for the fuel pump or take leads off the coil packs ?

Just created a new ElanScan file starting from cold and stuck it in the ElanScan section.

[chrism]

Hey Simonbuk I've got one of these (with instr on the back) if you wanna try it...

[simonbuk]

OK cheers Chris - I maybe up sometime to borrow that !!

[simonbuk]

Your exhaust cam will be aligned with the crank because your timing is right, but intake could be out of sync.

I'm thinking the faster your rpm, the more your injectiors will put in, if the valves close too early you won't have the right mixture as a result?

Would it be something easy to check if i got the belt cover off ? Is it visually wrong or is it more in depth than that ?

[Tuga2112]

Would it be something easy to check if i got the belt cover off ? Is it visually wrong or is it more in depth than that ?

yes. i took a little video of my exaust cam being out of alignment

[simonbuk]

OK cheers, i assume the cover cannot be removed without taking the engine mount out and jacking the side of the engine up a bit ? (as I believe this is what you have to do when doing a cambelt change ?)

[Tuga2112]

OK cheers, i assume the cover cannot be removed without taking the engine mount out and jacking the side of the engine up a bit ? (as I believe this is what you have to do when doing a cambelt change ?)

depends on your luck.

Pinky has explained it before, but i dont know where, im sure if he see this will elaborate. (or copy paste hes explanation if he remembers where he has done it before)

in my experience, if the bolt in the middle of the cover is installed. you have no option but to remove the engine mount.

if that bolt is missing. you can (with a little of elbow grease) remove the cover without removing the engine mount. which I have done after adjusting the belt to confirm the tension was right

[simonbuk]

Thanks again - I'll have a look

[dapinky]

Basically, if you remove the high pressure hose from the PAS pump (3/4" nut), and can get the centre bolt out, then it is possible to remove the top belt cover - but it is easier to undo the mounting and raise the engine a bit on a jack if you are in that position anyway (just the single big horizontal bolt should be enough).

[simonbuk]

Have you checked compression?

Just done a cold compression test -

155/145/140/155.

Will do a hot one when i've had a chance to take it out, but have to wait for a new phone to be delivered as my current one was in my back pocket whilst i rolled around on my concrete drive yesterday

Also did a vacuum test - 16 (thingies) which i think is in an acceptable range (15-19 ?), also hit the throttle and it went to zero than came back to 16 which i believe indicates that theres no exhaust blockage.

More fiddling to come......

[simonbuk]

Compression test hot -

140/135/133/145.

ETA - actually just realised - never had my foot and the throttle

How much of a difference would it make ?!

[simonbuk]

Anybody got anymore ideas on this please ? I'm at a loss as to what to look for/check next ?

1. New O2 sensor.
2. Checked/cleaned air temp sensor.
3. Got base timing checked.
4. Checked for air leaks.
5. Turbo boosting to max .65 bar according to Elan scan.
6. Engine getting up to normal operating temperature.
7. Compression test carried out
8. Vacuum test carried out.

Loss of power at higher revs , throws more and more petrol in as the revs get higher.

????
Air/fuel ratio OK at lower rev range.

[Tuga2112]

i May have asked this before. but here it goes

have you cheked if the injectors are clicking fine ?

my thinking is that a partially gummed up injector may be fine to close on time at low revs. but taking too long at high revs which would overfuel.

a bottle of redex can help.

[simonbuk]

OK cheers - worth a go at this moment in time !

I guess it would be hard to hear clicking at the higher engine revs as the engine sound will be booming at that point

[simonbuk]

Just went back and looked at an ElanScan file .

Played with different parameters and looked at the Spark Advance. Reading up on it it will advance the spark more and more the higher the revs rise. Looking at a file, after about 4000rpm it's dropped back off quite a bit - What would stop it being advanced at this point ?

[simonbuk]

This may have been a total waste of time

When asked by the Dyno people 'How much power do you think it's got - I replied with '150-160bhp ?' as that's the figure quoted all the time depending on whether it's got a cat or not.

Turns out they give their figures at the wheels . So 126 bhp at the wheels probably sounds spot on .

They still suggested the air/fuel ratio was getting worse as the revs rise so maybe not out of the woods yet. At least I can stop buying more testing tools