Engine Testing Advice Required

[onenastyviper]

Hi, my MR2 race car engine is not happy and just wondered if anyone has any tips?

Last event, it started to misfire on throttle and felt down on power but idled OK.
I changed plugs as they looked a little worse for wear (i.e. 2mm gaps across the board) and #1 seemed a lot more sooty than the rest.
- this made no difference.
I checked the OBD data and I had misfire on #1 recorded.

Anyway, the problem is my car is offroad so I can't test drive it on the road and I have an FIA cutout to save the battery which means that I lost all the usual ECU data.

So I did some checks today with an OBD reader:
1. Engine Off: TPS reads 11% -> 77% WoT (checked by pressing accelerator and doublechecked at throttle body)?

2. I started the car and waited for the idle to drop to normal (@1500rpm down to 780ish) my OBD reader can view misfire count and I could see #1 misfiring like a good'un then it settled down after #5-10minutes of idling.

3. Idle timing (after the car is left idling) is about 18-19deg <- I can't drive it around so this figure is purely from warm-up.

4. Now, once warmed up, it only misfires when I rev the engine and if I hang the throttle the misfire disappears when the revs reach a stable figure (this is all only stationary testing).

I know it's probably not a lot of information and the inability to drive it around makes diagnostics a bit more difficult but if anyone has any advice then it would be appreciated.

Thanks in advance :-)

[jonbill]

Try swapping coil and plug 1 and  2 over as first test and see if the problem moves, if not do the same with injectors.
If the problem stays on 1 after that.. Not sure [emoji848]

[krazysteve]

coil pack suspect then can break down when hot, as mentioned swap packs over see if fault follows
Have you got live data on your reader?   fuel trims stft and ltft plus you can check 02 sensors to see if they are working correct.
will give you an idea if running healthy.

[shnazzle]

77% seems slightly low but possible. Won't have anything to do with this. 11% is spot on so it closes well.

As said; swap coils and check for a bad one (I have a spare from @Tomo70 I can pass on if needed).
Timing is a bit too advanced for operating temp. Should be at 14ish Dev advance at idle. Suspect it's running a tad lean. So, usual thing... Have you cleaned the MAF recently?

And check o2s as also said. But clean MAF first.

[onenastyviper]

Well, I have just bought a new compression tester and the checked the cold engine compression:
#1 = 140
#2 = 130
#3 = 135
#4 = 135

I also swapped #1 & #2 coil packs - noticed that all of them have a crack along 80% of their length: will be buying new ones.

Started engine and it was not misfiring as badly as when it was first started yesterday but #2 did seem to be the ony cylinder misfiring.
I did not rev the engine becuase I just wanted it to warm up for a hot compression test.

Anyway, the results of the warm test:
#1 = 130
#2 = 135
#3 = 135
#4 = 135

So, I thought these were a low so put a bit of oil into the bore and retested:
#1 = 150
#2 = 150
#3 = 155
#4 = 150

I will be checking the compression tester gauge tomorrow at work...

[onenastyviper]

Yes, yes I am quoting myself becuase I just had a really stupid thought - what would compression test readings be if the throttle was still closed?

Well, I have just bought a new compression tester and the checked the cold engine compression:
#1 = 140
#2 = 130
#3 = 135
#4 = 135

I also swapped #1 & #2 coil packs - noticed that all of them have a crack along 80% of their length: will be buying new ones.

Started engine and it was not misfiring as badly as when it was first started yesterday but #2 did seem to be the ony cylinder misfiring.
I did not rev the engine becuase I just wanted it to warm up for a hot compression test.

Anyway, the results of the warm test:
#1 = 130
#2 = 135
#3 = 135
#4 = 135

So, I thought these were a low so put a bit of oil into the bore and retested:
#1 = 150
#2 = 150
#3 = 155
#4 = 150

I will be checking the compression tester gauge tomorrow at work...

[jonbill]

Lower than it should be[emoji4]

[onenastyviper]

Lower than it should be[emoji4]

Gets better - just checked them again - holding the throttle open this time 
Cold: 150, 150, 150, 150

After warming up: 140, 140, 140, 140
- lower perhaps because the warm up process burnt off the oil inside the bores reducing the seal effect?

I will check try and check the gauge tomorrow at work and I hope it is reading low by at least 20psi 

[onenastyviper]

Lower than it should be[emoji4]

Gets better - just checked them again - holding the throttle open this time 
Cold: 150, 150, 150, 150

After warming up: 140, 140, 140, 140
- lower perhaps because the warm up process burnt off the oil inside the bores reducing the seal effect?

I will check try and check the gauge tomorrow at work and I hope it is reading low by at least 20psi 

Argh...the gauge is accurate 

Does toyota sell rebuild kits for engines?

[jonbill]

I'm sure they do but you can source rings and bearing sets in good brands and gasket set, crank seals, water pump and everything else you need for a rebuild for < £300 on ebay.

But with your new coils you may find you don't feel the need!

[1979scotte]

Surprisingly consistent across all 4 cylinders