Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Cylinder 4 low compression

Hello. We had our toyota yaris timing belt changed yesterday . As soon as we got our car it started idling the garage told us it had a low compression in cylinder 4 fault. The machainic stated that to get it fixed we needed to pay him again. But Before we got the timing chain fixed it never idled shacking now it dose. My question is could the replacing of timing chain be the cause.?

You need to provide the year model and mileag on the car. You also state on one hand it has a belt and on the other hand it has a chain.

It should have a chain. If the chain was worn out that usually means the rest of the engine is also worn out and low compression is a part of that.

It could also be that the chain timing is not correct but that should affect all cylinders; not just one.

1 Like

Its a 2007 toyota yaris it has 105 000 miles on it. We had the timing chain replaced not belt sorry mistake. And the Mechanic stated there is low pressure in cylinder 4 hence the misfire

chains last a long time. does the owners manual say to change timing chain? of course anyone would change the chain if it made noise or rattled as many timing chain tensioners do have issues. many cars have issues with the timing sprockets failing as some control timing advance and are feed by oil pressure.
so, why did you change it?

1 Like

All Yaris’ have a timing chain. If the mechanic installed it improperly, it could have bent a valve in only 1 cylinder before the mechanic corrected it. Impossible to tell from the internet. You need to know why one cylinder is low - rings, bent valve, bad sealing valves. Only one of those 3 might be the mechanic’s fault but hard to say for sure.

1 Like

Why was the chains replaced? Noisy, jumped teeth, broke?

A chain that is gone at 105k miles in most cases means the motor oil was not changed often enough and especially if the miles driven involved mostly short hop driving. A 105k miles in 12 years points to light use and that generally means oil changes more often.

I would be curious about the compression readings on the other cylinders. If the others are comparatively low then I’d say the engine is prematurely worn out.

1 Like

It’s simple enough to run a leak down test on #4 to see if a valve is the problem.

1 Like

I think we need to know why the chain was replaced.

1 Like

Hello the Machinic said valve cylinder number 4 has low pressure instead of pumping 150 its pumping 50 . We got the timing chain changed because it was rattling. The machanic said we need more money to get the valve checked again. We have already £600…

Timing chain was rattling and shacking

Yeah, I got that. Re-read my post. it MIGHT be the mechanic’s fault but very hard to pinpoint unless you are looking into the engine and seeing the reason for low compression.


Oh sorry . Yeah thank you fir help

Timing chain was rattling very noisy

car has noisy chain/rattle that mechanic observes prior to job
he may also notice a miss or not smooth idle. maybe not
replaces chain and noise is gone but now he detects a miss
he checks compression and only 1 cyl is low.

1 Like

Yes he noticed the rattle before fixing . Did the computer test check which showed the timing chain needed changing . Hence the change. But the car did not have idle problem. Which it has now and noise is different from before.

what will he do to fix it? i got the pay him more part. the yaris has a VVT sprocket. was that changed? he is qualified to work on vvt motors?

He just said he will need to remove engine again. Sprockets not changed

seen this scenario before. noisy timing chain. new parts. low compression. next step is dicey. there was damage all along from loose chain? or botched chain repair?