odd gas analyser readings

rob83ke70 · Post by **rob83ke70** » Thu Apr 16, 2009 7:31 am

I have a 1995 hyundai sonata, 2 litre 16v DOHC engine, running rather badly at idle... customer's vehicle, not mine...

now the story starts a few weeks back. the car was booked in for a timing belt. I started it up, drove into the workshop, and turned it off and replaced the timing belt, I did not test drive it before I did the timing belt. When restarting it, it started smooth(ish) and then got rougher and rougher at idle to the point where you could not drive it. I then double checked the cam timing, ok, checked the plugs/filters etc. the plugs were obliterated (worn badly and fouled) the leads were arcing to the engine, the fuel filter was blocked, and the o2 sensor wasn't doing its job. the air filter was fairly clean. I can't find any vacuum leaks either.

All this has improved the car to the point where it is drivable, but it still is far from correct.

fuel pressure is a bit under 200kpa at idle, (keeping in mind vacuum is around 15" mercury at idle because it runs rough) and with no vacuum it goes to 250kpa. with 20" vacuum applied it drops back to 150kpa. Injector duration is 3.2 milliseconds at idle. The four gas reads around 1500 HC, 1% CO, Air fuel ratio around 18:1. I can't find any vacuum leaks.

Air flow sensor is a horrible looking karmen vortex type, I've substituted another one temporarily and it did not make any difference.

Compression test on engine showed all cylinders approx 170psi give or take a fraco. I'm quite sure that cam timing is spot on. Other than the really really bad idle, the vehicle drives really really well.

Oh, and the exhaust isn't blocked up either, I checked that. Throttle body is clean and passages to idle control motor are clean. It was suggested to me that it could be a faulty idle control motor but I really can't see how that affects the emissions readings so much, wouldn't that just make the idle speed run really weird?

I'm jumping to the conclusion that I have leaking or blocked injectors and they are going to come out and be tested and ultrasonically cleaned. Unless I think of something better?? Any ideas??

It doesn't log any DTC's either, or turn the MIL on.

Robert.

rob83ke70 · Post by **rob83ke70** » Thu Apr 16, 2009 7:31 am

oh, coolant temp sensor is within spec as well.

steptoe · Post by **steptoe** » Thu Apr 16, 2009 8:34 am

Now, that'll teach you not to take it for a test drive before hand won't it! I bet the customer says it was fine before you touched it too ! If the old belt was slack or stretched and the new one goes in to pull everything back into spec that is where it is probably gone to crap ? The customer is always right (so they may well be fibbing too) What type of exhaust analyser are you using and has it been calibrated when it should be ?

What spec is the fuel pump supposed to be at ?
Have you tried taking it for a spin with the fuel pressure gauge taped to the windscreen to watch what happens?
Conincidence occurs in your trade a fair bit don't it ?

Matatak · Post by **Matatak** » Thu Apr 16, 2009 7:35 pm

Are you 100% that both Cams and the Crank are lined up perfectly ?

my guess would be one of the Camwheels is out one tooth going on previous experience.

Xtreme_RX · Post by **Xtreme_RX** » Fri Apr 17, 2009 8:18 pm

I would have to agree with Matatak. It sounds like the cam wheel is 1 tooth out.
These 2L DOHC Hyundai sonata's are a bucket of crap I sell so much engine rebuild items it’s not funny

rob83ke70 · Post by **rob83ke70** » Fri Apr 17, 2009 11:04 pm

first thing to check when I get it back in then. I was 110% sure it was right because I got it a tooth out and then re fitted the belt, I realised this before fitting the covers back on it.

Fuel pressure is supposed to be, I say SUPPOSED to be according to infamous repco auto tech, 250kpa at idle and 300kpa with no vac on the reg. I say this is a bit hard to beleive though.

Customer said it was running a bit weird/fluffy at idle before it came in, and thus far has been really good about it, he's not overly happy that it hasn't been looked after up until now in terms of servicing but thats not our problem as this was the first time we had seen the car.

I can't remember the brand of gas analyser I'm using, but its been pretty accurate on all the other cars I've been using...

I had another sonata (owned by a friend) in yesterday and on the gas analyser as part of a tune up, it was running around 18-20:1 air fuel ratio, but other than that everything was good, HC around 140ppm, and co around .5%, and not down on power at all. it has a rather large split in the exhaust piping along the seam in the mild steel tube though and I think it was sucking air in before the rear muffler.

Coincidences happen a fair bit..... or something like that.... we had a lady come in and complain about a scratch from "one of the young blokes must have bottomed the car out" but the thing is, there are three of us at work, and the apprentice was at tafe the day that car was in, the car was never on the hoist, and I myself drove the car in/out of the shed and didn't bottom it out or hit anything at all....... not quite sure whats going on there.

The nice one of the week was the commodore in for a rwc that wouldn't start shortly afterward for the customer, I went out there with some tools and found very very dirty battery terminals, cleaned them, explained this to the customer and she was happy as. I really love customers that are understanding and easy to get along with. I wouldn't rip anyone off or do the dodgy on anyone, and I'd rather just be straight up and fix the car and get on with it. If you are nice, you generally get a lot further than if you are a pain in the proverbial....

Robert.

steptoe · Post by **steptoe** » Sat Apr 18, 2009 9:23 am

I agree with Extremes view on the sonata.They have been appearing around the traps as abandoned. I am certain though that if they had been looked after and serviced correctly they would not be as bad.

Seen the fuel pressure issue before when owner finally decided for himself being trained as a 'mechanic' OS that it was time the 500, 000 km engine was replaced with another used engine, due to performance issues. My mate the mechanic was his mate and at least the owner was honest when confronted and my diagnosis was the lacking fuel pressure, missing about 50kpa. Customer complaned the pump was not all that old (my record keeping system pays off) yet when checked it was 6 years and 220, 000km old as a 'new' pump. I had to intervene and tell customer not to tell the mechanic how to do his job. New fuel pump, clean tank free of dirty black stuff and guess what - it solved the problem!

rob83ke70 · Post by **rob83ke70** » Sat Apr 18, 2009 10:03 am

hmmm. interesting. missing about 50kpa.... One way to find out for sure, I need to put a gauge on my mate's sonata with the same engine and compare... but I'm not sure I'm curious enough to drive/ride all the way to narromine to do this yet.

So the thought is that the fuel pressure is low, making the car run lean, although not that lean, and that is causing my problem? The injector duration at idle is 3.2ms, this is a smidge on the high side?

Robert

rob83ke70 · Post by **rob83ke70** » Mon Apr 27, 2009 9:38 pm

the injectors have been removed and tested, found to be quite ok, not leaking, and flowing reasonably acceptable, going to be cleaned/reassembled anyway, but not the problem.

that leaves three things: cam timing out, fuel pressure too low, or ect/o2 sensor problem. As the car is putting out excessive hydrocarbons, but seems to be on the lean side of normal in terms of air/fuel ratio, I would suggest the electronic side of things is probably working correctly, leaving it as a mechanical problem.

Robert.

steptoe · Post by **steptoe** » Mon Apr 27, 2009 11:07 pm

c'mon, I'm waiting to hear it is the fuel pressure....

Diagnosis of this nature really requires a high pressure pump mounted on a 20 litre plactic drum complete with its own power supply, shove it in the pax side floor hook up fuel supply and return lines with a gauge - ready to swap between cars.

rob83ke70 · Post by **rob83ke70** » Tue Apr 28, 2009 11:42 pm

Ok here is the diagnosis and solution:

The cam timing was out. Exhaust cam advanced a tooth and inlet cam retarded a tooth, thus giving cam overlap on exhaust/inlet strokes, and the excessive hydrocarbons out the tailpipe. Marks lined up with each other on cam sprockets, but were one tooth too high, they line up in more than one place it would seem, and the cams naturally sit with them lined up in the wrong position. The cams have moved a tooth each when I took the belt off, and as they still lined up I did not realise.

Purely a mechanical problem, the o2 sensor was working and as the HC output was too high, it was leaning the AFR off as much as it could. Also, hence the reason why the "lopey idle" as if the cams were reground.

Car still idling a smidge high, but running smooth as now

Very happy. I will remember this for next time I do one of these belts.

Horrible bloody thing to get everything lined up too, had to hold both cams with spanners, while fitting the belt, trying not to move the oil pump pulley and keep the belt on the idlers and crank, all at once. Two person job if there ever was one. Give me an ej25 sohc timing belt anyday

Robert.

Matatak · Post by **Matatak** » Tue Apr 28, 2009 11:54 pm

nothing beats experience in our job mate.

sometimes with DOHC's you can get some Grips and clamp the Cam pulleys together before taking the old belt off, especially helpful when doing them solo.

rob83ke70 · Post by **rob83ke70** » Wed Apr 29, 2009 7:40 am

I've got some of those... sometimes they are really good, sometimes not so good. Probably should have used them on this particular job. The last half a dozen belts I've done on DOHC four cylinders have been a slip off, slip on, hang on was that supposed to be a hard thing? sort of job

Some of the DOHC opel engines are a little bit weird to line everything up, and an ej DOHC subaru engine is a bit odd, but thats what mirrors are made for

Oh and nothing is quite like a kia carnival, three belts, the rear exhaust/inlet cam belt being the best...

Nothing beats experience anyway, and thats what I've got out of the whole thing. The customer now has a car that runs beautiful as well

Robert.

steptoe · Post by **steptoe** » Wed Apr 29, 2009 9:51 am

Bunnings sell a great tool for these twin cam wheels. Consists of two washers (10 - 20 cents each) to jam in to lock the two sprockets together and a bolt (under $1) through the guts to hold said washers in place _ before you remove old belt. Fuji was smart lining up things off valve spring tension with EA82's !!

rob83ke70 · Post by **rob83ke70** » Wed Apr 29, 2009 9:04 pm

lol thats pretty good... probably work as good as the fancy ones too