Compression Results

[digger]

surely over fueling (except in cause of faulty injector) causing bore wash will affect all cylinders and result in lower numbers across the board.

[ForcedFirebird]

Some of you may have followed my saga on E30Tech. http://www.e30tech.com/forum/showthread.php?t=117652

I remember now :(

You had issues with the machine shop and ended up rebuilding on your own.

Please don't give up, keep that IX alive!

[jeffnhiscars]

Since the o2 is before the cat I don't see how the cat can effect your readings but it is def possible that the sensor has a connection issue or that your ECU is not up to par in correcting the mixture.

[EyExR]

So I visited Dennis at OMG Motorsports in Farmingdale. I've been wanting to get over there for a while now as I see they're doing some really cool things for our 'community'. VERY cool guy and he knows his stuff. He did a smoke test and it revealed some small vac leaks at the cam plugs (not a big deal really...). So I will get that squared away when I rebuild.

He also tested resistance at the CTS and it read good. My AFM is new and I had cleaned my ICV not too long ago. But it is original so still somewhat suspect. The throttle position sensor also 'clicks' at the correct spot. That seems good.

He suggested that I check for continuity at the ECU end of the CTS. I'll do that next. Perhaps I have a bad harness?

My cap, rotor, coil, and plug wires are all new and I do get good spark at all plugs. No doubt they are fouled up from excessive fuel, however.

My hope is to get this car running with the proper fuel/air mixture and then tear her down. Yeah. I'd bet good money I'll find a couple of polished cylinder walls and probably a ton of carbon buildup on the piston tops...

[ForcedFirebird]

Just because the TPS clicks doesn't mean anything, you need to read dead short at opposing pins in idle or WOT mode with a multimeter. Should test the sensors at the ECU connector as that is what the ECU actually sees after the harness.

If you have a later model with the round connector under the manifold, this connector often corrodes and can throw off CTS readings, make injectors misfire, not fir or all three.

o2 sensor being bad can cause the ECU to run rich, so can exhaust leaks pre-o2 sensor.

The ICV "shouldn't" cause it to run rich, but may - usually it will stick and cause low or high idle.

[EyExR]

Just because the TPS clicks doesn't mean anything, you need to read dead short at opposing pins in idle or WOT mode with a multimeter. Should test the sensors at the ECU connector as that is what the ECU actually sees after the harness.

If you have a later model with the round connector under the manifold, this connector often corrodes and can throw off CTS readings, make injectors misfire, not fir or all three.

o2 sensor being bad can cause the ECU to run rich, so can exhaust leaks pre-o2 sensor.

The ICV "shouldn't" cause it to run rich, but may - usually it will stick and cause low or high idle.

Thanks! I'll test those things too.

The C191 connector under the manifold looks good. No corrosion at all and well-seated. Although I never rule anything out.

This is my 3rd O2 sensor and I believe this running rich issue may have been an ongoing problem even before my initial rebuild. Over the years the plugs have looked very similar to what I posted. I had always assumed it was mostly oil but I'm thinking it may have been fuel the entire time. Killing my first engine, accelerating the failure of the initial rebuild and now this latest rebuild. Would polished cylinder walls point DIRECTLY to the problem?

Is there any other way of checking the fuel/air mixture besides just looking at plugs and checking codes? It would be nice to get results instantly while I go through the list of possible culprits...

[ForcedFirebird]

Widebend is the only real way to monitor fuel accurately.

Yes, if the walls are polished, 99% of the time is either poor break in, cylinder washing, or both.

Codes with these old ECU's really aren't of much help as they only will let you know once something has completely failed, or is unplugged.

[EyExR]

Ok. Maybe I'll look into wideband. I don't want this to ever happen again.

So I'll have some time this weekend to start pecking through the list of possible problems. I plan on pulling my injectors and fuel rail and running my fuel pump with a switch. My question is when I do this, nothing at all should come out of the injectors. Correct?

[ForcedFirebird]

Correct.

[EyExR]

Cool. Thanks!

Question regarding the CTS: When you guys unplug this while the car is idling do you get any change at all? I don't... It's a 1991 FWIW...

[EyExR]

Okay. I had time to do some tests today to try and figure out why I'm running rich. I did the entire ECU pinout tests and some things came back a bit off. I'm not sure if they are the cause, however. Car has been sitting cold. Ambient temperature was 40 degrees F for all tests.

My reference sensor (CPS) (pins 47 and 48 ) read 833 ohms. The range is supposed to be 540 +/- 54 ohms.

The idle Air Stabilizer Valve (ICV) read 46.4 ohms. It's supposed to be 40 ohms.

Everything else seemed fine. The CTS had the correct resistance between pin 45 and ground. And my TPS was was functioning properly too..

I opened up the air filter box and I found my filter was wet from coolant. I'm not sure why...

So I replaced the air filter, cleaned and burned off the spark plugs, cleaned my ICV, cleaned the MAF, sprayed contact cleaner on every sensor and plug and added some dielectric grease to the C191 just in case.

I also pulled the fuel injectors and ran the fuel pump. No leaks...

I went for a 20 minute drive (car was surging a bit and revving high at idle...) and then my check engine light came on again. Got home and did the stomp test - 1222. Just like I had before. Pulled the plugs - and they already were fouled from fuel.

I guess my next course of action is to swap in another ECU, check timing, and do another valve adjustment. I've already done a fuel pressure test and it looked good. The return line is not crimped and I put a new FPR on...

Am I missing something? What else can I do?

I heard the purge valve kick on when doing these tests but could my charcoal canister be a culprit. What about my brake booster?

[ForcedFirebird]

Check the vacuum line on the fuel pressure regulator. Make sure the diaphragm isn't ripped and drawing fuel through it.

You can disconnect the charcoal feed from the bottom of the throttle body and cap the nipple there. That will eliminate that.

Also, pull up the fuel rail from the manifold, leaving the injectors attached along with the fuel lines and crank the car while paying attention to the spray pattern of the injectors. If one or all of them are dripping instead of spraying nice, it will cause rich conditions.

[EyExR]

Check the vacuum line on the fuel pressure regulator. Make sure the diaphragm isn't ripped and drawing fuel through it.

You can disconnect the charcoal feed from the bottom of the throttle body and cap the nipple there. That will eliminate that.

Also, pull up the fuel rail from the manifold, leaving the injectors attached along with the fuel lines and crank the car while paying attention to the spray pattern of the injectors. If one or all of them are dripping instead of spraying nice, it will cause rich conditions.

How would I check the vacuum line at the FPR? It has vacuum... How do I know if the diaphragm is torn? This is a new FPR that I put on for the latest rebuild, too. I really doubt it's shot.

For the injectors - am I to let them spray down into the cylinders? I'm assuming you can pry them up enough to look for the pattern but not get gas all over the place? It's pretty tight in there.

Could I have a bad catalytic converter?

anyone want to buy an essentially new iX with issues?? lol. seriously considering dumping this. I've been working on this car for years with no success.

[EyExR]

Ok. Did some more tests today. I did another fuel pressure test and it was dead on perfect.

I also swapped in another ECU and put in some new plugs.

The car idles a little rough but that could be the ICV making up for the compression loss on my bad cylinder...

I made sure I had a 1444 code before I hit the road.

The car was actually running incredibly strong for all its issues. But then the Check Engine light came on. Went home and did the stomp test. Now I'm getting 1221. O2 sensor out of range or bad.

???

I had a 1222 on my last ECU now a 1221 on this one? What gives?

I made sure the plug was seated correctly and tried again. Same thing.

Strange

[EyExR]

I forgot to mention I have M50 injectors. I don't see a problem with that but I'll put back my M20 injectors to see. And I'll check spray patterns on both for the heck of it.

Vacuum is not pulling fuel at the FPR so the diaphragm is good.

I'm going to do the valve adjustment next, check timing and open up my cap and rotor to make sure everything looks right and then finally check spark at every plug.