Odd Lambda 1 Code + Failed E test

[canadiankid]

So, I have a 1990 325ix. Recently failed the 2 speed idle e test. It passed the rev test(2500RPM) pretty good, but failed the idle test(800RPM) miserably. It failed on both Hydrocarbons and CO emissions at twice the limit. It also has the Lambda 1 check engine light.

So, I replaced:
Spark plugs
Coolant temperature sensor(2 prong)
O2 sensor

It has a nice idle till it heats up, then it starts to surge. It only fluctuates about 50-75 RPM which isnt really noticeable on the tac, but you can definitely hear it. That is why I replaced the temperature sensor. I reset the CEL by pulling the battery when I just replaced the O2 sensor. What happens is when I start to drive it, the CEL light comes on and goes off right away, then it comes on again, I let off the gas a bit and it goes off. This goes on for about 10 cycles and then it goes on and stays on.

I cant think of what to change next. A friend came over and checked the injectors with some sort of listening tool, said they sound good.

Another issue is when idling, if you give it gas semi fast its fine, but if you go to rev it quickly the car hesitates big time and wont catch. It quickly recovers and goes back to idling. This happens whether the engine is hot or cold. That is only if you quickly rev it. If you smoothly give it gas, it will rev smooth right through all the RPMs. Any ideas what would cause this?

I would go get another e test, but I suspect it will fail again because of the CEL code and surging idle still present.


Any help greatly appreciated.

[e30vert]

Check the intake rubber boot for cracks or any leaks that will let air into the intake behind the MAF sensor. Make sure the clamps in that area are tight as well. Surging can be caused by intake vacuume leaks! Essentially what is happening as air is "sipping" by the ECU attempts to balance that added air with fuel and then as the air is reduced so is the fuel. The ECU is "hunting" for the right mixture which it cannot maintain as external air is being allowed in that it cannot regulate. Air that comes in through the intake passes through the MAF which is like a big air flap that has an electrically heated sensor in it. As air passes over the sensor it is cooled - so more air means cooler sensor. Less air means hotter sensor and the ECU uses that sensor along with others to determine the right amount of fuel to allow to the Injectors (i.e. Injector Duty Cycle)

[canadiankid]

There has been a development here. I realized the car wasn't heating up all the way. Replace t-stat, let it warm up all the way, everything was fine. Then CEL comes on again after a few minutes. I did a pump check comes back 1221 instead of lambda 1(1222), which boggles my mind because I just replaced the o2 sensor. Should I be looking at wiring harness, OR is it possible to ruin an o2 sensor if the car never heated up all the way and was running rich? I ran the car probably only 100-150 km(60-90 miles) on the new o2 sensor before I replaced the t-stat. Other than that, I still think I have a small intake leak which I havent gotten around to smoke testing it(small idle surge about 50-60rpm). Besides the slight idle surge engine sounds completely normal.

[Gregs///M]

Be sure your throttle position sensor is properly adjusted. You should hear a faint click (with engine off) when you move the throttle off rest slightly. Test is electrically following the repair manual or better yet, the electrical troubleshooting manual which can be found on this site.

Also check the feedback from the AFM. That can cause the quick gas, hesitation issue.

[jlevie]

A 1221 or a 1222 code can be caused by invalid data from the O2 sensor (bad sensor, wiring fault, or bad input section in the DME), or they can be caused by an upset in the A/F ratio (intake leaks, injector or fuel problems, misfires, bad AFM, etc).

[canadiankid]

So a 1221(o2 sensor) fault code CAN be caused by an intake leak? If so that is what I will hunt for next as it has a brand new o2 sensor.

[canadiankid]

Smoke test complete. No leaks. Mechanic said icv is stuck(explains idle issue). Going to replace that right away. CEL still comes on with 1222 code. After a reset comes on while crusing, let off gas, it goes off. Repeat ten times and them stays on. Mechanic plays with bimmers and he says the engine runs perfect and doesnt know why the light is on. Fuel related issue? I am going to replace the fuel filter. Any other ideas? I am OCD about a car running perfect and a CEL screws with my head especially when the engine runs so smooth.

[jlevie]

If the ICV is stuck that could mimic an intake leak.

[canadiankid]

Ok, I still haven't resolved this. I have replaced with new parts: o2 sensor, plugs, temp sender, temp sensor, t-stat. Used icv corrected the idle surge. Symptoms still present: CEL 1222, throttle hesitation from idle. If I clear the CEL it comes on once warm and only while under constant throttle. If it comes on an I let off the gas it goes away. This will repeat for about 5 mins till it stays on permanently. I took apart the intake. MAF has no resistance in flapper. Throttle plate appears to have no clearance but I don't have a .0015" feeler. Any help is appreciated.

[jlevie]

With what you have replaced and negative results from the smoke test (assuming it was properly conducted), I'd wonder about the TPS, AFM, FPR, DME, and injectors. But the 1222 code and hesitation off idle strongly suggest intake leaks.

A smoke test done properly means replacing the AFM with an adapter for smoke injection, plugging the exhaust, and holding 2-4psi of smoke pressure in the intake for a while. Some smoke test machines have a flow meter that will tell if smoke is moving into the system once pressure is achieved. If the flow meter indicates flow it is necessary to hold pressure until the leak becomes visible.

[canadiankid]

Thanks for the info. I just got off the phone with a friend and was advised to take a better look at the afm. So I will electrically test that next and likely replace it with a known working one to see for sure.

[canadiankid]

How do you test the afm? With it out of the car pins 9-8 and 9-7 are open. Pins 5-9 I get 560 ohms(temp now is 24C) and pins 5-7 vary with flapper from 100 to 1200 ohms. I read online about it needing to be in the car. How would you get probes on the pins then?

[MattPro]

How do you test the afm? With it out of the car pins 9-8 and 9-7 are open. Pins 5-9 I get 560 ohms(temp now is 24C) and pins 5-7 vary with flapper from 100 to 1200 ohms. I read online about it needing to be in the car. How would you get probes on the pins then?

I've used this guide to test an AFM before, you can test it out of the car successfully.

http://www.the944.com/afm.htm

(scroll down to where it says "Testing the AFM's Potentiometer")

[canadiankid]

Does anyone have test #'s for a 90' ix? I tried to get that black cap off. It has been siliconed on and I am afraid I will break it if I rip it off. Although, hudging by that I am assuming it has been repaired before.

[canadiankid]

Replaced afm with known good one. Old one was bad with resistance test. Maybe an exhaust leak before the o2 sensor if the smoke test didnt plug the exhaust? I am going to call the mechanic on monday to see if that was done. What else is left, fuel pressure now?