Engine Volume Air Flow 3.2L

[DG624]

I have an 86 3.2 L with some minor modifications: S.WOng Chip, CAT by pass, extrude hone intakes, larger TB S. Wong. Before my last two modifications (TB, Extrude Hone) my RWHP was around 210. I had the car rechecked at the same dyno and came out with less around 189 RWHP. My air/fuel reading was very rich between 9 and 10 and I have a cold start problem with a surging idle (1200 down to 200 and up again).

I checked the Volume air flow and the intake air temp reading was not giving the 5 volt required for terminals #1 and 4 and #3. The idle position switch was OK so was the idle control valve. The throttle body switch was checked as was the Mass Air Flow Arm. Air leaks were checked but it still may be a problem. DO I have to replace my Air Flow box?

[scarceller]

What's the AFR at idle? and what is it when just cruising with foot on the gas? Basically you are running very rich. Have you also checked the Cyl Head Temp sensor resistance? At room temp needs to be around 2500 ohms and with engine fully warm it needs to drop down under 200 ohms. Check the cyl head temp sensor next as it's often the cause of rich mixtures. Also the hunting idle is a red flag that your way rich.

Other possibility is fuel pressure to high.

[Quicksilver]

The stock 3.2 is not needing more runner volume to increase power. Increasing the intake will lower port velocity which doesn't help. If you had increased the displacement enlarging the intake would be called for. I wouldn't expect increasing the intake volume to kill the power by 10% though.

What the 3.2 does need is "some exhaust". Jerry Woods estimates that there is about 20 HP available in exhaust. The CAT bypass should help plus it will increase the sound output some. What it really needs is a set of 1-5/8" primary headers.

The fact that you have some mixture issues tells you that the tune is not right but don't expect more then you started with when you get it fixed. If you wake up the exhaust the additional breathing could partly take advantage of the increase in port volume and get you a larger gain.

[scarceller]

The mixture, even with the changes you made should not deviate much. The motronic in these cars measures air flow coming in via the AFM and does so very well, so if airflow is improved or made worse it does not matter. The code just looks at the air flow inbound and calculates fuel directly based on the amount of air it sees. More air = more fuel and visa-versa so for you to be that rich means something else is likely wrong. Start with the CHT sensor and fuel pressure.

[gliding_serpent]

Stuck fuel injector? If you have a wide-band sensor in, you can unplug one injector at a time and record the changes in AFR. If one leans things out far more than the others, is may be getting stuck open.

Lots of possibilities. I ran into a similar rich issue with my car. It may expose itself again this spring when I wake it up as I never fully addressed it (I suspect my issue was one of tune with my old chip, which I ironically hope to partly resolve with Sal's MAF/injector/chip solution).

[ischmitz]

I agree with Sal here. To get as rich as what you describe something is wrong. Most likely the CHT is open causing the mixture to go full rich.

A quick test: measure resistance between pin 13 and pin 16 on the 35-pin DME connector after unplugging it from the DME. With a cold engine it should be between 1kOhm - 3 kOhm. If it's open there is your issue. Or, unplug the CHT sensor and stick a paper clip into the harness connector. This shorts it and tells the DME the engine is fully warmed up. I bet running will not change when you unplug it and greatly improve once the paper clip goes in.

Ingo

[prschmn]

+1 for Sals advice-and others-esp. CHT sensor.

[gliding_serpent]

Good stuff for my own diagnostic tool box.

[DG624]

My ability to check is limited to my volt meter. I had the injectors cleaned and checked by Marren about two years ago. I will try the Cyl Head Sensor next. I have also heard that it may be an air leak. The rich mixture was a the high end above 5000 RPM...at low RPM it was around 11-10.

Sal I feel that the increase in air flow can't be that great and the Motronic should compensate. I think more exhaust flow would help also but I have not decided on a system yet.

[kuehl]

Have you pulled all the spark plugs and looked at their color?

[Quicksilver]

The issues from an air leak will be at its worst at low RPM when the intake vacuum is high. At higher RPMs with low intake vacuum it won't effect the performance much.

[DG624]

I checked the Cylinder Head Temp sensor and it was OK. The spark plugs were good when I replaced them without any oil or carbon. The intake gaskets are all new as is the vacuum line at the back of the engine.

I think the problem is with the Air Flow meter...the sensors are not showing any voltage. I will look for an air leak also.

[DG624]

I finally took the car to an expert that said my O2 sensor was bad...I hope that this solves the problem.