Need help with nagging issue.

[sv650_ck]

For the first 5 minutes or so after the car is started I get lean tip-in and overall leaner AFRs (~13) when in boost. This also happens when the car is hot and shut off for a short period for gas, mail, etc. and then restarted. After 5 minutes or so the fueling is very consistent with no lean tip-in and AFRs around 12. Car also intermittently goes into open loop mode around 10" of vaccum with AFRs around 11.5. Just recently, also intermittently, while crusing in vacuum, AFR's will cycle off scale full lean for 5 to 10 sec before settling down.

There are no CEL's to give me clue. I've replaced the front O2 sensor, plugs, wires and coil pack. I'm thinking possibly the TPS is going bad but looking for some recommendations. Thanks.

[Tom @ Fast Forward]

Check the blue light on the card. It should not come on until you enter boost. Also, when you start the car, turn the key on and wait for a few seconds for the card to calibrate, then start the car.

let me know when the problem is occuring, when the blue light comes on with respect to the onset of boost. If, for example, it is coming on at 10" Hg, that could be the problem.

[sv650_ck]

Blue light is only on when in boost.

When does the pc-pro clamp the TPS voltage - boost onset? What other sensors can can cause the ecu to run open loop?

Leaving the key on before starting doesn't have an impact.

[Tom @ Fast Forward]

Sounds like it is running correctly.

TPS is clamped when the blue light comes on. The TPS can cause the ECU to go open loop off boost all by itself without the aid of the PC-Pro. The stock ECU does that under some circumstances of load.

If the blue light only comes on under boost, leaving the key on longer won't make a difference. It is already working correctly.

Could be a dying O2 sensor? They are heated and take time to warm up. Normally only a minute or so but it could be taking longer as it is dying? Just a guess. When mine was dying, it started running richer and richer under cruise. Maybe yours is the heater going bad? Has it been like this from day one or just started?

[sv650_ck]

O2 sensor is new and is Bosch's latest design that heats up quickly. I'm not sure a bad 02 sensor would cause the ecu to go open loop like the TPS will? I'm also getting the monentary hesitations (goes way lean) that feels like the engine is being shut off and on. Maybe the TPS is controlling the injectors to some degree. Whatever it is it's getting worse and will hopefully set an engine code that will be useful.

[Tom @ Fast Forward]

My bad. I missed the point that it is actually going open loop. Are you monitoring with an OBD scanner? If so, what is the TPS doing when it goes open loop? TPS should be around 5 % at idle, ~10-15% at cruise. You might pull the belt off the blower and unplug the cards to see what it does without boost. That would direct us a bit.

I was suggesting the O2 as a reason to go lean.

I can't think of anything that would do it and then go away after 5 minutes????? Especially when the engine is already warm like a stop at the mail box.

What is the vacuum at idle?

[sv650_ck]

I'm ordering one of these scanners to do some further troubleshooting. Will let you know what I find out - thanks.

http://www.myscantool.com/

[Bodhi]

I'm interested to hear what you find. I'll occasionally see the lean tip-in on my car. Specifically, it happens in the following scenario:

* light load going up a hill
* less than 10% throttle.
* right at transition from atmospheric to boost

The WB reports AFRs ~17:1 and there is noticeable hesitation. The problem can be cured by the application of more throttle. :)

[Tom @ Fast Forward]

When that happens, do you have the blue light on the cards or not?


I'm interested to hear what you find. I'll occasionally see the lean tip-in on my car. Specifically, it happens in the following scenario:

* light load going up a hill
* less than 10% throttle.
* right at transition from atmospheric to boost

The WB reports AFRs ~17:1 and there is noticeable hesitation. The problem can be cured by the application of more throttle. :)

[Bodhi]

When that happens, do you have the blue light on the cards or not?

Not sure. I'll verify the lights the next time my official PCPro Monitoring Tech (aka wife) is in the car. OP -sorry for the hijack. :chris:

[sv650_ck]

My bad. I missed the point that it is actually going open loop. Are you monitoring with an OBD scanner? If so, what is the TPS doing when it goes open loop? TPS should be around 5 % at idle, ~10-15% at cruise. You might pull the belt off the blower and unplug the cards to see what it does without boost. That would direct us a bit.

I was suggesting the O2 as a reason to go lean.

I can't think of anything that would do it and then go away after 5 minutes????? Especially when the engine is already warm like a stop at the mail box.

What is the vacuum at idle?

Finally got my scanner - TPS @ idle 0%, ~10% cruising @ ~14"vac. PC Pro clamps to ~85-90% when going into boost.

~19" vacuum at idle.

Also goes open loop ~5-10" vacuum with TPS around 17%. Does this all the time. This doesn't bother me too much but the lean tip-in and leaner afr's whenever the car is started (hot or cold) for the first 5 minutes or so bugs me.

[Tom @ Fast Forward]

Now that you have the scanner, what is the TPS doing during that first 5 minutes and is it showing open or closed loop?

Are you running stock injectors?

[sv650_ck]

Haven't had a chance to take the car out due to the daily afternoon thunderstorms but did take some TPS readings.

Closed Throttle - 404 ohms, .55vdc
WOT - 1032 ohms, 3.73vdc

Readings were taken at the PCPro TPS input wire (purple) referenced to gnd. Voltage readings on the on the PCPro output wire (purple/yellow) were the same as the input.

Anything out of whack?

[Tom @ Fast Forward]

Those are normal for non-boost running. The input signal is simply passed through. CAn you take those same in/out readings under WOT? We think the output might be hanging a second or two before dropping when the input and boost go away.

[sv650_ck]

Meters showing PCPro TPS input/output voltage. At the start of the vid, car is running open loop at ~7.5"vac. I did notice that the TPS input voltage exceeds the PCPro output voltage when it's close to WOT.

http://i16.photobucket.com/albums/b34/sv650_ck/th_MOV06120.jpg (http://s16.photobucket.com/albums/b34/sv650_ck/?action=view&current=MOV06120.flv)

This shows the intermittent surging (full lean) I occasionaly get. I had suspected a bad TPS sensor but the voltages look good.

http://i16.photobucket.com/albums/b34/sv650_ck/th_MOV06125.jpg (http://s16.photobucket.com/albums/b34/sv650_ck/?action=view&current=MOV06125.flv)

[Tom @ Fast Forward]

Do you actually feel it when the lean pulse occurs? Mine turned out to be an ignition power wire (BLK/WHT) towards the front of the engine that was occassionally touching the engine and it finnaly wore through the insulation and would randomly touch the block. Finally, it touched the block long enough to blow the fuse and let me find it.

[sv650_ck]

Feels like the engine shuts down. Hopefully the problem will eventually get bad enough to become obvious.

[Tom @ Fast Forward]

The real problem is that it doesn't throw a CEL. You should pull the plugs and see if they are uniform in color.

[sv650_ck]

Got some new symptoms today. Started the car and the idle jumped to ~2300rpm and after 30secs or so it would oscillate between 1000 and 1500rpm. Didn't see any obvious vacuum leaks.

Pulled the tb and iac valve. IAC valve was in the open position and stayed there whether or not power was applied. After cleaning you can see the diaphram move ~1/8". Valve is open when power is applied and closes when power is removed.

Is this how it supposed to operate? Any other testing to make sure it's okay before reinstalling?

[John Miles]

Finally got my scanner - TPS @ idle 0%, ~10% cruising @ ~14"vac. PC Pro clamps to ~85-90% when going into boost.

~19" vacuum at idle.

Also goes open loop ~5-10" vacuum with TPS around 17%. Does this all the time. This doesn't bother me too much but the lean tip-in and leaner afr's whenever the car is started (hot or cold) for the first 5 minutes or so bugs me.

Those TPS percentages seem out of line. You should see 10-15% at idle (and never less than that) from my experience.

[Tom @ Fast Forward]

If you can get a vacuum gauge on it, I would be curious as to the vacuum readings when it surges like that.

On my 99, I see 5-7% reading on the TPS at idle when warmed up.

It still seems like a vacuum leak. The worse the leak, the higher the RPM swings. Doesn't take a lot of leak.

Just out of curiosity, have you ever checked to see if the lower pivot bolt on you alternator is tight? It is the ground return for the alternator and we have seen various problems with it not tight.


Got some new symptoms today. Started the car and the idle jumped to ~2300rpm and after 30secs or so it would oscillate between 1000 and 1500rpm. Didn't see any obvious vacuum leaks.

Pulled the tb and iac valve. IAC valve was in the open position and stayed there whether or not power was applied. After cleaning you can see the diaphram move ~1/8". Valve is open when power is applied and closes when power is removed.

Is this how it supposed to operate? Any other testing to make sure it's okay before reinstalling?

[sv650_ck]

I think I finally got the problem isolated to the IAC valve. With the the IAC connector unplugged (and idle readjusted) the issues I was having have gone away. Cleaning the valve helped a little but symptoms were still there. Guess it's time for a new valve. Seems to run fine with it disconnected just takes a couple of minutes to warm up. Thanks for the help.

[Tom @ Fast Forward]

Are you sure you have the hoses connected to it correctly? The one closest to the end of the valve (firewall?) is the one that goes to the BTB and the exhaust side of the valve cover. The hose closest to the electrical connector, goes to the VDB.