nickhance

Something is really wrong with my car and I can't even tell. It's been runing great since I've been driving it again, so I don't know what exactly is wrong.

Here's my test results from yesterday:
RPM: 2360
CO%: 21.27 (limit 1.10) <-- 21 times over!
HC: 600 (limit 275)
NOx: 295 (limit 3600) <-- Well under the limit

Now I've replaced the throttle position sensor a few months ago and ever since I did that it hasn't run quite right. The old TPS was definately gone, as the new one made it run signicantly better. But it idles fairly high (1400+ RPM) and stumbles quite a bit on idle until it's warmed up. I can't turn the idle down any farther as it's already gasping for air at idle (I can hear the ISV hiss as it pulls in air trying to correct the stumbling idle). I have the TPS adjusted so it clicks right as soon as it's off-idle and I don't think you can install one of them backwards. I was pretty careful when I was putting it in.

I think it might be the O2 sensor, but I've got an Air/Fuel meter in the car. It reads on the rich/stoich line most of the time and doesn't move around much. Before I put the new TPS (new from the dealer) on the car, it would bounce around everywhere unless I was on the throttle. Now it's rock solid on the high end of the stoich scale. I hit like 1-2 green LED's and never anything more. This is my Air/Fuel gauge

A few other things that have bugged me with the car are:
- It uses oil. It'll use more oil if I'm on the turbo pretty hard, and its quite a bit more than it should be (I can't give specifics, I haven't had the car back on the road long enough yet).
- It will boil coolant down to a certain level in the tank. The coolant boiling happens too quickly for the release hose to relieve the pressure and it will push coolant out the top of the cap.

It's the two issues above that have me worried about the seals on the turbo. The car is still fast as hell and the turbo feels quite strong, but I'm really uneasy with the boiling coolant.

Thanks for all your help.
Nicholas

Mike S

Well, high CO and low NO indicate that you are running rich....way rich. I doubt the TPS is the problem here. Since you said that you can't get it to idle below 1400rpm, that makes me think that you have multiple vacuum leaks. You should be pulling at least 18in Hg at idle when the car is warm. If not, its time to start replacing vacuum lines until you find it. Check the venturi under the intake as well. The vacuum leaks will also cause the rich condition youare seeing.

Those narrow band Air/Fuel meters are useless. It's a 0-1V scale so the resolutions is horrible. It's fairly cheap to replace the 02 and it wouldn't hurt if you don't know when it was last replaced. The main question is how long have you been running the car this rich. If you run rich for a long period of time you may have killed the catalytic converter.

Matt H

Vacuum to begin with and I wouldnt be shocked if you have a bad injector. That car is running WAY WAY rich.
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luckett

Sounds like you have unburned fuel going out the exhaust. When was the last time you changed the wear components in the ignition system (plugs, dist. cap/rotor)? Plugs gapped correctly? Ignition wires ok? Coil resistance ok? Air meter working properly?

Might as well change the O2 sensor if it hasn't been done in a while.

nickhance

I just turned tweaked the idle adjustment screw on the throttle body and it's helped settle the idle a bit, but I want to test for the other items. I'll take the car out and get a reading on the vaccuum level, but how can I test the other items?

The dist. cap and rotor are new, so they should be alright. I'll check the plugs when I return to town in a few days. What would you guys recommend I do to diagnose the problem and what in what order should I proceed?

nickhance

Okay. I turned the idle adjustment screw this morning to prevent the car starving for air and stumbling idle this morning, now I'm idling at 1600 RPM when it's warmed up. I just took the car for a quick rip around town and it's holding between 17 and 18in Hg at idle, but the idle is really high. The Air/Fuel meter was down to around the middle stoich when it was cold, but it went back up to the rich/stoich line at idle after the car was warmed up. What is wrong with my baby?!

luckett

micrometer and a shop manual for the resistance specs.

don't assume that. take it off and inspect the contact points.

start at the plugs and work your way back down the ignition system checking every component along the way.

Matt H

Replace plugs, replace 02 (surely fouled if the car is running THAT rich), use a vacuum gauge on the lines (check the FRP, damper, and there is a vacuum supply for the charcoal canister on the drivers side of the firewall which I will be is also bad).

Check wires for burn marks, bare spots, etc. Start the car at night and watch for the light show (shows arcing).
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Legoland951

If its rich, why not start with the obvious by adjusting the AFM? That takes care of 95 percent of running rich problems for me.

KuHL 951

Adjusting the AFM or do you mean re-tracking the wiper arms? I know you can test them and I have several times but have never seen any adjustment. Are you talking about the adjustment at the throttle body?

Legoland951

The only a/f adjustment on that car is the AFM. Take the black cover off and there is a round dial you can click and adjust. It does take someone who knows what they are doing. If its rich, the AFM is reading more air coming through than it really is so you want to click against the spring to "close" the flap more. The simple way to do it is to disconnect the O2 sensor, rev the engine to 2k rpm, and adjust the dial at the position where the rpm is the highest. An exhaust gas analyzer "smog machine" helps alot when you are doing the adjustment. My smog guy lets me adjust it while its on the dyno.

KuHL 951

That's good to know, I've never had my AFM on the 951 apart yet only on a couple early cars. Any info where I can read up further on this? Would adjusting this AFM dial correct the A/F at idle and tend to mask another faulty component or should it be adjusted after other components are checked and proved to be working OK?. Sorry for all the questions

Legoland951

Not many other failures can cause the car to run full rich. Do the easiest, least expensive, and most effective thing before you start with other items. So far, if my cars are running lean, there is a vacuum leak somewhere and if its running rich, its the AFM. Smog in Ca is a serious business and takes a semi act of god to pass. Most of my cars pass with adjusting the AFM and very few times, a replacement of the catalytic converter. The only time it still didn't pass was from a wrong setting in the DME where some idiot tinkered with it.

Mike S

You definitely have a vacuum leak. If you're only reading 18in. at 1600+rpm that isn't good. Start tracking down the leak or the car will never idle properly. Vacuum leaks are a pain in the butt on these cars and they're very common. I'm in the 20's for vacuum at 1600rpm (22in to be exact). This means you're probably idling down around 12in at 850rpm where you should be.

Legoland951

Vacuum leak should make the car run lean, not rich. However, you still may have a problem with vacuum leak on top of a very badly adjusted AFM towards the rich side.