Just got my 3 inch exhaust installed. Not real happy with my AFR's. Idle ranges from 15-18 and cruising is around 14.7. Under heavy load it drops to high11/12's. I installed 720cc secondaries and am running a 1.7 rtek. Also, as I accelerate, the car is very jerky, and the idle pulses heavily unless I really slam on the throttle. The lambda gauge reflects this and shows my AFR's jumping up and down with the pulsing.

There's only one thing I can think that might be causing this. I bought a dowpipe from someone on here and it came with an O2 sensor in it, I had to cut off a green clip and install my type of clip for the harness. Is it possible that its the wrong O2 sensor? Would an O2 sensor cause above issues without tossing a CEL at me?

 

Forgot to mention, I'm running a walbro as well. Could a clogged fuel filter cause the car to run lean?

 

The more I read, I come to realize that my AFR's aren't REALLY crazy, I'd still like them richer. But what would cause the car to buck and pulse while casually accelerating?

I'm still running 550 primaries, but I was under the impression from all the reading I did that they would be sufficient at my boost level (~10psi).

 

Sorry, replying to my own topic again, but felt I should add that it gets worse the warmer the engine is.

 

Anybody? Not even sure where to start diagnosing, could really use some input from some veterans.

 

The pulsing could just be a typical TPS problem.

What boost are you running? Stock intercooler?

 

I had very similar issues . my afrs would bounce from lean to rich at idle , and any thing under ful throttle would buck , as though i was learning to drive a stick. Turns out my narrow band was well vague causing my afrs to look bouncy and my tps was way out of wack. i would ohm the tps and reset values(with a warmed up engine) to 1k ohm and that will probly get rid of the bucking. As for the surging idle , my case was no bac . Not certain if this solves my issues as i went on to redo all the harness' and move battery to my bin behind drivers seat .

 

It is the stock TMIC. I plan on water/meth injection to make it more efficient.

Boost went up to 10~11 psi.

Did some more driving yesterday to really pinpoint where my #'s are. Whats a normal idle AFR? When the car is cold, it idles around 15. When it fully warmed up, its closer to 17. If the car sits idling for a while I can watch the AFR climb to 18 almost 19. (I'm assuming its because the TMIC is heat soaking).

As for the surging, it only does in under certain conditions. Like I said, if I slam the pedal down, she takes off like lighting, and it's glorious If I accelerate very casually, it's still a smooth increase in speed. It's that mid-line acceleration that causes the throttle to surge. And it really feels like it has something to do with pedal position. AND it gets worse as the car warms up, which leads me to believe the cold start system is working properly.

The car goes into closed loop properly. At cruising speeds, it's around 14-15. And it fuels properly under boost (dropping to the 11-12 range).

So my two main concerns are the idle AFR, is it to be expected to be that high, especially when sitting for long periods of time in the wonderful 114 degree AZ heat. And the surging. Which like said above, I believe to be a TPS issue as well. So I'll bring that into spec this weekend.

 

Whats a normal idling AFR?

 

Turns out TPS was 1kohm low. Runs much better now. Man, when the turbo and the secondaries kick in.... she's like a bat out of hell..

 

so many problems result from the tps being out of wack

 

Bah, the problem has re-surfaced. It seems to be more dramatic if I start the car when it isn't cold. Does that make sense? First thing in the morning when I drive it for 30 minutes to work it runs great. The way home, it runs great. But if I park the car in the garage for an hour and get back in to run an errand, it surges like made if I don't drive like a granny, or a teenage boy with a lead foot. So I'm trying to figure out the variables here...

On a side note, part of me is wondering if my stock primaries are maxing out. I'm only pushing about 10psi, but at lower RPM's and with light to medium load on the engine at around ~3 psi my AFR's can hit 16's. Granted if I slam my foot down and load the turbo up it seems to do a little better, but until the secondaries fire, it seems a little gutless. I was under the impression my 550 primaries would be ok though until I reached around 12 psi?

 

Alright. Scratch what I just said. It surged on the way to work this morning. UGh. It seems I'm back to square one.

 

I would recalibrate your wideband. 15:1 fuel when cold? 17-19:1 idle when warm? Way too lean. A normal idle ratio is 13:1 Some people can get 14:1 These engines are NOT happy above that. Those numbers are way too high your car would hesitate like mad and sound awful. I think you should start with that simple check. How is your fuel pressure? Are the injectors clean?

 

Im going to agree with beefhole, idling at 18 or 19:1 would idle like crap

 

replace your o2 sensor, its a sheilded wire and ive had interferance problems with a oxygen sensor that had been cut and twisted back togather 2 times. the car had simular problems to yours, but no wideband so i don't know the afr's it was running. but an o2 sensor is pretty cheap.

 

I'll start with re-calibrating the WB, just to see if that helps. It makes me wonder though, it shows the car running stoich (14~15) when it goes into loop at cruising speeds, and it shows numbers dropping to the 10-12 range under heavy boost. Which is why I never suspected the WB in the past.

The secondaries are almost new. The primaries I'm not so sure of... Haven't checked fuel pressure yet, as I need to by the adapter for my gauge since there's no Schroeder valve anywhere.

I'll get a new narrowband O2 as well.

And I suppose I'll mess with the TPS again this weekend as well. I've deducted that the surging has no correlation to RPM or PSI. It *feels* like a pedal position thing. I forgot to check the TPS for a smooth transition between closed and WOT, perhaps there's a dead spot in the TPS.

Looks like I've got my weekend planned...

And thanks for all the help so far gents, really appreciate it.

Edit:O2 sensors are $75 for an OEM one! Yikes... They have universals, but I'd have to splice it again...

 

It was mentioned to me by aaron that by the time i would get the tps in tune , the car would have cooled down quite a bit. He said tune it drive it then check it to make sure it is still in tune after reheated , Etc.

 

OR you could just rotate the warm up 1500 RPM cam ( what ever it's call'd)thermowax?. instead of wasting gas and adding to global warming...

also o reilly's has direct fit o2 sensors for 50sih.

 

The car was fully warmed up the first time I adjusted the TPS, but can someone explain why it matters?

 

Wow... the direct fit on Checker's website (o'reilly in AZ) is $399?!

 

Just out of curiosity, which kind of sensor are you using for your wideband? And how close is it to the turbo? The cheaper sensors can burn out pretty quick, even the better sensors will burn out if they are too close to the heat straight off the turbine.

 

I'm using an innovate motorsports WB. It's mounted a little over halfway down my corksport downpipe.

 

That's probably far enough away, if you have more than one bung on the DP, use the one farthest from the turbo for your wideband, those sensors are expensive. Did you buy the unit used? If so, the sensor may be shot, but try to find a means of diagnosing it before you go buy a new one... just a possibility.

 

Just splice in a $18 bosch O2 sensor for christ sakes. Use the wire from the old sensor and you wont have to hack any of the harness....

It amazes me when people pay that much extra for a 1-wire o2 sensor...