Hi!
I went for a drive today and the AFRs weren't out of the ordinary on the first drive. I came back to the car after about an hour and a half and the AFRs were abnormally high on startup (16 or so)

I let the car idle for a while and it hangs around 14.5 - 14.7 which is normal. If I drive around and give it some throttle the AFRs jump up around 15-16 for a second before settling down to 13.2 - 13.6 @ 3000rpm or so. They usually go down the other way to 13 or so depending on the load.

In 6th gear I am able to cruise comfortably at 3K with a relatively normal AFR (14.2). The coolant gauge is reading 3 bars and there isn't any overheating.

The air temperature sensor in the Haltech is reading 43 degrees celcius or so, is this normal? I understand there would be some heatsoak.

The strange thing is, I haven't changed anything that would affect the fuel or ignition timing. I did however drive around for a bit last week without the 2P VTEC pressure switch connected to the solenoid, but the car ran fine that whole week after I had reconnected it. I can't imagine that would have damaged anything internally however but I could be wrong.

I know it's hard to diagnose over the net but if anyone has had anything similar happen let me know!

Cheers!

 

Update:

Any chance this could be due to a dying fuel pump? I am seeing high AFRs now at idle (around 17-18).

If I blip the throttle the AFRs drop but are still on the lean side.

 

Check your manifold for cracks. Exhaust leaks will make your AF's show lean.

 

Do you have a way to check your fuel pressure? Really would help to have known what your base fuel pressure was prior to the issue occurring and compare it to what it is now, so that may not help much anyway.

A dying fuel pump will act worse as the car (and pump) get warmer. When my pump was dying we could get one or two good pulls on the dyno when the engine was cool before the fueling would drop off significantly as the pump got hotter and hotter. What pump do you have in there?

43 deg. C (110 deg F) sounds normal for air temp (actually, pretty good depending on the ambient temp).

Could it be some bad gas? Dirty injectors? Do you feel any misfiring or skips when it happens?

 

I'll definitely check the exhaust for cracks and leaks, I didn't have that luxury yesterday unfortunately. I was almost 45km away from home and the thought of limping the car that long distance on a lean fuel mixture makes me ill

The car definitely leans out a lot more when the engine is hot, after I limped it to it's second destination I tried to just let it idle at 14.7 but it was jumping straight to the 17's and 18's.

I drove it this morning and it was idling as you would expect a cold engine would. It was around the 12s, 13s on the 1st coolant bar and gradually went up to 14.

I decided to stop at the petrol station straight away while it was on the 1st coolant bar and filled it right up to the top and added some Techron injector cleaner.

I turned the engine over and it was idling lean for a little bit (15 - 16) but dropped down again shortly after. I managed to get it to safety (e.g. a place where the gates are locked overnight) so I'm not worried about it getting towed away by some thugs

On partial throttle the AFR still climbs a little bit so I'm sure it is a fuel related issue. I will check all the voltages for the fuel pump and make sure the wiring isn't fried.

Updates to come and thanks for all the help!

 

I had problems like this before I set o2 feedback on aem v1. the tuner limited the feedback to 20% either way as the map could get messed up if it changes too much.

 

What do you mean exactly? I removed my exhaust recently to install some 70A diff mounts. Would I have to perform another free air calibration for the Haltech wideband?

The car was running fine after I had reinstalled the exhaust and driven it a good 45km though, but on the second startup that day it was rubbish

I just placed an order for a FB340 after hearing some horror stories about the Aeromotive pumps, I was planning on doing this anyway but was hoping the pump would stand the test of time

 

A little update.

I got the new FB340 pump in today, ran the SOS rewire kit which was a pain in the ass.

Engine ran fine on cold start, engine starts to shudder on a hot engine after blipping the throttle and sits at ~15.1 AFR

So defeated, honestly don't know what the problem is

 

Sounds like common heat soak issue to me. No matter what set up ive run, ive always had similar symptoms to varying degrees. The worst is always after driving the car for some time and then parking it to come back 15-30 min later. Ive experienced cases where the engine literally is surging/chugging back and forth at idle for a min or so or until I hit the throttle a few times. Seeing 18 - 00 afr

Regardless, the FB340 is a good pump. Ive run one the same one for 5-6 years now NA and boosted.

 

It never used to do this though, even in the worst summer heat (35 degrees celcius). It's currently winter at the moment in Australia and the max temps I'll see all day are 16 degrees or so.

I took the exhaust off recently, do I need to recalibrate my wideband? I wouldn't think so but who knows?