BC

Newly rebuilt from injection labs in Colorado.

PorKen

None of the MAFs I've gotten from InjLabs has read exactly the same at idle and WOT. Of (3), I've only had to return (2) because they were way off... (I hate MAFs.) Anyhu, not likely the problem you are describing, though.

Age of spark plug wires?

Rob Edwards

The MAF was originally in my GTS when I bought it. I sent it to Kevin and then put it onto the stroker. Early in the tuning process we thought something was wonky so I ended up sending it to John Speake to evaluate it. According to John the MAF was/is spot on, so I think it's good. FWIW.

BC

It's the original in the car now Rob. I used yours to drive the car just when I was sending the original off. Yours is now in the box. But I did cross check and it acts the same way. It's something either randomly wrong with ignition or some issue with the brains. I have not swapped the brains.

PorKen

Rob - would you mind if I borrowed your MAF?

I'd like to log a couple runs on my 'closed course' to compare it with my other InjLabs MAFs, for an overall baseline.

Rob Edwards

Ken-

Sure, PM me an address and I'll send it up after I get it back from BC.

BC

I may test that MAF one more time but then I can return it ASAP.

Does anyone have a stock LH box that I can test? Maybe an lh and an ezk to test separately?

BC

Got some more gas in the car today after some work traveling early in the week and drove around a bit. The Wide band 02 is now saying that with the newer injectors that it is SUPER rich when the 02 correction is not happening. Meaning I unplug the LM-1's analog output to the LH and it goes from 14.1 at idle to 11.9 and 12.3

Very strange.

When the LH IS getting the 02 sensor info, it will basically do what its supposed to do which is drive around at 14 or so AF.

WOT will end up at 11.9 or so by near redline (can't look at the display too long when going that fast).

I guess I could lean out the MAF with that screw that Ken always talks about but then what? Why did this change so drastically? The car is essentially running about the same it was with the other injectors.

The bobble/hesitation/ still happens where it normally happens so it has nothing to so with the injectors.

The MAF made no difference ( to this issue - car ran better overall)

A new tempII made no difference (to this issue, car ran and started better overall)

BC

I forgot that I even posted the rich issue after I replace them last week.

This is weird. It STAYS that rich permanently now without the 02 loop input.

PorKen

Have you checked the fuel pressure?

It's easy on a '86 to kink the short return hose from the FPR if it is not just the right length. It must have a smooth curve.

BC

I'll check. I was checking it during the injector work because I should probably replace it.

Where would you want to see the idle with the 02 disconnected on an open air box/H-pipe no cat, small muffler combo?

BC

I wanted to bring this thread back up. I have been driving the SAR car regularly again as I am working on the 91S4 I am selling (needed an ignition switch and some other things) -

This issue is so frustrating as it persists through all of the other issues i Have addressed and looked at.

To review: Its a hesitation that will shudder the entire car if you hit it right. It only happens when:

1) You are NOT in WOT
2) You are under 2900rpm
3) You are over 2100rpm

If you hit the WOT switch it goes away instantly.


I have noticed recently that it happens in all gears, differently in each gear, because of the speed of acceleration and the amount of work the engine must do to accelerate.

In the first few gears, it just seems like you have turned something on. MMMMMMMWHAP! MMMMMMMMWHAP! as it goes past 2900rpm. Like the tune map changes drastically (which as shown by the Wide Band 02 that I ran with for several weeks - is the AFR changing from 14.5 to 13.8 or so)
Its not gradual - its instantaneous.

In the later gears it just feels like the car has no guts below 2900 rpm and most of the time if you are at around 2300rpm it will do this quite noticeable (to me) shaking.

In this video of a completely different car in a completely different setting, you can hear essentially what I am talking about at around 31 seconds into the movie, as the driver gets on and off the gas in the corners.



I understand that there is a Keep it Simple Stupid principle, but I think that from all of the evidence, something is not letting the enrichment happen at part throttle like its supposed to.

To review:

New MAF
New Temp II
All grounds checked
New injectors


The car DOES have some form of aftermarket chips - but it has been stated that these do not ever affect 02 loop operational running. And it only happens that I can see in that state.


I will get megasquirt probably for this car, but even then, I have to fix this as I would either sell the LH system or use it in the race car possibly. Either way I have to fix this.

BC

Still driving the car every day. Still does the stumble/wavering at the same spot in the rev range every day.

A couple ideas (and please see above post as well).

1) anyone suggest unplugging vac reference for FPR?
2) Anyone suggest replacing the FPR randomly?
3) Does anyone believe what I describe is ignition related?

Z

No
No
Yes

BC

K. How so? Same part in the rev range, same throttle input, always stops and starts at the same time.