Hesitation off-idle and waveform


New Member
I have been working on a tune (using tunerpro RT) on my 85 T-type (upgraded to 87 ECU and related wiring). I have successfully tuned most aspects of this modified car (small cam, CAI, ported intake and upgraded turbo downpipe) with some success, but have come across a stumbling block. The car has a tip-in hesitation, especially noticeable just coming off-idle, that results in a small "hiccup". It falls on it's face for just a moment and then catches itself. VE table is getting really close, Long terms mostly in the 122-128 range. I stuck my scope on the ECU to see what I could gather and found this:


You can see the injector (in red) start to open on nearly every crank pulse, but more importantly not quite so. The yellow waveform is the ESC signal and the green is the cam sensor. Nothing changes in the RPM/spark side; cam, crank, est, and esc never skip a beat. I am used to the injector on-time lengthening to increase the amount of fuel, this looks more like multi-strike ignition. The on-time of those erratic injection signals is also ~ 1.3 ms, not much time to allow any fuel in at all. Looking through the .bin I don't see any fields of asynch pulses or such that might account for it. This happens each time I give it a decent stab of the throttle. The above waveform is with a stock 87 GN tune in a separate ECU. The result is the same if using my socketed ECU and my custom tune. Any ideas?


New Member
Some more information: After the engine was rebuilt and some aftermarket unknown injectors were added, the car ran terrible. I replaced the injectors with stock (and flow tested to ensure even volume). Even then, the MAF tables, PE, AE, and cranking fuel have all needed quite a bit more fuel. Like the Inj constant was changed (stock) Replaced the MAF with a remanufactured MAF with no difference. I question air filter at the end of the MAF and if the airflow is disturbed that much due to the non-stock set-up. I have search a ton for tuning information on this platform, but little is available; if one of you guys are sitting on a treasure chest of table information, that would be awesome if you shared! Thanks!


Texas, Where are you from
Reading along and puzzled but when I got to the remanufactured maf I said self, this is what I would look into if it were mine. A newer style maf and translator would be my next step. Those old maf and reman old maf have a notoriously bad reputation.
I have had good luck with wrecking yard mafs and translators on our stuff.


Shake for me, girl. I wanna be your backdoor man.
Ya, I fully agree. Reman MAFs are junk. Go Translator and LS maf. Also not knowing your goals and turbo but if you plan making more hp than stock I would look at larger injectors than stock.


New Member
Thanks guys for the response. Found my answer, those extra injection pulses are asynchronous pulses for AE. The tunerpro RT .xdf gives me no tables to adjust AE. I was able to get a .ecm file for tunercat and have loaded and reviewed the .bin with the tunerpro defintitions. The tunercat definition has 6 different AE tables, plus additional wastegate dc tables and more. So I will work with a few of those to give me some additional fueling. I agree with the MAF and upgrading, but not planning on making any real performance changes on this hot-air vehicle for quite some time. I have a turbo mustang and a few other projects that need to get finished first!


As I interpret what you've said, you're using an 87 ECU, stock 87 MAF, stock 87 ignition and stock 28# injectors. Two questions, stock Bosch 233 fp regulator? and which chip(s) are using? The last time I used TunerPro the xdf file was written for a stock chip. Since you're looking at the tables, I assume you have a prom burner. Correct?

Very few people make their own bins these days which is why I ask, however I've been doing it for my 87 GN since I bought it new. I'll help if I can, just need clarification before I jump in with both feet. Oh, and I'm impressed (should say jealous) of the o'scope you have. But I digress ...