Low RPM Load Hesitation/Slow Boost
 

I'm tired of searching. For the past 3 weeks I've been doing everything possible to get my car running right. I've done it almost all and now I need good advice. The hesitation comes on under light load below 3k rpms, maybe going up a slight hill. It does it worse when its colder and not completely warm. Even after it warms up it seems very sluggish all the way around. The car will crank up and idle fine. Was having a hard time cranking before and then I adjusted TPS and set idle. I've got the idle set right around 750 and when it gets completely warm its around 1k. I believe its running rich also. Cannot understand why. These are the things I have. 87T2, about 15k on RR Rebuild, street port, TB mod, walbro, koyo, blah blah. This car is my DD and I don't have a shitload of time to work on it because I'm working a lot, and it has to drive me to work because its my only car.

New Sard FPR - Vac off 39psi Idle 32psi

New 02 sensor

New plugs 7s, 9s

New Fuel Filter

New Borg Warner Thermosensor

Witchhunter cleaned injectors

Grounded ECU (4 wires)
Grounded Boost sensor
Grounded Coils all per Archives
And I made the RR Grounding Kit

No Emissions

Adjusted TPS 1k resting - 5.5 WOT

Has a rough idle but I would attribute that to the TB Mod and street port.

Its certainly running rich because after a hard pull I get A LOT of fire like 3 or more full seconds of flame encompassing the back of the car and after normal driving the bumper is darkening. I've been under the impression it could be a few other things, IAT sensor, AFM, or maybe even shitty TPS even tho its been adjusted and tested. I've probably forgotten to list some things I've got or done but if you ask I'll tell you. I haven't had time to run the Codes or test any of the damn voltages on the sensors or at the ECU because my multimeter is shit. I need help and after lots and lots of searching I can't seem to come up with anything. I know that I need to test all those but either I can't just yet. Hit me with anything


Chris

have you taken a compression check to see how your rebuild is doing?

wow dude, you just described the same problem my car is having to a > T < . Lumpy, rough idle. Bogs and sluggish under light load. Let me know how it turns out if you get it fixed.

No I haven't done a compression test. I can't imagine why it would have a slow compression leakdown after only 15k miles. I don't hardly ever redline it or boost it to hell and back. I haven't bumped up the boost. I'm running premix also. The first tank I ran it without the MOP it ran fantastic. The second I mixed it too rich and it ran like shit so I drained the last quarter of a tank out and went back to the ounce a gallon mix. Could running it so rich that half a tank have screwed the injectors up?? Some of you ask how rich, I put in 16 ounces of premix to 13 gallons of gas.

I just took out the front leading and trailing plugs. The leading are a little black but the electrode is just lightly brown but the trailing are completely black like its not burning the fuel. And that would account for why I burned almost a quarter tank of gas last night only going 35 ish miles boosting once. It wasn't using gas this bad until I did that grounding job either.

Where can I buy the Intake Air Temp sensor? And maybe a new AFM? Or a fucking standalone would probably solve my problem.

Well I unhooked the ground that I had going to the Trailing coil and it seemed to get a shitload better gas mileage on the way to work, that was boosting 4 or 5 times. So no one knows where to get the AIT sensor??? Aaron? Hailers? Icemark?

Was any of hte hesitation fixed as well? Or was there just better gas mileage?

AIT sensor is on the TB elbow under the intercooler.

I know where its at. Where can I BUY one? And no it didn't fix the hesitation. I'm gonna throw some more money at it. Someone suggested ECU solder points??? Gonna do a search and figure that shit out. I'm gonna replace the upper/lower intake mani gasket and buy the IAT sensor. Then its back to the ole TPS and injectors. For some reason I have a feeling that the problem is going to lie in those. Anyone have any more advice or a similar problem that they had???

The car is unbelievably jerky when I let off the gas anywhere under 2500 rpms but I always thought that might be a byproduct of the street port, TB Mod and no emissions. Everyone else says its TPS.

5.5k ohms is too high for the TPS, try swapping it out with a different one. it should read about 4.1k-4.6k ohms at WOT, 1k at idle and sweep cleanly.

this could also indicate that there is a grounding issue still though, i see all your grounds but how about the battery to chassis/engine?

I have all of my grounding wires, 3 4gauge wires going to a mounting spot on the firewall. Then they attatch to a single 4gauge wire that runs thru the firewall to my optima redtop in the passenger storage bin. The same with the power wire running from alt, starter connect to one thats not mounted to the firewall of course and runs thru the firewall to the battery.

then try swapping the TPS and see how it registers.

Yea I have to get one off of someone on the forum first. I got my last one from guitarjunkie. Another $30 into the pit.

The FPR reads like 32psi on idle. Is that too high? I've seen some posts that say it should be around 28-29.

41psi is what the FSM sais iirc, that is low if anything.

bucking is normally caused by leaning out so you may have too low of fuel pressure which will be more noticeable pre-secondary injector staging so that is one possibility but the TPS still sounds faulty to me, it could be a combination of the 2.

Its 41psi with the vac line off, and ign on, at least thats what i've read.

If I were running it 10 pounds too low for a month then it would have blown up already.

curious so i checked the FSM, the fuel pressure at idle should be 28.4psi and with the vacuum line disconnected it should be at 34.1-39.8psi. i went off the haynes manual and that is what i remembered but it doesn't match the FSM test specs.

Yea just looked at the FSM on teamfc3s and thats what it says alright. It just seems a little high to me. Its stock injectors and new fuel filter.

a few PSI won't make a huge difference, richer is less likely to hurt anything or cause issues like this than being on the lean side.

But almost 5psi richer would make the car seem sluggish and if it was getting that much at a lower RPM then it would almost be choking it or wanting to bog it down correct? And the car runs richer when its cold anyway. I think this is why I don't see it hesitate a whole lot once its warmer. Because when it is cold the its almost running double rich.

if you want to be sure then invest in a wideband, it is an invaluable tool and can save your motor if you are running lean.

Yea I know I'm running rich because of the plugs and brown bumper. Do you know where I can purchase the AIT sensor. I can steal it off my N/A Parts car correct? But I'd like to have a new one just to make sure.