hesitation at 3-4000 RPM

ryanlindenberg · Post by **ryanlindenberg** » June 13th, 2005, 2:18 am

hey i'm having a problem under light boost my car will hesitate and jerk a little bit between 3000 and 4000 RPM. it's pretty weird, it will stumble a little bit and then will pull really hard after that. i have tried retarding the timing, it seemed to help a little bit but didn't make it go away completely. i tried increasing and decreasing the fuel but that doesn't seem to help.

i have a BPT GTX running stock boost. i do have a vacuum leak right now which i should be able to fix on tuesday...do you think this would have anything to do with my problem? i have a haltech e6x. could any of you haltech guys share with me what kind of fuel and timing you are running at these RPM ranges?

another thing that could possibly be a problem is that hose that runs from the fuel pressure regulator to that plastic sensor thing on the driver's side of the engine (right next to the breather opening)...the problem being that while my car was on the dyno the boost pressure snapped the fitting off of the sensor. the sensor isn't hooked up to the haltech or anything though so i don't know if it would effect it any. the other side of the sensor is hooked up to the intake manifold(this is the side that broke off). i just took the hose off and put a vacuum cap over the intake port.

thanks.

forcedairram · Post by **forcedairram** » June 13th, 2005, 9:00 pm

When turbocharging a bp you would be best off to unplug your vics solenoid, it only takes one electrical connector and it will stay open at all times. So just jerk the white electrical connector and you should be good.I had the same problem until i unplugged it, shouldnt throw any check engine lights, atleast mine didnt.

What did the car run on the dyno and at how much boost?

BuGS · Post by **BuGS** » June 13th, 2005, 11:16 pm

Hmm ya mine does the same thing. Sometimes the check engine like will pop on. I was thinking it was something to do with fuel. I guess I will try the Vics thing. Thanks.

Also anyone know what timing the car should be at? Right now I am at stock 10 degrees.

forcedairram · Post by **forcedairram** » June 13th, 2005, 11:27 pm

if you dont have a turbo it shoudnt be a problem, well on the naturally aspirated engine i noticed it leaned out a little bit under light throttle around 4k, but the problem was easily solved by adding more fuel with the S AFC II. This little hesitation is drastically increased on turbo engines, it can be tuned around but it is a very big hassle

jaydog5678 · Post by **jaydog5678** » June 14th, 2005, 1:34 pm

ryanlindenberg wrote:
another thing that could possibly be a problem is that hose that runs from the fuel pressure regulator to that plastic sensor thing on the driver's side of the engine (right next to the breather opening)...the problem being that while my car was on the dyno the boost pressure snapped the fitting off of the sensor. the sensor isn't hooked up to the haltech or anything though so i don't know if it would effect it any. the other side of the sensor is hooked up to the intake manifold(this is the side that broke off). i just took the hose off and put a vacuum cap over the intake port.

thanks.

You don't need that plastic garbage running to the regulator. Just run the vaccum line straight into the intake manifold to the regulator or tee it off with another line...

Fix the vaccum leak/s and retest. Recheck the condition of the ignition setup if you can and that includes the cap, rotor, button, and plugs. Make sure the heat range is correct and the gap is still o.k.

forcedairram wrote:
When turbocharging a bp you would be best off to unplug your vics solenoid, it only takes one electrical connector and it will stay open at all times. So just jerk the white electrical connector and you should be good.I had the same problem until i unplugged it, shouldnt throw any check engine lights, atleast mine didnt.

The GTX engines are a little diff. then the N/A versions, so they don't have the same manifolds or VICS.

Timing should be btwn 9-11 degrees.

ryanlindenberg · Post by **ryanlindenberg** » June 15th, 2005, 12:06 am

yea i hooked the FPR right up to the manifold...it helped some. it seems to only be hesitating over a very small load range. if i hit the gas pretty hard it won't hesitate at all. or if i accelerate slowly it won't do it either. just in between the 2 it does it. maybe i'll try adding more fuel again, on the bright side my vacuum leak is fixed and my car starts really good now that i have my BAC valve hooked up correctly.

when you say 9-11 degrees are you talking about the base timing for the BPs with factory ecu?

and jaydog is right about the GTX not having VICS so that's not the problem.

what kind of gap are you running on your plugs? i think i'm at .035 or something right now.

it's kinda nice to know i'm not the only one that has this problem

jaydog5678 · Post by **jaydog5678** » June 15th, 2005, 7:11 pm

I had a stumbling problem at WOT because the spark plug gap was too wide and perhaps I had one range hotter than I should have. The gap should be small anywhere btwn .29 and .32 and seems to work well for turbocharched engines. The stock timing is 9-11 degrees BTDC (before top dead center) or base timing at idle.

In your case, double check the fuel maps at those load ranges. If everything is o.k., look to the spark plugs and the rest of the ingnition.

ryanlindenberg · Post by **ryanlindenberg** » June 16th, 2005, 1:33 pm

ok, i'll try gapping my plugs to .030 and check out my plug wires...i was also thinking about upgrading my plug wires since i have an MSD 6A. i'll keep you updated.

ryanlindenberg · Post by **ryanlindenberg** » June 17th, 2005, 7:08 pm

well i regapped my plugs to .030 and checked all my wires, the 4th cyl spark plug wire was shot. i replaced that one and took it out again...the problem was still there but not as much. i began leaning out the fuel and it seems to have helped a lot...it only does it occasionally now so after a little more tuning i think i will have it fixed.

ran into a new problem today with my A/C dilemma though...i'm trying to figure out how to get the A/C to work since it doesn't work without the factory ECU in. i found 2 relays next to the firewall on the far passenger side of the engine bay. i unplugged the relay closest to the firewall and began testing wires with my multimeter, i found a big red wire that had continuity to the wire that goes to the A/C compressor...so i was like sweet i'll just get this relay to work and my A/C will work...i ran a wire from the + post on the battery to a switch and then to the blue/black wire on the relay. i flipped the switch, the fan for the A/C came on and i thought i would be done. not the case, the fan for the A/C turns on only when the ignition is in the off or accessory position. when in the ON position it will shut off. the blower motor for circulating air in the cabin also came on when the A/C fan would turn on. so i have no idea what this relay does...the relay right next to it (farther from the firewall) also had a thick red wire and this wire had continuity with the wire going to the A/C compressor too....AHHHH!!! anyone know what needs to be done to get my A/C working? i'm roasting like a chicken in my car. and no smart a-- comments about how minnesota isn't warm

...well ok maybe a couple.

wickedmx3 · Post by **wickedmx3** » June 22nd, 2005, 6:05 pm

It is ironic that this came up because that hesitation that your talking about just happened to me 2 saturdays ago as I was leaving HIN.

I had it happen about a month back, but I ended up with a broken axle and a disconnected plug that left my car limping home. I replugged it, reset the ECU and I was up and running again once the axle was changed. I thought the hesitation problem was due to the unpluged wire...but no...as I left HIN, we jump right on the highway, rolling in a row with 25 to 30 hiooked up imports and domestics, just so they did not get any ideas about that being "just" and MX-3, I punched it as we came off the ramp in 3rd gear, the car flew forward, hesitated and then picked up again and flew down the highway. It did not happen again, but when I think about it now, yeah, right about 4 to 5 thousand RPM's.

I am running a BPT GTX as well, and I know the spark plugs are gapped at .32.

FroSTeD · Post by **FroSTeD** » June 22nd, 2005, 8:22 pm

I have some kind of hesitation too. But it is a bit different.

I only get it in 5th gear when I am WOT for like 2-3 seconds and the boost is at maximum. It accelerate, then cut, accelerate .5 seconds, cut and so on, like an electronic cut off or something. It is pretty weird as it doesn't do it in other gears, or maybe I just never floor the car for a long time in the other gears.

It's not a really cool feeling. I have the bp26 ECU & harness, but the harness is not in good shape. (has been rebuilt)

ryanlindenberg · Post by **ryanlindenberg** » June 23rd, 2005, 12:36 am

yea i've done more tuning and it has improved but it is still definetly there. it rarely happens in the 3000 rpm range but is more frequent in the 3500 range now. i'm probably going to switch to some magnacore wires and if i take my car to the dyno to get tuned again i will have him look at it. mine doesn't really cut though...it kinda sputters then pulls really hard. i dunno, hopefully we can get it figured out because it's really annoying. sounds like it must be something in the motor causing our problems since we have a variety of ECUs with the same basic problems. pretty weird.

Flashpoint2 · Post by **Flashpoint2** » June 23rd, 2005, 5:08 am

are you sure there's no play in the turbine shaft? Sometimes they'll wobble at certain RPMs.. that might explain why it only happens around 3500, and then smooths out and pulls hard.

ryanlindenberg · Post by **ryanlindenberg** » June 24th, 2005, 2:23 am

my turbo has 1000 miles on it.

Flashpoint2 · Post by **Flashpoint2** » June 24th, 2005, 3:23 pm

So? id check anyway. Sometimes stuff is faulty even when its new.

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hesitation at 3-4000 RPM

hesitation at 3-4000 RPM

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Re: hesitation at 3-4000 RPM