Hiccups (vid + dyno graph)

[Neejay]

Ok, so I finally got a video of my problem:

http://www.youtube.com/watch?v=0bzLSEK7fPo



RB25, FMIC, walbro 255 + fpr, mbc 10-11psi, turbo back exhaust, stock ecu (definitely getting it tuned after seeing this from this point of view)

Thoughts, opinions, suggestions?

[Cameron]

nick your videos not working... at least for me.

[USMCgetsome]

your fuel pump is slowly malfunctioning! Mine kept doing the same HICCUPS then it went to a good 1 sec pause wot and then finally i got a new pump and it was all solved! wtf! i swear that it was the most challenging troubleshooting i had to learn to fix. It always made 43psi at idle and would increase with revs. But while driving it would hiccup for a sec or half a sec then it would continue to go up the rev. also look into a hard wire kit for the fuel pump.

[Neejay]

nick your videos not working... at least for me.

Works for my friend and on my phone

your fuel pump is slowly malfunctioning! Mine kept doing the same HICCUPS then it went to a good 1 sec pause wot and then finally i got a new pump and it was all solved! wtf! i swear that it was the most challenging troubleshooting i had to learn to fix. It always made 43psi at idle and would increase with revs. But while driving it would hiccup for a sec or half a sec then it would continue to go up the rev. also look into a hard wire kit for the fuel pump.

You know, you bring up a good point, seeing as how a well known moron installed it. Ill double check that as well. Someone else mentioned they had the same problem and it turned out to be their mafs.

[flatrate]

sounds ignition related to me... check plug gap and your coils..

[Yellow4g63]

Did you try to close the gap more to see if it still happens?

[Neejay]

sounds ignition related to me... check plug gap and your coils..

Did you try to close the gap more to see if it still happens?

Funny you say that you guys mentioned that. I changed my spark plugs 1 step colder to: BKR7E (4644) @ .028 and it fixed the problem for a few weeks. Could that have temporarily bandaided weak coils?

Man, I should just put it in the shop. I'm tired of this.

[gawdzilla]

looks like a fueling issue to me... also you can see the lean spikes. could be your tune or your fuel pressure/pump. put a fp gauge on it and see how your fuel pressure looks.

a spark blowout is more of a stuttering and won't really clear up as you run more rpm/load.

[Neejay]

looks like a fueling issue to me... also you can see the lean spikes. could be your tune or your fuel pressure/pump. put a fp gauge on it and see how your fuel pressure looks.

a spark blowout is more of a stuttering and won't really clear up as you run more rpm/load.

I guess I need to get another fp gauge for the inside of the car. I have one in the lines (SARD), but obviously hard to look at it while driving lol

[USMCgetsome]

change the pump it's only $100 and will make the headache go away. I trouble shot that damn problem for 1 1/2 years. Kept checking mafs/injectors/ecu/grounds/alternator/fuel pressure reg/fuel pressure indicator/coils/igniters/spark plugs/ a buddy brought over a walbro 255lph fuel pump and i couldn't believe that it kept causing the hiccup.

[gawdzilla]

I guess I need to get another fp gauge for the inside of the car. I have one in the lines (SARD), but obviously hard to look at it while driving lol

just use some more fuel hose and extend the feed line so you can tape the gauge to your windshield.

[USMCgetsome]

lol! i love the idea! i always wondered if it bent a certain way that it would cause an inaccurate reading

[gawdzilla]

if it's pinched yea, but i've done it before and it worked fine. verified my supra fuel pump couldn't kep up

[lazyboi444]

hey neejay were u on alpharetta hwy this morning around 7:30 to 7:40. I seen a burgundy coupe like yours with a primered front bumper, hauling a**. What sounded like a RB25 under the hood

[Largekid]

I agree with a fueling issue. I'd check the fuel pressure and maybe put in a new pump. Also hard wire it...easy to do and helps the pump out.

[flatrate]

gap plugs down to .026 or lower and report back, it goes lean because it misfires...

A fuel issue doesnt even really make sense.. it would make sense if it leaned out under higher RPMs or something like that, but for it to miss from a fueling issue at that low of an RPM would indicate other fueling issues then just a fuel pump... its getting fuel... maybe something electrical

Its missing around peak torque, lots of cylinder pressure there lots of load, ignition issues IS the problem... try gapping the plugs down...

what are they even gapped at now? also use dieletric grease when reinstalling the coil packs.. make sure the springs in the coils are making good contact with the plug...dont be affraid to stretch them out some to get more contact pressure against the plug...

[Neejay]

hey neejay were u on alpharetta hwy this morning around 7:30 to 7:40. I seen a burgundy coupe like yours with a primered front bumper, hauling a**. What sounded like a RB25 under the hood

ha...nah, I live in clayton county and my front bumper is painted.

I agree with a fueling issue. I'd check the fuel pressure and maybe put in a new pump. Also hard wire it...easy to do and helps the pump out.

I'll hardwire the fuel pump...research suggests that this won't hurt anything, but actually help. Might as well...

gap plugs down to .026 or lower and report back, it goes lean because it misfires...

A fuel issue doesnt even really make sense.. it would make sense if it leaned out under higher RPMs or something like that, but for it to miss from a fueling issue at that low of an RPM would indicate other fueling issues then just a fuel pump... its getting fuel... maybe something electrical

Its missing around peak torque, lots of cylinder pressure there lots of load, ignition issues IS the problem... try gapping the plugs down...

what are they even gapped at now? also use dieletric grease when reinstalling the coil packs.. make sure the springs in the coils are making good contact with the plug...dont be affraid to stretch them out some to get more contact pressure against the plug...

This will be the first thing I do (regap). I'm currently using BKR7E (4644) @ .028 Does the grease go into the tip of the coil where the spring is?

Thanks a lot guys for your suggestions/help.

[flatrate]

yes just put a small amount in each end of the coil pack... make sure the gounds on the intake manifold are tight and clean.. wouldnt hurt to file it a bit on the wire side and manifold side, if you replaced the plugs and it went away, thats a pretty good indicator that something ignition related it up...

start saving for some new coils!

[mattblancarte]

I could be wrong, as I'm not a trained professional, but I'm on the side of fuel supply being the issue.

In both instances of the hiccup, your a/f is reading a lean-out. The first one at 3300-3400 rpm looks like you are leaning out to 12.1.

The second at 4000-4125 looks to be leaning WAY out to 17 a/f as it comes back in from the hiccup.

Plenty of spark, not enough fuel?

Would be surprised to find you blowing out the spark at 10-11 psi with a .28 gap. I ran a .28 gap on bkr7e plugs on my recent tune at 15+ psi. That being said, tightening the gap probably won't hurt.

If you were blowing out spark, wouldn't you expect to read a rich mixture?

Any chance you could record fuel pressure during a run?

Knock sensor?

[meet07]

How in the world is your torque that high?? Is that the benifit of keeping the factory intake manifold and TB??

And what about checking the base timing?

Hope you fix it....

[USMCgetsome]

it's the pump! not that pump but your fuel pump. lol.

[mott6904]

it goes lean because it misfires...

Im curious to hear your theory behind this. A misfire caused by lack of spark would create a rich condition.

From the video it does seem to be a ignition issue but the af graph says different.

[flatrate]

The dyno isnt going to catch a 5+ point move in less than 100 RPMS like its showing, its obviously an ignition problem, or a dyno pick up issue.

The wideband readings normally go lean because the sensor doesnt pick up unburnt raw fuel, the cylinders basicly an airpump at that paticular moment..

For a fuel pump to cause that issue is very unlikely, i mean really, is the fuel pump shutting off? intermintantly quiting at the same RPMS everytime..

It would more likely be an injector than a fuel pump.. if you wanna stay on your fuel theorys...

Im not claiming to be an expert but fueling seems unlikely IMO

[mattblancarte]

The wideband readings normally go lean because the sensor doesnt pick up unburnt raw fuel, the cylinders basicly an airpump at that paticular moment..

Nope, a wide band will definitely pick up on unburnt raw fuel... that's what it's for.

http://www.youtube.com/watch?v=1mb4VmDd0ao

To create that lean condition on the dyno graph, you'd have to remove fuel from the mix.

I'm not saying that it's 100% his fuel pump, but I'm saying it's pretty likely (based on that a/f graph) that the fuel supply is being compromised somehow.

More data would be good here, though.

[WhatsADSM]

So to be honest I have personally had this issue before and I have ended up tracking it down to either the pump or ignition (had both issues exhibit similar behavior).

Also I have definately seen some widebands where a temporary ignition event miss actually causes the wideband to read lean just as flatrate was mentioning.

Try to gap the plugs a little lower first. Maybe even temporarily wire in a 12v and ground from the battery to the coil pack harness to ensure you have a good supply and ground.

However as others have mentioned walbros are pretty unreliable pumps and I have had 3 walbro pumps die on me since I have been in this hobby and only 1 of the 3 flat out stopped flowing any fuel. The other 2 died and flowed about half as much as they should, so the car would cruise around town just fine, however when you got into some decent boost the car would break up. It would not surprise me in the least bit if that was the issue.

Good news is I am almost sure it is either ignition miss related (i.e. weak coils) or a dying walbro. So it should be relatively easy to cheap and easy to find and fix.

Edit: After watching the video I am also more inclined to think it is fuel related. That is a pretty big hickup there, and IIRC my fuel related breakups were more like that where it would have fewer larger breakups, where my ignition related issues would be typically smaller breakups. IMO give the plugs and quick gap lower to maybe .024 and if that doesn't do anything get a new pump.
Modified by WhatsADSM at 10:59 PM 3/9/2010

[mattblancarte]

After looking at that graph again, it looks like the a/f is a bit lean from 2800 rpm to 4600. The hiccups seem to be accents to a whole chunk of lean.

[ItzGenX]

Ignition misfires can cause lean spikes too (not rich) as many of you are thinking. An oxygen sensor reads exactly what it's named for, oxygen. Unburned fuel or not, if the combustion never took place, it will consist of a lot of unburned OXYGEN and fuel. This excess oxygen will register as a lean spike to the oxygen sensor due to the unburned oxygen out numbering the amount of fuel present. The oxygen sensor is just a scale that measures how much oxygen vs unburned fuel is present. When a miss occurs there is a massive amount of oxygen present compared to the unburned fuel in it.

If the pump was doing these silly hiccups, it should do it more randomly across the rpm range. For example, dyno run 1 may do it at 3k, then at 5k and dyno run 2 may do it at 2k, 5k, 6k. If it always ends up happening at the same rpm ranges, then it gives a sign to be ignition or cas problem.

Simple test can be just turn down the boost and see if the problem goes away. Doing so will reduce cylinder pressure and if the spark was being blown out, bringing the pressure down will make it run like a champ again. Usually stumbles from spark blowout happen at peak torque which is where yours seems to be having these hiccups. Reduce plug gap and see if it works better. If it does (even for a short while), then it's narrowed down to a spark problem. Now you got to see if your coils are on their way out or if it's just a weak set.

A fuel pump taking a dump leaves a different type of sign. If it's doing a random on/off symptom it would happen at random rpm under load, not always peak torque. If it were a 'weak' fuel pump then it will begin to lean out towards the top of the rpm range vs the low end. More fuel is required at higher rpm than the mid range due to more amounts of injection/combustion events per minute. A weak pump's sign of failure is a gradual lean out as the rpm gets higher due to dropping fuel pressure.

Modified by ItzGenX at 4:45 PM 3/10/2010
Modified by ItzGenX at 4:49 PM 3/10/2010

[ItzGenX]

Nope, a wide band will definitely pick up on unburnt raw fuel... that's what it's for.

http://www.youtube.com/watch?v=1mb4VmDd0ao

To create that lean condition on the dyno graph, you'd have to remove fuel from the mix.

I'm not saying that it's 100% his fuel pump, but I'm saying it's pretty likely (based on that a/f graph) that the fuel supply is being compromised somehow.

More data would be good here, though.

In the video he uses a rag which totally overwhelms the sensor with fuel and not giving oxygen much of a chance to flow into the rag.

An engine doesn't run like this as there will always be flowing air regardless of a misfire or not. Even if the supplied amount of fuel vs air in a normal situation would come out to be 12:1 afr, unburned situations leaves WAY more air then fuel present which can register as a lean blip on the wideband on a running engine.

[WhatsADSM]

Simple test can be just turn down the boost and see if the problem goes away. Doing so will reduce cylinder pressure and if the spark was being blown out, bringing the pressure down will make it run like a champ again. Usually stumbles from spark blowout happen at peak torque which is where yours seems to be having these hiccups. Reduce plug gap and see if it works better. If it does (even for a short while), then it's narrowed down to a spark problem. Now you got to see if your coils are on their way out or if it's just a weak set.

Modified by ItzGenX at 4:45 PM 3/10/2010

Modified by ItzGenX at 4:49 PM 3/10/2010

While I agree with much of what you said, particularly about the wideband reading lean under a miss.. I do NOT agree that reducing boost is a sure fire way to diagnose that it is a ignition related issue and not a fuel related issue.

Reducing the boost level will infact make the spark needed to jump the gap less, just as you are saying... However it will also make the demands on the fuel pump much less since their is less air mass entering the cylinder. Moral of the story, I'm sure when he turns down the boost the problem will get better or completely go away... However that doesn't mean it is neccesarily a spark issue, it could still be a weak pump.

[mattblancarte]

In the video he uses a rag which totally overwhelms the sensor with fuel and not giving oxygen much of a chance to flow into the rag.

An engine doesn't run like this as there will always be flowing air regardless of a misfire or not. Even if the supplied amount of fuel vs air in a normal situation would come out to be 12:1 afr, unburned situations leaves WAY more air then fuel present which can register as a lean blip on the wideband on a running engine.

I was thinking that the unburnt fuel would overwhelm the unburnt oxygen in that scenario to cause a rich condition, but what you've written makes sense.