Idling Hiccup/Intermittent Stumble, Diagnosis?

[Ski Bum]

I was hoping that some of you Mitsu gurus could help me diagnose an intermittent idling hiccup my GSX has. The hiccup is intermittently present at any rpm level while in neutral, I have not noticed any surging or power loss while driving.

First I suppose I should list what I have already replaced/fixed and we can go from there. My profile has my current mods as well.

- NGK BPR7ES, gapped to .028" (could they be too cold)
- New Accel 8mm wires
- Cleaned throttle body
- Vaccum/boost leak test (replaced gaskets, no longer leaks)
- Timing belt, balance belt and all drive belts
- Timing Belt Idler Pulley
- Timing Belt Tenshioner Pulley
- Timing Belt Hydraulic Tenshioner
- Balance Shaft Belt Tenshioner Pulley
- Water pump
- Oil change mobil one and factory filter (alot smaller than fram that was repalced?)
- new Oil cap
- New BISS screw and o ring
- new Thermostat (160*)
- new Radiator cap
- flushed coolant and replaced
- new fuel filter
- new o2 sensor
- refurbished ECU (motoguys garage from ebay)

Hopefully I didnt leave anything out. Along with that I have adjusted the base timing to 5 degrees advance and set the idle the best I could to 800rpms.

The car passed smog with flying colors and was actually very clean, below average in 2 of 3 categories, even here in California.

Possible problem areas:

- The car has a catylitic converter which could be clogged? Not sure about that, am planning on replacing with straight pipe.

- There is a slight exhaust leak between the turbo exhaust port flange and o2 housing flange.

- Upon inspection of the plugs there is carbon fouling on the lower half of the plug (on the threads, not the tip). Along with the carbon fouling on the plugs a black liquid sputters out of the exhaust tip. I dont have an AFR gauge but my hunch is that I'm running rich. Could the hiccup I'm hearing be the rich exhaust reigniting within the exhaust system?

Aside from that is there anything I have missed?

 

[I_eat_DSM's]

I did not see a fuel pump in your profile, you replaced the fuel filter, you replaced most of your spark stuff, and you said you don't notice anything while driving so that leads me away from thinking that you have a spark or a fuel problem. I would check your timing and make sure it's dead on, and one thing you can do to get an idea of how rich you are running is to take a whiff of your exhaust. (sounds weird I know but if you work on DSM's enough you'll be sniffing lots of exhausts while trying to figure something out)


The possibilities I see are your hacked MAF causing you to have a little hiccup, (wouldn't surprise me) you're igniting a little bit of rich mixture in your exhaust, (you passed smog well so I kinda doubt it) your possibly clogged cat is giving you a lil trouble, (quite possible turbo cars don't like tons of backpressure) or your timing is a little off.

I would start with the timing, and end with putting in the straight pipe. If you don't notice anything while driving and your timing is fine I personally wouldn't worry about it too much. If it's a true problem the monster will grow worse and then decide to rear it's big ugly head and then it'll be easier to diagnose.

Lemme know how it goes!

 

[Ski Bum]

I did not see a fuel pump in your profile, you replaced the fuel filter, you replaced most of your spark stuff, and you said you don't notice anything while driving so that leads me away from thinking that you have a spark or a fuel problem. I would check your timing and make sure it's dead on, and one thing you can do to get an idea of how rich you are running is to take a whiff of your exhaust. (sounds weird I know but if you work on DSM's enough you'll be sniffing lots of exhausts while trying to figure something out)

Lemme know how it goes!

I'm planning on putting in a walbro 190 soon along with a rewire kit. That is definitely on the list of things to do.

The timing is as dead on as I can get it by just looking at the mark at the angle available.

The exhaust smells a bit like unburnt fuel and as I mentioned before sputters a black, carbon mixed liquid. The car likes to mark its territory with the stuff if I let it idle in one spot too long

 

[I_eat_DSM's]

I would recommend trying an unhacked maf and see where that gets you. The 2g upgrade is a good thing if you aren't going to go with a MAFT setup!

 

[KoolTrix]

I'm not sure if they will help you...but I'm having idle problems, and when we unplugged the MAP Sensor, my Car's Idle dropped, but hestitates...so I called a local mechanic, he suggested I replace it, you know like fix the Mass Airflow blah blah blah...Check into that maybe...I'm not mechanic, and Probably shouldnt be giving out advice...but just a suggestion to check out. I'll bite my tongue if I'm way off basis...LoL...
(Just trying to help...)

 

[Ski Bum]

I would recommend trying an unhacked maf and see where that gets you. The 2g upgrade is a good thing if you aren't going to go with a MAFT setup!

I tired your suggestion and put in a stock MAF using the same filter as was used with the hacked MAF. With the stock MAF the car idles MUCH smoother. There are however 2 things that are happening now that didnt happen before.

1. Once the car reaches normal temp the idle falls into a pattern of rising and falling about 150-200 rpms between 750-950 rpms. The time between each change is about 1 second, basically back and forth, as if the ecu is trying to stabilize the ecu and then something stops it and the cycle continues. In conjunction with the rpm's rising the vacuum drops and then returns as the rpm's drop again. Basically the rpm gauge and the vacuum gauge do the exact opposite, one rises while the other falls and then the opposite. The vacuum reading is from both the factory boost gauge and an Autometer mechanical boost gauge.

Could this be due to one of the "idle surge" culprits? ISC, TPS? Why would this new pattern arrise from an unmodified MAF and not from the hacked MAF I had in it?

2. At WOT after 5500 rpm's the car starts to studder. It appears like fuel cut to me. This never happend with the hacked MAF. btw, My MBC is set at 14psi. Am I getting too much air or too much fuel? (no afr either )

 

[I_eat_DSM's]

Fuel cut is a massive JERK as the ECU cuts off the fuel and you wonder if you just hit a brick wall, or if that was your first taste of fuel cut. I don't think you are hitting fuel, but I want you to do this http://www.vfaq.com/mods/BISS-1G.html and tell me how it works out!

 

[i'm boosted]

An suggestion for you number two issue appears to be ignition, either plugs or wires. Check your plugs again. If they appear to be ok proceed to wires. I was at the track and at about 5500 - 6000rpm my car would studder to. After explaining the issue to one of my buddies that was there with me, he told me to replace the plugs. After replacing them no more studdering. Again either plugs or wires.

-Brian

 

[Ski Bum]

Fuel cut is a massive JERK as the ECU cuts off the fuel and you wonder if you just hit a brick wall, or if that was your first taste of fuel cut. I don't think you are hitting fuel, but I want you to do this http://www.vfaq.com/mods/BISS-1G.html and tell me how it works out!

I have felt that, but only while on empty and making a sharp turn, starvation I suppose. This is more of a studder than hitting a wall.

I have done that exact adjustment following those instructions (I have it printed out sitting on my desk right now ) but that was with the hacked MAF. I will repeat the process with the stock MAF and report back, thanks again.

An suggestion for you number two issue appears to be ignition, either plugs or wires. Check your plugs again. If they appear to be ok proceed to wires. I was at the track and at about 5500 - 6000rpm my car would studder to. After explaining the issue to one of my buddies that was there with me, he told me to replace the plugs. After replacing them no more studdering. Again either plugs or wires.

-Brian

I'm sure my plugs are fine, they are brand new, less than 200 miles gapped at .028", 1 step colder NGK's.

Short of testing the resistance of the wires what should I look for? Could it berelated to the coil as well?

 

[Ski Bum]

Ok, I tried the BISS adjustment per the instructions and the idle didnt seem to change at all. It still wanders up and down while the vacuum changes.

I did notice a hissing coming from under the intake manifold where that junction of vacuum lines is. I havent yet been able to pin point where it is coming from but I'm going to hook up a compressor and do a pressure test and see if I can find it then. They are really hard to get to though.

EDIT* I did the pressure test and at a steady 20 psi there were 3 leaks:

1. the oil cap barely leaked
2. the oil dipstick barely leaked
3. the throttle linkage on the throttle body. Right where the the shaft connected to the throttle linkage inserts into the throttle body leaks. While it was leaking I could change the hissing sound from the escaping air and almost stop the leak by manually opening and closing the throttle as well as wiggling the whole spring/cable/throttle linkage piece around.

Is there a seal of sorts that could be worn that is causing that leak? Should that part of the throttle bodyhave any leaks?

I did try the old fashion trick of spraying carb cleaner on potential vacuum leaks while the engine runs on that part of the throttle body but there was no change.

EDIT* just found this http://www.ca.dsm.org/faq/tb-shaftseals.html , seems to me like the thing to do.

 

[I_eat_DSM's]

It could be the seals where your between the TB and the intake manifold or between the TB and the J pipe but I doubt it. People make a big fuss about having to replace the TB shaft seals but isn't that big of a deal. After you replace that your idle should calm down if the boost leak is your only problem. How many inches of mercury to do you pull at idle?? Also have you eliminated your EGR? If not I highly recommend it because it removes ALOT of lines that will possibly create boost leaks!

Your Hayne's or Chiltons manual will have instructions for checking your coil, and if your let the car idle at night and watch the plug wires you can sometimes see arcing if they are bad. I wouldn't try too hard to diagnose the studder problem until you can get your car to idle properly.

If you cover up the leaks on the TB with your fingers while the car is running does it idle fine? If not then it probably isn't the source of your idle problem. Here's a good way to check idle issues.

#1 Make sure the engine temp sensor wires are connected. Check and make sure the wires going to the sensors on the coolant outlet elbow are connected. On one side there should be a sensor with two wires on it and on the other side there should be a sensor with only one wire.

#2 Make sure that the idle switch is connected and that it is being depressed all the way when the throttle is closed. It is the switch with only one connector running to it on your throttle body.

#3 The lines that connect to the intake mani AFTER the TB are the most important for your idle because they are the main places for a VAC leak to occur because it's INSIDE the intake mani AFTER the throttle body where the vac is by FAR the strongest. However, try this: Pinch off each of the four lines coming off the throttle body with your fingers. (four assuming you haven't done an EGR delete) Check the lines on the intake mani. If I'm not forgetting something (it's 4:40AM) there is one that runs to the PCV and is very short, one that runs to the brake booster that is one the back, one that runs to the fuel pressure reg, and another on the front a few inches torwards the driver's side from the PCV hose. Check all that and then let me know how it's going man!

 

[andymoraitis]

Short of testing the resistance of the wires what should I look for? Could it berelated to the coil as well?

I think you've received some excellent advice in this thread and I can appreciate that you're keeping us well informed on everything you've tried. I do think you need to test the coil packs and rule them out as a potential problem. Nevertheless, you're going in the right direction. As far as the wires, I had a bad set when I first bought my car and while the resistance checked out fine, I replaced them anyway and it helped in eliminating my stuttering issues. Since yours are new, you may want to check the coil packs first before doing so. Also, unless you're running some serious boost, I would go back to a stock heat range plug. I actually run on stock heat range under heavy boost (26psi) so you may be loading the 7's up (it's a possibility). I'd like for you to read your plugs or post a picture of them so we can read them for you. Also, try reducing the gap a bit to .026 and see if that helps the situation.

Keep us posted.

Andy

 

[Ski Bum]

I_eat_DSM's, I will run through your list and check out thiose things. I wont be able to do so untill wednesday though, work

I have blocked off the EGR and plugged the 4 vacuum lines that plug into the throttle body.

In regards to the idle switch, I have a feeling it may be intermittently bad. Sometimes when I unplug it the idle will rise and other times there is no effect.


andymoraitis, I'll pull the plugs and post a picture and also run with stock heat range and see how it goes.

Thanks for the help guys!

 

[I_eat_DSM's]

When you do the plugs you need make a good hard WOT pull, shut the car down immediately, and then pull them to be able to tell anything.

 

[Ski Bum]

When you do the plugs you need make a good hard WOT pull, shut the car down immediately, and then pull them to be able to tell anything.

I havent heard of that method before but it makes sense. I should be able to perform some of these tests tomorrow. I'll post the results.

Ok, I pulled the plugs and took some pics of them. I'm no expert but they look normal to me. I went ahead and replaced these plugs (BPR7ES) with some stock heat range NGK's (BPR6ES) to see how they work.

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I also checked all of the coolant sensors and they were all connected and appear to be working properly, however I plan on testing them with a multimeter.

 

[Ski Bum]

I added some pictures to my previous post of the plugs after some WOT pulls.

Also I just ordered replacement oil seals for the throttle body shaft. NAPA was able to get them straight from Kentucky for $9 a piece. I should be able to dissamble the throttle body and replce the seals this weekend. After that I'll do another pressure/leak test and see if the throttle body shaft is the only leak I have :fingers crossed:

 

[I_eat_DSM's]

Hrmmm.... I'm not the greatest plug reader in the world since that's more of an old school trade but they look a little lean. Was that RIGHT after a WOT pull? As in WOT, turn off car, and then pull over?

 

[Ski Bum]

Hrmmm.... I'm not the greatest plug reader in the world since that's more of an old school trade but they look a little lean. Was that RIGHT after a WOT pull? As in WOT, turn off car, and then pull over?

Yep, like neighbors screaming at me as I run WOT down the street then jump out of the car and burn my hands I'll do the same thiong with the stock heat range plugs and see if there is a difference.

I'm gettin an EGT gauge this coming tuesday so I'll have a pretty good idea then if I'm running lean or rich. I'll keep my fingers crossed for 1300* or below.

Also Napa jut called saying seals are in so I'll do that today and see how she runs afterwards.

*EDIT* I pulled the TB and dissambled it exposing the old seals, one had split in half and the other while still intact was hard as a rock. They popped out no problem, I polished the shaft and cleaned the TB thoroughly and repalced the seals with the new Chicago Rawhide seals. I reassembled everything and then adjusted the TPS so it read .9k ohms at closed throttle. At WOT it was supposed to read 5k ohms but mine read 5.7k ohms which may be ok considering how old it is, I hope at least. Next I decided that I would P&P the throttle body intake elbow as well as polish the outside for some bling appeal

I also checked the resistance of the ISC sensor wire that routes into the wiring harness which is supposed to register between 28-31 ohms. With my multimeter I could not get any readings other than 77k ohms. With the multimeter set at 200 ohms I couldnt get anything to register? Maybe I did something wrong? Could the resistance be that off?

I'll reinstall the TB today and post back haow she runs and how much PSI it will hold now.

 

[Ski Bum]

Ok, So the newly sealed TB is back in the car along with a properly adjusted TPS. I also cut away alot of the intake filter box and recharged the K&N filter that was really dirty.

With everything back together the varying idle is still there It sometimes runs as smooth as a sewing machine then it will change and sputter at around 500 rpms then sit at 1200 rpms for a few minutes, it never quite settles. I'm thinking the ISC may be defective.

While driving I am getting more boost spiking then before. The boost will hit the 14psi I have the MBC set to then spike to about 16-17 by redline. Also I am now definitely hitiing fuel cut. During WOT at close to redline the car falls on its face and feels like hitting a wall. Could the boost spike be raising the boost to high for the stock fuel system, especially now that I have the stock MAF in?

I havent yet run another pressure test to see if there are any other leaks, will do so asap.

 

[I_eat_DSM's]

Definitely sounds like you have a boost leak. You are probably spiking because you are leaking enough pressure somewhere to mess with the MBC's operation, and you are probably fuel cutting becuase you are wasting air with the leak.

 

[andymoraitis]

The plugs look OK so there's no crazy revelation there. I think you need to start looking at the ISC and TPS to verify that they're working correctly. I have very small misses at idle, but no surging like you have. I also agree that another boost leak test is in order.

Keep at it, you're almost there!

Andy

 

[Ski Bum]

Ok, I ran another boost leak test. Anything over 15psi and the oil cap and dipstick start to leak. I bought a new oil cap and the dipstick could be replaced as well. I managed to duct tape them both down to keep them sealed to continue the test. Should they still leak at that pressure? At 23psi two things occur, 1) the fuel pressure regulator begins vibrating which creates this harmonic resonance sound sort of like running your finger across the top of a wine glass. The vacuum line that goes from the FPR to the intake duct eventually wants to pop off from the pressure. I pinched off the line to bypass that and revelaed that 2 of the injectors leak at where they meet the block and further up the shaft of the injectors. The dealership, amazingly has the lower seals instock so I'll pick those up, replace and see how it goes.

 

[I_eat_DSM's]

I wouldn't be surprised if it were your lower injector seals giving you all this hell. I've seen it before, and I know I'll see it again. I hope they fix it for you!

 

[Ski Bum]

I wouldn't be surprised if it were your lower injector seals giving you all this hell. I've seen it before, and I know I'll see it again. I hope they fix it for you!

Got the new seals in and it now holds the 23psi no problem. The old seals were rock hard and full of fractures.

Now, at 24psi the valve cover gasket starts leaking just a little bit on the left front corner of the block. I figure that might be ok untill it develops further.

*EDIT* I believe this is whats called irony.

 

[Ski Bum]

I'm about to set fire to this car

So After I installed the new injector seals, I start up the car, it turns right over idles up to about 1800 smoothly then tapers down to 800rpms and purrs. I'm thinking, great I'm making progress. I then proceed to to drive the car, slowly at first then made a few WOT passes so I can watch the boost for creeping and get a feel of how things are. It ran great,no fuel cut and no boost spikes, 14psi all the way to redline as it should be, the way have it setup. I decide that I'm feeling so good that I'd treat the GSX to some octane booster and a full tank of gas. As I'm pulling into the auto parts store the car begins to sputter really bad. It felt like it wasnt getting any fuel. I'm thinking, man did I forget to connect something right, are the injectors seated right? I run in grab the octane booster and start the car again, still sputtering. Now it will barely move. The normally 3 minute drive back home from the parts store takes me 10 as I limp along. Something is wrong

Once home I checked the timing, dead on. MAde sure everything is connected, check. I then pulled each plug wire off indivdually to see what happens. Cylinders 4, 2 and 1 are firing normally while cylinder 3 is not firing at all. I pulled the plugs, checked out ok, tried another set just incase, same thing. I then check the coild, plenty of spark all the way to the end of the wire. I then performed a quick compression test and then depression set in. Cylinder 4 130, cylinder 3 120, cylinder 2 110, cylinder 1 120. Something is wrong. I ran a compression test a month ago and got 152 from every cylinder, textbook.

What I am thinking is that all of the fine tuning and updating I have been doing has begun putting more and more stress on something internally. Before I sealed the engine pressure was able to escape prolonging something that was already breaking. Once everything was tight, all the pressure was then forced on that part that was breaking. They always say that parts tend to wear out together and when you replace one you should replace them all.

I'm thinking back now to an earlier instance where I was getting a stange noise from the engine. It was sort of like ball bearing rattling around while the engine wound down after bringing up the rpm's. Someone said it may be a spun bearing(s)? When I first got the car the timing belt and balance belt was a mess, probably the cause.

Anyways, I dont know what to do now. Leak down test? New motor? Can I pull the valve cover off and see whats going on?

On top of this I have an appointment wednesday at the dealership for warranty work on the transfer case!