Strange Hesitation - Possible Miss

[JSarv]

Alright I posted this in Nasioc, but apparently you have to NOT search and ask a stupid question to get a reply. If anyone has any insight please help me out.

I'm going to do a comp. test tom. night and through my 255 pump in.

Sorry I don't feel like typing it again but here is the link

Odd hesitation 2/3/4th - Searched - Factory 2.0L Turbo Powertrain - NASIOC

Any input will be greatly appreciated

Jerod

[Timdog1650]

Wow, well it seems like you covered most of your bases. I doubt very much that compression is your issue if the car runs normally most of the time. How many miles are on the car at it's current level of tune, would there be any reason to even suspect a blown motor?

Fueling definitely sounds like it could be an issue, since a slight hesitation could be indicative of either a dying fuel pump or a clogged injector, but if the car runs normally most of the time and starts on a cold motor I would doubt very much that your pump is kaput.

Since you're doing the compression test, check the coil packs (swap them around cylinder to cylinder see if anything changes), then maybe check to make sure everything is installed/clipped/torqued properly. It's weird that you're getting what sounds like a characteristic misfire but not throwing a code. Any chance it's the open loop/closed loop transition of a UTEC that is perhaps causing some hesitation? It can seem intermittent since you're rarely at the same load site every single time you accelerate through an RPM based on where your foot is on the pedal.

Sorry I can't be more helpful, but this is really an oddball problem. If you can't find any good answers, try PM'ing the description of your problem to either RiftsWRX or AZscoobie on Nasioc, they might throw you a bone and have something helpful to try to diagnose the problem.

~Tim

[JSarv]

Wow, well it seems like you covered most of your bases. I doubt very much that compression is your issue if the car runs normally most of the time. How many miles are on the car at it's current level of tune, would there be any reason to even suspect a blown motor?

Fueling definitely sounds like it could be an issue, since a slight hesitation could be indicative of either a dying fuel pump or a clogged injector, but if the car runs normally most of the time and starts on a cold motor I would doubt very much that your pump is kaput.

Since you're doing the compression test, check the coil packs (swap them around cylinder to cylinder see if anything changes), then maybe check to make sure everything is installed/clipped/torqued properly. It's weird that you're getting what sounds like a characteristic misfire but not throwing a code. Any chance it's the open loop/closed loop transition of a UTEC that is perhaps causing some hesitation? It can seem intermittent since you're rarely at the same load site every single time you accelerate through an RPM based on where your foot is on the pedal.

Sorry I can't be more helpful, but this is really an oddball problem. If you can't find any good answers, try PM'ing the description of your problem to either RiftsWRX or AZscoobie on Nasioc, they might throw you a bone and have something helpful to try to diagnose the problem.

~Tim

Wow quick reply! I've thought about the swapping the Coil packs out, will give it a shot, I'm running enginuity on the stock ECU.

OL/CL transition seems to be on par. I've been learning more about it, but this happens at a steady throttle. I can't remember the exact % but its somewhere around 17% throttle. I did also notice its not noticeable in 1st but in 2nd and 3rd its very noticeable.


I know I have an exhaust leak, and I'm 99% sure its post turbo. But I'm going to replace all the gaskets from the engine back (ordered pre-turbo gaskets today)

Half of me is praying i have a blown ringland. The other half doesn't want to deal with that just yet.

My beater will be done in about a week so I wont have to drive the Rex everyday.

Anyway, I'm thinking its a fuel problem, I know its running rich, so it could be a dip in the A/F and my datalog isn't picking it up.

again thanks, you were very helpful. Maybe I'm just imaging things!?! Could be that 600whp Vette I drove Sunday, making things feel "not Right"

lol

[SD_GR]

Since it could be an A/F issue it could be something even simpler -- like a dirty MAF. Have you considered cleaning the MAF? You can pick up some electronics/plastics safe spray at Pep Boys for $6 or so and give it a shot, see what happens.

[JSarv]

Since it could be an A/F issue it could be something even simpler -- like a dirty MAF. Have you considered cleaning the MAF? You can pick up some electronics/plastics safe spray at Pep Boys for $6 or so and give it a shot, see what happens.

Cleaned it last week when I checked my plugs out. No help.

[Death To Ricers]

I am having almost the same problem, but after the hesitation there is kinda like a jumping. This is how mine goes: Throttle-Hesitation-jump-jump-jump-normal. It seems like it is only when the AC is on too. I am 100% stock.

[SD_GR]

Jerod, could you have a vacuum leak somewhere? This could account for the delay in building boost.

Death To Ricers, are your MAF and air filter clean?

Neither of you guys is getting a CEL? Ever?

[Death To Ricers]

Death To Ricers, are your MAF and air filter clean?

Neither of you guys is getting a CEL? Ever?

Yep, no CEL. I will check my MAF, and air filter.

[JSarv]

Jerod, could you have a vacuum leak somewhere? This could account for the delay in building boost.

Death To Ricers, are your MAF and air filter clean?

Neither of you guys is getting a CEL? Ever?

Could be, but I am seeing consistent 9lbs of vacuum at idle. I "could" have a vacuum leak, but I've ruled that out.

Yes I DID have a cel. I did a little experiment a week ago, trying copper plugs. I bought #6 and #7 copper plugs, datalogged with my stock Iridium #6's. Did the same run with #7 copper's, results were actually noticeable in temps and what not, boost came on a bit sooner when back to back runs were done. Then I shut it down went to restart it and it was having a single misfire (forgot which cylinder).

Swapped to #6 coppers and just didn't seem to run the same, was getting a slight amount of fine feedback (nothing serious like -1.05 in low load/low rpms)

Put back in the Iridiums, now I've always "felt" this hesitation, but after I did the "plug test" it seems that it has gotten worse.


Rice: sounds like you have an A/C clutch issue. Could be Maf as well.

But I'm 99% sure I'm in OL when this is happening.

17% throttle low load.
That should be OL right?

My stored Fine KC is 0's.... My timing is INSANELY conservative. IAM is at 16 *Has never dropped*

[SD_GR]

Well wait -- is the hesitation happening at map transition (from OL to CL)?

Are the tubes to the BCS OK?

Are the ground connections OK?

Death To Ricers: With the motor on, pop the hood. Turn on the A/C, and look at the A/C clutch to make sure it's engaging (it should be). What you're looking for is the little "triangle" that's "inside" the A/C comrpessor's pulley to start spinning when the A/C kicks on. If it does, and there are no weird noises when the A/C comes on/off, I know of no other way to diagnose an A/C clutch problem at home. OTOH it could be that your problem is really happening under load, and the A/C is presenting that load. Does the hesitation happen uphill with the A/C off but in a high gear ratio? If so, suspect MAF/air cleaner first IMO.

[JSarv]

Well wait -- is the hesitation happening at map transition (from OL to CL)?

Are the tubes to the BCS OK?

Are the ground connections OK?

No transition is smooth, I believe right when it should be (like I said I'm still learning the whole "OL/CL" thing) - The delay is VERY minimal nothing strange in the transition.

I think its in Open Loop (constant throttle low load) when this is happening. So could it be a sensor?

Grounds look good, tom. I'm also going to do the "ground mod"

[SD_GR]

So could it be a sensor?

I believe so, but don't know which one it could be. My first guess, the MAF, has already been eliminated.

[Timdog1650]

Try doing an ECU reset. You might pop a code once the ECU has been reset, at which point that might help. Also, note if the problem is better for a while after a reset or resumes immediately after the reset.

[JSarv]

Try doing an ECU reset. You might pop a code once the ECU has been reset, at which point that might help. Also, note if the problem is better for a while after a reset or resumes immediately after the reset.

It has been reset about 4 times since the "plug test."

The only thing that I have noticed with the MAF is I am not seeing G/S like other logs I have seen. I am seeing around 200g/s at 6k in 3rd gear. Some other TD04 logs I have seen around 205-210 at the same revs.

I guess it could be MAF, but nothing else is strange.

When should boost come on with the TD04? I thought around 2800 in 3rd... ?

[SD_GR]

Consider removing the TPS connector, eyeballing it closely, and putting it back on. I almost wish you had a PO122 to complain about, that'd make everything simpler. I remembered this older thread:
http://www.clubwrx.net/forums/genera...lp-please.html

I wonder if that's useful at all... without a code to go with, it's harder to troubleshoot.