Bucking and Poor Idle

[QuickSilverGSX9]

Alright, first off, I don't believe I have the classic idle surge. However, my idle is kind of choppy, it's enough that I and others have noticed it. To fix this choppy idle I have: Swapped ECU's, swapped MAF's, swapped injectors (from 680cc to stock 450's), tested and swapped ISC's, checked plug wires, and even cleaned my EGR vavle. As far as I can tell, I think swapping the injectors and cleaning the EGR valve has helped slightly, but that may just be my mind playing tricks on me. What else could possibly cause a choppy idle?

Second problem is that under crusing speeds, especially low throttle, the car will buck. Not violentely, but enough that it's noticable. What can cause my car to buck at low/constant throttle? I really need an insight on this, I've tried a lot of things (see above). The choppy idle may or may not have something to do with this.

-Bill

 

[LandoAWD]

Originally posted by QuickSilverGSX9
Alright, first off, I don't believe I have the classic idle surge. However, my idle is kind of choppy, it's enough that I and others have noticed it. To fix this choppy idle I have: Swapped ECU's, swapped MAF's, swapped injectors (from 680cc to stock 450's), tested and swapped ISC's, checked plug wires, and even cleaned my EGR vavle. As far as I can tell, I think swapping the injectors and cleaning the EGR valve has helped slightly, but that may just be my mind playing tricks on me. What else could possibly cause a choppy idle?

Second problem is that under crusing speeds, especially low throttle, the car will buck. Not violentely, but enough that it's noticable. What can cause my car to buck at low/constant throttle? I really need an insight on this, I've tried a lot of things (see above). The choppy idle may or may not have something to do with this.

-Bill

My money is on a pressure leak for both problems.

 

[QuickSilverGSX9]

By pressure leak, do you mean an intake leak?

-Bill

 

[LandoAWD]

Originally posted by QuickSilverGSX9
By pressure leak, do you mean an intake leak?

-Bill

Correct. Do a full pressure test.

 

[Benji]

I have a very similar problem.

Under crusing and moderate acceleration i feel the car being hesitant sometimes. When hitting 8 lbs/boost, the car misfires badly, popping exhaust, etc ... and the o2 sensor (old and NEW replacement) shows 0.00 to 0.1V. What makes it worse it that after it's warmed up completely and shut off, then restarted before it's had time to cool off, it is undriveable. It feels like it's running on 3 cylinders. I have a datalogger and have NOT noticed anything out of the ordinary. No knock, normal timing, normal airflow, etc ...

I am running a MAF-T blow through on the stock 14b and stock SMIC. Boost leak is not out of the question, but nearly impossible as I have pressure tested when this problem first started. I am ruling out spark as the cause because I have replaced the wires, plugs and coils. Could this be fuel? I am running a 190lph Walbro that is only 6 months old, stock 450's with the stock FPR.

Any advice?

 

[aaron93tsi]

i dont know why mine is doing this...but mine also pops around 8-11lbs.

 

[Kinetic Boost]

I'm also having the same problem with the weird idle and also at low trottle the car will buck as well but only at low throttle. I think its a boost leak but I did a boost leak test and I fixed all the big leaks but when I do the boost leak test my boost gauge only shoots up to 3psi so i know theres a leak somewhere, but not sure where at yet.

I also have the gm maft but with a fmic and also got my emmission controls removed not sure if that could also be a factor. I have been told that it could be the maft but im still not sure.

 

[Benji]

Originally posted by Kinetic Boost
I'm also having the same problem with the weird idle and also at low trottle the car will buck as well but only at low throttle. I think its a boost leak but I did a boost leak test and I fixed all the big leaks but when I do the boost leak test my boost gauge only shoots up to 3psi so i know theres a leak somewhere, but not sure where at yet.

I also have the gm maft but with a fmic and also got my emmission controls removed not sure if that could also be a factor. I have been told that it could be the maft but im still not sure.

I doubt it's the translator. I swapped one in my car from a vehicle that is working just fine.

 

[Kinetic Boost]

Yeah I truly think its a boost leak myself I just need to find it.

 

[QuickSilverGSX9]

Well, I performed a leakdown test like Lando suggested. It seems I may be leaking from my injectors (at the o-rings into the head). Awhile back my friend removed my injectors to look at my coil packs, when he removed them he put them on my head which was just drive and therefore VERY hot. Long story short, he melted my o-rings and the plastic end pieces to my injectors. I got new o-rings but the plastic end pieces were pretty trashed on 3 out of the 4 injectors, we tried to fix them but it didn't really work, 2 were actually completely cracked in half.

I pressure tested at 20 psi (it read 20 psi on my boost gauge and on the regulator on the compressor), but it rapidly dropped once the compressor was off...it sounded originally like the air was escaping into the head via open valves and through the TB. However, I accidentilly moved an injector and the pitch of the moving air changed. I didn't actually feel any air rushing out of the o-rings though, so I'm not positive if they are actually leaking or not. Either way, I'm trying to get ahold of new plastic end pieces for my injectors as we speak.
-Bill

 

[JuiceGsTurbo024]

whats up i got the same problem! when crusing low speed it starts to buck and feel crazy but when driving normal and taking it to 4k it feels fine and i just let the RPMS drop and then everything goes back to normal i think its something witha vacum leak or a presure leak well let me know if you fix your probelm with somethign well thanks

 

[crotchkiller]

Sounds like your belt may be off a tooth or so. You may also want to check the closed throttle switch.

 

[Lts_Fly7]

When I had this happen on my 99 DSM, i changed the plugs. worked like a charm. I dont know if thats same thing. again, im not the worlds best mechanic...by far. just my 2cents

 

[Kinetic Boost]

I also fixed my problem turned out I had a huge leak on my j-pipe. some how stupid me didnt notice it but my friend came over to help an dhe found it in about 2 seconds! I think I was just to frustrated on the car and my mind wasnt really concentrating. I also had one on the lower insulator on one of my injectors.

 

[TalonR]

I actually just fixed a problem just like this.....It was my intake gasket leaking and it was driving me nuts.....To find the leak I just sprayed some carb/fuel injector cleaner around the gaskets of both throttle body and intake. When the cleaner got sucked up and the RPM's rose, I found my vacuum leak

 

[racer]

I have same problem but im N/A !!?? What could be on mine,everyting is tested and works grate.

 

[Kinetic Boost]

Try changing your plug wires theres a guy that posted here that also has a n/t and it seemed to work for him so you may want to look into that.

 

[racer]

as i said we tested everyting that can comes on ur mind and all works good.i have aftermarket 8mm ACSEL wires that are only one year old and have like 7-8k miles on them and plugs are like 8 months old with like 4-5 k on them.We tested them one by one and all work grate.We run the engine on 3 cilindars with each plug out by time,and it was all good.I duno.All i know is that Im sick of shit and I defenetly wont buy me , , ever again.

 

[Alvaro3Jr]

Spark plug wires that are a year old doens't indicate that they are good. You should try swapping them out.

 

[racer]

maaaan,the damn wires looks like new.There is no any kind of wear going on.If i give it to u,u'll think they brand new.They are very solid and i dont think they'll ever go bad.