At Wake the Dragon this past April, a strange issue popped up on my '04. At mid RPMs and low throttle angle, I intermittently get a significant bogging (almost like it's running really rich). Sometimes it's enough that the car will actually refuse to accelerate, and it kind of coughts and sputters. I've witnessed this in 2nd & 3rd gear agressive driving when transitioning between brake & light gas. I've also experienced it in 4th gear cruising on the street, and 6th gear on the highway at high speeds. It is usually between 3k & 4k rpm, and when I've got a very light engine load (just above costing). If I increase throttle angle when it starts to bog, it only gets worse.

I've noticed that my fuel economy seems to be worse lately, even on mostly highway tanks. The car isn't showing any CEL's, and isn't pending on any either. Billman tried the MAP thump and it didn't seem to have any effect. I've run fuel injector cleaner through it and that didn't seem to have any effect.

My primary thoughts are MAP or primary o2 sensors as the culprit, but without a CEL it's rather hard to diagnose. I've just been driving it around like normal lately, hoping eventually the culprit gets worse and I get a CEL.

The car's powertrain is completely stock except for a cooling plate (billman thought this could be the culprit, but experiencing the issue at highway speeds tells me probably not), and SPEC clutch. Nothing was changed on the car around the time the issue surfaced.

I'm lost at this point - anyone out there got some thoughts?

 

Do a compression check or it could be heat blog

 

If it happens at a specific engine rpm it could be your TPS.

 

I've had it happen multiple places between about 2500 & 4000 rpm, but I wouldn't say it's consistantly the exact same places all the time. Probably unlikely to be multiple bad spots in that range on TPS, right?

Also, wouldn't it be more consistant if that were the case?

(hope i don't sound argumentative - I do appreciate the ideas!)

 

I don't think it's heat bog since i've experienced it even on the highway when i'd been going a steady 70+ for at least 20 minutes.

I could do compression check, but hoping for more simple diagnoses to start with. Dang, I don't even know where that gauge is anymore!

 

its probably something else

 

Coilpacks/ plugs? I'd just pull the plugs..bogging is becase the cyl doesnt fire eithier cuz of bad ignition/bad mix, right?

so if your coilpacks are on its way out/plugs are fouled badly you might get some "bogging" which would actually be misfiring, but if it didnt misfire enough the CEL might not illuminate? I had this happen on my camaro..I didnt click on the plug wire til it clipped, and it fell off - I ran on 7 cyl fine for miles until I romped on it, when it did I could FEEL the shudder...then, when I let off, it felt fine...the CEL illuminated after I could feel the misfire myself.

 

Oh, and doesnt the TPS only check the THROTTLE position? not RPM? So if it WAS the tps, if you were evenly on the throttle it would do that, right? Isnt it easy to check? DMM, check the voltage out - if its not a smooth transition from 0->0.5ish(forget the actual number) then its a bad TPS.

 

i checked plugs along with billman back at wake the dragon - no signs of any issue. good thought though. I may pull them again to see if it's gotten any worse.

 

Do you still have a cat? A blockage in the exhaust will cause that same type of problem. It is possible that the cat material is collapsing.