Hello all! I couldn’t find a thread with specifics of this issue without the problem being the basic things i replaced/fixed down below.
I recently bought an 01 gs300 with 163k and it had a hesitation on throttle snaps/jabs and felt like it was stuttering on the test drive. NBD this is my 3rd gs300 and i thought i could fix it easy.
Previous owner said he had done spark plugs, so i checked the usual ignition coil connector suspects, as well as the wiring to the connectors, BOOM one of them was all jacked up and the wiring harness to the connectors was green and corroded. Put a new set of NGK plugs in, replaced coil connectors and rebuilt the wiring harness til i found good wires with no corrosion, also found a vacuum leak with the smoke tester (fixed it), and threw known good coil packs, wires and the throttle body from my parts car in.
Car was running way better if you drove it like a grandpa, still had the throttle snap/jab issue where it bogs down and misfires BUT it was driving and idling okay as long as you didn’t get on throttle too fast. Drove it to work one day acting how it normally has, went to leave and when i got in and started it up the idle was rough with the occasional misfire, tried driving it home and it just bucked and stuttered so bad it was unsafe to drive. Eventually made it home and had codes for every cyl misfire except 5 and a random misfire code as well. Also noticed if i reset the ecu by disconnecting battery it would idle smooth with no misfires and drive how it was before just still didn’t like hard throttle snaps. Once it re learns values it runs like crap again.
Sorry for the book i could give more info but that’s the basics of it. I have access to techstream at work and could provide more info and data if needed. Thank you for any responses and advice for things to look for.
I recently bought an 01 gs300 with 163k and it had a hesitation on throttle snaps/jabs and felt like it was stuttering on the test drive. NBD this is my 3rd gs300 and i thought i could fix it easy.
Previous owner said he had done spark plugs, so i checked the usual ignition coil connector suspects, as well as the wiring to the connectors, BOOM one of them was all jacked up and the wiring harness to the connectors was green and corroded. Put a new set of NGK plugs in, replaced coil connectors and rebuilt the wiring harness til i found good wires with no corrosion, also found a vacuum leak with the smoke tester (fixed it), and threw known good coil packs, wires and the throttle body from my parts car in.
Car was running way better if you drove it like a grandpa, still had the throttle snap/jab issue where it bogs down and misfires BUT it was driving and idling okay as long as you didn’t get on throttle too fast. Drove it to work one day acting how it normally has, went to leave and when i got in and started it up the idle was rough with the occasional misfire, tried driving it home and it just bucked and stuttered so bad it was unsafe to drive. Eventually made it home and had codes for every cyl misfire except 5 and a random misfire code as well. Also noticed if i reset the ecu by disconnecting battery it would idle smooth with no misfires and drive how it was before just still didn’t like hard throttle snaps. Once it re learns values it runs like crap again.
Sorry for the book i could give more info but that’s the basics of it. I have access to techstream at work and could provide more info and data if needed. Thank you for any responses and advice for things to look for.
If ignition / harness / battery terminal issues are fixed, then I would suspect fuel pressure issues. Demand for fuel increases at high acceleration speeds, and often on older cars the fuel pump / filter / strainer is not delivering enough fuel at that point.
If not, you will need to do a compression test and cylinder leakdown test to sort out head gasket issues.
If not, you will need to do a compression test and cylinder leakdown test to sort out head gasket issues.
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If not, you will need to do a compression test and cylinder leakdown test to sort out head gasket issues.
fuel pressure was in spec around 45 psi. will be doing a compression and leakdown test either today or tomorrow to rule the head gasket out. used the combustion gas tester that you put on radiator or reservoir and it came out good but idk how much i trust those things. will report back Originally Posted by DundukovEM
If ignition / harness / battery terminal issues are fixed, then I would suspect fuel pressure issues. Demand for fuel increases at high acceleration speeds, and often on older cars the fuel pump / filter / strainer is not delivering enough fuel at that point.If not, you will need to do a compression test and cylinder leakdown test to sort out head gasket issues.
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Yeah, they are not reliable at all.Originally Posted by jacefletch
used the combustion gas tester that you put on radiator or reservoir and it came out good but idk how much i trust those things
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Head gasket is good after running tests. The MAF readings have always been off and not what they should be on the techstream so i decided to get a new one and it drives good again, same as how it was after i rebuilt the harness, changed plugs, etc.Originally Posted by DundukovEM
Yeah, they are not reliable at all.
still having the same issue where if you snap the throttle hard it’ll sliiightly misfire just a few times then rev up normal, and if you get on throttle too hard after stopping or doing a rolling stop it’ll have just a slight hesitation but then drive fine no issues or misfires moving.
also has the occasional idle misfire sitting at a stop light in drive or even in park after you start it, cold or warm doesn’t matter. Thinking i might have to go further back on the harness and rewire it more as i don’t think i got all the corroded wires. any more info is appreciated tho to steer me in the right direction.
I think you got them all already. Fuel, air, compression and ignition. That's it.
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One thing i did try this week was unplugging the TPS while the car was running and misfiring real rough during idle and of course the idle shot up to like 1500 rpm but it ran really smooth and im wondering if the wiring has corroded to the TPS. i have three known good TPS’ and they all acted the same when swapped around which is leading me to believe that could be the issue. The TPS readings looked fine on techstream tho so it’s just throwing me for a loop. Originally Posted by DundukovEM
I think you got them all already. Fuel, air, compression and ignition. That's it.
The TPS cannot cause a misfire. It can mess up the RPM and throttle response, but not the misfire. The ignition is much more likely.
Driver
I disagree with DundukovEM, if your car runs fine for a few hours and then starts to stumble, that actually might be the TPS. These cars have a hybrid throttle body system, where it's only cable driven to a certain point and the computer handles the rest. Imagine dumping enough fuel into the cylinders to go WOT without the throttle position sensor knowing where it is and defaulting to only doing the cable-driven action, and you can see where a misfire could happen without tripping any codes. WOT fuel, with 65% throttle. Of course WOT is a dramatic example, but any discrepancy between what the engine is told to do and what the engine is able to do can cause a misfire in this scenario.
I'm guessing you already checked fuel trims and those look normal. Do they change when you've just started it after the battery's been disconnected vs. when it's misfiring later? The weird one I had was that it passed a vacuum leak test, so we were gunning after the fuel system until I found a hole in the air intake resonator box that sits between the MAF and the throttle body. Didn't show up on the vacuum leak test, or maybe I just missed it, but was making it run horrifically lean.
Check your O2 sensor voltages? If your upstream O2 sensor is giving weird, unreliable readings, your fuel trims can become erratic.
You've ruled out most of the common suspects, but there's a couple elephants in the room; timing, and the ECU.
You could have a VVT system problem of some sort. That causes it to stumble at higher speeds, but also can cause misfires at idle. I'd verify all the stuff that's easy to get to, like the VVT solenoid, the voltage to the solenoid (need an oscilloscope to view that), and if there's a blockage in the VVT feed line. If all of those check out fine, it's *probably* not your ECU, but it still might be your timing. Biggest suspect after that is the VVT timing gear.
If any of these things are off, you can drive around for literally a thousand miles before the check engine light comes on with a VVT system or timing related code. On my car, if you disconnect the battery, it might run for hundreds of miles without the code coming back, or only 50. If you're disconnecting the battery a lot, it wouldn't surprise me if you never got a code for what the actual issue is, be it the TPS or the VVT system.
The ECU itself, like I said before, you usually need an oscilloscope to see if it's good or not. Backprobing the usual suspects to see if there's any issues is always a good option. Especially since you seem really trigger-happy with replacing wiring, have you been measuring the wiring and noticed voltage drops and/or extra resistance? Before replacing wiring, have you ruled out that it doesn't go all the way back to the ECU? ECU can drop voltage and end up not controlling things properly. It's rare, but it happens, and it's one of the reasons I said to backprobe the VVT solenoid with an oscilloscope. I'd do the same to the ignition coils and fuel injectors, too, just to be safe. If it's all cylinders except 5, you should only need to do all this on one cylinder.
These engines are new enough that fuel, air, compression, and ignition are no longer the only things you need to worry about. On these computerized systems with all the bells and whistles, you gotta worry about the ECU, VVT system, throttle body, what day of the week it is, and if you had lunch at 8AM or 9AM today.
I'm guessing you already checked fuel trims and those look normal. Do they change when you've just started it after the battery's been disconnected vs. when it's misfiring later? The weird one I had was that it passed a vacuum leak test, so we were gunning after the fuel system until I found a hole in the air intake resonator box that sits between the MAF and the throttle body. Didn't show up on the vacuum leak test, or maybe I just missed it, but was making it run horrifically lean.
Check your O2 sensor voltages? If your upstream O2 sensor is giving weird, unreliable readings, your fuel trims can become erratic.
You've ruled out most of the common suspects, but there's a couple elephants in the room; timing, and the ECU.
You could have a VVT system problem of some sort. That causes it to stumble at higher speeds, but also can cause misfires at idle. I'd verify all the stuff that's easy to get to, like the VVT solenoid, the voltage to the solenoid (need an oscilloscope to view that), and if there's a blockage in the VVT feed line. If all of those check out fine, it's *probably* not your ECU, but it still might be your timing. Biggest suspect after that is the VVT timing gear.
If any of these things are off, you can drive around for literally a thousand miles before the check engine light comes on with a VVT system or timing related code. On my car, if you disconnect the battery, it might run for hundreds of miles without the code coming back, or only 50. If you're disconnecting the battery a lot, it wouldn't surprise me if you never got a code for what the actual issue is, be it the TPS or the VVT system.
The ECU itself, like I said before, you usually need an oscilloscope to see if it's good or not. Backprobing the usual suspects to see if there's any issues is always a good option. Especially since you seem really trigger-happy with replacing wiring, have you been measuring the wiring and noticed voltage drops and/or extra resistance? Before replacing wiring, have you ruled out that it doesn't go all the way back to the ECU? ECU can drop voltage and end up not controlling things properly. It's rare, but it happens, and it's one of the reasons I said to backprobe the VVT solenoid with an oscilloscope. I'd do the same to the ignition coils and fuel injectors, too, just to be safe. If it's all cylinders except 5, you should only need to do all this on one cylinder.
These engines are new enough that fuel, air, compression, and ignition are no longer the only things you need to worry about. On these computerized systems with all the bells and whistles, you gotta worry about the ECU, VVT system, throttle body, what day of the week it is, and if you had lunch at 8AM or 9AM today.