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1999 Gs300, 203,000 miles. No Check engine lights on.
So my girlfriend's car ( 1999 gs300 ) has recently given us an issue with what seems to be a hesitation in the form of a miss-fire, but only from a dead stop with moderate/heavy throttle and also, when you give it above 20% throttle between 35 and 45 mph. The problem definiently depends on load. if the AC is on the issue is worse. Turn AC off, the hesitation becomes very light ( about a 50% decrease ).
New Denso Platinum plugs 2 years ago
New NGK plug wires 2 days ago
Air sensor cleaned with CRC spray
New air filter ( today )
Other than that the car runs as smooth as can be.
The only thing that is not "perfect" with her car is the air hose that goes to the upper nipple on the factory intake tube is broke/dangling there. It's been like this for a while though ( before the problem ever even existed ). Picture of hose is circled in red ( not her engine bay, just a google'd picture for reference ).
My question is, Could this "unregistered" air cause and issue like this, or am I needing to dig deeper? Possibly weak coil-packs? I plan on taking the throttle body off this week and doing a deep clean.
Yes, fix it! Mine was broken for a very long time with no issues, then slowly things began to happen (yes no codes) then finally, the car wouldnt even start! It just cranked. I replaced it, never happened again. Its a pain in the *** to fix, but its a VERY expensive piece, its like $280 to replace. See what fabrication you can use to fix it.
Yes, fix it! Mine was broken for a very long time with no issues, then slowly things began to happen (yes no codes) then finally, the car wouldnt even start! It just cranked. I replaced it, never happened again. Its a pain in the *** to fix, but its a VERY expensive piece, its like $280 to replace. See what fabrication you can use to fix it.
wow..... that little plastic piece on the air intake tube caused all your problems and went away from simply replacing it?!
Thank you so much for the reply, I'm going to fix it this week!
Not saying its your current problem, but it may lead to other issues, or probably is currently in the beginnings of MY venture. My car was running lean due to the post MAF air and finally my car said eff you and decided to never start LoL
I also had the same problem. I had a big crack underneth that same part and my car was acting crazy, even shuts off because the rpm would drop. after fixing that huge crack, my car was normal again.
Will update soon. I removed the TB today and gave it a good cleaning. For 200k miles and possibly never been cleaned it wasn't bad at all ( should have taken pics ).. The intake manifold side was spotless/ looked brand new. JB-welding the plastic nipple back on the intake tube and will see how that does it. Also have the battery unhooked so I have a fresh start. If this doesn't fix it, it nearly has to be coil packs/ coil pack boots.
Sorry to say... but that JB weld wont hold Gonna have to get a bit more ingenuitive to fix that Hopefully you at least not only cleaned, but sanded the hell out of it to hold.
Also, I'd check the bottom side of the resonator to be sure it hasnt cracked around the edges. Being that it sits over the exhaust manifold, it becomes very brittle with age.
Had the crack issue, it does cause a bog during throttle but I can say you have other issues.
If it started after doing the spark plugs or moving any of the coil pack wiring, I can almost guarantee that is the cause.
Heat causes the shielding on the wires to get brittle. Once you move them after it's been heat treated for years on top of the engine, the plastic just breaks off like twigs.
Once that happens it will cause a short. It happened to me on the first day of a week long vacation. After having timing belt and valve cover seals done at a shop.
Unwrap the shielding and check all 3 sets of wires coming from ignitor to coil pack.
Get a new harness or new wires. In a jam you can wrap them.
Try that first and report back.
Last edited by TW99GS300; 11-02-16 at 08:06 PM.
Reason: grammatic error
Yes I did JB weld the plastic nipple back on. Two coats, with dry time in between. total length drying, 36 hours. Solid as a rock. This did not fix the issue.
hooked the car up to one of those balling $10,000 scanners and found cylinder 2 pinging random miss-fires.
Bought a new set of coil packs. Upon removing them, cylinder 2 rubber boat was completely broken and trashed.
Installed new coils ( can't believe the harness clips didn't break! ) and let the car warm completely up to operating temperatures. Typically then I could give it heavy blimps of throttle and it would miss every single time off idle like clock work. That as of now is completely GONE! Test drive might possibly be later tonight or tomorrow.
I do want to thank every single person who inputted their thoughts and ideas.
I'll report back with a solid confirmation after a good long drive
10-30-16, 04:32 PM
Broken intake tube/ hesitations ?
Mine was broken for a very long time with no issues, then slowly things began to happen (yes no codes) then finally, the car wouldnt even start! It just cranked. I replaced it, never happened again. Its a pain in the *** to fix, but its a VERY expensive piece, its like $280 to replace. See what fabrication you can use to fix it.
Gonna have to get a bit more ingenuitive to fix that 
