92 Ls 400 No Throttle Response

[bngejmpr]

I have recently purchased a 92 LS 400 w/148K. When the vehicle is COLD it is like driving a new one, no issues what-so-ever. After driving for at least 30 minutes (sometimes longer) the vehicle will begin to skip, hesitate, misfire, only slightly noticable at first, while at crusing speed. This becomes increasingly noticable until the vehicle will begin to buck violently. Upon stopping two new problems appear, first, the idle is now flunctuating up and down almost to the point of shutting off the engine, this is constant either in park or drive. Secondly, and most importantly, now, intermitantly, when you attempt to accelerate there is no throttle response, none. I dont't know how else to describe it. It's as if the transmission neturaled out but there is no change in the RPM's, I mash the accelerator and NOTHING happens. After several tense seconds the engine responds, abruptly, and off we go until I lift off the gas or stop, then it's a crap-shoot as to when it will do this again.

Mechanic suggested Throttle body cleaning, done, only made idle surge worse.

Suggested replacing ecm/ecu, done, no change

Going broke and bald at the same time.

Have read about trunk wiring several times tonight. I will try that tommorow.

Any suggestions are greatly appreciated

Thank You

[landar]

Are there any codes?

http://www.lexls.com/tutorials/intro/codereading.html

[bngejmpr]

no codes, no lights,

[landar]

Hmmm, bucks violently yet no codes? I would think with the symptoms that you described, surely the computer would

pick up something. You did do the code jumper thing even though the Check Engine Light(CEL) is not on?

I know this is kind of generic but it does sound(to me anyway) like a fuel delivery problem.

So, Seafoam that sucker! :D (just kidding...kinda).

I would do some digging in the forums on fuel-air delivery issues.

Dont know enough about the specifics to give more detail, but if I run across somthing, I will let you know. Stick around long enough

and there is no end to the amount of information and advice you can receive on this board. :o

Also, look at this repair site for info on the EFI system. Your lack of throttle response smacks of a TPS issue.

http://www.lexls.com/tutorials/EFI/

I know this will sound somewhat crazy, but the good news is that it acts up so dramatically. Those are usually easier

to find than the really small, subtle issues.

Count your blessings, Happy Thanksgiving!

[bngejmpr]

Thanks so much for the response, yes, we did the jumper thing, also checked the trunk wiring this morning and all is fine there. Were this a Ford or Chevy I would go straight to the fuel pump, (getting hot and cutting out). Could it really be that simple? So many posters with similar problems, not exact perhaps, but close, and all seem to have come to different solutions.

Thanks for the help, any additional is appreciated.

Happy Thanksgiving all......

[Leadfoot]

Please humour me and just confirm that the Check Engine Light actually lights when the ignition is switched on, I remember reading one thread where the bulb was blown and that threw everyone! Normal output is a steady flashing sequence. You said no lights above, just want to eliminate the obvious, no disrespect to your mechanical ability!

It may be related to the throttle position sensor, please check as per the attached doc.

Fuel issues do not tend to come up on the computer system so I think you may be right there. The 92 has a separate cold start injector system that will aid cold running, and it could be a problem with this that is causing the misfire once the system has warmed up and its getting over fueled. When your car misfires is there a strong fuel smell from the exhaust pipes? When was the fuel filter last changed? Is there is stong pulse on the fuel damper on the fuel rail?

TPS.pdf

[bngejmpr]

Yes, check engine light is opperational. The TPS is working normaly. Throttle body removed per instructions and throughly cleaned. Cover shield removed, fuel filter appeared brand new, changed anyway, flow direction of removed filter correct. Throttle body removal revealed new air filter, MAF sensor appeared recently cleaned, recleaned anyway.

When the vehicle misfires the exhaust smell does not change, nor when the idle begins to flunctuate. No smoke or appearance of unburnt fuel.

Lost me on the strong pulse on the fuel damper on the fuel rail, will have to research and find someone smarter than me to help with answer to that one. Will let you know.

thank you so much for your help

[MR. LEX]

Wow that's funny no check engine light. I've only had that problem once. In an 94 LS400 it was the ignition coils. You have two of them. And they go for about $65.00 per coil. And when the coils start to go bad you won't get a check engine light. But the good thing once that's fix you're good for about another 120,000 or 130,000 miles.

[chimba]

Hi, don't jump yet. if u still have the problem, i'm the X insane, this might sound crazy, turn your ac off and drive, see what happens, good luck