98 LS Lugging when accelerated
#1
Driver School Candidate
Thread Starter
98 LS Lugging when accelerated
My 98 LS 164k always run like new. Now its acting up. I would appreciate some feedback. Has anyone had this happen, and what caused it.
• Symptom
Engine idles smooth, cruises at low and high speed smooth. (Good gas mileage)
However, acceleration at any speed causes it to hesitate and what we called in the carb days "bog down" until an effortless cruise is established.
• NO CEL ,no old codes stored.
• Current state of maintenance
VVTI valves are new and working, sparkplugs are 7 month's old Denso IK20 Ir. Pulled them, look clean with the exception of one that is very slightly off color from the rest.
Coils are dry w/no carbon scoring, dielectric added to their contacts and harness connections.
Injectors are all clicking away nicely.
All vacuum lines replaced, pcv, and its grommet and hose new.
In an act of desperation I pulled every harness connector and hit 'em with contact cleaner and dielectric.
MAF got cleaning while I was at it.
That is what I've done so far.
I spoke to my trusted mechanic of 15 years. He gives me two possibilities, 1: Fuel pump/filter, 2: Low fuel press under acceleration.
I then went to an "Import Specialist", and told him everything as I'm describing to you guys ^^^^.
His direction in the prognosis is aimed at the ignition system ie: maybe a bad coil.
He does have a Toyota Tech Tool.
Thanks
Comments and Ideas welcome.
• Symptom
Engine idles smooth, cruises at low and high speed smooth. (Good gas mileage)
However, acceleration at any speed causes it to hesitate and what we called in the carb days "bog down" until an effortless cruise is established.
• NO CEL ,no old codes stored.
• Current state of maintenance
VVTI valves are new and working, sparkplugs are 7 month's old Denso IK20 Ir. Pulled them, look clean with the exception of one that is very slightly off color from the rest.
Coils are dry w/no carbon scoring, dielectric added to their contacts and harness connections.
Injectors are all clicking away nicely.
All vacuum lines replaced, pcv, and its grommet and hose new.
In an act of desperation I pulled every harness connector and hit 'em with contact cleaner and dielectric.
MAF got cleaning while I was at it.
That is what I've done so far.
I spoke to my trusted mechanic of 15 years. He gives me two possibilities, 1: Fuel pump/filter, 2: Low fuel press under acceleration.
I then went to an "Import Specialist", and told him everything as I'm describing to you guys ^^^^.
His direction in the prognosis is aimed at the ignition system ie: maybe a bad coil.
He does have a Toyota Tech Tool.
Thanks
Comments and Ideas welcome.
#2
Moderator
I'd simply try bypassing the fuel pump resistor short circuiting the +B and Fp at the diag. connector.
#3
Driver School Candidate
Thread Starter
I'm beginning to think I have a bad/going bad coil.
Does anyone know how to isolate which one it is?
Toyota Tech stream would be how, but I don't have that.
Does anyone know how to isolate which one it is?
Toyota Tech stream would be how, but I don't have that.
#4
A bad coil would cause a misfire condition which the ECM should pick up pretty easily and turn on the check engine light.
Last edited by djamps; 06-14-17 at 10:39 PM.
#5
Moderator
+1 sounds like a fuel pressure issue. Good 1st step advice here. You need to make sure the fuel pump is switching to 'full speed' under load. Normally it runs at half speed until you put your foot in it. Bypassing the resistor puts it at 'full speed' at all times which will rule out relay/ecm issues with regard to the fuel pump.
A bad coil would cause a misfire condition which the ECM should pick up pretty easily and turn on the check engine light.
A bad coil would cause a misfire condition which the ECM should pick up pretty easily and turn on the check engine light.
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