paulpas

I just spend the afternoon taking the throttle body apart to try to fix my issue with hesitation. All parts were surprisingly clean and I sprayed a bunch of penetrating lube on both sides of the throttle assembly (front/back) to prevent binding. The ISV looks clean, I was unable to take the TPS off because the bottom screw is too rusted and I started to strip it--I stopped before I went past the point of no return.

With that all said and done, the car still has an issue of hesitating at light throttle--it had this before I did the throttle body work. This happens when it's in drive or neutral. There is a new battery in the car. I have no codes indicating an issue.

It's as if that 1-3mm of throttle that you give to maintain a nice slow cruising speed is a sweet spot for it to hesitate. When I do harder accelerations I feel a oscillating surge that's very subtle. It has the same timing as the hesitation at part throttle.

I had a thought, could it be the O2 sensor?

Thanks

Paul

V8BOB

I had a similar issue, this oscillating surge. Turned out to be a bad thermostat. It should be at a minimum 87* C warmed up. I was only at about 75*C. So the car couldn't decide if it was warmed up enough or not. I changed out the thermostat and all was good.
Bob

paulpas

How did you measure the coolant temp? I'd like to verify mine.

V8BOB

I just went by the temp gauge. It was down at about 75* even after running an hour. I think there is a way to read the temp through the climate control but I would need to look in to that more. My gas mileage dropped also. I was getting 20mpg and dropped to 13 mpg.
Bob

toml99

One barely noticeable "oscillating surge" I had while on highway doing 60 went away after new caps/rotors/wires/plugs. If you have no idea when any of those were changed, they all need it. The fact you have no codes makes me want to check things like that that won't throw a code. Bad coolant temp sensor would also do what Bob had, but should show code...I've replaced 3 of them over the years, and if bad will really effect mileage.
To show coolant temp on CC you need to check value on channel 6 and use the table in the book to figure out actual coolant temp.....To do that you turn ignition on/hold outside temp/hold off/release outside temp then release off....use warmer/cooler to go up down thru the 22 diagnostic channels. Easier to borrow/rent/have someone use an infrared temp tester and point @ radiator/thermostat/etc and see what the temp is, but if you've never messed with that diagnostic cc thing, it's pretty cool for old school technology. I can send/post the conversion table if you don't have it. You can also test the $18(aftermarket) Motronic coolant temp sensor(below passenger distributor), but if it's old, I'd just replace it as they always seem to run better with a new one. Since you have no codes, think of the obvious(plugs/wires/fuel filter/airfilter) first before digging too deep....BTDT. Good luck, Tom

paulpas

I appreciate your responses, but the immediate issue is the hesitation. I'm reluctant to randomly buy parts and guess the issue, but I'll do what I have to do. Does anyone have any specifics that they could tell me besides "plugs, wires"

Kneale Brownson

I recall Audifans.com postings years ago about V8 hesitation being related to the ISV system, but I don't recall the fix.

yodasfro

Have you checked the TPS connector for corrosion? It's easy to get at right in the front of the motor. I'd also check to see if it is adjusted properly. A new O2 sensor will probably help too.