Shaggy1970

My 98 runs like a top no issues when its cold outside, but when the outside air Temp get above 75 degrees the truck barley runs. It throws no codes whatsoever, but when its warm out it can't idle right, coughs and hesitates all through the rev range. I don't want to just throw parts at it and spend hundreds of dollars guessing. Any help would be appreciated. Already searched all forums and can't find anything.

02_Black_On_White

what are your ECT's going to? anything above 200ish is an issue. Bad T-stat could be sticking, clean the MAF and TPS (might as well replace if high mileage)

Shaggy1970

Coolent Temp is normal, Cleaned the MAF and replaced the throttle position sensor about six months ago.

Its almost like its not receiving the right air fuel mixture when the outside air temp gets hot. Its got a K&N Cold air intake on it, wonder if the heat under the hood has something to do with it. Maybe O2 sensor, but no codes and again it runs flawless when the temp outside is mild or cold.

2thousand5.4

Sounds like it could be a bad IAT sensor. Warmer air is less dense so timing and injector pulse has to be adjusted to make the engine run like it should (the computer does this). So you sensor could be reading that the air is super hot or super cold and causing the fuel trims and timing to be off. You can try cleaning it with MAF cleaner.

akdoggie

Definitely something to do with an air sensor. They are the ones that set the computer to ambient air. IAT most likely like 2000 said. That is where I'd put my focus.

Shaggy1970

IAT sounds resonable is that the same as IAC? Will go to Napa and throw some money at it and see what happens.

2thousand5.4

Nope those are 2 different things. IAC is idle air control and IAT Is intake air temperature sensor. The IAT is on the intake elbow near the MAF

Shaggy1970

So 29 dollars down the drain, Swapped the IAT no difference.

02_Black_On_White

to be completely fair you might as well just sell it with that mentality... It's an 18 year old truck these things happen, can't expect to get the right part for the fix 100% of the time....It probably needed a new IAT anyways, but without codes it's hard to actually pinpoint these mystery issues. We do the best we can, sometimes we get it right but not always.

fordguy2100

that's more than $29 down the drain you wasted on that thing. First step is take that off then go find your other problems