RedVA4x4

Hello all,

This is my first post and as I can do some automotive things I don't have the tools or knowledge to do more extensive things or the "lingo" associated with it so, I'll need plain English and spelled out acronyms.

Here is my problem. My truck (160,000) has been running rough lately i.e. Starts up great but then some hesitation, then runs smooths as could be and then after reaching operating temperature and stopping off to shop in a store or whatever, it is very hard to restart if left for 20 minutes. I don't drive the truck on a daily basis.

I decided to replace the spark plugs(NGK) the spark plug wires (genuine Toyota), the distributor cap and rotor button (Toyota) and a new air filter. It ran much better but still had some of the same problems and then got worse again. I took up to a local gas station for them to diagnose and check the timing as I don't have a timing light. They said the timing was fine. They couldn't get the truck to act up long enough with their gauges attached to find out what the problem was. They asked to keep the truck another day and try again. The heat wave broke that night and They said it has been running well since then and that maybe it has something to do with the heat wave we have had in the Mid-Atlantic recently. They thought Possibly the Ignition Coil was acting up. I replaced the ignition coil myself the next day and it has been running beautiful. Then today we had our first of many to come 90+ degree days after a nice 4 days of low 80's and it is starting to do the same thing again. It does appear that ambient air temperature above 90 degrees affects/ contributes to this problem. The Mass Air Sensor is only two years old.

Any Ideas why it acts up when 90 + degrees but fine below that? Very curious indeed.

RedVA4x4

Since nobody responded to this thread I took the truck to another service center. They diagnosed that it was probably the Electronic Coolant Temperature Sensor or ECT. It runs great now.