Hey guys,

So I've had my Sol for a few months now, bought it towards the end of last fall, so haven't really run it at all in hot weather yet (in NC, so it's just warming up for the year). I've noticed recently that on the particularly warm days (90 F +) it has a strange issue that as someone new to an older car I don't know how to diagnose. When I start the car up for the first time of the day, it always starts right up, no problems. But driving, and once the engine heats up, it has a significant issue at lower RPMs. If I stop at a stop light it'll be idling in the range of 500 or so, which is lower than it should be, but when I press the gas to get going again (before I let out the clutch at all) pretty much nothing happens. If anything, it often drops even lower -- to barely enough to keep running -- until I mess with the gas for another 5-10 seconds it seems to get things together and get going. While I'm driving, too, if I push the clutch in and just coast and RPM drops to idle, it does the same when I try to get it back up to speed to let the clutch out again.
I'm probably missing some specific info here that might help, so please ask if there's anything that might make it clearer. It's a 95 Del Sol with the D16, manual, 224k. I never had this issue in colder weather, and I'm pretty stuck on where to go from here that doesn't involve taking it to the professionals.

Any thoughts I can look in to?

 

When was the last time you cleaned the throttle body and/or idle air control valve?

 

Yes start by cleaning the throttle body and IACV. Check the TPS, IAT, and ECT sensors with a volt ohm meter.

This is assuming that the check engine light works but is not on. If any codes are present, check them out.

 

Honestly didn't even know that was something that needed to be done, but I appreciate the pointers, I'll look into that.

The CEL is clear and it's not showing any warnings, so I'm stumped on that front, but I'll see about cleaning the throttle body and IACV.

 

I just realized you recently bought the car used - did the previous owner give you any maintenance records?

I would hold off on cleaning, replacing, or doing anything in favor of gathering some basic information. The problem you're reporting could be caused by numerous factors - possibly more than one of them.

Here are some of the metrics I'd be interested in:

• fuel pressure (within spec?)
  • stopped
  • at idle
  • under load (say, 3K rpm)
• short term fuel trim
  • at idle
  • under load (3K rpm)
• timing within spec?
  • idle
  • does it advance properly under load?
• ignition wire resistance within spec?
• compression on all four cylinders within spec and no large deviations?

 

The heat-related stuff makes me wonder about cam/crank sensor and the igniter...

 

I checked out the ignition wire resistance last month when it was having a different issue, that was fine, and did a compression test shortly after I bought it just to make sure things were fine -- no important deviations there. I'll get some numbers on the fuel pressure, I've got a gauge installed, but don't have a reader to check the short term fuel trim so may have to wait on that one.

I was thinking it might be a sensor of some sort due to the heat related issue, not that I know a whole lot about it but that seemed like it might be the most likely thing to have issue with temperature changes.

 

Try fuel filter also

 

IACV, spark plugs, spark plug wires, bad gasoline, PGMFI relay...

 

To me it sounds like something is wrong with a sensor once it gets up to temperature. Try back probing the TPS once the engine is hot and take voltage readings off of it at various positions with the engine off (ignition switch must be on). Look for smooth consistent movements. Also compare them to readings with the engine cold (a good sensor will act the same at any temp).

The distributor problem also sounds possible. If you have a distributor you could swap in, that's always helpful to eliminate possibilities. There are 7 individual components in the distributor alone (3 sensors, cap, rotor, ignitor & coil).

I doubt It's the idle valve cause it's position is inconsequential once you open the throttle.

 

So I'm now moderately convinced I've got a blown head gasket, might that have had anything to do with this issue?

 

Wouldn't be the first thing on the list but nothing a compression test wouldn't rule out. Sounds more like an electrical leak as they get worse as the engine gets hot like a igniter coil breaking down

 

I'm convinced for other reasons that I've got a bad head gasket. I've got a compression loss, drops evenly from 170 on the first cylinder to 145 on the fourth, got bubbles coming up in the coolant reserve tank at any speed above idle, and I've got intermittent white/light grey smoke. That coupled with the overheating and a consistent loss of coolant and I can't think of anything else it would be. Sound like a head gasket to you guys?