Jack Murphy

Hello everybody, I’ve been having some interesting problems with my girlfriends 93 Del Sol SI with the D16Z6 manual

First of all, about after a week after we got it, it hard started in the driveway. The RPMs would shoot up to 2k like they normally did, and it started quickly like usual, but instantly after that initial spike, the car died. It did this 2 or 3 times before I was able to start it and keep it running. BUT once I got it to stay on it ran like a champ like it’s supposed to. This is a very intermittent problem but seems to be getting more often. At first it was once a week, and now it’s about 1 out of 10 starts..

It had a half tank of gas but my girlfriend occasionally runs it very low on gas. (I told her not to do that to old cars!!) it seems to do this more when it’s been parked in the sun for a long time, so heat may have something to do with it?

The owner before us did a complete tune up with new coils and plugs, wires, dizzy, filters ect.. and said he never experienced this problem……

[EDIT: (possibly helpful details about how it starts) When it fires up it does this thing where it jumps to 2k RPMs then IMMEDIATELY drops off to 1.2k or so. then slowly comes back up to like 1.7k - 2k where it idles until it warms up. after a few minutes it'll drop to 1k. Is this fuel pump lag? is it a sign of anything? it's always done this since we got it.]

I’ve read up on it as much as I could. The things I’ve heard are

-Main Relay
-fuel pump (I can hear it prime)
-Speed sensor
-MAP sensor
-Dirty butterfly valve
-ECU
-ECT sensor (problem #2 correlation?)

On to PROBLEM #2

The car seems to stay weirdly cold always. Like rarely above a quarter gauge, although sometimes it does get above that to what I’ve come to believe is “Normal operating temp” a little under half. I’ve been telling her she needs a new thermostat but we’ve yet to get one. And while the coolant is drained we might as well put in a new ECT sensor for good measure. Am I on target with the thermostat diagnosis? Would this have anything to do with problem #1 in causing it to hard start?

Thank you for any info you can give. I’m just looking for ideas at this point. Please help!!

mk378

Clean the IACV first. It controls air flow into the engine during starting and idling. Anyone with that generation of Civic should re-solder their main relay pre-emptively.

Overcooling has to be the thermostat. Note that the thermostat is in the lower hose, don't take the upper hose fitting off of the top of the head.

Jack Murphy

Thanks so much for the quick reply! i'll try to clean the IACV tonight and update with any changes.

Jack Murphy

Hello again, I changed the thermostat and ECT sensor and sanded/re grounded all 4 engine grounds and I thought the problem had disappeared. It worked fine for about 2 weeks and then one day did the start and stall a couple times while trying to start the car after putting gas in it. Really confused what it could be now, because it's never given me a problem once it's warmed up.
My list of possibilities is:
IAT
FITV
IACV
MAP sensor
TPS sensor
Trans Speed Sensor
Ignition module/coil?
Main Relay?
Fuel pump?

if anyone can offer a next step in troubleshooting or help me cross some of these off that would be great. Thank you!

demon6666699999

I would start with cleaning the IAC. For starters there is only one coil, not coils. So i would question if it was actually replaced. If you question him, then replace it. Then the ignition control module, which is right next to the coil under the cap. Trans speed sensor shouldn't cause a starting problem. Never seen a IAT or MAP go bad, and they are tough to test because you would have to check the resistance at the point of failure. Which is hard to do without an oscilloscope. Would think your pump is fine, you don't have a fast idle thermal control valve. I would re-solder the main relay like already said. If the contacts aren't cracked yet, they will be.

If your so inclined here is the diagram if you want to test the ignition system.