1991 Camry DX w/stock 4-cyl (1.8?), automatic trans w/overdrive, 242k miles

Over last 6 months, especially since June, with increasing frequency, I notice this pattern after start when on city streets with frequent stops:

- Minutes 6-7 after cold start (outside temp 60): runs normally

- Minutes 7-16 after cold start: hesitates and runs rough at low RPM. Idle is rough. When I start from idle, I have to use the gas pedal very carefully to avoid killing the engine--basically, I have to accelerate verrrry slowly. It's easy to give a bit too much gas and kill the engine. Threatens to die often when shifting, too.

During this period, when RPM is fairly low--sorry, no tach--and I give it more gas, it threatens to die, or outright dies.

This could happen at idle and from idle start as noted above. Happens at most or all gear shifts (it's an automatic). Can also happen in high gear at 25-35 or 40 if I try to speed up quickly for some reason, but this condition seldom occurs. When accelerating while cruising at 20-35, forcing RPM up by deliberately downshifting usually reduces or eliminates symptoms.

I'm usually on the freeway going 50-70 after the 11th-13th minute so here's what happens there. Car still runs rough for awhile, difficulty climbing the first long hill. If I shift down the problem seems to lessen or go away.

- Minutes 20 after cold start and thereafter: seems to run normally again

Any thoughts? Investigation will be done by mechanic, not me, so it may take awhile as I look for a good smart one.

Could bad gas do this? I switched gas stations, can't tell yet if problem is improving since I drive it so little (less than 20 gallons past 4 months).

(Anyone who knows somebody in the San Francisco East Bay area--ie, Berkeley, Oakland, Walnut Creek, etc--or Solano or Napa County who likes to take on a problem like this, please let me know. I'm new here and had to leave behind a wonderful Minnesota mechanic.)

 

For those 6-7 minutes after cold start you have no problem?

Then have problems?

Then 20 minutes after cold start no problems?

Thus only between say minutes 8 and 19 after cold start there are problems?

 

Yes, that's how it goes. The times are approximate, although the first 6-7 minute period without issues is almost exact.

 

Could be a number of things.

Bad 02 sensor (typically first one coming off head), engine coolant temp sensor for computer, cold start injector fails to turn off.

Might review past post on this issue at this site as someone else had the same issue. Thought problem was the O2 sensor.

At cold start, computer is in open loop mode. After coolant warms up it goes into closed loop mode and now relies on various sensors such as O2 to operate. If a sensor is bad, the engine can have issues as the computer receives a bad sensor signal.

 

Thank you. I will pass this on to the mechanic once I find one.

 

Can also check for trouble codes. The 91 does not use a code reader but has a built-in system displaying codes via the check engine light.

 

Thanks. I just looked under hood and found the Diagnostics box on the left wheel well. Opened it, it's gummed up but I can see where my former mechanic has used it. Appears I must have the 3SFE engine (VIN 4th character is "S"), I know it's a 4-cyl and doesn't look like previous owner replaced it. So if I ever have enough time for an adventure....

 

Yes, 3SFE.

Always worth a shot on checking codes. If doing this, do so after engine is hot and running rough and making several trips with engine hot at restart. Computer needs monitor several trips (engine off/on and drives) before it will set a code.

If cold starting engine and all runs OK, computer may reset codes.

 

Thanks for the tips about how to get an accurate code reading. I'd never have guessed it could be that tricky.