707eric

I have 1999 Tacoma 3.4l. The truck has intermittent warm start issues. Occasionally after the truck has warmed up if you park for 5-10 minutes it will have a hard time starting. The engine will crank and you hear it trying to start but it just wont "catch" for lack of a better word. Usually within a minute or two of attempting to start it will fire and run fine.

The other day I was driving and I got on it and I later noticed the check engine light was on. I checked it with a code tester and it came back as error code P0171: System too Lean (Bank 1)

So far the following has been done

Replaced IAC Valve
Replaced MAF Sensor
Replaced ECT Sensor
Replaced Fuel Pump
Replaced Fuel Filter
Cleaned and Balanced Injectors
Replaced TPS
Cleaned Throttlebody
New Plugs
New Air Filter (non-oiled air filter)
Checked Valve Clearance

Any ideas?

Champion

Check your battery man. I know it sounds stupid. If your battery is dry it will be really funky when it heats up without any water in it. And a battery without water in it CAN throw a code.

707eric

Battery appears to be ok. Its also not very old about 3 years on a 84 month battery so should have another 1-2 years of good life left.

I also forgot to mention in original post both O2 sensors have already been replaced.

Champion

That's tricky man. My next guess would be something with the exhaust. Possibly your cat....not to be pessimistic. Ugh, I hope for your sake it's not.

KU_MechE

Same problem and I've done everything in bold plus new plug wires, new coils, and front O2. I just ordered a fuel pressure test kit to continue diagnosis.

Jmyers224

I'm having the exact same issue and ran across your post. It fires back up fine if I start it back up immediately but if I wait 10 min or so there's a 20 min window it wont start. I'm thinking it's an electrical component/connection that is heating up and failing. Did you ever figure it out?

707eric

I really haven't been driving the truck too much. I replaced the battery in the past 6 months and it hasn't happened since. I am not sure if it is coincidence or it is actually fixed. With the limited amount I now drive it and how infrequent the issue occurs it is hard to say if the issue is fixed. If your battery is a few years old it wouldn't hurt to replace it.

707eric

I will update this in case others have the issue. In the past nine months I have been driving the truck a lot more than I had been. The truck started surging while driving which made it really uncomfortable to drive. I cleaned the MAF but that only helped for about 50 miles.

I ended up replacing the MAF with one from Toyota and the surging stopped. It has been about 6 months now since I replaced the MAF and (knock on wood) I have not had a recurrence of the surging or the hot start. The hot start issue had gotten to the point were it happened just about every time I drove it.

Hope this helps others.

Buckaroo5

This sounds like a classic MAF issue but you say you replaced it so I am befuddled.....I hate to ask but did you install a Denso? Some folks claim that is really important - I can't confirm it myself. Check the electrical connection and make sure it is secure.....Also, for those folks that clean the MAF and have the issue come back quickly, make sure you are removing the sensor and spraying the two very thin wires which are located down the throat of the MAF. I initially was just cleaning the temperature sensing bulb which is not the issue.....I have 203,000 miles and I have had the P0171 about every 30,000 miles since I hit 130,000 miles. MAF is original, cleaning it solves the problem for another 30,000 miles... Buckaroo

707eric

Read my last post, the issue is resolved, I was just giving an update.

The originally listed parts were the parts the previous owner said he had replaced. The MAF was cleaned thoroughly wire, bulb, etc. The new MAF I installed was direct from Toyota and I think is a Denso. Its been 6 months or so I didn't and haven't need to mess with it since.