Hard start when ambient temperature high...

[BadMojo]

So, I've been trying to troubleshoot a problem I've been having at startup. Car will start fine first thing in the morning. Never have any idle problems, warm idle is at ~700rpm.

However, it seems that when the ambient temp is high I always have trouble starting the car.

For example: Go to work at 8am, car starts fine. Park car for 8 hours, heat hits 90+ degrees. I'll often have to crank the car and give it some throttle to get it to start. When it does start, idle will dip down to ~ 400pm nearly stall out and then jump up to a normal idle. The car *does* seem to be a bit down on power when the outside temp. is high.

I believe I'm running rich and can smell some fuel in the exhaust at startup. I've checked the MAF connector, coolant temp sensor connector AND replaced the coolant temp sensor since it was slightly corroded.

I'm going to try to pull any codes again this weekend and will recheck my ignition timing.

Any other thoughts?

Thanks, guys!

[NISTECH]

Ecm is seeing a lower coolant temp then it actually is, therefore it is richening it up more. Make sure the 2 coolant temp terminals in the connector are really clean and also try to bend them closed slightly to get a better fit on the 2 pins in the coolant sensor.

[BadMojo]

Ecm is seeing a lower coolant temp then it actually is, therefore it is richening it up more. Make sure the 2 coolant temp terminals in the connector are really clean and also try to bend them closed slightly to get a better fit on the 2 pins in the coolant sensor.

Thanks! I'll hit it with some contact cleaner today.

[BadMojo]

Well...did some work on the car today. Timing was somehow off. It was advanced probably to about 24° BTDC. Corrected that to 20° and checked the codes on the ECU.

I got a code 34 (knock sensor). Would you recommend checking it with a multimeter first or do you think the code is correct and I should just replace the knock sensor?

Also, if the sensor is bad, I'm assuming replacing it requires removing the upper part of the intake manifold?

Thanks again!

Edit: Still have the intermittent hard start problem.
Modified by BadMojo at 8:23 PM 7/30/2005

[NISTECH]

Knock sensor wont cause a hard start. But yes you should replace it, they tend to crack,thats why you get the code. Replace the sensoe and the short subharness going to it. You do not need to remove the intake manifold. Remove your oil filter and you can gain access to it that way.

[BadMojo]

Knock sensor wont cause a hard start. But yes you should replace it, they tend to crack,thats why you get the code. Replace the sensoe and the short subharness going to it. You do not need to remove the intake manifold. Remove your oil filter and you can gain access to it that way.

Thanks, Nistech. I'll take care of the knock sensor.

I'm still puzzled about the starting problem though...I've cleaned and examined the connectors to the coolant temp sensor and everything looks good unless there's a broken wire in the harness somewhere. Any recommendations on how to continue to troubleshoot this?

[NISTECH]

Use an ohm meter to check the resistance on the CTS when its cold.

[NISTECH]

Also if you havent done so already check al your grounds for good contact with the engine when cold.

[BadMojo]

Also if you havent done so already check al your grounds for good contact with the engine when cold.

Grounds are good. Cleaned a few corroded ones up, but still having problems. Check the CTS and it's good.

Since I fixed my timing (was off...at maybe 23-24 degrees BTDC), I've also had problems with the engine (again when starting on a warm engine) will run extremely rough for approx. 5-10 seconds. It actually runs rough enough to see the engine moving on the mounts and shake the car.

Since it only happens at startup, could it possibly be a O2 Sensor, MAF or IACV problem? The car seems to be down on power, but that could just be a poorly calibrated butt-dyno.

[NISTECH]

O2 does not come into play untill the car warms up or has run for a period of time after start up. Could be maf but I doubt it since it would do it more then just on start up. IT sounds as if the engine is just getting to much fuel, typically the CTS is the problem by your description. Although you said you checked it. So I am pretty much at a loss with out actually getting my hands on it to see exactly what its doing by my interpitation. Maybe its loosing spark on one or 2 of the cyl's due to arch out. Any moisture in the plug wells or in the cap maybe?

[BadMojo]

Yeah. It's really got me stumped. It's hard since it's intermittent and I can't always reproduce it.

I'll double check the CTS and I'll check the plugs. I just changed out the cap and rotor, and I have some new NGK plugs and NGK wires to put in (don't know the age of the old wires, but figured they were original to the car and due for a change).

I'll just go back and check the CTS and the ground, replace the wires and plugs as I planned to do and see what happens.

Thanks again! I really appreciate your help with this.

[BadMojo]

Would it be worth checking for a bad injector? The car idled so roughly today (for a good 15-20 seconds) that the entire car was shaking. I'm at a loss, other than to test every single electronic thing in the car with a multimeter and see if it's within spec.

[NISTECH]

Yea check the resistance on all 4 injectors when they are cold, also look for corrosion in thier conectors.

The checks are what needs to be done to find your problem. Do you have high idel when you start it or when it stops missing? Lack of air could cause it to run over rich when cold.

[BadMojo]

Yea check the resistance on all 4 injectors when they are cold, also look for corrosion in thier conectors.

The checks are what needs to be done to find your problem. Do you have high idel when you start it or when it stops missing? Lack of air could cause it to run over rich when cold.

Yeah. I'll definitely do that this weekend. I'm going to hit everything I can with the multimeter. MAF, injectors, CTS. I'll also double check my timing ignition timing again.

I have a set of used injectors, so if I find one that isn't reading right, I can swap in another.

The idle is fine once it evens out. Normally it'll idle cold at abot 1100 rpm and then drop to 750 or so when warm. It idles steady, but when started warm it *nearly* stalls and then jumps back to a normal idle.

If I get really stumped, I'm going to get something (guy in australia makes 'em) that'll let me read and log a number of parameters through a laptop connected to the Consult port. Pretty neat tool for those of us who can't afford the $5K+ for the real deal.

Thanks, again man. I still wish I could persuade you to move up here to the Rust Belt. I need a good Nissan mechanic 'round here. Tell you what...I'll give you a free case of PB Blaster if you move to PA.

[NISTECH]

Thanks, again man. I still wish I could persuade you to move up here to the Rust Belt. I need a good Nissan mechanic 'round here. Tell you what...I'll give you a free case of PB Blaster if you move to PA.

That and a cutting tourch, plasma cutter, lifetime supply of cutoff wheels for my diegrinder, a saw saw and I should be good to go in your area.